Document and Entity Information - USD ($)	12 Months Ended
Document and Entity Information - USD ($)	Dec. 31, 2017	Feb. 15, 2018	Jun. 30, 2017
Document and Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Entity Registrant Name	Employers Holdings, Inc.
Entity Central Index Key	0001379041
Current Fiscal Year End Date	--12-31
Entity Well Know Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Common Stock Shares Outstanding		32,705,816
Entity Public Float			$ 1,180,291,866
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	FY

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Investments:
Fixed maturity securities at fair value (amortized cost $2,421.0 at December 31, 2017 and $2,305.9 at December 31, 2016)	$ 2,463,400	$ 2,344,400
Equity securities at fair value (cost $116.7 at December 31, 2017 and $116.1 at December 31, 2016)	210,300	192,200
Short-term investments at fair value (amortized cost $4.0 at December 31, 2017 and $16.0 at December 31, 2016)	4,000	16,000
Total investments	2,677,700	2,552,600
Cash and cash equivalents	73,300	67,200
Restricted cash and cash equivalents	1,000	3,600
Accrued investment income	19,600	20,600
Premiums receivable (less bad debt allowance of $10.0 at December 31, 2017 and $9.8 at December 31, 2016)	326,700	304,700
Reinsurance recoverable for:
Paid losses	7,200	8,700
Unpaid losses	537,000	580,000
Deferred policy acquisition costs	45,800	44,300
Deferred income taxes, net	28,700	59,400
Property and equipment, net	13,900	22,200
Intangible assets, net	7,900	8,200
Goodwill	36,200	36,200
Contingent commission receivable–LPT Agreement	31,400	31,100
Other assets	33,700	34,600
Total assets	3,840,100	3,773,400
Claims and policy liabilities:
Unpaid losses and loss adjustment expenses	2,266,100	2,301,000
Unearned premiums	318,300	310,300
Total claims and policy liabilities	2,584,400	2,611,300
Commissions and premium taxes payable	55,300	48,800
Accounts payable and accrued expenses	23,700	24,200
Deferred reinsurance gain—LPT Agreement	163,600	174,900
Notes payable	20,000	32,000
Other liabilities	45,400	41,600
Total liabilities	2,892,400	2,932,800
Commitments and contingencies (Note 12)
Stockholders’ equity:
Common stock, $0.01 par value; 150,000,000 shares authorized; 56,695,174 and 56,226,277 shares issued and 32,597,819 and 32,128,922 shares outstanding at December 31, 2017 and 2016, respectively	600	600
Preferred stock, $0.01 par value; 25,000,000 shares authorized; none issued	0	0
Additional paid-in capital	381,200	372,000
Retained earnings	842,200	777,200
Accumulated other comprehensive income, net of tax	107,400	74,500
Treasury stock, at cost (24,097,355 shares at December 31, 2017 and December 31, 2016)	(383,700)	(383,700)
Total stockholders’ equity	947,700	840,600
Total liabilities and stockholders’ equity	$ 3,840,100	$ 3,773,400

Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Investments:
Amortized cost	$ 2,541.7	$ 2,438.0
Premiums receivable, bad debt allowance	$ 10.0	$ 9.8
Stockholders' equity
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	150,000,000	150,000,000
Common stock, shares issued (in shares)	56,695,174	56,226,277
Common stock, shares outstanding (in shares)	32,597,819	32,128,922
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	25,000,000	25,000,000
Preferred stock, shares issued (in shares)	0	0
Treasury stock, at cost (in shares)	24,097,355	24,097,355
Debt Securities [Member]
Investments:
Amortized cost	$ 2,421.0	$ 2,305.9
Equity Securities [Member]
Investments:
Amortized cost	116.7	116.1
Short-term Investments [Member]
Investments:
Amortized cost	$ 4.0	$ 16.0

Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues
Net premiums earned	$ 716.5	$ 694.8	$ 690.4
Net investment income	74.6	73.2	72.2
Net realized gains (losses) on investments	7.4	11.2	(10.7)
Gain on redemption of notes payable	2.1	0.0	0.0
Other income	0.8	0.6	0.2
Total revenues	801.4	779.8	752.1
Expenses
Losses and loss adjustment expenses	417.2	417.9	429.4
Commission expense	91.4	83.5	85.4
Underwriting and other operating expenses	139.9	136.1	135.2
Interest expense	1.4	1.6	2.7
Other expenses	7.5	0.0	0.0
Total expenses	657.4	639.1	652.7
Net income before income taxes	144.0	140.7	99.4
Income tax expense	42.8	34.0	5.0
Net income	101.2	106.7	94.4
Comprehensive income
Unrealized gains (losses) during the period (net of taxes of $8.9, $(1.0), and $(16.3) for the years ended December 31, 2017, 2016, and 2015, respectively)	19.9	(1.8)	(30.3)
Reclassification adjustment for net realized (gains) losses in net income (net of taxes of $2.6, $3.9, and $(3.7) for the years ended December 31, 2017, 2016, and 2015, respectively)	(4.8)	(7.3)	7.0
Other comprehensive income (loss), net of tax	15.1	(9.1)	(23.3)
Total comprehensive income	$ 116.3	$ 97.6	$ 71.1
Earnings per common share (Note 18):
Basic	$ 3.11	$ 3.29	$ 2.94
Diluted	3.06	3.24	2.90
Cash dividends declared per common share	$ 0.60	$ 0.36	$ 0.24
Net realized gains (losses) on investments
Net realized gains on investments before impairments on fixed maturity and equity securities	$ 8.8	$ 17.0	$ 6.5
Other than temporary impairments recognized in earnings	(1.4)	(5.8)	(17.2)
Net realized gains (losses) on investments	$ 7.4	$ 11.2	$ (10.7)

Consolidated Statements of Comprehensive Income (Parentheticals) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other Comprehensive Income Parenthetical [Abstract]
Other comprehensive income (loss), unrealized holding gain (loss) on securities arising during period, tax	$ 8.9	$ (1.0)	$ (16.3)
Other comprehensive income (loss), reclassification adjustment for sale of securities included in net income, tax	$ 2.6	$ 3.9	$ (3.7)

Consolidated Statements of Stockholders Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income, Net	Treasury Stock at Cost
Stockholders' equity, shares at Dec. 31, 2014		54,866,802
Stockholders' equity, value at Dec. 31, 2014	$ 686,800	$ 600	$ 346,600	$ 595,300	$ 106,900	$ (362,600)
Stock-based compensation (Note 14), shares		0
Stock-based compensation (Note 14), value	4,600	$ 0	4,600	0	0	0
Stock-options exercised, shares		463,466
Stock options exercised, value	7,600	$ 0	7,600	0	0	0
Vesting of restricted stock units, net of shares withheld to satisfy minimum tax withholding (Note 14), shares		259,186
Vesting of restricted stock units, net of shares withheld to satisfy minimum tax withholding (Note 14), value	(2,700)	$ 0	(2,700)	0	0	0
Dividend to common stockholders, shares		0
Dividend to common stockholders, value	7,700	$ 0	0	7,700	0	0
Stockholders' equity, shares at Dec. 31, 2015		55,589,454
Excess tax benefit from stock-based compensation	1,100	$ 0	1,100	0	0	0
Net income for the period	94,400	0	0	94,400	0	0
Change in net unrealized gains on investments, net of taxes	(23,300)	0	0	0	(23,300)	0
Stockholders' equity, value at Dec. 31, 2015	760,800	$ 600	357,200	682,000	83,600	(362,600)
Stock-based compensation (Note 14), shares		0
Stock-based compensation (Note 14), value	5,800	$ 0	5,800	0	0	0
Stock-options exercised, shares		586,132
Stock options exercised, value	9,600	$ 0	9,600	0	0	0
Vesting of restricted stock units, net of shares withheld to satisfy minimum tax withholding (Note 14), shares		50,691
Vesting of restricted stock units, net of shares withheld to satisfy minimum tax withholding (Note 14), value	(600)	$ 0	(600)	0	0	0
Acquisition of treasury stock (Note 13), shares		0
Acquisition of treasury stock (Note 13), value	(21,100)	$ 0	0	0	0	(21,100)
Dividend to common stockholders, shares		0
Dividend to common stockholders, value	$ 11,500	$ 0	0	11,500	0	0
Stockholders' equity, shares at Dec. 31, 2016	56,226,277	56,226,277
Net income for the period	$ 106,700	$ 0	0	106,700	0	0
Change in net unrealized gains on investments, net of taxes	(9,100)	0	0	0	(9,100)	0
Stockholders' equity, value at Dec. 31, 2016	840,600	$ 600	372,000	777,200	74,500	(383,700)
Stock-based compensation (Note 14), shares		0
Stock-based compensation (Note 14), value	6,900	$ 0	6,900	0	0	0
Stock-options exercised, shares		307,076
Stock options exercised, value	6,000	$ 0	6,000	0	0	0
Vesting of restricted stock units, net of shares withheld to satisfy minimum tax withholding (Note 14), shares		161,821
Vesting of restricted stock units, net of shares withheld to satisfy minimum tax withholding (Note 14), value	(2,200)	$ 0	(2,200)	0	0	0
Grant date fair value adjustment	(200)	$ 0	(1,500)	1,300	0	0
Dividend to common stockholders, shares		0
Dividend to common stockholders, value	$ 19,700	$ 0	0	19,700	0	0
Stockholders' equity, shares at Dec. 31, 2017	56,695,174	56,695,174
Net income for the period	$ 101,200	$ 0	0	101,200	0	0
Net impact of tax enactment on net unrealized gains on investments	0	0	0	(17,800)	17,800	0
Change in net unrealized gains on investments, net of taxes	15,100	0	0	0	15,100	0
Stockholders' equity, value at Dec. 31, 2017	$ 947,700	$ 600	$ 381,200	$ 842,200	$ 107,400	$ (383,700)

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating activities
Net income	$ 101,200	$ 106,700	$ 94,400
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	8,200	8,500	8,300
Stock-based compensation	6,800	5,800	4,600
Amortization of premium on investments, net	14,300	14,600	12,800
Allowance for doubtful accounts	200	(2,400)	4,300
Deferred income tax expense (benefit)	24,200	13,400	(5,600)
Net realized (gains) losses on investments	(7,400)	(11,200)	10,700
Gain on redemption of notes payable	(2,100)	0	0
Write-off of previously capitalized costs	7,500	0	0
Excess tax benefits from stock-based compensation	0	0	(1,200)
Change in operating assets and liabilities:
Premiums receivable	(22,200)	(1,200)	(9,600)
Reinsurance recoverable on paid and unpaid losses	44,500	47,200	44,300
Current federal income taxes	(2,700)	7,700	(3,900)
Unpaid losses and loss adjustment expenses	(34,900)	(46,500)	(22,200)
Unearned premiums	8,000	1,400	(1,900)
Accounts payable, accrued expenses and other liabilities	(7,000)	(4,200)	8,600
Deferred reinsurance gain–LPT Agreement	(11,300)	(14,600)	(17,500)
Contingent commission receivable–LPT Agreement	(300)	(1,900)	(2,800)
Other	15,300	(500)	(6,900)
Net cash provided by operating activities	142,300	122,800	116,400
Investing activities
Purchases of fixed maturity securities	(592,300)	(466,800)	(476,900)
Purchases of equity securities	(36,800)	(49,100)	(85,100)
Purchases of short-term investments	(8,200)	(10,000)	0
Proceeds from sale of fixed maturity securities	249,800	132,400	105,400
Proceeds from sale of equity securities	41,200	80,400	34,700
Proceeds from maturities and redemptions of fixed maturity securities	215,700	230,600	323,900
Proceeds from maturities of short-term investments	20,200	0	0
Net change in unsettled investment purchases and sales	5,800	0	0
Capital expenditures and other	(8,200)	(5,000)	(11,500)
Change in restricted cash and cash equivalents	2,600	(1,100)	8,300
Net cash used in investing activities	(110,200)	(88,600)	(101,200)
Financing activities
Acquisition of common stock	0	(21,100)	0
Cash transactions related to stock-based compensation	3,800	9,000	4,800
Dividends paid to stockholders	(19,700)	(11,500)	(7,700)
Redemption of notes payable	(9,900)	0	(60,000)
Payments on capital leases	(200)	0	(500)
Excess tax benefits from stock-based compensation	0	0	1,200
Net cash used in financing activities	(26,000)	(23,600)	(62,200)
Net increase (decrease) in cash and cash equivalents	6,100	10,600	(47,000)
Cash and cash equivalents at the beginning of the period	67,200	56,600	103,600
Cash and cash equivalents at the end of the period	73,300	67,200	56,600
Non-cash transactions
Financed property and equipment purchases	400	700	300
Non-cash exchange of fixed maturity investments for short-term investments	$ 0	$ 6,000	$ 0

Basis of Presentation	12 Months Ended
Basis of Presentation	Dec. 31, 2017
Basis of Presentation [Abstract]
Basis of Presentation	Basis of Presentation and Summary of Operations Nature of Operations and Organization Employers Holdings, Inc. (EHI) is a Nevada holding company. Through its wholly owned insurance subsidiaries, Employers Insurance Company of Nevada (EICN), Employers Compensation Insurance Company (ECIC), Employers Preferred Insurance Company (EPIC), and Employers Assurance Company (EAC), EHI is engaged in the commercial property and casualty insurance industry, specializing in workers' compensation products and services. Unless otherwise indicated, all references to the “Company” refer to EHI, together with its subsidiaries. In 1999, the Nevada State Industrial Insurance System (the Fund) entered into a retroactive 100% quota share reinsurance agreement (the LPT Agreement) through a loss portfolio transfer transaction with third party reinsurers. The LPT Agreement commenced on June 30, 1999 and will remain in effect until all claims under the covered policies have closed, the LPT Agreement is commuted or terminated, upon the mutual agreement of the parties, or the reinsurers' aggregate maximum limit of liability is exhausted, whichever occurs first. The LPT Agreement does not provide for any additional termination terms. On January 1, 2000, EICN assumed all of the assets, liabilities and operations of the Fund, including the Fund's rights and obligations associated with the LPT Agreement. See Notes 3 and 10. The Company accounts for the LPT Agreement as retroactive reinsurance. Upon entry into the LPT Agreement, an initial deferred reinsurance gain (the Deferred Gain) was recorded as a liability on the Company’s Consolidated Balance Sheets. The Company is entitled to receive a contingent profit commission under the LPT Agreement. The contingent profit commission is estimated based on both actual paid results to date and projections of expected paid losses under the LPT Agreement and is recorded as an asset on the Company's Consolidated Balance Sheets. Basis of Presentation The accompanying consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (GAAP). All intercompany transactions and balances have been eliminated in consolidation. The Company operates as a single operating segment, workers’ compensation insurance, through its wholly owned subsidiaries. The Company considers an operating segment to be any component of its business whose operating results are regularly reviewed by the Company's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance based on discrete financial information. Use of Estimates The preparation of the consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. As a result, actual results could differ from these estimates. The most significant areas that require management judgment are the estimate of unpaid losses and loss adjustment expenses (LAE), evaluation of reinsurance recoverables, recognition of premium revenue, recoverability of deferred income taxes, and valuation of investments. Pending Acquisition On August 11, 2017, the Company entered into a stock purchase agreement (Purchase Agreement) with Partner Reinsurance Company of the U.S. (PRUS) with respect to the acquisition (Acquisition) of all of the outstanding shares of capital stock of PartnerRe Insurance Company of New York (PRNY). The purchase price is equal to the sum of: (i) the amount of statutory capital and surplus of PRNY at closing (which is currently estimated to be approximately $40.0 million); and (ii) $5.8 million. The Company expects to fund the Acquisition with cash on hand. Pursuant to the Purchase Agreement, all liabilities and obligations of PRNY existing as of the closing date, whether known or unknown, will be assumed by PRUS. In addition, PartnerRe Ltd., the parent company of PRUS, has provided the Company with a Guaranty that unconditionally, absolutely and irrevocably guarantees the full and prompt payment and performance by PRUS of all of its obligations, liabilities and indemnities under the Purchase Agreement and the transactions contemplated thereby. The Company will not be acquiring any employees or ongoing business operations pursuant to the Acquisition. The Acquisition is subject to certain closing conditions, including, among other things, approval from the Department of Financial Services of the State of New York.

Changes in Estimates Level 1 (Notes)

12 Months Ended

Dec. 31, 2017

Changes in Estimates [Abstract]

Accounting Changes and Error Corrections

Changes in Estimates

The Company reduced its estimated loss and LAE reserves ceded under the LPT Agreement (LPT Reserve Adjustments) in each of the years 2016 and 2015 as a result of the determination that adjustments were necessary to reflect observed favorable paid loss trends in each of these years. There were no LPT Reserve Adjustments in 2017. The following table shows the financial statement impact related to the LPT Reserve Adjustments.



	2016			2015
	(in millions, except per share data)
LPT Reserve Adjustments	$	(5.0	)	$	(10.0	)
Cumulative adjustment to the Deferred Gain⁽¹⁾	(3.1		)	(6.4		)
Net income impact from this change in estimate	3.1			6.4
Earnings per common share impact from this change in estimate
Basic	0.10			0.20
Diluted	0.09			0.20


(1)	The cumulative adjustments to the Deferred Gain were also recognized in losses and LAE incurred in the Company's Consolidated Statements of Comprehensive Income, so that the Deferred Gain reflects the balance that would have existed had the revised loss and LAE reserves been recognized at the inception of the LPT Agreement.

The Company increased its estimate of Contingent commission receivable – LPT Agreement (LPT Contingent Commission Adjustments) in each of 2017, 2016, and 2015 as a result of the determination that adjustments were necessary to reflect observed favorable paid loss trends in each of those years. The following table shows the impact to the Consolidated Statements of Comprehensive Income related to these changes in estimates.



	2017			2016			2015
	(in millions, except per share data)
Change in estimate of Contingent commission receivable - LPT Agreement	$	0.3		$	1.9		$	2.8
Cumulative adjustment to the Deferred Gain⁽¹⁾	(0.3		)	(1.8		)	(2.6		)
Net income impact from this change in estimate	0.3			1.8			2.6
Earnings per common share impact from this change in estimate
Basic	0.01			0.06			0.08
Diluted	0.01			0.05			0.08


(1)	The cumulative adjustments to the Deferred Gain were also recognized in losses and LAE incurred in the Company's Consolidated Statements of Comprehensive Income, so that the Deferred Gain reflects the balance that would have existed had the revised loss and LAE reserves been recognized at the inception of the LPT Agreement.

The Company reallocated loss and LAE reserves from non-taxable periods prior to January 1, 2000 to taxable years, which reduced its effective tax rate in 2015. These changes in estimates were the result of the determination that a reallocation of reserves among accident years was appropriate to address a continuation of observed loss trends in 2015. The following table shows the financial statement impact of these changes in estimates.



	2015
	(in millions, except per share data)
Loss and LAE reserves reallocated to taxable years	$	56.3
Impact to effective tax rate	(15.4		)%
Net income impact from this change in estimate	$	15.3
Earnings per common share impact from this change in estimate
Basic	0.48
Diluted	0.47

No reallocations of losses and LAE reserves from non-taxable periods were made in 2017 or 2016.

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2017

Summary of Significant Accounting Policies [Abstract]

Significant Accounting Policies

Summary of Significant Accounting Policies

Cash and Cash Equivalents

The Company considers all liquid investments with maturities of less than three months, as measured from the date of purchase, to be cash equivalents.

Restricted Cash and Cash Equivalents

Restricted cash and cash equivalents represent cash and cash equivalents held in trust in order to secure certain of the Company's obligations and, accordingly, are restricted as to withdrawal or usage. As of December 31, 2017 and 2016 the Company held $24.5 million and $27.2 million, respectively, in trust for reinsurance obligations, of which $1.0 million and $3.6 million, respectively, represented restricted cash and cash equivalents.

Short-Term Investments

The Company considers all liquid investments with maturities of between three and twelve months, as measured from the date of purchase, to be short-term investments.

Investment Securities

The Company's investments in fixed maturity securities and equity securities are classified as available-for-sale and are reported at fair value with unrealized gains and losses excluded from earnings and reported as a separate component of stockholders' equity, net of deferred taxes, in accumulated other comprehensive income on the Company’s Consolidated Balance Sheets.

Investment income consists primarily of interest and dividends generated by investment securities. Interest is recorded as earned on an accrual basis and dividends are recorded as earned at the ex-dividend date. Interest income on mortgage-backed and asset-backed securities is determined using the effective-yield method based on estimated principal repayments. Mortgage-backed securities are adjusted for the effects of changes in prepayment assumptions on the related accretion of discount or amortization of premium of such securities using the retrospective method.

Realized gains and losses on investments are determined on a specific-identification basis.

When, in the opinion of management, a decline in the fair value of an equity security below its cost is considered to be “other-than-temporary,” the equity security's cost is written down to its fair value at the time the other-than-temporary decline is identified. The determination of an other-than-temporary decline for fixed maturity securities includes, in addition to other relevant factors, a presumption that if the market value is below cost by a significant amount for a period of time, a bifurcation of the write-down may be necessary based on the portion of the loss that is deemed to be a “credit loss”, which is considered a realized loss, and the portion that is deemed to be an “other than credit loss”, which is considered to be an unrealized loss. If management has the intent to sell the fixed maturity security or more likely than not will be required to sell the fixed maturity security before its anticipated recovery, the investment is written down to its fair value and the entire impairment is recorded as a realized loss in the Company's Consolidated Statements of Comprehensive Income. If management does not have the intent to sell or will not be required to sell the fixed maturity security but does not expect to recover the amortized cost basis of the fixed maturity security, the amount of the other-than-temporary impairment is bifurcated (see Note 6).

Recognition of Revenue and Expense

Revenue Recognition

Premiums written are recognized as revenues, net of any applicable underlying reinsurance coverage, and are earned over the term of the related policy. At the end of the policy term, payroll-based premium audits are performed on substantially all policyholder accounts to determine the actual amount of net premiums earned for that policy year. Earned but unbilled premiums include estimated future audit premiums based on the Company's historical experience. These estimates are subject to changes in policyholders' payrolls, economic conditions, and seasonality, and are continually reviewed and adjusted as experience develops or new information becomes known. Any such adjustments are included in current operations; however, they are partially offset by the resulting changes in losses and LAE, commission expenses, and premium taxes. The Company's premiums receivable on its Consolidated Balance Sheets included $64.2 million and $58.4 million of additional premiums expected to be received from policyholders for final audits at December 31, 2017 and 2016, respectively.

The Company establishes a bad debt allowance on its premiums receivable through a charge included in underwriting and other operating expenses in its Consolidated Statements of Comprehensive Income. This bad debt allowance is determined based on estimates and assumptions to project future experience. After all collection efforts have been exhausted, the Company reduces the bad debt allowance for write-offs of premiums receivable that have been deemed uncollectible. The Company's bad debt allowance was $10.0 million and $9.8 million at December 31, 2017 and 2016, respectively. The Company had write offs, net of recoveries of amounts previously written off, of $3.2 million, $6.0 million, and $2.4 million for the years ended December 31, 2017, 2016, and 2015, respectively.

Deferred Policy Acquisition Costs

Policy acquisition costs, those costs that relate directly to the successful acquisition of new or renewal insurance contracts, including underwriting, policy issuance and processing, medical and inspection, and sales force contract selling are deferred and amortized as the related premiums are earned. Amortization of deferred policy acquisition costs for the years ended December 31, 2017, 2016, and 2015, was $108.2 million, $104.5 million, and $103.9 million, respectively.

If the sum of a policy’s expected losses and LAE and deferred policy acquisition costs exceeds the related unearned premiums and projected investment income, a premium deficiency is determined to exist. In this event, deferred policy acquisition costs are immediately expensed to the extent necessary to eliminate the premium deficiency. If the premium deficiency exceeds deferred acquisition costs then a liability is accrued for the excess deficiency. There were no premium deficiency adjustments recognized during the years ended December 31, 2017, 2016, and 2015.

Unpaid Loss and LAE Reserves

Unpaid loss and LAE reserves represent management's best estimate of the ultimate net cost of all reported and unreported losses incurred for the applicable periods, less payments made. The estimated reserves for losses and LAE include the accumulation of estimates for all claims reported prior to the balance sheet date, estimates of claims incurred but not reported, and estimates of expenses for investigating and adjusting all incurred and unadjusted claims (based on projections of relevant historical data). Amounts reported are subject to the impact of future changes in economic, regulatory and social conditions. Management believes that, subject to the inherent variability in any such estimate, the reserves are within a reasonable and acceptable range of adequacy. Estimates for claims prior to the balance sheet date are continually monitored and reviewed, and as settlements are made or reserves adjusted, the differences are reported in current operations. Salvage and subrogation recoveries are estimated based on a review of the level of historical salvage and subrogation recoveries.

Reinsurance

In the ordinary course of business, the Company may purchase excess of loss reinsurance in order to protect it against the impact of large and/or catastrophic losses. Additionally, the Company is a party to the LPT Agreement (see Note 10). These reinsurance arrangements reduce the Company's exposure to such losses since its reinsurers are liable to the Company to the extent of the reinsurance protection provided. However, the Company remains liable for all losses it incurs to the extent that any reinsurer is unable or unwilling to make timely payments under its reinsurance agreements.

Balances due from reinsurers on unpaid losses, including an estimate of such recoverables related to reserves for incurred but not reported losses, are reported as reinsurance recoverables on the Company’s Consolidated Balance Sheets. Reinsurance recoverables on paid losses represents amounts currently due from reinsurers. Reinsurance recoverables on unpaid losses represents amounts that will be collectible from reinsurers once the losses are paid. Reinsurance recoverables on unpaid losses and LAE amounted to $537.0 million and $580.0 million at December 31, 2017 and 2016, respectively.

Ceded reinsurance premiums are accounted for on a basis consistent with those used in accounting for the underlying premiums, and are reported as reductions to arrive at net premiums written and earned.

Ceded losses and LAE are also accounted for on a basis consistent with those used in accounting for the original policies issued and the terms of the relevant reinsurance agreement, and are recorded as reductions to losses and LAE incurred.

Pursuant to the LPT Agreement, LAE is deemed to be 7% of total losses paid and are payable to the Company as compensation for management of the claims under the LPT Agreement. The Deferred Gain is amortized using the recovery method, whereby the amortization is determined by the proportion of actual reinsurance recoveries to total estimated recoveries through the life of the LPT Agreement, and is recorded in losses and LAE incurred in the Company's Consolidated Statements of Comprehensive Income. Any adjustment to the estimated loss and LAE reserves ceded under the LPT Agreement results in a cumulative adjustment to the Deferred Gain, which is also recognized in losses and LAE incurred in the Company's Consolidated Statements of Comprehensive Income, such that the Deferred Gain reflects the balance that would have existed had the revised reserves been recognized at the inception of the LPT Agreement.

Additionally, the Company is entitled to receive a contingent profit commission under the LPT Agreement. The contingent profit commission is equal to 30% of the favorable difference between actual paid losses and LAE and expected paid losses and LAE as established in the LPT Agreement based on losses paid through June 30, 2024. The contingent profit commission is paid every five years beginning June 30, 2004 for the first 25 years of the agreement. The Company could be required to return any previously received contingent profit commission, plus interest, in the event of unfavorable differences through June 30, 2024. The Company records an estimate of contingent profit commission in its Consolidated Balance Sheets as Contingent commission receivable–LPT Agreement and a corresponding liability is recorded as Deferred reinsurance gain–LPT Agreement. The Contingent commission receivable–LPT Agreement is reduced as amounts are received from participating reinsurers. The Deferred reinsurance gain–LPT Agreement is amortized using the recovery method. The amortization of the contingent profit commission is determined by the proportion of actual reinsurance recoveries to total estimated recoveries over the life of the contingent profit commission (through June 30, 2024), and is recorded in losses and LAE incurred in the Company's Consolidated Statements of Comprehensive Income. Any adjustment to the contingent profit commission under the LPT Agreement results in a cumulative adjustment to the Deferred Gain, which is also recognized in losses and LAE incurred in the Company's Consolidated Statements of Comprehensive Income, such that the Deferred Gain reflects the balance that would have existed had the revised contingent profit commission been recognized at the inception of the LPT Agreement.

Property and Equipment

Property and equipment are stated at cost less accumulated depreciation (see Note 7). Expenditures for maintenance and repairs are charged against operations as incurred.

Electronic data processing equipment, software, furniture and equipment, and automobiles are depreciated using the straight-line method over three to seven years. Leasehold improvements are carried at cost less accumulated amortization. The Company amortizes leasehold improvements using the straight-line method over the lesser of the useful life of the asset or the remaining original lease term, excluding options or renewal periods. Leasehold improvements are generally amortized over three to five years.

Obligations Held Under Capital Leases

Leased property and equipment meeting capital lease criteria are capitalized at the lower of the present value of the related lease payments or the fair value of the leased asset at the inception of the lease. Amortization is calculated using the straight-line method based on the term of the lease and is included in the depreciation expense of property and equipment. See Note 12 for additional disclosures related to capital leases.

Income Taxes

The Company accounts for income taxes under the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the Company's financial statements. Under this method, the Company determines deferred tax assets and liabilities on the basis of the differences between the financial statement and tax bases of assets and liabilities by using enacted tax rates in effect for the year in which the differences are expected to reverse. The effect of the recent change in tax rates on the Company's deferred tax assets and liabilities was recognized within continuing operations in income as of December 22, 2017, the date that the Tax Cuts and Jobs Act was enacted (Enactment) and created stranded tax effects within accumulated other comprehensive income that did not reflect the newly enacted tax rate. The Company reclassified the net tax effects from Accumulated other comprehensive income, net of tax, to Retained earnings as of the date of Enactment.

The Company records uncertain tax positions in accordance with ASC 740 on the basis of a two-step process. Recognition (Step 1) occurs when the Company concludes that a tax position, based solely on its technical merits, is more likely than not to be sustained upon examination. Measurement (Step 2) is addressed only if Step 1 has been satisfied. Under Step 2, the tax benefit is measured as the largest amount of benefit, determined on a cumulative probability basis, that is more likely than not to be realized upon ultimate settlement.

The Company recognizes deferred tax assets when it determines that such assets are more likely than not to be realized in future periods. In making such a determination, the Company considers all available positive and negative evidence, including future reversals of existing taxable temporary differences, tax-planning strategies, projected future taxable income, projected future tax rates, and results of recent operations. If the Company determines that it is not more likely than not that it could realize its deferred tax assets in future periods it would establish a deferred tax asset valuation allowance that would increase the Company's provision for income taxes. If the Company determines that it would be able to realize its deferred tax assets in the future in excess of its net recorded amount, the Company would make an adjustment to the deferred tax asset valuation allowance, which would reduce the provision for income taxes.

Credit Risk

Financial instruments that potentially subject the Company to concentrations of credit risk are primarily cash and cash equivalents (including restricted cash equivalents), short-term investments, investment securities, premiums receivable, and reinsurance recoverable balances.

The Company’s cash equivalents and short-term investments include investments in money market securities and securities backed by the U.S. government. The Company's investment securities are diversified throughout many industries and geographic regions and include investments in U.S. government and U.S. government-sponsored enterprises. The Company believes that it has no significant concentrations of credit risk from a single issue or issuer within its cash equivalents, short-term investments and investment securities other than concentrations in U.S. government and U.S. government-sponsored enterprises.

The Company's premiums receivable are generally diversified due to the large number of entities composing the Company's policyholder base and their dispersion across many different industries.

The Company monitors the financial condition of its reinsurers to minimize its exposure to significant losses from reinsurer insolvencies. The Company also obtains collateral from its reinsurers in order to mitigate the risks related to insolvencies. At December 31, 2017, $3.5 million of the Company's reinsurance recoverables were collateralized by cash or letters of credit and an additional $380.8 million was in trust accounts for reinsurance recoverables specifically related to the LPT Agreement.

Fair Value of Financial Instruments

The fair values of the Company's financial instruments have been determined using available market information and other appropriate valuation methodologies. Judgment is required in developing fair value estimates where quoted market prices are not available. Accordingly, these estimates are not necessarily indicative of the amounts that could be realized in a current market exchange. The use of different market assumptions or estimating methodologies may have an effect on the estimated fair value amounts.

The following methods and assumptions were used by the Company in estimating the fair value of its financial instruments:

Cash and cash equivalents, short-term investments, premiums receivable, accounts payable and accrued expenses, and other liabilities. The carrying amounts for each of these financial instruments as reported in the Company's Consolidated Balance Sheets approximate their fair values.

Investment securities. The Company’s investment securities are predominantly valued on the basis of actual market transactions or observable inputs. A small portion of the Company’s investment securities are valued on the basis of pricing models with significant unobservable inputs or nonbinding broker quotes. See Note 5.

Goodwill and Other Intangible Assets

The Company tests for impairment of goodwill and non-amortizable intangible assets in the fourth quarter of each year. At the end of each quarter, management considers the results of the previous analysis as well as any recent developments that may constitute triggering events requiring the impairment analysis of goodwill and other intangible assets to be updated. The Company has assessed the effects of current economic conditions on the Company's financial condition and results of operations and changes in the Company's stock price and determined that there were no impairments of these assets as of December 31, 2017 and 2016.

Intangible assets related to state licenses are not subject to amortization. Intangibles related to insurance relationships are amortized in proportion to the expected period of benefit over the next year.

The gross carrying value, accumulated amortization, and net carrying value for the Company's intangible assets, by major class, as of December 31, were as follows:



	2017							2016
	Gross Carrying Value		Accumulated Amortization			Net Carrying Value		Gross Carrying Value		Accumulated Amortization			Net Carrying Value
	(in millions)
State licenses	$	7.7	$	—		$	7.7	$	7.7	$	—		$	7.7
Insurance relationships	9.4		$	(9.2	)	0.2		9.4		$	(8.9	)	0.5
Total	$	17.1	$	(9.2	)	$	7.9	$	17.1	$	(8.9	)	$	8.2

During the years ended December 31, 2017, 2016, and 2015, the Company recognized $0.3 million, $0.3 million, and $0.5 million in amortization expenses associated with its intangible assets, respectively. These amortization expenses are included in the Company's Consolidated Statements of Comprehensive Income in underwriting and other operating expenses. Future amortization expenses associated with the Company's intangible assets are expected to be as follows:



Year	Amount
	(in millions)
2018	0.2
Total	$	0.2

Stock-Based Compensation

The Company provides stock-based compensation to its directors and certain of its employees, which is recognized in its Consolidated Statements of Comprehensive Income based on estimated fair values over the relevant service period (see Note 14).

New Accounting Standards	12 Months Ended
New Accounting Standards	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Standards	New Accounting Standards Recently Issued Accounting Standards In February 2018, the Financial Accounting Standards Board (FASB) issued ASU Number 2018-02, Income Statement - Reporting Comprehensive Income (Topic 220). The amendments in this update allow a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from Enactment. This update becomes effective for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. Early adoption is permitted for reporting periods for which financial statements have not yet been issued and should be applied in the period of adoption or retrospectively to each period (or periods) in which the effect of the change in the U.S. federal corporate income tax rate in the Tax Cuts and Jobs Act is recognized. The Company elected to early adopt this update and, accordingly, reclassified $17.8 million of net tax effects resulting from Enactment from Accumulated other comprehensive income, net of tax, to Retained earnings at December 31, 2017. In January 2017, the FASB issued ASU Number 2017-04, Intangibles-Goodwill and Other (Topic 350). This update simplifies the measurement of goodwill by eliminating the performance of Step 2 in the goodwill impairment testing. This update allows the testing to be performed by comparing the fair value of a reporting unit with its carrying amount and recognizing an impairment charge when the carrying amount exceeds fair value. Additionally, this update eliminates the requirements of any reporting unit with a zero or negative carrying value to perform Step 2, but requires disclosure of the amount of goodwill allocated to a reporting unit with zero or negative carrying amount of net assets. This update becomes effective for fiscal years beginning after December 15, 2019. The Company does not expect that this update will have a material impact to its consolidated financial condition and results of operations. In March 2017, the FASB issued ASU Number 2017-08, Receivables - Nonrefundable Fees and Other Costs (Subtopic 310-20). This update shortens the amortization period on callable debt securities held at a premium to the earliest call date, which now closely aligns the amortization period of premiums and discounts to expectations incorporated in the market pricing on callable debt securities. This update becomes effective for fiscal years beginning after December 15, 2018 and interim periods within those fiscal years, and early adoption is permitted. The Company does not expect that adoption of this update will have a material impact on its consolidated financial condition and results of operations. In January 2016, the FASB issued ASU Number 2016-01, Financial Instruments - Overall (Subtopic 825-10). This update replaces the guidance to classify equity securities with readily determinable fair values into different categories (trading or available-for-sale) and requires equity securities to be measured at fair value with changes in fair value recognized through net income. Additionally, this update eliminates the disclosure of the method and significant assumptions used to estimate the fair value of financial instruments measured at amortized cost. It requires financial instruments to be measured at fair value using the exit price notion. Furthermore, this update clarifies that an evaluation of deferred tax assets related to available-for-sale securities is needed, in combination with an evaluation of other deferred tax assets, to determine if a valuation allowance is required. This update became effective for fiscal years beginning after December 15, 2017, including interim periods within those fiscal years. The Company has determined this update will result in a reclassification adjustment, net of tax, to retained earnings from accumulated other comprehensive income, which will be determined based on the fair value of securities at the effective date of adoption. In February 2016, the FASB issued ASU Number 2016-02, Leases (Topic 842). This update provides guidance on a new lessee model that includes the recognition of assets and liabilities arising from lease transactions on the balance sheet. Additionally, the update provides clarity on the definition of a lease and the distinction between finance and operating leases. Furthermore, the update requires certain qualitative and quantitative disclosures pertaining to the amounts recorded in the financial statements. This update becomes effective for annual reporting periods, including interim periods within those annual periods, beginning after December 15, 2018 and early adoption is permitted. Currently, the Company is analyzing the impact of the new standard on its current accounting policies, internal controls, and lease contracts. Upon completion of these and other assessments, the Company will evaluate the impact of adopting the new standard on its consolidated financial condition and results of operations. In May 2014, the FASB issued ASU Number 2014-09, Revenue from Contracts with Customers (Topic 606). This update clarifies the principles for recognizing revenue and develops revenue standards to improve revenue recognition guidance. This update requires an entity to recognize revenue as performance obligations are met in order to reflect the transfer of promised goods or services to customers in an amount that reflects the consideration the entity is entitled to receive for those goods or services. In applying this guidance companies are required to: (1) identify the contract(s) with a customer; (2) identify the performance obligations in the contract(s); (3) determine the transaction price; (4) allocate the transaction price to the performance obligations in the contract(s); and (5) recognize revenue when, or as, the entity satisfies a performance obligation. In August 2015, the FASB issued ASU 2015-14, Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date, which deferred the effective date of ASU 2014-09 to annual reporting periods beginning after December 15, 2017, and interim reporting periods within that annual reporting period. Insurance contracts are not within the scope of this updated guidance. The Company has analyzed revenue streams within the current business operation and determined the adoption of this standard will not have an impact on its consolidated financial condition and results of operations.

Fair Value of Financial Instruments

12 Months Ended

Dec. 31, 2017

Fair Value of Financial Instruments [Abstract]

Fair Value of Financial Instruments

The carrying value and the estimated fair value of the Company's financial instruments as of December 31, were as follows:



	2017				2016
	Carrying Value		Estimated Fair Value		Carrying Value		Estimated Fair Value
Financial assets	(in millions)
Investments (Note 6)	$	2,677.7	$	2,677.7	$	2,552.6	$	2,552.6
Cash and cash equivalents	73.3		73.3		67.2		67.2
Restricted cash and cash equivalents	1.0		1.0		3.6		3.6
Financial liabilities
Notes payable (Note 11)	$	20.0	$	23.6	$	32.0	$	33.0

Assets and liabilities recorded at fair value on the Company's Consolidated Balance Sheets are categorized based upon the levels of judgment associated with the inputs used to measure their fair value. Level inputs are defined as follows:


•	Level 1 - Inputs are unadjusted quoted market prices for identical assets or liabilities in active markets at the measurement date.


•	Level 2 - Inputs other than Level 1 prices that are observable for similar assets or liabilities through corroboration with market data at the measurement date.


•	Level 3 - Inputs that are unobservable that reflect management's best estimate of what willing market participants would use in pricing the assets or liabilities at the measurement date.

The Company uses third party pricing services to assist with its investment accounting function. The ultimate pricing source varies depending on the investment security and pricing service used, but investment securities valued on the basis of observable inputs (Levels 1 and 2) are generally assigned values on the basis of actual transactions. Securities valued on the basis of pricing models with significant unobservable inputs or nonbinding broker quotes are classified as Level 3. The Company performs quarterly analyses on the prices it receives from third parties to determine whether the prices are reasonable estimates of fair value, including confirming the fair values of these securities through observable market prices using an alternative pricing source, as it is ultimately management’s responsibility to ensure that the fair values reflected in the Company’s consolidated financial statements are appropriate. If differences are noted in these analyses, the Company may obtain additional information from other pricing services to validate the quoted price.

The Company bases all of its estimates of fair value for assets on the bid price, when available, as it represents what a third-party market participant would be willing to pay in an arm's length transaction.

For securities not actively traded, third party pricing services may use quoted market prices of similar instruments or discounted cash flow analyses, incorporating inputs that are currently observable in the markets for similar securities. Inputs that are often used in the valuation methodologies include, but are not limited to, broker quotes, benchmark yields, credit spreads, default rates, and prepayment speeds. There were no adjustments to prices obtained from third party pricing services as of December 31, 2017 and 2016 that were material to the consolidated financial statements.

These methods of valuation will only produce an estimate of fair value if there is objectively verifiable information to produce a valuation. If objectively verifiable information is not available, the Company would be required to produce an estimate of fair value using some of the same methodologies, making assumptions for market-based inputs that are unavailable.

The Company's estimates of fair value for its financial liabilities are based on a combination of the variable interest rates for notes with similar durations to discount the projection of future payments on notes payable. The fair value measurements for notes payable have been determined to be Level 2 at each of the periods presented.

Each of the Company's insurance operating subsidiaries is a member of the Federal Home Loan Bank of San Francisco (FHLB). Members are required to purchase stock in the FHLB in addition to maintaining collateral deposits that back any funds advanced. Investment in FHLB stock is recorded at cost, as purchases and sales of these securities are at par value with the issuer. FHLB stock is considered a restricted security and is periodically evaluated by the Company for impairment based on the ultimate recovery of par value. Due to the nature of FHLB stock, its carrying value approximates fair value and was determined by the Company to be Level 3 at each of the periods presented.

Certain of the Company's privately placed asset-backed securities (ABS) are designated as level 3 primarily due to restrictions on resale. Third party pricing based on actual transactions are typically not available for these securities due to the limited nature of observable pricing inputs.

The following table presents the items in the Company's Consolidated Balance Sheets that are stated at fair value and the corresponding fair value measurements.



	December 31, 2017						December 31, 2016
	Level 1		Level 2		Level 3		Level 1		Level 2		Level 3
	(in millions)
Fixed maturity securities
U.S. Treasuries	$	—	$	137.0	$	—	$	—	$	127.4	$	—
U.S. Agencies	—		11.8		—		—		12.8		—
States and municipalities	—		642.5		—		—		851.6		—
Corporate securities	—		1,118.0		—		—		956.7		—
Residential mortgage-backed securities	—		389.3		—		—		258.0		—
Commercial mortgage-backed securities	—		106.0		—		—		95.5		—
Asset-backed securities	—		58.8		—		—		35.4		7.0
Total fixed maturity securities	$	—	$	2,463.4	$	—	$	—	$	2,337.4	$	7.0
Equity securities
Industrial and miscellaneous	$	181.7	$	—	$	—	$	167.2	$	—	$	—
Non-redeemable preferred (FHLB stock)	—		—		4.7		—		—		4.9
Other	23.9		—		—		20.1		—		—
Total equity securities	$	205.6	$	—	$	4.7	$	187.3	$	—	$	4.9
Short-term investments	$	—	$	4.0	$	—	$	—	$	16.0	$	—

Certain cash equivalents, principally money market securities, are measured at fair value using the net asset value (NAV) per share. The following table presents cash equivalents at NAV and total cash and cash equivalents carried at fair value on the Company's Consolidated Balance Sheets.



	December 31, 2017		December 31, 2016

Cash and cash equivalents at fair value	$	34.3	$	9.7
Cash equivalents measured at NAV, which approximates fair value	39.0		57.5
Total cash and cash equivalents	$	73.3	$	67.2

The following table provides a reconciliation of the beginning and ending balances that are measured using Level 3 inputs for the year ended December 31, 2017.



	Level 3 Securities
	2017			2016
	(in millions)
Beginning balance, January 1	$	11.9		$	—
Transfers out of Level 3⁽¹⁾	(7.0		)	—
Purchases and sales, net	(0.2		)	11.9
Ending balance, December 31	$	4.7		$	11.9


(1)	Transferred from Level 3 to Level 2 because observable market data became available for the securities.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Investments

12 Months Ended

Dec. 31, 2017

Investments [Abstract]

Investments

The cost or amortized cost, gross unrealized gains, gross unrealized losses, and estimated fair value of the Company’s investments were as follows:



	Cost or Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
At December 31, 2017	(in millions)
Fixed maturity securities
U.S. Treasuries	$	135.8	$	2.0	$	(0.8	)	$	137.0
U.S. Agencies	11.3		0.5		—			11.8
States and municipalities	617.0		25.5		—			642.5
Corporate securities	1,103.4		18.0		(3.4		)	1,118.0
Residential mortgage-backed securities	388.3		3.6		(2.6		)	389.3
Commercial mortgage-backed securities	106.5		0.4		(0.9		)	106.0
Asset-backed securities	58.7		0.3		(0.2		)	58.8
Total fixed maturity securities	2,421.0		50.3		(7.9		)	2,463.4
Equity securities
Industrial and miscellaneous	100.8		81.5		(0.6		)	181.7
Non-redeemable preferred (FHLB stock)	4.7		—		—			4.7
Other	11.2		12.7		—			23.9
Total equity securities	116.7		94.2		(0.6		)	210.3
Short-term investments	4.0		—		—			4.0
Total investments	$	2,541.7	$	144.5	$	(8.5	)	$	2,677.7

At December 31, 2016
Fixed maturity securities
U.S. Treasuries	$	124.1	$	3.5	$	(0.2	)	$	127.4
U.S. Agencies	11.9		0.9		—			12.8
States and municipalities	833.0		24.7		(6.1		)	851.6
Corporate securities	942.3		18.9		(4.5		)	956.7
Residential mortgage-backed securities	255.9		4.7		(2.6		)	258.0
Commercial mortgage-backed securities	96.1		0.4		(1.0		)	95.5
Asset-backed securities	42.6		—		(0.2		)	42.4
Total fixed maturity securities	2,305.9		53.1		(14.6		)	2,344.4
Equity securities
Industrial and miscellaneous	100.5		67.4		(0.7		)	167.2
Non-redeemable preferred (FHLB stock)	4.9		—		—			4.9
Other	10.7		9.4		—			20.1
Total equity securities	116.1		76.8		(0.7		)	192.2
Short-term investments	16.0		—		—			16.0
Total investments	$	2,438.0	$	129.9	$	(15.3	)	$	2,552.6

The amortized cost and estimated fair value of the Company's fixed maturity securities at December 31, 2017, by contractual maturity, are shown below. Expected maturities differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties.



	Amortized Cost		Estimated Fair Value
	(in millions)
Due in one year or less	$	220.5	$	221.3
Due after one year through five years	766.6		782.1
Due after five years through ten years	754.7		772.1
Due after ten years	125.7		133.8
Mortgage and asset-backed securities	553.5		554.1
Total	$	2,421.0	$	2,463.4

The following is a summary of investments that have been in a continuous unrealized loss position for less than 12 months and those that have been in a continuous unrealized loss position for 12 months or greater as of December 31, 2017 and 2016.



	December 31, 2017						December 31, 2016
	Estimated Fair Value		Gross Unrealized Losses			Number of Issues	Estimated Fair Value		Gross Unrealized Losses			Number of Issues
Less than 12 months:	(dollars in millions)
Fixed maturity securities
U.S. Treasuries	$	86.0	$	(0.5	)	28	$	33.3	$	(0.2	)	14
States and municipalities	—		—			—	200.9		(6.1		)	50
Corporate securities	307.6		(2.3		)	113	289.5		(4.1		)	101
Residential mortgage-backed securities	165.0		(0.8		)	45	137.5		(2.6		)	51
Commercial mortgage-backed securities	41.8		(0.2		)	19	48.0		(1.0		)	21
Asset-backed securities	29.3		(0.2		)	25	30.1		(0.2		)	20
Total fixed maturity securities	629.7		(4.0		)	230	739.3		(14.2		)	257
Equity securities	13.9		(0.6		)	24	13.6		(0.6		)	28
Total less than 12 months	$	643.6	$	(4.6	)	254	$	752.9	$	(14.8	)	285

12 months or greater:
Fixed maturity securities
U.S. Treasuries	$	23.4	$	(0.3	)	10	$	—	$	—		—
Corporate securities	53.2		(1.1		)	17	15.2		(0.4		)	5
Residential mortgage-backed securities	77.1		(1.8		)	32	—		—			—
Commercial mortgage-backed securities	25.1		(0.7		)	8	—		—			—
Total fixed maturity securities	178.8		(3.9		)	67	15.2		(0.4		)	5
12 months or greater	$	178.8	$	(3.9	)	67	$	16.9	$	(0.5	)	10

Total available-for-sale:
Fixed maturity securities
U.S. Treasuries	$	109.4	$	(0.8	)	38	$	33.3	$	(0.2	)	14
States and municipalities	—		—			—	200.9		(6.1		)	50
Corporate securities	360.8		(3.4		)	130	304.7		(4.5		)	106
Residential mortgage-backed securities	242.1		(2.6		)	77	137.5		(2.6		)	51
Commercial mortgage-backed securities	66.9		(0.9		)	27	48.0		(1.0		)	21
Asset-backed securities	29.3		(0.2		)	25	30.1		(0.2		)	20
Total fixed maturity securities	808.5		(7.9		)	297	754.5		(14.6		)	262
Equity securities	13.9		(0.6		)	24	15.3		(0.7		)	33
Total available-for-sale	$	822.4	$	(8.5	)	321	$	769.8	$	(15.3	)	295

The Company recognized impairments on fixed maturity securities of $0.5 million (consisting of nine securities) during the year ended December 31, 2017. The other-than-temporary impairments recognized during this year were the result of the Company's intent to sell these securities. There were no other-than-temporary impairments recognized on fixed maturity securities during the years ended December 31, 2016 and 2015. The Company determined that the remaining unrealized losses on fixed maturity securities at December 31, 2017, 2016, and 2015 were primarily the result of changes in prevailing interest rates and not the credit quality of the issuers. The fixed maturity securities whose fair value was less than amortized cost were not determined to be other-than-temporarily impaired given the lack of severity and duration of the impairment, the credit quality of the issuers, the Company’s intent to not sell the securities, and a determination that it is not more likely than not that the Company will be required to sell the securities at an amount less than its amortized cost.

The Company recognized impairments on equity securities of $0.9 million (consisting of seven securities), $5.8 million (consisting of thirty-seven securities) and $17.2 million (consisting of twenty-seven securities) during the years ended December 31, 2017, 2016, and 2015, respectively. The other-than-temporary impairments recognized during these years were the result of the Company's intent to sell the securities and/or the severity and duration of the change in fair values of these securities. The impairments on equity securities in 2016 and 2015 were primarily due to the downturn in the energy sector that occurred during the fourth quarter of 2015 and the first quarter of 2016. Certain unrealized losses on equity securities were not considered to be other-than-temporary due to the financial condition and near-term prospects of the issuers, and the Company's intent to hold the securities until fair value recovers to above cost.

Net realized gains on investments and the change in unrealized gains (losses) on fixed maturity and equity securities are determined on a specific-identification basis and were as follows:



	Years Ended December 31,
	2017			2016			2015
Net realized gains (losses) on investments	(in millions)
Fixed maturity securities
Gross gains	$	4.7		$	1.9		$	0.5
Gross losses	(2.2		)	(0.7		)	(0.4		)
Net realized gains on fixed maturity securities	$	2.5		$	1.2		$	0.1
Equity securities
Gross gains	$	9.3		$	16.6		$	8.1
Gross losses	(4.4		)	(6.6		)	(18.9		)
Net realized gains (losses) on equity securities	$	4.9		$	10.0		$	(10.8	)
Total	$	7.4		$	11.2		$	(10.7	)

Change in unrealized gains (losses)
Fixed maturity securities	$	3.9		$	(28.9	)	$	(22.2	)
Equity securities	17.5			14.9			(13.7		)
Total	$	21.4		$	(14.0	)	$	(35.9	)

Net investment income was as follows:



	Years Ended December 31,
	2017			2016			2015
	(in millions)
Fixed maturity securities	$	70.4		$	68.5		$	68.8
Equity securities	6.9			7.4			5.9
Short-term investments	0.1			—			—
Cash equivalents and restricted cash	0.6			0.4			0.1
Gross investment income	78.0			76.3			74.8
Investment expenses	(3.4		)	(3.1		)	(2.6		)
Net investment income	$	74.6		$	73.2		$	72.2

The Company is required by various state laws and regulations to hold securities or letters of credit in depository accounts with certain states in which it does business. These laws and regulations govern not only the amount but also the types of securities that are eligible for deposit. As of both December 31, 2017 and 2016, securities having a fair value of $1,009.7 million were on deposit.

Certain reinsurance contracts require the Company's funds to be held in trust for the benefit of the ceding reinsurer to secure the outstanding liabilities assumed by the Company. The fair value of fixed maturity securities and restricted cash and cash equivalents held in trust for the benefit of ceding reinsurers at December 31, 2017 and 2016 was $24.5 million and $27.2 million, respectively.

Property and Equipment

12 Months Ended

Dec. 31, 2017

Property and Equipment [Abstract]

Property, Plant and Equipment Disclosure

Property and Equipment

Property and equipment consists of the following:



	As of December 31,
	2017			2016
	(in millions)
Furniture and equipment	$	1.7		$	2.3
Leasehold improvements	2.9			4.3
Computers and software	54.2			59.0
Automobiles	1.1			1.2
Property and equipment, gross	59.9			66.8
Accumulated depreciation	(46.0		)	(44.6		)
Property and equipment, net	$	13.9		$	22.2

Depreciation expenses related to property and equipment for the years ended December 31, 2017, 2016, and 2015 were $7.9 million, $8.2 million, and $7.8 million, respectively. Internally developed software costs of $2.1 million and $1.3 million were capitalized during each of the years ended December 31, 2017 and 2016, respectively.

Income Taxes

12 Months Ended

Dec. 31, 2017

Income Taxes [Abstract]

Income Taxes

The Company files a consolidated federal income tax return. The insurance subsidiaries pay premium taxes on gross premiums written in lieu of some states' income or franchise taxes.

The Tax Cuts and Jobs Act significantly revised U.S. corporate income tax law by, among other things, reducing the corporate statutory income tax rate from 35% to 21%, beginning January 1, 2018. This reduction in the corporate statutory income tax rate required the Company to re-evaluate certain of its deferred tax assets and liabilities, as of the date of Enactment, to reflect the revised income tax rates applicable to future periods.

The Company believes that it has made a reasonable estimate of the income tax effects of the Tax Cuts and Jobs Act as of and for the year ended December 31, 2017. However, the Company was required to base certain of its estimates and assumptions on incomplete information and/or preliminary interpretations of the effects of Enactment. As a result, the Company may need to reflect further adjustments to its deferred tax assets and liabilities recorded as of December 31, 2017 in future periods upon obtaining, preparing, or analyzing additional information about facts and circumstances that existed as of that date that, if known at that time, would have affected the income tax effects initially reported. The Company does not expect the amounts of any future income tax adjustments that may be required to be made to the Company’s deferred tax assets and liabilities as of December 31, 2017 to be material.

The Company's provision for income taxes consisted of the following:



	Years Ended December 31,
	2017		2016		2015
Current tax expense:	(in millions)
Federal	$	17.9	$	20.3	$	9.5
State	0.7		0.3		1.1
Total current tax expense	18.6		20.6		10.6
Deferred federal tax expense (benefit):
Impact of tax Enactment	7.0		—		—
Other	17.2		13.4		(5.6		)
Total deferred federal tax expense (benefit)	24.2		13.4		(5.6		)
Income tax expense	$	42.8	$	34.0	$	5.0

The difference between the statutory federal tax rate of 35% and the Company's effective tax rate on net income before income taxes as reflected in the Consolidated Statements of Comprehensive Income was as follows:



	Years Ended December 31,
	2017			2016			2015
	(in millions)
Expense computed at statutory rate	$	50.4		$	49.3		$	34.8
Tax-advantaged investment income	(7.6		)	(8.5		)	(8.6		)
Pre-Privatization reserve adjustments, excluding LPT	—			—			(15.3		)
LPT deferred gain amortization	(4.0		)	(4.7		)	(4.9		)
LPT Reserve Adjustment	—			(1.1		)	(2.2		)
Stock based compensation	(3.4		)	(1.6		)	—
Impact of tax Enactment	7.0			—			—
Other	0.4			0.6			1.2
Income tax expense	$	42.8		$	34.0		$	5.0

On January 1, 2000, EICN assumed the assets, liabilities, and operations of the Fund pursuant to legislation passed in the 1999 Nevada Legislature (the Privatization). Prior to the Privatization, the Fund was a part of the State of Nevada and therefore was not subject to federal income tax; accordingly, it did not take an income tax deduction with respect to the establishment of its unpaid loss and LAE reserves. Due to favorable loss experience after the Privatization, it was determined that certain of the pre-Privatization unpaid loss and LAE reserves assumed by EICN as part of the Privatization were no longer necessary and the unpaid loss and LAE reserves were reduced accordingly. Such a downward adjustment of pre-Privatization unpaid loss reserves increased GAAP net income by $15.3 million for the year ended December 31, 2015, but did not increase taxable income. There were no downward adjustments of pre-Privatization unpaid loss reserves for the years ended December 31, 2017 and 2016. A downward adjustment of pre-Privatization unpaid loss reserves, excluding the LPT, was $56.3 million for the year ended December 31, 2015.

The LPT Reserve Adjustments for the years ended December 31, 2016 and 2015 increased GAAP net income by $3.1 million and $6.4 million, respectively, but did not increase taxable income. There were no LPT Reserve Adjustments in 2017. The LPT Contingent Commission Adjustments increased net income by $0.3 million, $1.8 million, and $2.6 million during 2017, 2016, and 2015, respectively, but did not increase taxable income.

As of December 31, 2017 and 2016, the Company had no unrecognized tax benefits.

The Company paid $21.3 million, $13.7 million and $12.7 million in income taxes during the years ended December 31, 2017, 2016, and 2015, respectively.

Tax years 2014 through 2017 remained open and are subject to full examination by the federal taxing authority. The significant components of deferred income taxes, net, were as follows as of December 31:



	2017				2016
	Deferred Tax				Deferred Tax
	Assets		Liabilities		Assets		Liabilities
	(in millions)
Unrealized capital gains, net	$	—	$	28.5	$	—	$	40.1
Deferred policy acquisition costs	—		9.7		—		15.7
Intangible assets	—		1.7		—		2.9
Loss reserve discounting for tax reporting	29.0		—		51.7		—
Unearned premiums	12.8		—		20.9		—
Allowance for bad debt	2.1		—		3.4		—
Stock-based compensation	2.5		—		4.4		—
Accrued liabilities	4.2		—		8.1		—
Minimum tax credit	20.0		—		27.8		—
Other	2.8		4.8		9.7		7.9
Total	$	73.4	$	44.7	$	126.0	$	66.6
Deferred income taxes, net	$	28.7			$	59.4

Enactment had no impact on the amount of the Company's minimum tax credit as of December 31, 2017. Despite a repeal of the corporate alternative minimum tax, the Company's minimum tax credit will be recognized (subject to annual limits) over the period from January 1, 2018 through December 31, 2021.

Deferred tax assets are required to be reduced by a valuation allowance if it is more likely than not that all or some portion of the deferred tax asset will not be realized. Realization of the deferred income tax asset is dependent on the Company generating sufficient taxable income in future years as the deferred income tax charges become deductible for tax reporting purposes. Although realization is not assured, management believes that it is more likely than not that the net deferred income tax asset will be realized.

Liability for Unpaid Losses and Loss Adjustment Expenses

12 Months Ended

Dec. 31, 2017

Liability for Unpaid Losses and Loss Adjustment Expenses [Abstract]

Liability for Unpaid Losses and Loss Adjustment Expenses

Accounting for workers' compensation insurance requires the Company to estimate the liability for the expected ultimate cost of unpaid losses and LAE (loss reserves) as of a balance sheet date. Loss reserve estimates are inherently uncertain because the ultimate amount the Company will pay for many of the claims it has incurred as of the balance sheet date will not be known for many years. The estimate of loss reserves is intended to equal the difference between the expected ultimate losses and LAE of all claims that have occurred as of a balance sheet date and amounts already paid. The Company establishes loss reserves based on its own analysis of emerging claims experience and environmental conditions in its markets and review of the results of various actuarial projections. The Company's aggregate carried reserve for unpaid losses and LAE is the sum of its reserves for each accident year and represents its best estimate of outstanding loss reserves.

The amount by which estimated losses in the aggregate differ from those previously estimated for a specific time period is known as reserve “development.” Reserve development is unfavorable when losses ultimately settle for more than the amount reserved or subsequent estimates indicate a basis for reserve increases on open claims, causing the previously estimated loss reserves to be ''deficient.'' Reserve development is favorable when estimates of ultimate losses indicate a decrease in established reserves, causing the previously estimated loss reserves to be ''redundant.'' Development is reflected in the Company's operating results through an adjustment to incurred losses and LAE during the period in which it is recognized.

Although claims for which reserves are established may not be paid for several years or more, the Company does not discount loss reserves in its financial statements for the time value of money, in accordance with GAAP.

The three main components of reserves for unpaid losses and LAE are case reserves, incurred but not reported (IBNR) loss reserves, and LAE reserves.

When claims are reported, the Company establishes individual estimates of the ultimate cost of each claim (case reserves). These case reserves are continually monitored and revised in response to new information and for amounts paid.

IBNR is an actuarial estimate of future payments on claims that have occurred but have not yet been reported. In addition to this provision for late reported claims, the Company also estimates and makes a provision for the extent to which the case reserves on known claims may develop and for additional payments on closed claims, known as “reopening.” IBNR reserves apply to the entire body of claims arising from a specific time period, rather than a specific claim. Most of the Company's IBNR reserves relate to estimated future claim payments on recorded open claims.

LAE reserves are the Company's estimate of the future expenses of investigating, administering, and settling claims that will be paid to manage claims that have occurred, including legal expenses. LAE reserves are established in the aggregate, rather than on a claim-by-claim basis. LAE reserves are categorized between defense and cost containment, and adjusting and other.

A portion of the Company's obligations for losses and LAE are ceded to unaffiliated reinsurers. The amount of reinsurance that will be recoverable on its losses and LAE reserves includes both the reinsurance recoverable from excess of loss reinsurance contracts, as well as reinsurance recoverable under the terms of the LPT Agreement.

The Company uses actuarial methods to analyze and estimate the aggregate amount of unpaid losses and LAE. Management considers the results of various actuarial projection methods and their underlying assumptions, among other factors, in establishing reserves for unpaid losses and LAE.

Judgment is required in the actuarial estimation of loss reserves, including the selection of various actuarial methodologies to project the ultimate cost of claims. Specifically, judgment is required in the following areas: the selection of projection parameters based on historical company data; the use of industry data and other benchmarks; the identification and quantification of potential changes in parameters from historical levels to current and future levels due to changes in future claims development expectations; and the weighting of differing reserve indications resulting from alternative methods and assumptions.

The following table represents a reconciliation of changes in the liability for unpaid losses and LAE.



	Years Ended December 31,
	2017			2016			2015
	(in millions)
Unpaid losses and LAE at beginning of period	$	2,301.0		$	2,347.5		$	2,369.7
Less reinsurance recoverable, excluding bad debt allowance, on unpaid losses and LAE	580.0			628.2			669.5
Net unpaid losses and LAE at beginning of period	1,721.0			1,719.3			1,700.2
Losses and LAE, net of reinsurance, incurred during the period related to:
Current year	447.3			452.9			456.9
Prior years⁽¹⁾	(18.5		)	(18.4		)	(7.2		)
Total net losses and LAE incurred during the period⁽¹⁾	428.8			434.5			449.7
Paid losses and LAE, net of reinsurance, related to:
Current year	76.9			78.7			75.4
Prior years⁽²⁾	343.8			354.1			355.2
Total net paid losses and LAE during the period⁽²⁾	420.7			432.8			430.6
Ending unpaid losses and LAE, net of reinsurance	1,729.1			1,721.0			1,719.3
Reinsurance recoverable, excluding bad debt allowance, on unpaid losses and LAE	537.0			580.0			628.2
Unpaid losses and LAE at end of period	$	2,266.1		$	2,301.0		$	2,347.5

(1)

Losses and LAE, net of reinsurance, incurred during the period related to prior years and Total net losses and LAE incurred during the period included in the above table excludes the impact of the amortization of the Deferred Gain and LPT Reserve Adjustments (Note 10). Including these amounts, Losses and LAE, net of reinsurance, incurred during the period related to prior years was $(30.1) million, $(35.0) million, and $(27.6) million and Total net losses and LAE incurred during the period was $417.2 million, $417.9 million, and $429.4 million for the years ended December 31, 2017, 2016, and 2015, respectively.

(2)

Paid losses and LAE, net of reinsurance, related to prior years and Total net paid losses and LAE during the period included in the above table excludes the impact of the amortization of the Deferred Gain and LPT Reserve Adjustments (Note 10). Including these amounts, Paid losses and LAE, net of reinsurance, related to prior years was $332.2 million, $337.5 million, and $334.8 million and Total net paid losses and LAE during the period was $409.1 million, $416.2 million, and $410.2 million for the years ended December 31, 2017, 2016, and 2015, respectively.

In 2017, the Company had $18.5 million of favorable prior accident year loss development, which included $17.4 million of favorable development on its voluntary risk business and $1.1 million of favorable development related to its assigned risk business. In 2016, the Company had $18.4 million of favorable prior accident year loss development, which included $17.0 million of favorable development on its voluntary risk business and $1.4 million of favorable development related to its assigned risk business. In 2015, the Company had $7.2 million of favorable prior accident year loss development, which included $9.0 million of favorable prior accident year loss development on its voluntary risk business, which was partially offset by $1.8 million of unfavorable loss development related to its assigned risk business. The favorable prior accident year loss development on voluntary business in 2017 and 2016 was the result of the Company's determination that adjustments were necessary to reflect observed favorable paid loss trends. Paid loss trends have been impacted by cost savings associated with accelerated claims settlement activity that began in 2014 and continued through 2017.

In California, where the Company's operations began in 2002, the actuaries' and management's initial expectations of ultimate losses and patterns of loss emergence and payment were based on benchmarks derived from analyses of historical insurance industry data in California. No historical data from the Company's California insurance subsidiary existed prior to July 1, 2002; however, some historical data was available for the prior years for some of the market segments the Company entered in California, but was limited as to the number of loss reserve evaluation points available. The industry-based benchmarks were judgmentally adjusted for the anticipated impact of significant environmental changes, specifically the enactment of major changes to the statutory workers' compensation benefit structure and the manner in which claims are administered and adjudicated in California. The actual emergence and payment of claims by the Company's California insurance subsidiary have been more favorable than those initial expectations through 2008, due in part to the enactment of the major changes in the California workers' compensation environment. The Company's recent loss experience, from 2010 through 2016, indicates an upward trend in medical and indemnity costs that are reflected in its loss reserves. Loss experience in 2017 indicated a slight downward movement in medical and indemnity costs per claim. The Company's indemnity claims frequency (the number of claims expressed as a percentage of payroll) decreased year-over-year for the past three years. The Company's reserve estimates assume that increasing medical cost trends will continue and will impact the Company's long-term claims costs and loss reserves.

The Company continues to develop its own loss experience in California and will rely more on its experience and less on historical industry data in projecting its reserve requirements as such data becomes available. As the actual experience of the Company emerges, it will continue to evaluate prior estimates, which may result in additional adjustments in reserves.

In Nevada, the Company has compiled a lengthy history of workers' compensation claims payment patterns based on the business of the Fund and EICN, but the emergence and payment of claims in recent years has been more favorable than in the long-term history in Nevada with the Fund. The expected patterns of claim payments and emergence used in the projection of the Company's ultimate claim payments are based on both the long and short-term historical paid data. In recent evaluations, claim patterns have continued to emerge in a manner consistent with short-term historical data. Consequently, the Company has relied more heavily on claim projection patterns observed in recent years in Nevada.

Loss reserves shown in the Company's Consolidated Balance Sheets are net of $35.0 million and $28.1 million for anticipated subrogation recoveries as of December 31, 2017 and 2016, respectively.

The Company compiles and aggregates its claims data by grouping the claims according to the year in which the claim occurred (“accident year”) when analyzing claim payment and emergence patterns and trends over time. For the purposes of defining claims frequency, the number of reported claims includes any claim that has case reserves and/or loss and LAE payments associated with them.

The Company analyzed the usefulness of disaggregation of its results and determined the characteristics associated with the policies and the related unpaid loss reserves, incurred losses, and payment patterns are similar in nature. As such, the following tables show the Company's historical incurred and cumulative paid losses and LAE development, net of reinsurance, as well as IBNR loss reserves and the number of reported claims on an aggregated basis as of December 31, 2017 for each of the previous 10 accident years.



	Incurred Losses and LAE, Net of Reinsurance
	Years Ended December 31,																				As of December 31, 2017
Accident Year	2008⁽¹⁾		2009⁽¹⁾		2010⁽¹⁾		2011⁽¹⁾		2012⁽¹⁾		2013⁽¹⁾		2014⁽¹⁾		2015⁽¹⁾		2016⁽¹⁾		2017		IBNR		Cumulative number of reported claims
	(in millions, except claims counts)
2008	$	315.9	$	315.3	$	317.8	$	329.2	$	329.5	$	335.1	$	336.9	$	343.8	$	341.4	$	342.1	$	15.4	28,088
2009			255.4		266.9		279.0		280.1		283.6		283.7		291.2		290.5		290.5		13.5		22,673
2010					204.9		224.4		228.1		246.1		250.2		262.0		259.9		258.8		19.8		18,543
2011							253.7		267.3		272.0		277.4		296.3		292.6		288.8		27.5		19,571
2012									348.8		359.9		360.9		386.4		388.2		382.8		50.7		25,972
2013											452.6		460.6		478.6		472.6		468.9		73.6		28,816
2014													463.4		445.8		432.9		434.6		86.1		28,449
2015															422.2		425.8		423.9		98.7		26,993
2016																	419.0		414.6		140.8		25,305
2017																			412.4		244.6		21,214
Total																			$	3,717.4



	Cumulative Paid Losses and LAE, Net of Reinsurance
	Years Ended December 31,
Accident Year	2008⁽¹⁾		2009⁽¹⁾		2010⁽¹⁾		2011⁽¹⁾		2012⁽¹⁾		2013⁽¹⁾		2014⁽¹⁾		2015⁽¹⁾		2016⁽¹⁾		2017
	(in millions)
2008	$	71.1	$	155.4	$	201.8	$	234.7	$	255.3	$	271.1	$	284.2	$	293.6	$	300.7	$	307.1
2009			59.0		130.6		174.1		202.0		219.3		232.1		242.3		249.5		255.1
2010					47.1		105.6		143.8		171.7		190.7		206.2		215.4		221.3
2011							47.4		115.1		162.6		193.8		217.5		230.1		238.2
2012									58.6		148.3		214.2		261.4		289.9		305.0
2013											68.5		184.4		263.8		317.4		346.1
2014													65.3		172.7		248.9		297.2
2015															65.5		174.5		246.9
2016																	65.6		166.8
2017																			63.5
Total																			$	2,447.3
All outstanding liabilities for unpaid losses and LAE prior to 2007, net of reinsurance																			364.2
Total outstanding liabilities for unpaid losses and LAE, net of reinsurance																			$	1,634.3


(1)	Data presented for these calendar years is required supplementary information, which is unaudited.

The following table represents a reconciliation of claims development to the aggregate carrying amount of the liability for unpaid losses and LAE:



	December 31, 2017
	(in millions)
Liabilities for unpaid losses and LAE, net of reinsurance	$	1,634.3
Reinsurance recoverable on unpaid losses	537.0
Unallocated LAE (adjusting and other)	94.8
Total liability for unpaid losses and LAE	$	2,266.1

The following table presents the average annual percentage payout of incurred claims by age, net of reinsurance, as of December 31, 2017 and is presented as required supplementary information, which is unaudited:



Average Annual Percentage Payout of Claims by Age, Net of Reinsurance
Year 1		Year 2		Year 3		Year 4		Year 5		Year 6		Year 7		Year 8		Year 9		Year 10
16.7	%	24.3	%	16.1	%	10.8	%	6.9	%	4.7	%	3.4	%	2.5	%	2.0	%	1.9	%

Reinsurance

12 Months Ended

Dec. 31, 2017

Reinsurance [Abstract]

Reinsurance

The Company purchases reinsurance from third parties in the normal course of its business in order to manage its exposures. The Company's reinsurance coverage is provided on both a quota share and excess of loss basis.

The effects of reinsurance on the Company's written and earned premiums and on its losses and LAE incurred were as follows:



	Years Ended December 31,
	2017						2016						2015
	Written			Earned			Written			Earned			Written			Earned
	(in millions)
Direct premiums	$	719.5		$	712.5		$	691.0		$	691.0		$	684.9		$	686.0
Assumed premiums	10.2			10.0			10.4			10.6			12.8			12.8
Gross premiums	729.7			722.5			701.4			701.6			697.7			698.8
Ceded premiums	(6.0		)	(6.0		)	(6.8		)	(6.8		)	(8.4		)	(8.4		)
Net premiums	$	723.7		$	716.5		$	694.6		$	694.8		$	689.3		$	690.4
Ceded losses and LAE incurred	$	(0.5	)				$	0.1					$	10.1

Ceded losses and LAE incurred includes the amortization of the Deferred Gain, LPT Reserve Adjustments, and LPT Contingent Commission Adjustments.

Excess of Loss Reinsurance

The Company has consistently maintained excess of loss reinsurance coverage to protect it against the impact of large and/or catastrophic losses in its workers' compensation business. The Company currently maintains reinsurance for losses from a single occurrence or catastrophic event in excess of $10.0 million and up to $200.0 million, subject to certain exclusions. This current reinsurance program is effective July 1, 2017 through June 30, 2018. The coverage under the Company's annual reinsurance programs that ended July 1, 2017 and 2016 was $190.0 million and $193.0 million, in excess of its $10.0 million and $7.0 million retention on a per occurrence basis, respectively. The reinsurance coverage includes coverage for acts of terrorism, excluding nuclear, biological, chemical, and radiological events. Any liability outside the coverage limits of the reinsurance program is retained by the Company.

LPT Agreement

Recoverables from reinsurers on unpaid losses and LAE amounted to $537.0 million and $580.0 million at December 31, 2017 and 2016, respectively. At each of December 31, 2017 and 2016, $438.9 million and $465.5 million, respectively, of those recoverables was related to the LPT Agreement that was entered into in 1999 by the Fund and assumed by EICN. Under the LPT Agreement, substantially all of the Fund's losses and LAE on claims incurred prior to July 1, 1995, have been ceded to three unaffiliated reinsurers on a 100% quota share basis. Investments totaling $380.8 million and $355.7 million at December 31, 2017 and 2016, respectively, have been placed in trust by the three reinsurers as security for payment of the reinsured claims. Under the LPT Agreement, initially $1.5 billion in liabilities for the incurred but unpaid losses and LAE related to claims incurred prior to July 1, 1995, were reinsured for consideration of $775.0 million. The LPT Agreement provides coverage up to $2.0 billion. Through December 31, 2017, the Company has paid losses and LAE claims totaling $749.3 million related to the LPT Agreement.

The Company amortized $11.3 million, $11.7 million, and $11.4 million of the Deferred Gain for the years ended December 31, 2017, 2016, and 2015, respectively. Additionally, the Deferred Gain was reduced by $3.1 million and $6.4 million for the years ended December 31, 2016 and 2015, respectively, due to favorable LPT Reserve Adjustments and by $0.3 million, $1.8 million, and $2.6 million for the years ended December 31, 2017, 2016, and 2015, respectively, due to favorable LPT Contingent Commission Adjustments (Note 2).

Notes Payable

12 Months Ended

Dec. 31, 2017

Notes Payable [Abstract]

Notes Payable

Notes payable is comprised of the following:



	December 31,
	2017		2016
	(in millions)
Dekania Surplus Note, due April 29, 2034	$	10.0	$	10.0
Alesco Surplus Note, due December 15, 2034	10.0		10.0
ICONS Surplus Note, due May 24, 2034	—		12.0
Total	$	20.0	$	32.0

EPIC has a $10.0 million surplus note to Dekania CDO II, Ltd. issued as part of a pooled transaction. The note matures in 2034 and became callable by the Company in 2009. The terms of the note provide for quarterly interest payments at a rate 425 basis points in excess of the 90-day LIBOR. Both the payment of interest and repayment of the principal under this note and the surplus notes described in the succeeding two paragraphs are subject to the prior approval of the Florida Department of Financial Services. Interest paid during each of the years ended December 31, 2017, 2016, and 2015 was $0.6 million, $0.5 million, and $0.5 million. Interest accrued as of December 31, 2017 and 2016 was $0.1 million.

EPIC has a $10.0 million surplus note to Alesco Preferred Funding V, LTD issued as part of a pooled transaction. The note matures in 2034 and became callable by the Company in 2009. The terms of the note provide for quarterly interest payments at a rate 405 basis points in excess of the 90-day LIBOR. Interest paid during each of the years ended December 31, 2017, 2016, and 2015 was $0.5 million, $0.5 million, and $0.4 million, respectively. Interest accrued as of December 31, 2017 and 2016 was less than $0.1 million.

EPIC had a $12.0 million surplus note to ICONS, Inc. issued as part of a pooled transaction. This note was purchased by EHI in May 2017 for $9.9 million, resulting in a $2.1 million gain, and is no longer deemed to be outstanding on a consolidated basis. Interest paid to third parties during each of the years ended December 31, 2017, 2016, and 2015 was $0.3 million, $0.6 million and $0.6 million, respectively. Interest accrued as of December 31, 2016 was $0.1 million.

In 2010, the Company entered into a credit facility, under which the Company was provided with: (a) $100.0 million line of credit through December 31, 2011; (b) $90.0 million line of credit from January 1, 2012 through December 31, 2012; (c) $80.0 million line of credit from January 1, 2013 through December 31, 2013; (d) $70.0 million line of credit from January 1, 2014 through December 31, 2014; and (e) $60.0 million line of credit from January 1, 2015 through December 31, 2015. Amounts outstanding bore interest at a rate equal to, at our option: (a) a fluctuating rate of 1.75% above prime rate or (b) a fixed rate that is 1.75% above the LIBOR rate then in effect. Interest paid during the year ended December 31, 2015 totaled $1.3 million. In accordance with the terms of the contract, the remaining principal balance of $60.0 million was repaid on the credit facility in 2015.

Principal payment obligations on notes payable outstanding at December 31, 2017, were as follows:



Year	Principal Due
	(in millions)
2018 - 2022	$	—
Thereafter	20.0
Total	$	20.0

Commitments and Contingencies

12 Months Ended

Dec. 31, 2017

Commitments and Contingencies [Abstract]

Commitments and Contingencies Disclosure

Commitments and Contingencies

Leases

The Company leases office facilities and certain equipment under operating and capital leases. Most leases have renewal options, typically with increased rental rates during the option period. Certain of these leases contain options to purchase the property at amounts that approximate fair market value; other leases contain options to purchase at a bargain purchase price. At December 31, 2017, the remaining lease terms expire over the next ten years.

The future lease payments for the next five years on these non-cancelable operating and capital leases at December 31, 2017, were as follows:



Year	Operating Leases		Capital Leases
	(in millions)
2018	$	4.8	$	0.3
2019	4.8		0.3
2020	4.2		0.2
2021	2.8		0.2
2022	1.8		0.1
Thereafter	7.9		—
Total	$	26.3	$	1.1

Included in the future minimum capital lease payments are future interest charges of $0.1 million. Facilities rent expense was $4.8 million, $4.9 million, and $4.9 million for the years ended December 31, 2017, 2016, and 2015, respectively.

Property held under capital leases is included in property and equipment as follows:



Asset Class	2017			2016
	(in millions)
Automobiles	1.1			1.2
	1.1			1.2
Accumulated amortization	(0.3		)	(0.6		)
Total	$	0.8		$	0.6

Contingencies Surrounding Insurance Assessments

All of the states where the Company's insurance subsidiaries are licensed to transact business require property and casualty insurers doing business within the respective state to pay various insurance assessments. The Company accrues a liability for estimated insurance assessments as direct premiums are written, losses are recorded, or as other events occur in accordance with various states' laws and regulations, and defers these costs and recognizes them as an expense as the related premiums are earned. The Company had an accrued liability for guaranty fund assessments, second injury funds assessments, and other insurance assessments totaling $12.4 million and $18.6 million as of December 31, 2017 and 2016, respectively. These liabilities are generally expected to be paid over one to eighty year periods based on individual state's regulations. The Company also recorded an asset of $14.1 million and $21.6 million, as of December 31, 2017 and 2016, respectively, for prepaid policy charges still to be collected in the future from policyholders, or assessments that may be recovered through a reduction in future premium taxes in certain states. These assets are expected to be realized over one to ten year periods in accordance with their type and each individual state's regulations.

Stockholders' Equity	12 Months Ended
Stockholders' Equity	Dec. 31, 2017
Stockholders' Equity Attributable to Parent [Abstract]
Treasury Stock	Stockholders' Equity Stock Repurchase Programs On February 16, 2016, the Board of Directors authorized a share repurchase program for up to $50.0 million of the Company's common stock from February 22, 2016 through February 22, 2018 (the 2016 Program). The Company expects that its common stock may be purchased at prevailing market prices through a variety of methods, including open market or private transactions, in accordance with applicable laws and regulations and as determined by management. The timing and actual number of shares repurchased will depend on a variety of factors, including the share price, corporate and regulatory requirements, and other market and economic conditions. Repurchases under the 2016 Program may be commenced, modified, or suspended from time-to-time without prior notice, and the 2016 Program may be suspended or discontinued at any time. Through December 31, 2017, the Company has repurchased a total of 724,381 shares of common stock at an average price of $29.08 per share, including commissions, for a total of $21.1 million under the 2016 Program. The Company made no repurchases of common stock during the year ended December 31, 2017. Since the Company's initial public offering in January 2007 through December 31, 2017, the Company has repurchased a total of 24,097,355 shares of common stock at an average cost per share of $15.92, which is reported as treasury stock, at cost, on its Consolidated Balance Sheets.

Stock-Based Compensation

12 Months Ended

Dec. 31, 2017

Stock-Based Compensation [Abstract]

Stock-Based Compensation

The Employers Holdings, Inc. Amended and Restated Equity and Incentive Plan (the Plan) is administered by the Compensation Committee of the Board of Directors, which is authorized to grant, at its discretion, awards to officers, employees, non-employee directors, consultants, and independent contractors. The maximum number of common shares reserved for grants of awards under the Plan was 5,500,000 shares, prior to reductions for grants made. The Plan provides for the grant of stock options (both incentive stock options and nonqualified stock options), stock appreciation rights, shares of restricted stock, restricted stock units (RSUs), performance stock units (PSUs), and other stock-based awards.

Commencing in 2017, employees who were awarded RSUs and PSUs are entitled to receive dividend equivalents for eligible awards, payable in cash, when the underlying award vests and becomes payable. If the underlying award does not vest or is forfeited, dividend equivalents with respect to the underlying award will also fail to become payable and will be forfeited. These awards are not considered participating securities for the purposes of determining earnings per share.

As of December 31, 2017, the only incentive awards outstanding under the Plan were nonqualified stock options, RSUs, and PSUs.

Compensation costs are recognized based on expected performance, if applicable, net of any estimated forfeitures on a straight-line basis over the requisite employee service periods. Forfeiture rates are based on historical experience and are adjusted in subsequent periods for differences in actual forfeitures from those estimated. Net stock-based compensation expense recognized in the Company's Consolidated Statements of Comprehensive Income was as follows:



	Years Ended December 31,
	2017		2016		2015
Stock-based compensation expense related to:	(in millions)
Stock options	$	0.5	$	0.7	$	1.0
RSUs	2.0		1.9		2.0
PSUs	4.3		3.2		1.6
Total	6.8		5.8		4.6
Less: related tax benefit	2.4		2.0		1.6
Net stock-based compensation expense	$	4.4	$	3.8	$	3.0

Stock Options

The fair value of the stock options granted is estimated using a Black-Scholes option pricing model that uses the assumptions noted in the following table. During the years ended December 31, 2016 and 2015, the expected stock price volatility used to value the stock options granted in 2016 and 2015 was based on the volatility of the Company's historical stock price since February 2007. No stock options were granted in 2017. The expected term of the stock options granted in 2016 and 2015 was calculated using the 'plain-vanilla' calculation provided in the guidance of the SEC's SAB No. 107. The dividend yield was calculated using amounts authorized by the Board of Directors. The risk-free interest rate is the yield on the grant date of the stock options of U.S. Treasury zero coupon securities with a maturity comparable to the expected term of the stock options.

The Company anticipates issuing new shares of common stock upon the exercise of its outstanding stock options.

The fair value of the stock options granted during the years ended December 31, 2016 and 2015 was calculated using the following weighted average assumptions:



	2016		2015
Expected volatility	38.0	%	38.0	%
Expected life (in years)	4.8		4.8
Dividend yield	1.3	%	1.0	%
Risk-free interest rate	1.4	%	1.6	%
Weighted average grant date fair values of stock options granted	$8.46		$7.63

Changes in outstanding stock options for the year ended December 31, 2017 were as follows:



	Number of Stock Options		Weighted-Average Price		Weighted Average Remaining Contractual Life
Stock options outstanding at December 31, 2014	1,521,290		$	17.45	2.9 years
Granted	80,800		24.20		6.2 years
Exercised	(463,466	)	16.43
Forfeited	(17,079	)	20.21
Stock options outstanding at December 31, 2015	1,121,545		18.31		2.8 years
Granted	67,431		27.72		6.2 years
Exercised	(586,132	)	16.39
Expired	(6,075	)	22.48
Forfeited	(32,673	)	24.35
Stock options outstanding at December 31, 2016	564,096		21.04		3.3 years
Exercised	(307,076	)	19.44
Forfeited	(9,673	)	24.45
Stock options outstanding at December 31, 2017	247,347		22.90		3.4 years
Exercisable at December 31, 2017	156,517		21.71		2.8 years

At December 31, 2017, the Company had yet to recognize $0.5 million of unamortized expense related to stock option grants and expects to recognize these costs on a straight-line basis over the next 27 months. The fair value of stock options vested and the intrinsic value of outstanding and exercisable stock options as of December 31, were as follows:



	2017		2016		2015
	(in millions)
Fair value of stock options vested	$	0.6	$	0.8	$	1.3
Intrinsic value of outstanding stock options	5.3		10.6		10.1
Intrinsic value of exercisable stock options	3.6		7.6		8.5

The intrinsic value of stock options exercised was $7.6 million, $7.6 million, and $4.0 million for the years ended December 31, 2017, 2016, and 2015.

RSUs

The Company has awarded RSUs to non-employee members of the Board of Directors and certain employees of the Company. The RSUs awarded to non-employee members of the Board of Directors generally vest on the first anniversary of the award date. RSU grants allow each non-employee Director to decide whether to defer settlement of the RSUs until six months after termination of Board service or settle the RSUs at vesting. Dividend equivalents are granted to Directors who elected to defer settlement of the RSUs after the grants vested. RSUs awarded to employees of the Company have a service vesting period of approximately four years from the date awarded and vest 25% on or after each of the subsequent four anniversaries of such date. These RSUs are subject to accelerated vesting in certain limited circumstances, such as: retirement, death or disability of the holder, or in connection with a change of control of the Company.

Changes in outstanding RSUs for the year ended December 31, 2017 were as follows:



	Number of RSUs		Weighted Average Grant Date Fair Value
RSUs outstanding at December 31, 2014	306,867		$	19.15
Granted	112,048		24.19
Forfeited	(7,749	)	20.99
Vested	(92,133	)	19.74
RSUs outstanding at December 31, 2015	319,033		20.71
Granted	100,218		28.20
Forfeited	(21,872	)	24.87
Vested	(72,995	)	21.56
RSUs outstanding at December 31, 2016	324,384		22.55
Granted	87,276		37.94
Forfeited	(13,711	)	29.28
Vested	(70,877	)	24.97
RSUs outstanding at December 31, 2017	327,072		25.85
Vested but unsettled RSUs at December 31, 2017	152,644		19.54

At December 31, 2017, the Company had yet to recognize $4.2 million of unamortized expense related to outstanding RSUs and expects to recognize these costs on a straight-line basis over the next 39 months. The grant date fair value of RSUs vested and the intrinsic value of vested RSUs for the years ended December 31, were as follows:



	2017		2016		2015
	(in millions)
Grant date fair value of RSUs vested	$	1.8	$	1.6	$	1.7
Intrinsic value of RSUs vested	2.8		2.1		2.2

The intrinsic value of outstanding RSUs was $14.5 million, $12.8 million, and $8.7 million at December 31, 2017, 2016, and 2015.

PSUs

The Company has awarded PSUs to certain employees of the Company as follows:



Date of Grant	Target Number Awarded	Fair Value on Date of Grant		Aggregate Fair Value on Date of Grant
				(in millions)
March 2015⁽¹⁾	110,000	$	24.20	$	2.7
March 2016⁽¹⁾	97,236	27.72		2.7
March 2017⁽¹⁾	97,440	37.60		3.7

(1)

The PSUs awarded in March 2015, 2016 and 2017 were awarded to certain employees of the Company and have a performance period of two years followed by an additional one year vesting period. The PSU awards are subject to certain performance goals with payouts that range from 0% to 200% of the target awards. The values shown in the table represent the aggregate number of PSUs awarded at the target level.

At December 31, 2017, the Company had yet to recognize $4.7 million of unamortized expense related to PSU grants and expects to recognize these costs on a straight-line basis over the next 24 months. This is based on the expectation of the Company achieving a 200% of target rate for the 2015 PSUs, a 200% of target rate for the 2016 PSUs, and a 127% of target rate for the 2017 PSUs.

Statutory Matters

12 Months Ended

Dec. 31, 2017

Stautory Matters [Abstract]

Statutory Financial Data Disclosure

Statutory Matters

Statutory Financial Data

The combined capital stock, surplus, and net income of the Company's insurance subsidiaries (EICN, ECIC, EPIC, and EAC), prepared in accordance with the statutory accounting practices (SAP) of the National Association of Insurance Commissioners (NAIC) as well as SAP permitted by the states of California, Florida, and Nevada, were as follows:



	December 31,
	2017		2016
	(in millions)
Capital stock and unassigned surplus	$	510.6	$	447.1
Paid in capital	349.8		349.8
Surplus notes	32.0		32.0
Total statutory surplus	$	892.4	$	828.9

Net income for the Company's insurance subsidiaries prepared in accordance with SAP for the years ended December 31, 2017, 2016 and 2015 was $116.8 million, $101.4 million, and $87.8 million, respectively.

Treatment of the LPT Agreement, deferred policy acquisition costs, fair value of financial instruments, and the surplus notes (see Notes 5, 10, and 11) are the primary differences in the SAP-basis capital stock and total surplus of the insurance subsidiaries of $892.4 million and $828.9 million, and the GAAP-basis equity of the Company of $947.7 million and $840.6 million as of December 31, 2017 and 2016, respectively. Under SAP accounting, the retroactive reinsurance gain resulting from the LPT Agreement is recorded as a special component of surplus (special surplus funds) in the initial year of the contract, and not reported as unassigned surplus until the Company has recovered amounts in excess of the original consideration paid. The special surplus funds are also reduced by the amount of extraordinary dividends as approved by the Nevada Division of Insurance. Under SAP, the surplus notes are recorded as a separate component of surplus. Under SAP, changes to the estimated contingent profit commission under the LPT Agreement are reflected in commission expense in the period that the estimate is revised.

Insurance Company Dividends and Regulatory Requirements and Restrictions

The ability of EHI to pay dividends on the Company's common stock and to pay other expenses will be dependent to a significant extent upon the ability of the Nevada domiciled insurance company, EICN, the California domiciled insurance company, ECIC, and the Florida domiciled insurance companies, EPIC and EAC, to pay dividends to their immediate holding company, Employers Group, Inc. (EGI) and, in turn, the ability of EGI to pay dividends to EHI. The amount of dividends each of the Company's subsidiaries may pay to their immediate parent is limited by the laws of its respective state of domicile.

On December 31, 2016, the legal structure of the Company's insurance subsidiaries changed such that all four of its insurance subsidiaries are now wholly owned by EGI (ECIC is no longer a wholly owned subsidiary of EICN and EAC is no longer a wholly owned subsidiary of EPIC). This change in legal structure allows each of the Company's insurance subsidiaries to pay dividends directly to EGI.

Nevada law limits the payment of cash dividends by EICN to its parent by providing that payments cannot be made except from available and accumulated surplus, otherwise unrestricted (unassigned), and derived from realized net operating profits and realized and unrealized capital gains. A stock dividend may be paid out of any available surplus. A cash or stock dividend prohibited by these restrictions may only be declared and distributed as an extraordinary dividend upon the prior approval of the Nevada Commissioner of Insurance (Nevada Commissioner). EICN may not pay such an extraordinary dividend or make an extraordinary distribution until the Nevada Commissioner either approves or does not disapprove the payment within 30 days after receiving notice of its declaration. An extraordinary dividend or distribution is defined by statute to include any dividend or distribution of cash or property whose fair market value, together with that of other dividends or distributions made within the preceding 12 months, exceeds the lesser of: (a) 10% of EICN's statutory surplus as regards to policyholders at the next preceding December 31; or (b) EICN's statutory net income, not including realized capital gains, for the 12-month period ending at the next preceding December 31. As of December 31, 2017, EICN had positive unassigned surplus of $196.7 million. During 2017, EICN did not pay any dividends. The maximum dividends that may be paid in 2018 by EICN without prior regulatory approval from the Nevada Department of Insurance is $19.9 million.

Under Florida law, without regulatory approval, EPIC and EAC may pay dividends if they do not exceed the greater of: the lesser of 10% of surplus or net income, not including realized capital gains, plus a 2-year carry forward; 10% of surplus, with dividends payable limited to unassigned funds minus 25% of unrealized capital gains; or, the lesser of 10% of surplus or net investment income plus a 3-year carry forward with dividends payable limited to unassigned funds minus 25% of unrealized capital gains. During 2017, EPIC and EAC did not pay any dividends. The maximum dividends that may be paid in 2018 by EPIC and EAC without prior regulatory approval from the Florida Office of Insurance Regulation (FOIR) is $15.9 million and $19.0 million, respectively.

ECIC is subject to regulation by the California Department of Insurance (California DOI). The ability of ECIC to pay dividends was further limited by restrictions imposed by the California DOI in its approval of the Company's October 1, 2008 reinsurance pooling agreement. Under that approval: (a) ECIC must initiate discussions of its business plan with the California DOI if its net written premium to policyholder surplus ratio exceeds 1.5 to 1; (b) ECIC will not exceed a ratio of net written premium to policyholder surplus of 2 to 1 without approval of the California DOI; (c) if at any time ECIC's policyholder surplus decreases to 80% or less than the September 30, 2008 balance, ECIC shall cease issuing new policies in California, but may continue to renew existing policies until it has (i) received a capital infusion to bring its surplus position to the same level as that as of September 30, 2008 and (ii) submitted a new business plan to the California DOI; (d) ECIC will maintain a risk based capital (RBC) level of at least 350% of the authorized control level; (e) should ECIC fail to comply with any commitments listed herein, ECIC will consent to any request by the California DOI to cease issuing new policies in California, but may continue to renew existing policies until such time that as ECIC is able to achieve full compliance with each commitment; and (f) the obligations listed shall only terminate with the written consent of the California DOI. During the years ended December 31, 2017, 2016, and 2015, ECIC was in compliance with these requirements.

Additionally, the California Insurance Holding Company System Regulatory Act limits the ability of ECIC to pay dividends to its parent. California law provides that, absent prior approval of the California Insurance Commissioner, dividends may only be declared from earned surplus. For purpose of this statute, earned surplus excludes amounts (1) derived from net appreciation in the value of assets not yet realized, or (2) derived from an exchange of assets, unless the assets received are currently realizable in cash. In addition, California law provides that the appropriate insurance regulatory authorities in the state of California must approve (or, within a 30 day notice period, not disapprove) any dividend that, together with all other such dividends paid during the preceding 12 months, exceeds the greater of: (a) 10% of the paying company's statutory surplus as regards to policyholders at the preceding December 31; or (b) 100% of net income for the preceding year. During 2017, ECIC paid an ordinary dividend in the amount of $38.0 million to its parent company, EGI. ECIC can pay $10.4 million of dividends through August 8, 2018 and $48.4 million thereafter without prior regulatory approval, provided that no dividends are paid prior to August 8, 2018.

EPIC and EAC are subject to regulation by the Florida Department of Financial Services (FDFS). Florida statute Section 624.408 requires EPIC and EAC to maintain minimum capital and surplus of the greater of $4.0 million or 10% of total liabilities. Florida statute Section 624.4095 requires EPIC and EAC to maintain a ratio of written premiums, defined as 1.25 times written premiums, to surplus of no greater than 10-to-1 for gross written premiums and 4-to-1 for net written premiums. During the years ended December 31, 2017, 2016, and 2015, EPIC and EAC were in compliance with these statutes.

Additionally, EICN, ECIC, EPIC, and EAC are required to comply with RBC requirements. RBC is a method of measuring the amount of capital appropriate for an insurance company to support its overall business operations in light of its size and risk profile. NAIC RBC standards are used by regulators to determine appropriate regulatory actions relating to insurers that show signs of weak or deteriorating conditions. As of December 31, 2017, 2016, and 2015, EICN, ECIC, EPIC, and EAC each had total adjusted capital above all regulatory action levels.

Accumulated Other Comprehensive Income, Net

12 Months Ended

Dec. 31, 2017

Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]

Accumulated Other Comprehensive Income, Net

Accumulated Other Comprehensive Income

Accumulated other comprehensive income is comprised of unrealized gains on investments classified as available-for-sale, net of deferred tax expense. The following table summarizes the components of accumulated other comprehensive income:



	Years Ended December 31,
	2017			2016
	(in millions)
Net unrealized gain on investments, before taxes	$	136.0		$	114.6
Deferred tax expense on net unrealized gains	(28.6		)	(40.1		)
Total accumulated other comprehensive income	$	107.4		$	74.5

Employee Benefit and Retirement Plans	12 Months Ended
Employee Benefit and Retirement Plans	Dec. 31, 2017
Employee Benefit and Retirement Plans [Abstract]
Compensation and Employee Benefit Plans	Employee Benefit and Retirement Plans The Company maintains a 401(k) defined contribution plan covering all eligible Company employees (the Employers 401(k) Plan). Under the Employers 401(k) Plan, the Company's safe harbor matching consists of 100% matching contribution on salary deferrals up to 3% of compensation and then 50% matching contribution on salary deferrals from 3% to 5% of compensation. The Company's matching contribution to the Employers 401(k) Plan was $1.9 million, $1.9 million, and $1.8 million for the years ended December 31, 2017, 2016, and 2015, respectively.

Earnings Per Share

12 Months Ended

Dec. 31, 2017

Earnings Per Share [Abstract]

Earnings Per Share

Earnings Per Common Share

Basic earnings per share, which includes no dilution from outstanding stock-based awards, is computed by dividing net income by the weighted average number of common shares outstanding for the period. Diluted earnings per share reflect the potential dilutive impact of all outstanding stock-based awards on earnings per share. Diluted earnings per share includes common shares assumed issued under the “treasury stock method,” which reflects the potential dilution that would occur if outstanding RSUs and PSUs vested, and stock options were to be exercised.

Commencing in 2017, certain stock-based compensation awards are eligible to receive dividend equivalents on awards that fully vest or become payable. These awards are not considered participating securities for the purposes of determining earnings per share.

The following table presents the net income and the weighted average shares outstanding used in the earnings per share common share calculations.



	Years Ended December 31,
	2017		2016		2015
	(in millions, except share data)
Net income	$	101.2	$	106.7	$	94.4
Weighted average number of shares outstanding–basic	32,501,576		32,434,580		32,070,911
Effect of dilutive securities:
Stock options	208,602		246,562		286,764
PSUs	271,738		222,594		155,768
RSUs	78,844		73,099		48,010
Dilutive potential shares	559,184		542,255		490,542
Weighted average number of shares outstanding–diluted	33,060,760		32,976,835		32,561,453

Diluted earnings per share excludes those outstanding stock options and any other common stock equivalents in periods where the inclusion of such stock options and common stock equivalents would be anti-dilutive. The following table presents the number of stock options, PSUs and RSUs that were excluded from the Company's calculation of diluted earnings per share.



	Years Ended December 31,
	2017	2016	2015
Stock options excluded as the exercise price was greater than the average market price	—	—	20,200
Stock options excluded under the treasury method, as the potential proceeds on settlement or exercise was greater than the value of shares acquired	—	89,221	257,405

Selected Quarterly Financial Data

12 Months Ended

Dec. 31, 2017

Selecled Quarterly Financial Data (Unaudited) [Abstract]

Quarterly Financial Information

Selected Quarterly Financial Data (Unaudited)

Quarterly results for the years ended December 31, 2017 and 2016 were as follows:



	2017 Quarters Ended
	March 31		June 30		September 30		December 31
	(in millions, except per share data)
Net premiums earned	$	175.3	$	171.7	$	187.9	$	181.6
Net realized gains on investments	2.2		1.1		4.1		—
Losses and loss adjustment expenses	109.0		106.1		116.9		85.2
Commission expense	21.5		21.5		23.7		24.7
Underwriting and other operating expenses	35.9		32.6		33.6		37.8
Other expenses	—		—		7.5		—
Income tax expense	6.3		7.8		7.0		21.7
Net income	23.2		24.8		21.9		31.3
Earnings per common share:
Basic	0.72		0.76		0.67		0.96
Diluted	0.70		0.75		0.66		0.94



	2016 Quarters Ended
	March 31		June 30		September 30		December 31
	(in millions, except per share data)
Net premiums earned	$	172.6	$	176.9	$	173.3	$	172.0
Net realized gains on investments	1.5		6.0		1.6		2.1
Losses and loss adjustment expenses	107.3		111.7		109.0		89.9
Commission expense	20.3		21.9		21.3		20.0
Underwriting and other operating expenses	36.3		33.6		31.7		34.5
Income tax expense	5.9		7.4		7.8		12.9
Net income	21.8		26.8		22.6		35.5
Earnings per common share:
Basic	0.67		0.82		0.70		1.10
Diluted	0.66		0.81		0.69		1.08

Significant Quarterly Adjustments

The second quarter of 2017 was favorably impacted by a $2.1 million gain from EHI's purchase of a $12.0 million notes payable.

The third quarter of 2017 was negatively impacted by a write-off of $7.5 million of previously capitalized costs relating to the development of information technology capabilities that had not yet been placed in service.

The fourth quarter of 2017 was impacted by: (1) favorable prior accident year loss development of $18.0 million; (2) a reduction in our current accident year loss provision rate for that reduced Losses and LAE by $10.6 million; and (3) $7.0 million in additional income tax expense from a revaluation of the Company's net deferred tax asset resulting from Enactment.

The second quarter of 2016 was impacted by: (1) an increase in net realized gains on investments, which resulted from sales of equity securities, which were undertaken in order to meet certain cash needs at the holding company; and (2) an increase in losses and loss adjustment expenses primarily due to four large losses totaling $6.5 million recognized during the quarter.

The fourth quarter of 2016 was impacted by favorable prior accident year loss development of $16.9 million.

Schedule II. Condensed Financial Information of Registrant

12 Months Ended

Dec. 31, 2017

Notes to Condensed Financial Statments [Abstract]

Schedule II. Condensed Financial Information of Registrant



Employers Holdings, Inc.

Condensed Balance Sheets

	December 31,
	2017			2016
Assets	(in millions, except share data)
Investments:
Investment in subsidiary	$	849.6		$	757.5
Fixed maturity securities at fair value (amortized cost $40.2 in 2017 and $14.7 in 2016)	41.4			16.0
Short-term investments at fair value (amortized cost $3.7 at December 31, 2017)	3.7			—
Total investments	894.7			773.5

Cash and cash equivalents	39.6			41.4
Accrued investment income	0.3			0.3
Federal income taxes receivable	4.2			9.6
Deferred income taxes, net	14.5			20.0
Other assets	0.8			0.7
Total assets	$	954.1		$	845.5

Liabilities and stockholders' equity
Accounts payable and accrued expenses	$	4.5		$	4.8
Intercompany payable	1.9			0.1
Total liabilities	6.4			4.9

Stockholders' equity:
Common stock, $0.01 par value; 150,000,000 shares authorized; 56,695,174 and 56,226,277 shares issued and 32,597,819 and 32,128,922 shares outstanding at December 31, 2017 and 2016, respectively	0.6			0.6
Preferred stock, $0.01 par value; 25,000,000 shares authorized; none issued	—			—
Additional paid-in capital	381.2			372.0
Retained earnings	842.2			777.2
Accumulated other comprehensive income, net of tax	107.4			74.5
Treasury stock, at cost (24,097,355 shares at December 31, 2017 and December 31, 2016)	(383.7		)	(383.7		)
Total stockholders' equity	947.7			840.6
Total liabilities and stockholders' equity	$	954.1		$	845.5



Employers Holdings, Inc.

Condensed Statements of Income

	Years Ended December 31,
	2017			2016			2015
	(in millions, except per share data)
Revenues
Net investment income	$	1.3		$	1.9		$	4.0
Net realized gains on investments	—			8.0			2.4
Total revenues	1.3			9.9			6.4

Expenses
Other operating expenses	15.2			13.8			13.8
Interest expense	—			—			1.1
Total expenses	15.2			13.8			14.9

Loss before income taxes and equity in earnings of subsidiary	(13.9		)	(3.9		)	(8.5		)
Income tax benefit	(5.8		)	(3.5		)	(3.3		)
Net loss before equity in earnings of subsidiary	(8.1		)	(0.4		)	(5.2		)
Equity in earnings of subsidiary	109.3			107.1			99.6
Net income	$	101.2		$	106.7		$	94.4

Earnings per common share:
Basic	$	3.11		$	3.29		$	2.94
Diluted	$	3.06		$	3.24		$	2.90

Cash dividends declared per common share	$	0.60		$	0.36		$	0.24



Employers Holdings, Inc.

Condensed Statement of Cash Flows

	Years Ended December 31,
	2017			2016			2015
	(in millions)
Operating activities
Net income	$	101.2		$	106.7		$	94.4
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Equity in undistributed earnings of subsidiary	(71.5		)	(107.1		)	(99.6		)
Realized gains on investments	—			(8.0		)	(2.4		)
Stock-based compensation	6.8			5.8			4.6
Excess tax benefits from stock-based compensation	—			—			(1.2		)
Amortization of premium on investments, net	0.1			0.4			0.9
Deferred income tax expense (benefit)	5.3			2.9			(4.6		)
Change in operating assets and liabilities:
Accounts payable and accrued expenses	(0.3		)	(0.7		)	1.7
Federal income taxes	5.4			(7.9		)	4.9
Other assets	(0.1		)	0.8			0.4
Intercompany payable	1.8			0.3			0.1
Other	—			(0.4		)	1.2
Net cash provided by (used in) operating activities	48.7			(7.2		)	0.4

Investing activities
Purchases of fixed maturity securities	(30.6		)	(31.0		)	(21.6		)
Purchases of equity securities	—			(3.6		)	(19.0		)
Purchases of short-term securities	(7.9		)	—			—
Proceeds from sale of fixed maturity securities	5.0			—			18.3
Proceeds from maturities and redemptions of investments	4.5			24.9			45.5
Proceeds from sale of equity securities	—			88.5			24.0
Capital contributions to subsidiary	(5.6		)	(8.0		)	—
Change in restricted cash equivalents	—			—			4.6
Net cash (used in) provided by investing activities	(34.6		)	70.8			51.8

Financing activities
Acquisition of common stock	—			(21.1		)	—
Cash transactions related to stock-based compensation	3.8			9.0			4.8
Dividends paid to stockholders	(19.7		)	(11.5		)	(7.7		)
Payments on notes payable	—			—			(60.0		)
Excess tax benefits from stock-based compensation	—			—			1.2
Net cash used in financing activities	(15.9		)	(23.6		)	(61.7		)

Net (decrease) increase in cash and cash equivalents	(1.8		)	40.0			(9.5		)
Cash and cash equivalents at the beginning of the period	41.4			1.4			10.9
Cash and cash equivalents at the end of the period	$	39.6		$	41.4		$	1.4

- Definition

The entire disclosure for condensed financial information, including the financial position, cash flows, and the results of operations of the registrant (parent company) as of the same dates or for the same periods for which audited consolidated financial statements are being presented. Alternatively, the details of this disclosure can be reported by the specific parent company taxonomy elements, indicating the appropriate date and period contexts in an instance document.

+ References + Details

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2017

Summary of Significant Accounting Policies [Abstract]

Cash and Cash Equivalents, Policy

Cash and Cash Equivalents

The Company considers all liquid investments with maturities of less than three months, as measured from the date of purchase, to be cash equivalents.

Restricted Cash and Cash Equivalents, Policy

Restricted Cash and Cash Equivalents

Investments, Policy

Short-Term Investments

The Company considers all liquid investments with maturities of between three and twelve months, as measured from the date of purchase, to be short-term investments.

Investment Securities

Realized gains and losses on investments are determined on a specific-identification basis.

Revenue Recognition, Policy

Revenue Recognition

Deferred Policy Acquisition Costs, Policy

Deferred Policy Acquisition Costs

Unpaid Loss and LAE Reserves, Policy

Unpaid Loss and LAE Reserves

Reinsurance, Policy

Reinsurance

Property, and Equipment, Policy

Property and Equipment

Property and equipment are stated at cost less accumulated depreciation (see Note 7). Expenditures for maintenance and repairs are charged against operations as incurred.

Lessee, Leases [Policy Text Block]

Obligations Held Under Capital Leases

Income Taxes, Policy

Income Taxes

Credit Risk, Policy

Credit Risk

The Company's premiums receivable are generally diversified due to the large number of entities composing the Company's policyholder base and their dispersion across many different industries.

Fair Value of Financial Instruments, Policy

Fair Value of Financial Instruments

The following methods and assumptions were used by the Company in estimating the fair value of its financial instruments:

Goodwill and Other Intangible Assets, Policy

Goodwill and Other Intangible Assets

The gross carrying value, accumulated amortization, and net carrying value for the Company's intangible assets, by major class, as of December 31, were as follows:



	2017							2016
	Gross Carrying Value		Accumulated Amortization			Net Carrying Value		Gross Carrying Value		Accumulated Amortization			Net Carrying Value
	(in millions)
State licenses	$	7.7	$	—		$	7.7	$	7.7	$	—		$	7.7
Insurance relationships	9.4		$	(9.2	)	0.2		9.4		$	(8.9	)	0.5
Total	$	17.1	$	(9.2	)	$	7.9	$	17.1	$	(8.9	)	$	8.2



Year	Amount
	(in millions)
2018	0.2
Total	$	0.2

Stock-based Compensation, Policy

Stock-Based Compensation

Changes in Estimates (Tables)

12 Months Ended

Dec. 31, 2017

Changes in Estimates [Abstract]

Change to Contingent Profit Commission [Table Text Block]



	2017			2016			2015
	(in millions, except per share data)
Change in estimate of Contingent commission receivable - LPT Agreement	$	0.3		$	1.9		$	2.8
Cumulative adjustment to the Deferred Gain⁽¹⁾	(0.3		)	(1.8		)	(2.6		)
Net income impact from this change in estimate	0.3			1.8			2.6
Earnings per common share impact from this change in estimate
Basic	0.01			0.06			0.08
Diluted	0.01			0.05			0.08


(1)	The cumulative adjustments to the Deferred Gain were also recognized in losses and LAE incurred in the Company's Consolidated Statements of Comprehensive Income, so that the Deferred Gain reflects the balance that would have existed had the revised loss and LAE reserves been recognized at the inception of the LPT Agreement.

Change Due to Estimated Reserves Ceded Under the LPT Agreement [Table Text Block]



	2016			2015
	(in millions, except per share data)
LPT Reserve Adjustments	$	(5.0	)	$	(10.0	)
Cumulative adjustment to the Deferred Gain⁽¹⁾	(3.1		)	(6.4		)
Net income impact from this change in estimate	3.1			6.4
Earnings per common share impact from this change in estimate
Basic	0.10			0.20
Diluted	0.09			0.20


(1)	The cumulative adjustments to the Deferred Gain were also recognized in losses and LAE incurred in the Company's Consolidated Statements of Comprehensive Income, so that the Deferred Gain reflects the balance that would have existed had the revised loss and LAE reserves been recognized at the inception of the LPT Agreement.

Change in Reserves for Non-taxable Periods [Table Text Block]



	2015
	(in millions, except per share data)
Loss and LAE reserves reallocated to taxable years	$	56.3
Impact to effective tax rate	(15.4		)%
Net income impact from this change in estimate	$	15.3
Earnings per common share impact from this change in estimate
Basic	0.48
Diluted	0.47

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2017

Summary of Significant Accounting Policies [Abstract]

Schedule of intangible assets table

The gross carrying value, accumulated amortization, and net carrying value for the Company's intangible assets, by major class, as of December 31, were as follows:



	2017							2016
	Gross Carrying Value		Accumulated Amortization			Net Carrying Value		Gross Carrying Value		Accumulated Amortization			Net Carrying Value
	(in millions)
State licenses	$	7.7	$	—		$	7.7	$	7.7	$	—		$	7.7
Insurance relationships	9.4		$	(9.2	)	0.2		9.4		$	(8.9	)	0.5
Total	$	17.1	$	(9.2	)	$	7.9	$	17.1	$	(8.9	)	$	8.2

Expected amortization expense table

Future amortization expenses associated with the Company's intangible assets are expected to be as follows:



Year	Amount
	(in millions)
2018	0.2
Total	$	0.2

Fair Value of Financial Instruments (Tables)

12 Months Ended

Dec. 31, 2017

Fair Value of Financial Instruments [Abstract]

Estimated fair value of financial instruments table

The carrying value and the estimated fair value of the Company's financial instruments as of December 31, were as follows:



	2017				2016
	Carrying Value		Estimated Fair Value		Carrying Value		Estimated Fair Value
Financial assets	(in millions)
Investments (Note 6)	$	2,677.7	$	2,677.7	$	2,552.6	$	2,552.6
Cash and cash equivalents	73.3		73.3		67.2		67.2
Restricted cash and cash equivalents	1.0		1.0		3.6		3.6
Financial liabilities
Notes payable (Note 11)	$	20.0	$	23.6	$	32.0	$	33.0

Fair value, assets and liabilities measured on recurring basis table

The following table presents the items in the Company's Consolidated Balance Sheets that are stated at fair value and the corresponding fair value measurements.



	December 31, 2017						December 31, 2016
	Level 1		Level 2		Level 3		Level 1		Level 2		Level 3
	(in millions)
Fixed maturity securities
U.S. Treasuries	$	—	$	137.0	$	—	$	—	$	127.4	$	—
U.S. Agencies	—		11.8		—		—		12.8		—
States and municipalities	—		642.5		—		—		851.6		—
Corporate securities	—		1,118.0		—		—		956.7		—
Residential mortgage-backed securities	—		389.3		—		—		258.0		—
Commercial mortgage-backed securities	—		106.0		—		—		95.5		—
Asset-backed securities	—		58.8		—		—		35.4		7.0
Total fixed maturity securities	$	—	$	2,463.4	$	—	$	—	$	2,337.4	$	7.0
Equity securities
Industrial and miscellaneous	$	181.7	$	—	$	—	$	167.2	$	—	$	—
Non-redeemable preferred (FHLB stock)	—		—		4.7		—		—		4.9
Other	23.9		—		—		20.1		—		—
Total equity securities	$	205.6	$	—	$	4.7	$	187.3	$	—	$	4.9
Short-term investments	$	—	$	4.0	$	—	$	—	$	16.0	$	—

Fair value, assets measured on recurring basis, unobservable input reconciliation table

The following table provides a reconciliation of the beginning and ending balances that are measured using Level 3 inputs for the year ended December 31, 2017.



	Level 3 Securities
	2017			2016
	(in millions)
Beginning balance, January 1	$	11.9		$	—
Transfers out of Level 3⁽¹⁾	(7.0		)	—
Purchases and sales, net	(0.2		)	11.9
Ending balance, December 31	$	4.7		$	11.9

Schedule of Cash and Cash Equivalents [Table Text Block]

The following table presents cash equivalents at NAV and total cash and cash equivalents carried at fair value on the Company's Consolidated Balance Sheets.



	December 31, 2017		December 31, 2016

Cash and cash equivalents at fair value	$	34.3	$	9.7
Cash equivalents measured at NAV, which approximates fair value	39.0		57.5
Total cash and cash equivalents	$	73.3	$	67.2

- Definition

Tabular disclosure of financial instruments measured at fair value, including those classified in shareholders' equity measured on a recurring or nonrecurring basis. Disclosures include, but are not limited to, fair value measurements recorded and the reasons for the measurements, level within the fair value hierarchy in which the fair value measurements are categorized and transfers between levels 1 and 2. Nonrecurring fair value measurements are those that are required or permitted in the statement of financial position in particular circumstances.

+ References + Details

Investments (Tables)

12 Months Ended

Dec. 31, 2017

Investments [Abstract]

Available-for-sale securities table

The cost or amortized cost, gross unrealized gains, gross unrealized losses, and estimated fair value of the Company’s investments were as follows:



	Cost or Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
At December 31, 2017	(in millions)
Fixed maturity securities
U.S. Treasuries	$	135.8	$	2.0	$	(0.8	)	$	137.0
U.S. Agencies	11.3		0.5		—			11.8
States and municipalities	617.0		25.5		—			642.5
Corporate securities	1,103.4		18.0		(3.4		)	1,118.0
Residential mortgage-backed securities	388.3		3.6		(2.6		)	389.3
Commercial mortgage-backed securities	106.5		0.4		(0.9		)	106.0
Asset-backed securities	58.7		0.3		(0.2		)	58.8
Total fixed maturity securities	2,421.0		50.3		(7.9		)	2,463.4
Equity securities
Industrial and miscellaneous	100.8		81.5		(0.6		)	181.7
Non-redeemable preferred (FHLB stock)	4.7		—		—			4.7
Other	11.2		12.7		—			23.9
Total equity securities	116.7		94.2		(0.6		)	210.3
Short-term investments	4.0		—		—			4.0
Total investments	$	2,541.7	$	144.5	$	(8.5	)	$	2,677.7

At December 31, 2016
Fixed maturity securities
U.S. Treasuries	$	124.1	$	3.5	$	(0.2	)	$	127.4
U.S. Agencies	11.9		0.9		—			12.8
States and municipalities	833.0		24.7		(6.1		)	851.6
Corporate securities	942.3		18.9		(4.5		)	956.7
Residential mortgage-backed securities	255.9		4.7		(2.6		)	258.0
Commercial mortgage-backed securities	96.1		0.4		(1.0		)	95.5
Asset-backed securities	42.6		—		(0.2		)	42.4
Total fixed maturity securities	2,305.9		53.1		(14.6		)	2,344.4
Equity securities
Industrial and miscellaneous	100.5		67.4		(0.7		)	167.2
Non-redeemable preferred (FHLB stock)	4.9		—		—			4.9
Other	10.7		9.4		—			20.1
Total equity securities	116.1		76.8		(0.7		)	192.2
Short-term investments	16.0		—		—			16.0
Total investments	$	2,438.0	$	129.9	$	(15.3	)	$	2,552.6

Investments classified by contractual maturity date table



	Amortized Cost		Estimated Fair Value
	(in millions)
Due in one year or less	$	220.5	$	221.3
Due after one year through five years	766.6		782.1
Due after five years through ten years	754.7		772.1
Due after ten years	125.7		133.8
Mortgage and asset-backed securities	553.5		554.1
Total	$	2,421.0	$	2,463.4

Unrealized loss on investments table



	December 31, 2017						December 31, 2016
	Estimated Fair Value		Gross Unrealized Losses			Number of Issues	Estimated Fair Value		Gross Unrealized Losses			Number of Issues
Less than 12 months:	(dollars in millions)
Fixed maturity securities
U.S. Treasuries	$	86.0	$	(0.5	)	28	$	33.3	$	(0.2	)	14
States and municipalities	—		—			—	200.9		(6.1		)	50
Corporate securities	307.6		(2.3		)	113	289.5		(4.1		)	101
Residential mortgage-backed securities	165.0		(0.8		)	45	137.5		(2.6		)	51
Commercial mortgage-backed securities	41.8		(0.2		)	19	48.0		(1.0		)	21
Asset-backed securities	29.3		(0.2		)	25	30.1		(0.2		)	20
Total fixed maturity securities	629.7		(4.0		)	230	739.3		(14.2		)	257
Equity securities	13.9		(0.6		)	24	13.6		(0.6		)	28
Total less than 12 months	$	643.6	$	(4.6	)	254	$	752.9	$	(14.8	)	285

12 months or greater:
Fixed maturity securities
U.S. Treasuries	$	23.4	$	(0.3	)	10	$	—	$	—		—
Corporate securities	53.2		(1.1		)	17	15.2		(0.4		)	5
Residential mortgage-backed securities	77.1		(1.8		)	32	—		—			—
Commercial mortgage-backed securities	25.1		(0.7		)	8	—		—			—
Total fixed maturity securities	178.8		(3.9		)	67	15.2		(0.4		)	5
12 months or greater	$	178.8	$	(3.9	)	67	$	16.9	$	(0.5	)	10

Total available-for-sale:
Fixed maturity securities
U.S. Treasuries	$	109.4	$	(0.8	)	38	$	33.3	$	(0.2	)	14
States and municipalities	—		—			—	200.9		(6.1		)	50
Corporate securities	360.8		(3.4		)	130	304.7		(4.5		)	106
Residential mortgage-backed securities	242.1		(2.6		)	77	137.5		(2.6		)	51
Commercial mortgage-backed securities	66.9		(0.9		)	27	48.0		(1.0		)	21
Asset-backed securities	29.3		(0.2		)	25	30.1		(0.2		)	20
Total fixed maturity securities	808.5		(7.9		)	297	754.5		(14.6		)	262
Equity securities	13.9		(0.6		)	24	15.3		(0.7		)	33
Total available-for-sale	$	822.4	$	(8.5	)	321	$	769.8	$	(15.3	)	295

Net realized gains and change in unrealized gains (losses), available for sale securities table

Net realized gains on investments and the change in unrealized gains (losses) on fixed maturity and equity securities are determined on a specific-identification basis and were as follows:



	Years Ended December 31,
	2017			2016			2015
Net realized gains (losses) on investments	(in millions)
Fixed maturity securities
Gross gains	$	4.7		$	1.9		$	0.5
Gross losses	(2.2		)	(0.7		)	(0.4		)
Net realized gains on fixed maturity securities	$	2.5		$	1.2		$	0.1
Equity securities
Gross gains	$	9.3		$	16.6		$	8.1
Gross losses	(4.4		)	(6.6		)	(18.9		)
Net realized gains (losses) on equity securities	$	4.9		$	10.0		$	(10.8	)
Total	$	7.4		$	11.2		$	(10.7	)

Change in unrealized gains (losses)
Fixed maturity securities	$	3.9		$	(28.9	)	$	(22.2	)
Equity securities	17.5			14.9			(13.7		)
Total	$	21.4		$	(14.0	)	$	(35.9	)

Investment income table

Net investment income was as follows:



	Years Ended December 31,
	2017			2016			2015
	(in millions)
Fixed maturity securities	$	70.4		$	68.5		$	68.8
Equity securities	6.9			7.4			5.9
Short-term investments	0.1			—			—
Cash equivalents and restricted cash	0.6			0.4			0.1
Gross investment income	78.0			76.3			74.8
Investment expenses	(3.4		)	(3.1		)	(2.6		)
Net investment income	$	74.6		$	73.2		$	72.2

- Definition

Tabular disclosure of available-for-sale securities which includes, but is not limited to, changes in the cost basis and fair value, fair value and gross unrealized gain (loss), fair values by type of security, contractual maturity and classification, amortized cost basis, contracts to acquire securities to be accounted for as available-for-sale, debt maturities, transfers to trading, change in net unrealized holding gain (loss) net of tax, continuous unrealized loss position fair value, aggregate losses qualitative disclosures, other than temporary impairment (OTTI) losses or other disclosures related to available for sale securities.

+ References + Details

Property and Equipment (Tables)

12 Months Ended

Dec. 31, 2017

Property and Equipment [Abstract]

Property, plant and equipment table

Property and equipment consists of the following:



	As of December 31,
	2017			2016
	(in millions)
Furniture and equipment	$	1.7		$	2.3
Leasehold improvements	2.9			4.3
Computers and software	54.2			59.0
Automobiles	1.1			1.2
Property and equipment, gross	59.9			66.8
Accumulated depreciation	(46.0		)	(44.6		)
Property and equipment, net	$	13.9		$	22.2

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2017

Income Taxes [Abstract]

Summary of income tax contingencies table

The Company's provision for income taxes consisted of the following:



	Years Ended December 31,
	2017		2016		2015
Current tax expense:	(in millions)
Federal	$	17.9	$	20.3	$	9.5
State	0.7		0.3		1.1
Total current tax expense	18.6		20.6		10.6
Deferred federal tax expense (benefit):
Impact of tax Enactment	7.0		—		—
Other	17.2		13.4		(5.6		)
Total deferred federal tax expense (benefit)	24.2		13.4		(5.6		)
Income tax expense	$	42.8	$	34.0	$	5.0

Reconciliation of federal staturoty income tax rates to the effective tax rates table



	Years Ended December 31,
	2017			2016			2015
	(in millions)
Expense computed at statutory rate	$	50.4		$	49.3		$	34.8
Tax-advantaged investment income	(7.6		)	(8.5		)	(8.6		)
Pre-Privatization reserve adjustments, excluding LPT	—			—			(15.3		)
LPT deferred gain amortization	(4.0		)	(4.7		)	(4.9		)
LPT Reserve Adjustment	—			(1.1		)	(2.2		)
Stock based compensation	(3.4		)	(1.6		)	—
Impact of tax Enactment	7.0			—			—
Other	0.4			0.6			1.2
Income tax expense	$	42.8		$	34.0		$	5.0

Deferred tax assets and liabilities

The significant components of deferred income taxes, net, were as follows as of December 31:



	2017				2016
	Deferred Tax				Deferred Tax
	Assets		Liabilities		Assets		Liabilities
	(in millions)
Unrealized capital gains, net	$	—	$	28.5	$	—	$	40.1
Deferred policy acquisition costs	—		9.7		—		15.7
Intangible assets	—		1.7		—		2.9
Loss reserve discounting for tax reporting	29.0		—		51.7		—
Unearned premiums	12.8		—		20.9		—
Allowance for bad debt	2.1		—		3.4		—
Stock-based compensation	2.5		—		4.4		—
Accrued liabilities	4.2		—		8.1		—
Minimum tax credit	20.0		—		27.8		—
Other	2.8		4.8		9.7		7.9
Total	$	73.4	$	44.7	$	126.0	$	66.6
Deferred income taxes, net	$	28.7			$	59.4

Liability for Unpaid Losses and Loss Adjustment Expenses (Tables)

12 Months Ended

Dec. 31, 2017

Liability for Unpaid Losses and Loss Adjustment Expenses [Abstract]

Changes in the liability for unpaid losses and LAE table

The following table represents a reconciliation of changes in the liability for unpaid losses and LAE.



	Years Ended December 31,
	2017			2016			2015
	(in millions)
Unpaid losses and LAE at beginning of period	$	2,301.0		$	2,347.5		$	2,369.7
Less reinsurance recoverable, excluding bad debt allowance, on unpaid losses and LAE	580.0			628.2			669.5
Net unpaid losses and LAE at beginning of period	1,721.0			1,719.3			1,700.2
Losses and LAE, net of reinsurance, incurred during the period related to:
Current year	447.3			452.9			456.9
Prior years⁽¹⁾	(18.5		)	(18.4		)	(7.2		)
Total net losses and LAE incurred during the period⁽¹⁾	428.8			434.5			449.7
Paid losses and LAE, net of reinsurance, related to:
Current year	76.9			78.7			75.4
Prior years⁽²⁾	343.8			354.1			355.2
Total net paid losses and LAE during the period⁽²⁾	420.7			432.8			430.6
Ending unpaid losses and LAE, net of reinsurance	1,729.1			1,721.0			1,719.3
Reinsurance recoverable, excluding bad debt allowance, on unpaid losses and LAE	537.0			580.0			628.2
Unpaid losses and LAE at end of period	$	2,266.1		$	2,301.0		$	2,347.5

(1)

(2)

Short-duration Insurance Contracts, Claims Development [Table Text Block]



	Incurred Losses and LAE, Net of Reinsurance
	Years Ended December 31,																				As of December 31, 2017
Accident Year	2008⁽¹⁾		2009⁽¹⁾		2010⁽¹⁾		2011⁽¹⁾		2012⁽¹⁾		2013⁽¹⁾		2014⁽¹⁾		2015⁽¹⁾		2016⁽¹⁾		2017		IBNR		Cumulative number of reported claims
	(in millions, except claims counts)
2008	$	315.9	$	315.3	$	317.8	$	329.2	$	329.5	$	335.1	$	336.9	$	343.8	$	341.4	$	342.1	$	15.4	28,088
2009			255.4		266.9		279.0		280.1		283.6		283.7		291.2		290.5		290.5		13.5		22,673
2010					204.9		224.4		228.1		246.1		250.2		262.0		259.9		258.8		19.8		18,543
2011							253.7		267.3		272.0		277.4		296.3		292.6		288.8		27.5		19,571
2012									348.8		359.9		360.9		386.4		388.2		382.8		50.7		25,972
2013											452.6		460.6		478.6		472.6		468.9		73.6		28,816
2014													463.4		445.8		432.9		434.6		86.1		28,449
2015															422.2		425.8		423.9		98.7		26,993
2016																	419.0		414.6		140.8		25,305
2017																			412.4		244.6		21,214
Total																			$	3,717.4



	Cumulative Paid Losses and LAE, Net of Reinsurance
	Years Ended December 31,
Accident Year	2008⁽¹⁾		2009⁽¹⁾		2010⁽¹⁾		2011⁽¹⁾		2012⁽¹⁾		2013⁽¹⁾		2014⁽¹⁾		2015⁽¹⁾		2016⁽¹⁾		2017
	(in millions)
2008	$	71.1	$	155.4	$	201.8	$	234.7	$	255.3	$	271.1	$	284.2	$	293.6	$	300.7	$	307.1
2009			59.0		130.6		174.1		202.0		219.3		232.1		242.3		249.5		255.1
2010					47.1		105.6		143.8		171.7		190.7		206.2		215.4		221.3
2011							47.4		115.1		162.6		193.8		217.5		230.1		238.2
2012									58.6		148.3		214.2		261.4		289.9		305.0
2013											68.5		184.4		263.8		317.4		346.1
2014													65.3		172.7		248.9		297.2
2015															65.5		174.5		246.9
2016																	65.6		166.8
2017																			63.5
Total																			$	2,447.3
All outstanding liabilities for unpaid losses and LAE prior to 2007, net of reinsurance																			364.2
Total outstanding liabilities for unpaid losses and LAE, net of reinsurance																			$	1,634.3


(1)	Data presented for these calendar years is required supplementary information, which is unaudited

Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Table Text Block]

The following table represents a reconciliation of claims development to the aggregate carrying amount of the liability for unpaid losses and LAE:



	December 31, 2017
	(in millions)
Liabilities for unpaid losses and LAE, net of reinsurance	$	1,634.3
Reinsurance recoverable on unpaid losses	537.0
Unallocated LAE (adjusting and other)	94.8
Total liability for unpaid losses and LAE	$	2,266.1

Short-duration Insurance Contracts, Schedule of Historical Claims Duration [Table Text Block]



Average Annual Percentage Payout of Claims by Age, Net of Reinsurance
Year 1		Year 2		Year 3		Year 4		Year 5		Year 6		Year 7		Year 8		Year 9		Year 10
16.7	%	24.3	%	16.1	%	10.8	%	6.9	%	4.7	%	3.4	%	2.5	%	2.0	%	1.9	%

Reinsurance (Tables)

12 Months Ended

Dec. 31, 2017

Reinsurance [Abstract]

Supplemental schedule of reinsurance premiums for insurance companies table

The effects of reinsurance on the Company's written and earned premiums and on its losses and LAE incurred were as follows:



	Years Ended December 31,
	2017						2016						2015
	Written			Earned			Written			Earned			Written			Earned
	(in millions)
Direct premiums	$	719.5		$	712.5		$	691.0		$	691.0		$	684.9		$	686.0
Assumed premiums	10.2			10.0			10.4			10.6			12.8			12.8
Gross premiums	729.7			722.5			701.4			701.6			697.7			698.8
Ceded premiums	(6.0		)	(6.0		)	(6.8		)	(6.8		)	(8.4		)	(8.4		)
Net premiums	$	723.7		$	716.5		$	694.6		$	694.8		$	689.3		$	690.4
Ceded losses and LAE incurred	$	(0.5	)				$	0.1					$	10.1

Ceded losses and LAE incurred includes the amortization of the Deferred Gain, LPT Reserve Adjustments, and LPT Contingent Commission Adjustments.

Notes Payable (Tables)

12 Months Ended

Dec. 31, 2017

Notes Payable [Abstract]

Schedule of long-term debt instruments table

Notes payable is comprised of the following:



	December 31,
	2017		2016
	(in millions)
Dekania Surplus Note, due April 29, 2034	$	10.0	$	10.0
Alesco Surplus Note, due December 15, 2034	10.0		10.0
ICONS Surplus Note, due May 24, 2034	—		12.0
Total	$	20.0	$	32.0

Schedule of maturities of long-term debt table

Principal payment obligations on notes payable outstanding at December 31, 2017, were as follows:



Year	Principal Due
	(in millions)
2018 - 2022	$	—
Thereafter	20.0
Total	$	20.0

- Definition

Tabular disclosure of long-debt instruments or arrangements, including identification, terms, features, collateral requirements and other information necessary to a fair presentation. These are debt arrangements that originally required repayment more than twelve months after issuance or greater than the normal operating cycle of the entity, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=84159872&loc=d3e21475-112644

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=75038535&loc=d3e64711-112823

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(e),(f))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=84159872&loc=d3e21538-112644

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=84159872&loc=d3e21506-112644

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28541-108399

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=84159872&loc=d3e21521-112644

+ Details

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2017

Commitments and Contingencies [Abstract]

Operating and capital leases schedule of future minimum lease payments table

The future lease payments for the next five years on these non-cancelable operating and capital leases at December 31, 2017, were as follows:



Year	Operating Leases		Capital Leases
	(in millions)
2018	$	4.8	$	0.3
2019	4.8		0.3
2020	4.2		0.2
2021	2.8		0.2
2022	1.8		0.1
Thereafter	7.9		—
Total	$	26.3	$	1.1

Schedule of capital leased asssets table

Property held under capital leases is included in property and equipment as follows:



Asset Class	2017			2016
	(in millions)
Automobiles	1.1			1.2
	1.1			1.2
Accumulated amortization	(0.3		)	(0.6		)
Total	$	0.8		$	0.6

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2017

Stock-Based Compensation [Abstract]

Schedule of compensation cost for share-based payment arrangements, allocation of share-based compensation costs by plan table

Net stock-based compensation expense recognized in the Company's Consolidated Statements of Comprehensive Income was as follows:



	Years Ended December 31,
	2017		2016		2015
Stock-based compensation expense related to:	(in millions)
Stock options	$	0.5	$	0.7	$	1.0
RSUs	2.0		1.9		2.0
PSUs	4.3		3.2		1.6
Total	6.8		5.8		4.6
Less: related tax benefit	2.4		2.0		1.6
Net stock-based compensation expense	$	4.4	$	3.8	$	3.0

Schedule of share-based payment award, stock options, valuation assumptions table

The fair value of the stock options granted during the years ended December 31, 2016 and 2015 was calculated using the following weighted average assumptions:



	2016		2015
Expected volatility	38.0	%	38.0	%
Expected life (in years)	4.8		4.8
Dividend yield	1.3	%	1.0	%
Risk-free interest rate	1.4	%	1.6	%
Weighted average grant date fair values of stock options granted	$8.46		$7.63

Schedule of share-based compensation arrangement by share-based payment award, options, vested and expected to vest, outstanding table

Changes in outstanding stock options for the year ended December 31, 2017 were as follows:



	Number of Stock Options		Weighted-Average Price		Weighted Average Remaining Contractual Life
Stock options outstanding at December 31, 2014	1,521,290		$	17.45	2.9 years
Granted	80,800		24.20		6.2 years
Exercised	(463,466	)	16.43
Forfeited	(17,079	)	20.21
Stock options outstanding at December 31, 2015	1,121,545		18.31		2.8 years
Granted	67,431		27.72		6.2 years
Exercised	(586,132	)	16.39
Expired	(6,075	)	22.48
Forfeited	(32,673	)	24.35
Stock options outstanding at December 31, 2016	564,096		21.04		3.3 years
Exercised	(307,076	)	19.44
Forfeited	(9,673	)	24.45
Stock options outstanding at December 31, 2017	247,347		22.90		3.4 years
Exercisable at December 31, 2017	156,517		21.71		2.8 years

Schedule of fair value of options vested and instrinsic value of outstanding and exercisable options table

The fair value of stock options vested and the intrinsic value of outstanding and exercisable stock options as of December 31, were as follows:



	2017		2016		2015
	(in millions)
Fair value of stock options vested	$	0.6	$	0.8	$	1.3
Intrinsic value of outstanding stock options	5.3		10.6		10.1
Intrinsic value of exercisable stock options	3.6		7.6		8.5

Schedule of share-based compensation, restricted stock and restricted stock units activity

Changes in outstanding RSUs for the year ended December 31, 2017 were as follows:



	Number of RSUs		Weighted Average Grant Date Fair Value
RSUs outstanding at December 31, 2014	306,867		$	19.15
Granted	112,048		24.19
Forfeited	(7,749	)	20.99
Vested	(92,133	)	19.74
RSUs outstanding at December 31, 2015	319,033		20.71
Granted	100,218		28.20
Forfeited	(21,872	)	24.87
Vested	(72,995	)	21.56
RSUs outstanding at December 31, 2016	324,384		22.55
Granted	87,276		37.94
Forfeited	(13,711	)	29.28
Vested	(70,877	)	24.97
RSUs outstanding at December 31, 2017	327,072		25.85
Vested but unsettled RSUs at December 31, 2017	152,644		19.54

Schedule of fair value of RSUs vested and instrinsic value of outstanding and vested RSUs table

The grant date fair value of RSUs vested and the intrinsic value of vested RSUs for the years ended December 31, were as follows:



	2017		2016		2015
	(in millions)
Grant date fair value of RSUs vested	$	1.8	$	1.6	$	1.7
Intrinsic value of RSUs vested	2.8		2.1		2.2

PSUs awarded to certain officers table

The Company has awarded PSUs to certain employees of the Company as follows:



Date of Grant	Target Number Awarded	Fair Value on Date of Grant		Aggregate Fair Value on Date of Grant
				(in millions)
March 2015⁽¹⁾	110,000	$	24.20	$	2.7
March 2016⁽¹⁾	97,236	27.72		2.7
March 2017⁽¹⁾	97,440	37.60		3.7

(1)

Statutory Matters (Tables)

12 Months Ended

Dec. 31, 2017

Stautory Matters [Abstract]

Statutory accounting practices disclosure table



	December 31,
	2017		2016
	(in millions)
Capital stock and unassigned surplus	$	510.6	$	447.1
Paid in capital	349.8		349.8
Surplus notes	32.0		32.0
Total statutory surplus	$	892.4	$	828.9

- Definition

Tabular disclosure of how the entity's reporting under GAAP as of the balance sheet date differs from the results based on prescribed and permitted accounting practices of the state or country of domicile in which a relevant statutory filing is made, or differences in results based on the National Association of Insurance Commissioners (NAIC) prescribed practices, or a combination thereof. Describes the accounting practices used and the related monetary effect on statutory surplus, net income, and risk-based capital. If an insurance enterprise's risk-based capital would have triggered a regulatory event had it not used a permitted practice, that fact is disclosed in the financial statements. Permitted statutory accounting practices include practices not prescribed but allowed by the domiciliary state insurance department regulatory authority.

+ References + Details

Earnings Per Share (Tables)

12 Months Ended

Dec. 31, 2017

Earnings Per Share [Abstract]

Net income and weighted average common shares outstanding used in earnings per share calculations table

The following table presents the net income and the weighted average shares outstanding used in the earnings per share common share calculations.



	Years Ended December 31,
	2017		2016		2015
	(in millions, except share data)
Net income	$	101.2	$	106.7	$	94.4
Weighted average number of shares outstanding–basic	32,501,576		32,434,580		32,070,911
Effect of dilutive securities:
Stock options	208,602		246,562		286,764
PSUs	271,738		222,594		155,768
RSUs	78,844		73,099		48,010
Dilutive potential shares	559,184		542,255		490,542
Weighted average number of shares outstanding–diluted	33,060,760		32,976,835		32,561,453

Antidilutive securities excluded from computation of earnings per share table

The following table presents the number of stock options, PSUs and RSUs that were excluded from the Company's calculation of diluted earnings per share.



	Years Ended December 31,
	2017	2016	2015
Stock options excluded as the exercise price was greater than the average market price	—	—	20,200
Stock options excluded under the treasury method, as the potential proceeds on settlement or exercise was greater than the value of shares acquired	—	89,221	257,405

Selected Quarterly Financial Data (Tables)

12 Months Ended

Dec. 31, 2017

Selecled Quarterly Financial Data (Unaudited) [Abstract]

Schedule of Quarterly Financial Information [Table Text Block]

Quarterly results for the years ended December 31, 2017 and 2016 were as follows:



	2017 Quarters Ended
	March 31		June 30		September 30		December 31
	(in millions, except per share data)
Net premiums earned	$	175.3	$	171.7	$	187.9	$	181.6
Net realized gains on investments	2.2		1.1		4.1		—
Losses and loss adjustment expenses	109.0		106.1		116.9		85.2
Commission expense	21.5		21.5		23.7		24.7
Underwriting and other operating expenses	35.9		32.6		33.6		37.8
Other expenses	—		—		7.5		—
Income tax expense	6.3		7.8		7.0		21.7
Net income	23.2		24.8		21.9		31.3
Earnings per common share:
Basic	0.72		0.76		0.67		0.96
Diluted	0.70		0.75		0.66		0.94



	2016 Quarters Ended
	March 31		June 30		September 30		December 31
	(in millions, except per share data)
Net premiums earned	$	172.6	$	176.9	$	173.3	$	172.0
Net realized gains on investments	1.5		6.0		1.6		2.1
Losses and loss adjustment expenses	107.3		111.7		109.0		89.9
Commission expense	20.3		21.9		21.3		20.0
Underwriting and other operating expenses	36.3		33.6		31.7		34.5
Income tax expense	5.9		7.4		7.8		12.9
Net income	21.8		26.8		22.6		35.5
Earnings per common share:
Basic	0.67		0.82		0.70		1.10
Diluted	0.66		0.81		0.69		1.08

Schedule II - Balance Sheet Parenthetical (Details) - USD ($) $ / shares in Units, $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Amortized cost	$ 2,541.7	$ 2,438.0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	150,000,000	150,000,000
Common stock, shares issued (in shares)	56,695,174	56,226,277
Common stock, shares outstanding (in shares)	32,597,819	32,128,922
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	25,000,000	25,000,000
Preferred stock, shares issued (in shares)	0	0
Treasury stock, at cost (in shares)	24,097,355	24,097,355
Parent Company [Member]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	150,000,000	150,000,000
Common stock, shares issued (in shares)	56,226,277	55,589,454
Common stock, shares outstanding (in shares)	32,128,922	32,216,480
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	25,000,000	25,000,000
Preferred stock, shares issued (in shares)	0	0
Treasury stock, at cost (in shares)	24,097,355	23,372,974
Debt Securities [Member]
Amortized cost	$ 2,421.0	$ 2,305.9
Debt Securities [Member] \| Parent Company [Member]
Amortized cost	14.7	40.2
Equity Securities [Member]
Amortized cost	116.7	116.1
Equity Securities [Member] \| Parent Company [Member]
Amortized cost	$ 0.0	$ 46.0

Changes in Estimates (Details) - USD ($)
$ / shares in Units, $ in Thousands

3 Months Ended

12 Months Ended

Dec. 31, 2017

Sep. 30, 2017

Jun. 30, 2017

Mar. 31, 2017

Dec. 31, 2016

Sep. 30, 2016

Jun. 30, 2016

Mar. 31, 2016

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2015

Dec. 31, 2014

Change in Accounting Estimate [Line Items]

Unpaid losses and loss adjustment expenses

$ 2,266,100

$ 2,301,000

$ 2,266,100

$ 2,301,000

$ 2,347,500

$ 2,369,700

Amortization of deferred gain

(11,300)

(11,700)

(11,400)

Net income

$ 31,300

$ 21,900

$ 24,800

$ 23,200

$ 35,500

$ 22,600

$ 26,800

$ 21,800

$ 101,200

$ 106,700

$ 94,400

Basic

$ 0.96

$ 0.67

$ 0.76

$ 0.72

$ 1.10

$ 0.70

$ 0.82

$ 0.67

$ 3.11

$ 3.29

$ 2.94

Diluted

$ 0.94

$ 0.66

$ 0.75

$ 0.70

$ 1.08

$ 0.69

$ 0.81

$ 0.66

$ 3.06

$ 3.24

$ 2.90

Change to Contingent Profit Commission [Member]

Change in Accounting Estimate [Line Items]

Change in estimate of contingent commission receivable

$ 300

$ 1,900

$ 2,800

Amortization of deferred gain

^[1]

(300)

(1,800)

(2,600)

Net income

$ 300

$ 1,800

$ 2,600

Basic

$ 0.01

$ 0.06

$ 0.08

Diluted

$ 0.01

$ 0.05

$ 0.08

Change Due to Estimated Reserves Ceded Under the LPT Agreement [Member]

Change in Accounting Estimate [Line Items]

Unpaid losses and loss adjustment expenses

$ 0

$ (5,000)

$ 0

$ (5,000)

$ (10,000)

Amortization of deferred gain

^[2]

(3,100)

(6,400)

Net income

$ 3,100

$ 6,400

Basic

$ 0.10

$ 0.20

Diluted

$ 0.09

$ 0.20

Due to change in reserves for non-taxable periods

Change in Accounting Estimate [Line Items]

Reserves reallocated to taxable years

$ 0

$ 56,300

Effective income tax rate reconciliation, percent

(15.40%)

Net income

$ 15,300

Basic

$ 0.48

Diluted

$ 0.47

[1]	The cumulative adjustments to the Deferred Gain were also recognized in losses and LAE incurred in the Company's Consolidated Statements of Comprehensive Income, so that the Deferred Gain reflects the balance that would have existed had the revised loss and LAE reserves been recognized at the inception of the LPT Agreement.
[2]	The cumulative adjustments to the Deferred Gain were also recognized in losses and LAE incurred in the Company's Consolidated Statements of Comprehensive Income, so that the Deferred Gain reflects the balance that would have existed had the revised loss and LAE reserves been recognized at the inception of the LPT Agreement.

Summary of Significant Accounting Policies (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Investments	$ 2,677,700,000	$ 2,552,600,000
Restricted cash and cash equivalents	1,000,000	3,600,000
Premiums receivable from policyholders for final audit	64,200,000	58,400,000
Premiums receivable, bad debt allowance	10,000,000	9,800,000
Write-offs, net of recoveries of amounts previously written off	3,200,000	6,000,000	$ 2,400,000
Deferred policy acquisition cost, amortization expense	108,200,000	104,500,000	103,900,000
Premium Deficiency	0	0	0
Unpaid losses	$ 537,000,000	580,000,000
LPT - loss expense as a percentange of losses paid, for management of LPT claims	7.00%
LPT favorable/ unfavorable difference, percentage	30.00%
LPT actual amounts paid versus expected amounts, period	every five years
LPT actual amounts paid versus expected amounts, expiration period	25
Collateralized by cash or letter of credit	$ 3,500,000
LPT collateral held in trust account	380,800,000	355,700,000
Intangible Assets, Net (Excluding Goodwill) [Abstract]
Intangible assets, gross carrying amount	17,100,000	17,100,000
Intangible assets, accumulated amortization	(9,200,000)	(8,900,000)
Intangible assets, net	7,900,000	8,200,000
Amortization of intangible assets	300,000	300,000	$ 500,000
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
Future amortization expense, year two	200,000
Intangible assets, future amortization total	200,000
Funds Held in Trust, Reinsurance Agreement [Domain]
Investments	24,500,000	27,200,000
Restricted cash and cash equivalents	1,000,000	3,600,000
Licensing Agreements [Member]
Intangible Assets, Net (Excluding Goodwill) [Abstract]
Intangible assets, gross carrying amount	7,700,000	7,700,000
Intangible assets, net	7,700,000	7,700,000
Service Agreements [Member]
Intangible Assets, Net (Excluding Goodwill) [Abstract]
Intangible assets, gross carrying amount	9,400,000	9,400,000
Intangible assets, accumulated amortization	(9,200,000)	(8,900,000)
Intangible assets, net	$ 200,000	$ 500,000
Leasehold improvements
Finite-Lived intangible assets, amortization method	amortized over three to five years
Electronic Data Processing Equipment, Software, Furniture and Equipment and Automobiles [Member]
Finite-Lived intangible assets, amortization method	straight-line method over three to seven years

Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	$ 2,677,700	$ 2,552,600
Cash and cash equivalents	73,300	67,200	$ 56,600	$ 103,600
Restricted cash and cash equivalents	1,000	3,600
Notes payable	20,000	32,000
Investments, fair value	2,677,700	2,552,600
Cash and cash equivalents, estimated fair value	73,300	67,200
Notes payable, fair value	$ 23,600	$ 33,000

- Definition

Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

+ References + Details

Fair Value of Financial Instruments Cash Equivalents at NAV and Total Cash and Cash Equivalents Carried at Fair Value (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents at fair value	$ 34.3	$ 9.7
Cash equivalents measured at NAV, which approximates fair value	39.0	57.5
Total cash and cash equivalents	$ 73.3	$ 67.2

Fair Value of Financial Instruments Fair Value of Financial Instruments, Reconciliation of Level 3 Securities (Details) - USD ($)
$ in Thousands

12 Months Ended

Dec. 31, 2017

Dec. 31, 2016

Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]

Beginning balance, January 1

$ 2,552,600

Transfers out of Level 3(1)

^[1]

(7,000)

$ 0

Ending balance, December 31

2,677,700

2,552,600

Fair Value, Inputs, Level 3 [Member]

Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]

Beginning balance, January 1

11,900

Purchases and sales, net

(200)

11,900

Ending balance, December 31

$ 4,700

$ 11,900

[1]	(1)Transferred from Level 3 to Level 2 because observable market data became available for the securities.

Investments (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	$ 2,541.7	$ 2,438.0
Gross unrealized gains	144.5	129.9
Gross unrealized loss	(8.5)	(15.3)
Investments	2,677.7	2,552.6
Deposit Assets
Investments	2,677.7	2,552.6
Assets Held-in-trust
Investments	2,677.7	2,552.6
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	2,421.0	2,305.9
Gross unrealized gains	50.3	53.1
Gross unrealized loss	(7.9)	(14.6)
Investments	2,463.4	2,344.4
Deposit Assets
Investments	2,463.4	2,344.4
Assets Held-in-trust
Investments	2,463.4	2,344.4
US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	135.8	124.1
Gross unrealized gains	2.0	3.5
Gross unrealized loss	(0.8)	(0.2)
Investments	137.0	127.4
Deposit Assets
Investments	137.0	127.4
Assets Held-in-trust
Investments	137.0	127.4
US Government Agencies Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	11.3	11.9
Gross unrealized gains	0.5	0.9
Gross unrealized loss	0.0	0.0
Investments	11.8	12.8
Deposit Assets
Investments	11.8	12.8
Assets Held-in-trust
Investments	11.8	12.8
US States and Political Subdivisions Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	617.0	833.0
Gross unrealized gains	25.5	24.7
Gross unrealized loss	0.0	(6.1)
Investments	642.5	851.6
Deposit Assets
Investments	642.5	851.6
Assets Held-in-trust
Investments	642.5	851.6
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	1,103.4	942.3
Gross unrealized gains	18.0	18.9
Gross unrealized loss	(3.4)	(4.5)
Investments	1,118.0	956.7
Deposit Assets
Investments	1,118.0	956.7
Assets Held-in-trust
Investments	1,118.0	956.7
Residential Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	388.3	255.9
Gross unrealized gains	3.6	4.7
Gross unrealized loss	(2.6)	(2.6)
Investments	389.3	258.0
Deposit Assets
Investments	389.3	258.0
Assets Held-in-trust
Investments	389.3	258.0
Commercial Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	106.5	96.1
Gross unrealized gains	0.4	0.4
Gross unrealized loss	(0.9)	(1.0)
Investments	106.0	95.5
Deposit Assets
Investments	106.0	95.5
Assets Held-in-trust
Investments	106.0	95.5
Asset-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	58.7	42.6
Gross unrealized gains	0.3	0.0
Gross unrealized loss	(0.2)	(0.2)
Investments	58.8	42.4
Deposit Assets
Investments	58.8	42.4
Assets Held-in-trust
Investments	58.8	42.4
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	116.7	116.1
Gross unrealized gains	94.2	76.8
Gross unrealized loss	(0.6)	(0.7)
Investments	210.3	192.2
Deposit Assets
Investments	210.3	192.2
Assets Held-in-trust
Investments	210.3	192.2
Industrial and miscellaneous
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	100.8	100.5
Gross unrealized gains	81.5	67.4
Gross unrealized loss	(0.6)	(0.7)
Investments	181.7	167.2
Deposit Assets
Investments	181.7	167.2
Assets Held-in-trust
Investments	181.7	167.2
Federal home loan bank stock
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	4.7	4.9
Gross unrealized gains	0.0	0.0
Gross unrealized loss	0.0	0.0
Investments	4.7	4.9
Deposit Assets
Investments	4.7	4.9
Assets Held-in-trust
Investments	4.7	4.9
Other equities
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	11.2	10.7
Gross unrealized gains	12.7	9.4
Gross unrealized loss	0.0	0.0
Investments	23.9	20.1
Deposit Assets
Investments	23.9	20.1
Assets Held-in-trust
Investments	23.9	20.1
Short-term Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	4.0	16.0
Gross unrealized gains	0.0	0.0
Gross unrealized loss	0.0	0.0
Investments	4.0	16.0
Deposit Assets
Investments	4.0	16.0
Assets Held-in-trust
Investments	4.0	$ 16.0
Required by various state laws and regulations to hold securities or letters of credit in depository account [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments	1,009.7
Deposit Assets
Investments	1,009.7
Assets Held-in-trust
Investments	$ 1,009.7

Investments, Amortized Cost and Estimated Fair Value (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Amortized Cost
Due in one year or less, amortized cost	$ 220.5
Due after one year through five years, amortized cost	766.6
Due after five years through ten years, amortized cost	754.7
Due after ten years, amortized cost	125.7
Mortgage and asset-backed securities, amortized cost	553.5
Total, amortized cost	2,421.0
Estimated Fair Value
Due in one year or less, fair value	221.3
Due after one year through five years, fair value	782.1
Due after five years through ten years, fair value	772.1
Due after ten years, fair value	133.8
Mortgage and asset-backed securities, fair value	554.1
Total, fair value	$ 2,463.4	$ 2,344.4

Investments, Continuous Loss Position (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($) shares	Dec. 31, 2016 USD ($) shares	Dec. 31, 2015 USD ($) shares
Estimated Fair Value
Estimated fair value, less than 12 months	$ 643.6	$ 752.9
Estimated fair value, 12 months or greater	178.8	16.9
Estimated fair value, total	822.4	769.8
Gross Unrealized Losses
Gross unrealized losses, less than 12 Months	4.6	14.8
Gross unrealized losses, 12 months or greater	(3.9)	(0.5)
Estimated unrealized loss, total position	$ 8.5	$ 15.3
Number of issues in loss position, less than 12 months \| shares	254	285
Number of issues in loss position, 12 months or greater \| shares	67	10
Number of issues in loss position, aggregate \| shares	321	295
Debt Securities [Member]
Estimated Fair Value
Estimated fair value, less than 12 months	$ 629.7	$ 739.3
Estimated fair value, 12 months or greater	178.8	15.2
Estimated fair value, total	808.5	754.5
Gross Unrealized Losses
Gross unrealized losses, less than 12 Months	4.0	14.2
Gross unrealized losses, 12 months or greater	(3.9)	(0.4)
Estimated unrealized loss, total position	$ 7.9	$ 14.6
Number of issues in loss position, less than 12 months \| shares	230	257
Number of issues in loss position, 12 months or greater \| shares	67	5
Number of issues in loss position, aggregate \| shares	297	262
Total impairments, value	$ 0.5	$ 0.0	$ 0.0
Total impairments, number of securitites \| shares	9	0	0
US Treasury Securities [Member]
Estimated Fair Value
Estimated fair value, less than 12 months	$ 86.0	$ 33.3
Estimated fair value, 12 months or greater	23.4	0.0
Estimated fair value, total	109.4	33.3
Gross Unrealized Losses
Gross unrealized losses, less than 12 Months	0.5	0.2
Gross unrealized losses, 12 months or greater	(0.3)	0.0
Estimated unrealized loss, total position	$ 0.8	$ 0.2
Number of issues in loss position, less than 12 months \| shares	28	14
Number of issues in loss position, 12 months or greater \| shares	10	0
Number of issues in loss position, aggregate \| shares	38	14
US States and Political Subdivisions Debt Securities [Member]
Estimated Fair Value
Estimated fair value, less than 12 months	$ 0.0	$ 200.9
Estimated fair value, total	0.0	200.9
Gross Unrealized Losses
Gross unrealized losses, less than 12 Months	0.0	6.1
Estimated unrealized loss, total position	$ 0.0	$ 6.1
Number of issues in loss position, less than 12 months \| shares	0	50
Number of issues in loss position, aggregate \| shares	0	50
Corporate Debt Securities [Member]
Estimated Fair Value
Estimated fair value, less than 12 months	$ 307.6	$ 289.5
Estimated fair value, 12 months or greater	53.2	15.2
Estimated fair value, total	360.8	304.7
Gross Unrealized Losses
Gross unrealized losses, less than 12 Months	2.3	4.1
Gross unrealized losses, 12 months or greater	(1.1)	(0.4)
Estimated unrealized loss, total position	$ 3.4	$ 4.5
Number of issues in loss position, less than 12 months \| shares	113	101
Number of issues in loss position, 12 months or greater \| shares	17	5
Number of issues in loss position, aggregate \| shares	130	106
Residential Mortgage Backed Securities [Member]
Estimated Fair Value
Estimated fair value, less than 12 months	$ 165.0	$ 137.5
Estimated fair value, 12 months or greater	77.1	0.0
Estimated fair value, total	242.1	137.5
Gross Unrealized Losses
Gross unrealized losses, less than 12 Months	0.8	2.6
Gross unrealized losses, 12 months or greater	(1.8)	0.0
Estimated unrealized loss, total position	$ 2.6	$ 2.6
Number of issues in loss position, less than 12 months \| shares	45	51
Number of issues in loss position, 12 months or greater \| shares	32	0
Number of issues in loss position, aggregate \| shares	77	51
Commercial Mortgage Backed Securities [Member]
Estimated Fair Value
Estimated fair value, less than 12 months	$ 41.8	$ 48.0
Estimated fair value, 12 months or greater	25.1	0.0
Estimated fair value, total	66.9	48.0
Gross Unrealized Losses
Gross unrealized losses, less than 12 Months	0.2	1.0
Gross unrealized losses, 12 months or greater	(0.7)	0.0
Estimated unrealized loss, total position	$ 0.9	$ 1.0
Number of issues in loss position, less than 12 months \| shares	19	21
Number of issues in loss position, 12 months or greater \| shares	8	0
Number of issues in loss position, aggregate \| shares	27	21
Asset-backed Securities [Member]
Estimated Fair Value
Estimated fair value, less than 12 months	$ 29.3	$ 30.1
Estimated fair value, total	29.3	30.1
Gross Unrealized Losses
Gross unrealized losses, less than 12 Months	0.2	0.2
Estimated unrealized loss, total position	$ 0.2	$ 0.2
Number of issues in loss position, less than 12 months \| shares	25	20
Number of issues in loss position, aggregate \| shares	25	20
Equity Securities [Member]
Estimated Fair Value
Estimated fair value, less than 12 months	$ 13.9	$ 13.6
Estimated fair value, total	13.9	15.3
Gross Unrealized Losses
Gross unrealized losses, less than 12 Months	0.6	0.6
Estimated unrealized loss, total position	$ 0.6	$ 0.7
Number of issues in loss position, less than 12 months \| shares	24	28
Number of issues in loss position, aggregate \| shares	24	33
Total impairments, value	$ 0.9	$ 5.8	$ 17.2
Total impairments, number of securitites \| shares	7	37	27

Investments, Net Realized Gains (Losses) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net realized gains (losses)
Net realized gains (losses) on investments	$ 7.4	$ 11.2	$ (10.7)
Change in unrealized gains (losses)
Change in unrealized gains (losses) on fixed maturity and equity securities	21.4	(14.0)	(35.9)
Debt Securities [Member]
Net realized gains (losses)
Gross gains from sales	4.7	1.9	0.5
Gross losses from sales	(2.2)	(0.7)	(0.4)
Net realized gains (losses) on investments	2.5	1.2	0.1
Change in unrealized gains (losses)
Change in unrealized gains (losses) on fixed maturity and equity securities	3.9	(28.9)	(22.2)
Equity Securities [Member]
Net realized gains (losses)
Gross gains from sales	9.3	16.6	8.1
Gross losses from sales	(4.4)	(6.6)	(18.9)
Net realized gains (losses) on investments	4.9	10.0	(10.8)
Change in unrealized gains (losses)
Change in unrealized gains (losses) on fixed maturity and equity securities	$ 17.5	$ 14.9	$ (13.7)

Net Investment Income (Details) - USD ($) $ in Millions	12 Months Ended
Net Investment Income (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Available-for-sale Securities	$ 2,677.7	$ 2,552.6
Investment income	78.0	76.3	$ 74.8
Investment expenses	(3.4)	(3.1)	(2.6)
Net investment income	74.6	73.2	72.2
Debt Securities [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income related to fixed maturity securities and short-term investments and cash equivalents	70.4	68.5	68.8
Equity Securities [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income related to equity securities	6.9	7.4	5.9
Short-term Investments [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income related to fixed maturity securities and short-term investments and cash equivalents	0.1	0.0	0.0
Cash and Cash Equivalents [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income related to fixed maturity securities and short-term investments and cash equivalents	$ 0.6	$ 0.4	$ 0.1

Property and Equipment Property and Equipment breakout (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property and Equipment [Line Items]
Property and equipment, gross		$ 59.9	$ 66.8
Accumulated depreciation, depletion and amortization, property and equipment		46.0	44.6
Property and equipment, net		13.9	22.2
Utilities operating expense, depreciation and amortization		7.9	8.2	$ 7.8
Payments to develop software		2.1	1.3
Asset impairment charges	$ 7.5	7.5
Furniture and equipment
Property and Equipment [Line Items]
Property and equipment, gross		1.7	2.3
Leasehold improvements
Property and Equipment [Line Items]
Property and equipment, gross		2.9	4.3
Computer and software
Property and Equipment [Line Items]
Property and equipment, gross		54.2	59.0
Automobiles
Property and Equipment [Line Items]
Property and equipment, gross		$ 1.1	$ 1.2

Income Taxes (Details) - USD ($)	3 Months Ended								12 Months Ended
Income Taxes (Details) - USD ($)	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statutory federal tax rate										35.00%
Current Income Tax Expense (Benefit), Continuing Operations [Abstract]
Current federal tax expense (benefit)										$ 17,900,000	$ 20,300,000	$ 9,500,000
Current state and local tax expense (benefit)										700,000	300,000	1,100,000
Current income tax expense (benefit)										18,600,000	20,600,000	10,600,000
Deferred Income Tax Expense (Benefit), Continuing Operations [Abstract]
Routine/other										17,200,000	13,400,000	(5,600,000)
Revaluation of deferred tax asset	$ 7,000,000									7,000,000	0	0
Deferred income tax expense (benefit)										24,200,000	13,400,000	(5,600,000)
Income tax expense	21,700,000	$ 7,000,000	$ 7,800,000	$ 6,300,000	$ 12,900,000	$ 7,800,000	$ 7,400,000	$ 5,900,000		42,800,000	34,000,000	5,000,000
Effective Income Tax Rate, Continuing Operations, Tax Rate Reconciliation [Abstract]
Expense computed at statutory rate										50,400,000	49,300,000	34,800,000
Dividends received deduction and tax-exempt interest										(7,600,000)	(8,500,000)	(8,600,000)
Pre-privatization reserve adjustment										0	0	(15,300,000)
LPT deferred gain amortization										(4,000,000)	(4,700,000)	(4,900,000)
LPT reserve adjustment										0	(1,100,000)	(2,200,000)
Stock based compensation										(3,400,000)	(1,600,000)	0
Revaluation of deferred tax asset	7,000,000									7,000,000	0	0
Income tax reconciliation, other										400,000	600,000	1,200,000
Downward adjustment of pre-privatization unpaid loss reserve										0	0	56,300,000
Net income	31,300,000	$ 21,900,000	$ 24,800,000	$ 23,200,000	35,500,000	$ 22,600,000	$ 26,800,000	$ 21,800,000		101,200,000	106,700,000	94,400,000
Unrecognized tax benefits	0				0					0	0
Income Taxes Paid, Net										21,300,000	13,700,000	12,700,000
Deferred Tax Liabilities [Abstract]
Unrealized capital gains, net	28,500,000				40,100,000					28,500,000	40,100,000
Deferred policy acquisition cost	9,700,000				15,700,000					9,700,000	15,700,000
Intangible assets	1,700,000				2,900,000					1,700,000	2,900,000
Other deferred tax liabilities	4,800,000				7,900,000					4,800,000	7,900,000
Total deferred tax liabilities	44,700,000				66,600,000					44,700,000	66,600,000
Deferred Tax Assets [Abstract]
Loss reserves discounting for tax reporting	29,000,000				51,700,000					29,000,000	51,700,000
Unearned premiums	12,800,000				20,900,000					12,800,000	20,900,000
Allowance for bad debt	2,100,000				3,400,000					2,100,000	3,400,000
Stock based compensation	2,500,000				4,400,000					2,500,000	4,400,000
Accrued liabilities	4,200,000				8,100,000					4,200,000	8,100,000
Minimum tax credit	20,000,000				27,800,000					20,000,000	27,800,000
Other deferred tax assets	2,800,000				9,700,000					2,800,000	9,700,000
Total deferred tax assets	73,400,000				126,000,000					73,400,000	126,000,000
Deferred income taxes, net	28,700,000				$ 59,400,000					28,700,000	59,400,000
Impact to the company's minimum tax credit due to tax enactment	$ 0									0
Change Due to Estimated Reserves Ceded Under the LPT Agreement [Member]
Effective Income Tax Rate, Continuing Operations, Tax Rate Reconciliation [Abstract]
Net income										0	3,100,000	6,400,000
Change to Contingent Profit Commission [Member]
Effective Income Tax Rate, Continuing Operations, Tax Rate Reconciliation [Abstract]
Net income										$ 300,000	$ 1,800,000	$ 2,600,000
Scenario, Forecast [Member]
Statutory federal tax rate									21.00%

Liability for Unpaid Losses and Loss Adjustment Expenses (Details) - USD ($)
$ in Millions

3 Months Ended

12 Months Ended

Dec. 31, 2017

Sep. 30, 2017

Jun. 30, 2017

Mar. 31, 2017

Dec. 31, 2016

Sep. 30, 2016

Jun. 30, 2016

Mar. 31, 2016

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2015

Prior year claims and claims adjustment expense Including LPT amortization and adj

$ (30.1)

$ (35.0)

$ (27.6)

Losses and loss adjustment expenses

$ 85.2

$ 116.9

$ 106.1

$ 109.0

$ 89.9

$ 109.0

$ 111.7

$ 107.3

417.2

417.9

429.4

Paid losses and LAE, including LPT amortization and adj related to prior periods

332.2

337.5

334.8

Payments for losses and loss adjustment expense including LPT amortization and adj

409.1

416.2

410.2

Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]

Unpaid losses and LAE, gross of reinsurance, at beginning of period

2,301.0

2,347.5

2,301.0

2,347.5

2,369.7

Loss reinsurance recoverable, excluding bad debt, on unpaid losses

580.0

628.2

580.0

628.2

669.5

Net unpaid losses and LAE at beginning of period

$ 1,721.0

$ 1,719.3

1,721.0

1,719.3

1,700.2

Losses and LAE, net of reinsurance, incurred in:

Current year

447.3

452.9

456.9

Prior years

(18.0)

(16.9)

(18.5)

^[1]

(18.4)

^[1]

(7.2)

^[1]

Total net losses and LAE incurred during the period

^[1]

428.8

434.5

449.7

Deduct payments for losses and LAE, net of reinsurance, related to:

Current year

76.9

78.7

75.4

Prior years

^[2]

343.8

354.1

355.2

Total net payments for losses and LAE during the period

^[2]

420.7

432.8

430.6

Ending unpaid losses and LAE, net of reinsurance

1,729.1

1,721.0

1,729.1

1,721.0

1,719.3

Loss reinsurance recoverable, excluding bad debt, on unpaid losses

537.0

580.0

537.0

580.0

628.2

Unpaid losses and LAE, gross of reinsurance, at end of period

2,266.1

2,301.0

2,266.1

2,301.0

2,347.5

Salvage and subrogation recoveries, value

$ 35.0

$ 28.1

35.0

28.1

Voluntary risk business

Losses and LAE, net of reinsurance, incurred in:

Prior years

(17.4)

(17.0)

(9.0)

Involuntary assigned risk business

Losses and LAE, net of reinsurance, incurred in:

Prior years

$ (1.1)

$ (1.4)

$ 1.8

[1]

[2]

Liability for Unpaid Losses and Loss Adjustment Expenses Historical Incurred Losses and LAE (Details)
$ in Millions

Dec. 31, 2017

USD ($)

Dec. 31, 2016

USD ($)

^[1]

Dec. 31, 2015

USD ($)

^[1]

Dec. 31, 2014

USD ($)

^[1]

Dec. 31, 2013

USD ($)

^[1]

Dec. 31, 2012

USD ($)

^[1]

Dec. 31, 2011

USD ($)

^[1]

Dec. 31, 2010

USD ($)

^[1]

Dec. 31, 2009

USD ($)

^[1]

Dec. 31, 2008

USD ($)

^[1]

Claims Development [Line Items]

Incurred losses and LAE, net of reinsurance

$ 3,717.4

Cumulative paid losses and LAE, net of reinsurance

2,447.3

Liabilities for unpaid losses and LAE, net of reinsurance

1,634.3

Accident years prior to 2007

Claims Development [Line Items]

Cumulative paid losses and LAE, net of reinsurance

364.2

Accident year 2007

Claims Development [Line Items]

Incurred losses and LAE, net of reinsurance

342.1

$ 341.4

$ 343.8

$ 336.9

$ 335.1

$ 329.5

$ 329.2

$ 317.8

$ 315.3

$ 315.9

IBNR

$ 15.4

Cumulative number of reported claims

28,088

Cumulative paid losses and LAE, net of reinsurance

$ 307.1

300.7

293.6

284.2

271.1

255.3

234.7

201.8

155.4

$ 71.1

Accident year 2008

Claims Development [Line Items]

Incurred losses and LAE, net of reinsurance

290.5

291.2

283.7

283.6

280.1

279.0

266.9

255.4

IBNR

$ 13.5

Cumulative number of reported claims

22,673

Cumulative paid losses and LAE, net of reinsurance

$ 255.1

249.5

242.3

232.1

219.3

202.0

174.1

130.6

$ 59.0

Accident year 2009

Claims Development [Line Items]

Incurred losses and LAE, net of reinsurance

258.8

259.9

262.0

250.2

246.1

228.1

224.4

204.9

IBNR

$ 19.8

Cumulative number of reported claims

18,543

Cumulative paid losses and LAE, net of reinsurance

$ 221.3

215.4

206.2

190.7

171.7

143.8

105.6

$ 47.1

Accident year 2010

Claims Development [Line Items]

Incurred losses and LAE, net of reinsurance

288.8

292.6

296.3

277.4

272.0

267.3

253.7

IBNR

$ 27.5

Cumulative number of reported claims

19,571

Cumulative paid losses and LAE, net of reinsurance

$ 238.2

230.1

217.5

193.8

162.6

115.1

$ 47.4

Accident year 2011

Claims Development [Line Items]

Incurred losses and LAE, net of reinsurance

382.8

388.2

386.4

360.9

359.9

348.8

IBNR

$ 50.7

Cumulative number of reported claims

25,972

Cumulative paid losses and LAE, net of reinsurance

$ 305.0

289.9

261.4

214.2

148.3

$ 58.6

Accident year 2012

Claims Development [Line Items]

Incurred losses and LAE, net of reinsurance

468.9

472.6

478.6

460.6

452.6

IBNR

$ 73.6

Cumulative number of reported claims

28,816

Cumulative paid losses and LAE, net of reinsurance

$ 346.1

317.4

263.8

184.4

$ 68.5

Accident year 2013

Claims Development [Line Items]

Incurred losses and LAE, net of reinsurance

434.6

432.9

445.8

463.4

IBNR

$ 86.1

Cumulative number of reported claims

28,449

Cumulative paid losses and LAE, net of reinsurance

$ 297.2

248.9

172.7

$ 65.3

Accident year 2014

Claims Development [Line Items]

Incurred losses and LAE, net of reinsurance

423.9

425.8

422.2

IBNR

$ 98.7

Cumulative number of reported claims

26,993

Cumulative paid losses and LAE, net of reinsurance

$ 246.9

174.5

$ 65.5

Accident year 2015

Claims Development [Line Items]

Incurred losses and LAE, net of reinsurance

414.6

419.0

IBNR

$ 140.8

Cumulative number of reported claims

25,305

Cumulative paid losses and LAE, net of reinsurance

$ 166.8

$ 65.6

Accident year 2016

Claims Development [Line Items]

Incurred losses and LAE, net of reinsurance

412.4

IBNR

$ 244.6

Cumulative number of reported claims

21,214

Cumulative paid losses and LAE, net of reinsurance

$ 63.5

[1]	Data presented for these calendar years is required supplementary information, which is unaudite

Liability for Unpaid Losses and Loss Adjustment Expenses Reconciliation of Claims Development to Aggregate Carrying Amount of the Liability for Unpaid Losses and LAE (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Liabilities for unpaid losses and LAE, net of reinsurance	$ 1,634.3
Reinsurance recoverable on unpaid losses	537.0	$ 580.0	$ 628.2	$ 669.5
Unallocated LAE	94.8
Unpaid losses and loss adjustment expenses	$ 2,266.1	$ 2,301.0	$ 2,347.5	$ 2,369.7

Liability for Unpaid Losses and Loss Adjustment Expenses Short Duration Insurance Contracts, Historcial Claims Duration (Details)	Dec. 31, 2017
Average annual percentage payout of incurred claims by age, net of reinsurance
Year one	16.70%
Year two	24.30%
Year three	16.10%
Year four	10.80%
Year five	6.90%
Year six	4.70%
Year seven	3.40%
Year eight	2.50%
Year nine	2.00%
Year ten	1.90%

Reinsurance Reinsurance Premium Note (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Premiums Written, Net
Direct premiums, written	$ 719.5	$ 691.0	$ 684.9
Assumed premiums written	10.2	10.4	12.8
Gross premiums, written	729.7	701.4	697.7
Ceded premiums written	(6.0)	(6.8)	(8.4)
Premiums written, net	723.7	694.6	689.3
Premiums Earned, Net
Direct premiums earned	712.5	691.0	686.0
Assumed premiums earned	10.0	10.6	12.8
Gross premiums, earned	722.5	701.6	698.8
Ceded premiums earned	(6.0)	(6.8)	(8.4)
Premiums earned, net	716.5	694.8	690.4
Ceded losses and LAE incurred	$ (0.5)	$ 0.1	$ 10.1

Reinsurance Excess of Loss (Details) - USD ($) $ in Millions	12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2016
Effects of Reinsurance [Line Items]
Retention amount on a per occurrence basis		$ 10.0	$ 7.0
Excess of retention amount on a per occurrence basis		$ 190.0	$ 193.0
Scenario, Forecast [Member]
Effects of Reinsurance [Line Items]
Retention amount on a per occurrence basis	$ 10.0
Maximum reinsurance for losses from single occurence or event	$ 200.0

Reinsurance LPT Agreement (Details) - USD ($)
$ in Thousands

12 Months Ended

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2015

Reinsurance Agreement [Line Items]

Available-for-sale Securities

$ 2,677,700

$ 2,552,600

Unpaid losses

537,000

580,000

Recoverables was related to the LPT agreement

$ 438,900

465,500

Reinsurance quota share, percentage

100.00%

LPT collateral held in trust account

$ 380,800

355,700

Ceded premiums written

6,000

6,800

$ 8,400

Coverage provided under LPT agreement

2,000,000

Paid losses and LAE claims related to LPT

749,300

Amortization of deferred gain

11,300

11,700

11,400

LPT Agreement [Member]

Reinsurance Agreement [Line Items]

Liabilities for the incurred but unpaid losses and LAE related to claims prior to July 1, 1995

1,500,000

Ceded premiums written

775,000

Change Due to Estimated Reserves Ceded Under the LPT Agreement [Member]

Reinsurance Agreement [Line Items]

Amortization of deferred gain

^[1]

3,100

6,400

Change to Contingent Profit Commission [Member]

Reinsurance Agreement [Line Items]

Amortization of deferred gain

^[2]

$ 300

$ 1,800

$ 2,600

[1]	The cumulative adjustments to the Deferred Gain were also recognized in losses and LAE incurred in the Company's Consolidated Statements of Comprehensive Income, so that the Deferred Gain reflects the balance that would have existed had the revised loss and LAE reserves been recognized at the inception of the LPT Agreement.
[2]	The cumulative adjustments to the Deferred Gain were also recognized in losses and LAE incurred in the Company's Consolidated Statements of Comprehensive Income, so that the Deferred Gain reflects the balance that would have existed had the revised loss and LAE reserves been recognized at the inception of the LPT Agreement.

Notes Payable Outstanding (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Debt Instrument [Line Items]
Notes payable		$ 20,000	$ 32,000
Redemption of notes payable		9,900	0	$ 60,000
Gain on redemption of notes payable	$ 2,100	2,100	0	0
Dekania Surplus Note [Member]
Debt Instrument [Line Items]
Notes payable		$ 10,000	10,000
Notes payable, maturity date		Apr. 30, 2034
Notes payable, callable		2009
Interest rate, basis points in excess of the 90-day LIBOR		425
Cash paid for interest		$ 600	500	500
Accrued interest		100	100
ICONS Surpuls Note [Member]
Debt Instrument [Line Items]
Notes payable	$ 12,000	0	12,000
Redemption of notes payable		9,900
Gain on redemption of notes payable		2,100
Cash paid for interest		300	600	600
Accrued interest			100
Alesco Surplus Note [Member]
Debt Instrument [Line Items]
Notes payable		$ 10,000	$ 10,000
Notes payable, maturity date			Dec. 15, 2034
Notes payable, callable		2009
Interest rate, basis points in excess of the 90-day LIBOR		405
Cash paid for interest		$ 500	$ 500	400
Accrued interest		$ 100	$ 100
Line of Credit [Member]
Debt Instrument [Line Items]
Notes payable					$ 60,000	$ 70,000	$ 80,000	$ 90,000	$ 100,000
Line of credit, percentage above prime rate		1.75%
Line of credit, percentage above LIBOR rate		1.75%
Cash paid for interest				1,300
Line of credit facility, decrease, repayments				$ 60,000

Notes Payable Principal payment obligations on notes payable outstanding (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Schedule of Capitalization, Long-term Debt [Line Items]
Repayments of principal in next twelve months	$ 0.0
Repayments of principal in year two	0.0
Repayments of principal in year three	0.0
Repayments of principal in year four	0.0
Repayments of principal in year five	0.0
Repayments of principal after year five	20.0
Notes payable	$ 20.0	$ 32.0

Commitments and Contingencies Future Lease Payments (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Commitments and Contingencies [Abstract]
Remaining lease terms expire over the next	10 years
Future lease payments for non-cancelable operating and capital leases, in years	5 years
Operating Leases, Future Minimum Payments Due [Abstract]
Operating leases, future minimum payments due, current	$ 4.8
Operating leases, future minimum payments, due in two years	4.8
Operating leases, future minimum payments, due in three years	4.2
Operating leases, future minimum payments, due in four years	2.8
Operating leases, future minimum payments, due in five years	1.8
Operating leases, future minimum payments, due thereafter	7.9
Operating leases, future minimum payments due	26.3
Capital Leases, Future Minimum Payments Due [Abstract]
Capital leases, future minimum payments due, current	0.3
Capital leases, future minimum payments due in two years	0.3
Capital leases, future minimum payments due in three years	0.2
Capital leases, future minimum payments due in four years	0.2
Capital leases, future minimum payments due in five years	0.1
Capital leases, Future minimum payments due thereafter	0.0
Capital leases, future minimum payments due	1.1
Future interest charges included in capital lease payments	0.1
Facilities rent expense	$ 4.8	$ 4.9	$ 4.9

Commitments and Contingencies Property held under capital leases is included in property and equipment (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Property held under capital leases
Accumulated depreciation, depletion and amortization, property and equipment	$ (46.0)	$ (44.6)
Automobiles
Property held under capital leases
Property held under captial leases	1.1	1.2
Assets Held under Capital Leases [Member]
Property held under capital leases
Property held under captial leases	1.1	1.2
Accumulated depreciation, depletion and amortization, property and equipment	(0.3)	(0.6)
Total property held under capital leases	$ 0.8	$ 0.6

Commitments and Contingencies Contingencies Surrounding Insurance Assessments (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Loss Contingencies [Line Items]
Amount of Insurance-related assessment liability	$ 12.4	$ 18.6
Payment period for assessment liability based on individual states regulations	one to eighty year periods
Other assets, prepaid policy surcharges	$ 14.1	$ 21.6
Expected realization period for assets related to policy surcharges	one to ten year periods

Stockholders' Equity (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended	24 Months Ended	132 Months Ended
	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2017	Feb. 16, 2016
Accelerated Share Repurchases [Line Items]
Stock Repurchase Program, Authorized Amount				$ 50.0
Stock repurchased during period, shares	0	724,381	24,097,355
Accelerated share repurchases, final price paid per share		$ 29.08	$ 15.92
Stock Repurchased During Period, Value		$ 21.1

Stock-Based Compensation Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum number of shares reserved for grants	5,500,000
Grant date fair value adjustment	$ (0.2)
Stock-based compensation expense [Abstract]
Stock-based compensation expense	6.8	$ 5.8	$ 4.6
Less: related tax benefit	2.4	2.0	1.6
Net stock-based compensation expense	4.4	3.8	3.0
Stock Option [Member]
Stock-based compensation expense [Abstract]
Stock-based compensation expense	0.5	0.7	1.0
Restricted stock units (RSUs)
Stock-based compensation expense [Abstract]
Stock-based compensation expense	2.0	1.9	2.0
Performance shares units [Member]
Stock-based compensation expense [Abstract]
Stock-based compensation expense	4.3	$ 3.2	$ 1.6
Retained Earnings
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grant date fair value adjustment	$ 1.3

Stock-Based Compensation Fair Market Value of Stock Options Granted, Calculated (Details) - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Fair Market Value of Stock Options Granted, Calculated [Abstract]
Expected volatility	38.00%	38.00%
Expected life (in years)	4 years 274 days	4 years 274 days
Dividend yield	1.30%	1.00%
Risk free interest rate	1.40%	1.60%
Weighted average grant date fair value	$ 8.46	$ 7.63

Stock-Based Compensation Changes in Outstanding Stock Options (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average grant date fair value		$ 8.46	$ 7.63
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of outstanding options or share units	247,347	564,096	1,121,545	1,521,290
Number of options or share units, granted	0	67,431	80,800
Stock-options exercised, shares	(307,076)	(586,132)	(463,466)
Number of options or share units, expired		(6,075)
Number of options or share units, forfeited	(9,673)	(32,673)	(17,079)
Number of exercisable options or share units	156,517
Weighted average exercise price, grants		$ 27.72	$ 24.20
Weighted average exercise price, exercises	$ 19.44	16.39	16.43
Weighted average exercise price, expirations		22.48
Weighted average exercise price, forfeitures	24.45	24.35	20.21
Weighted average exercise price, outstanding	22.90	$ 21.04	$ 18.31	$ 17.45
Weighted average exercisable price	$ 21.71
Weighted average remaining contractual life	3 years 150 days	3 years 125 days	2 years 300 days	2 years 324 days
Share-based compensation expense, deferred	$ 0.5
Share-based compensation expense, Period for Recognition	27 months
Options vested, fair value	$ 0.6	$ 0.8	$ 1.3
Options outstanding, intrinsic value	5.3	10.6	10.1
Options exercisable, intrinsic value	3.6	7.6	8.5
Options exercised, intrinsic value	$ 7.6	$ 7.6	$ 4.0
Stock Options Granted [Domain]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average remaining contractual life		6 years 73 days	6 years 73 days
Stock Options Exercisable [Domain]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average remaining contractual life	2 years 300 days
Restricted stock units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Service vesting period for options awarded	4 years
Vesting rights for options awarded	vest 25% on or after each of the subsequent four anniversaries of such date
Number of outstanding options or share units	327,072	324,384	319,033	306,867
Number of options or share units, granted	87,276	100,218	112,048
Number of options or share units, forfeited	(13,711)	(21,872)	(7,749)
Number of vested options or share units	(70,877)	(72,995)	(92,133)
Weighted average exercise price, grants	$ 37.94	$ 28.20	$ 24.19
Weighted average exercise price, forfeitures	29.28	24.87	20.99
Weighted average exercise price, vested	24.97	21.56	19.74
Weighted average grant date fair value	$ 25.85	$ 22.55	$ 20.71	$ 19.15
Share-based compensation expense, deferred	$ 4.2
Share-based compensation expense, Period for Recognition	39 months
Options vested, fair value	$ 1.8	$ 1.6	$ 1.7
Options outstanding, intrinsic value	14.5	12.8	8.7
Options exercisable, intrinsic value	$ 2.8	$ 2.1	$ 2.2
Restricted Stock Units Vested but Unsettled [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of outstanding options or share units	152,644
Weighted average grant date fair value	$ 19.54

Stock-Based Compensation Performance Share Awards (Details) - USD ($)
$ / shares in Units, $ in Millions

12 Months Ended

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2015

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Performance share awards, minimum payout

0.00%

Performane share awards, maximum payout

200.00%

Performance share awards, expected target

127.00%

200.00%

Performance share awards, ultimate payout

200.00%

Performance shares units [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Number of outstanding options or share units

97,440

^[1]

97,236

^[1]

110,000

Share-based compensation options, exercise price on grant date

$ 37.60

^[1]

$ 27.72

^[1]

$ 24.20

Fair value of awards awarded on grant date

$ 3.7

^[1]

$ 2.7

^[1]

$ 2.7

Share-based compensation expense, deferred

$ 4.7

Share-based compensation expense, Period for Recognition

24 months

[1]

Statutory Matters Statutory Matters (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2018	Aug. 09, 2018	Aug. 08, 2018
Statutory Accounting Practices [Line Items]
Capital stock and unassigned surplus	$ 510.6	$ 447.1
Paid in capital	349.8	349.8
Surplus notes	32.0	32.0
Total statutory surplus	892.4	828.9
SAP, net income amount	116.8	101.4	$ 87.8
Total stockholders’ equity	$ 947.7	$ 840.6
Will maintain a risk based capital (RBC) level of at least	350.00%
EICN
Statutory Accounting Practices [Line Items]
Capital stock and unassigned surplus	$ 196.7
Extraordinary dividends, approves or does not disapprove the payment within	30 days
Percentage of surplus of EICN's statutory surplus as regards to policyholders	10.00%
Dividends paid, without approval of regulatory agency	$ 0.0
EICN \| Scenario, Forecast [Member]
Statutory Accounting Practices [Line Items]
Maximum dividends that may be paid without prior approval				$ 19.9
EPIC
Statutory Accounting Practices [Line Items]
Percentage of surplus used to calculate the lesser of 10% of surplus or net income, not including realized capital gains, plus a 2-year carry forward.	10.00%
Percentage of surplus used to calculate 10% of surplus, with dividends payable limited to unassigned funds minus 25% of unrealized capital gains	10.00%
Percentage of surplus used to calculate the lesser of 10% of surplus or net investment income plus a 3-year carry forward with dividends payable limited to unassigned funds minus 25% of unrealized capital gains	10.00%
Percentage of unassigned gains used to calculate 10% of surplus, with dividends payable limited to unassigned funds minus 25% of unrealized capital gains	25.00%
Percentage of unassigned gains used to calculate the lesser of 10% of surplus or net investment income plus a 3-year carry forward with dividends payable limited to unassigned funds minus 25% of unrealized capital gains	25.00%
Dividends paid, without approval of regulatory agency	$ 0.0
EPIC \| Scenario, Forecast [Member]
Statutory Accounting Practices [Line Items]
Maximum dividends that may be paid without prior approval				15.9
EAC
Statutory Accounting Practices [Line Items]
Dividends paid, without approval of regulatory agency	$ 0.0
EAC \| Scenario, Forecast [Member]
Statutory Accounting Practices [Line Items]
Maximum dividends that may be paid without prior approval				$ 19.0
ECIC
Statutory Accounting Practices [Line Items]
ECIC must initiate discussions of its business plan with the California DOI if its premium to policyholder surplus ratio exceeds	1.5 to 1
ECIC will not exceed a ratio of premium to policyholder surplus of	2 to 1
If at any time ECIC's policyholder surplus decreases to	80.00%
Dividends paid, without approval of regulatory agency	$ 38.0
ECIC \| Scenario, Forecast [Member]
Statutory Accounting Practices [Line Items]
Maximum dividends that may be paid without prior approval					$ 48.4	$ 10.4
EAC and EPIC
Statutory Accounting Practices [Line Items]
Total statutory surplus	$ 4.0
Florida statute section 624.408 requires EPIC and EAC to maintain minimum capital and surplus of the greater of $4.0 million or 10% of total liabilities.	10.00%
Used to calculate ratio of written premium to surplus	1.25
Net gross premiums to surplus ratio. Florida statute section 624.4095 requires net gross premiums times 1.25 not exceed this ratio.	10-to-1
Net written premiums to surplus ratio. Florida statute section 624.4095 requires net written premiums times 1.25 not exceed this ratio.	4-to-1

Accumulated Other Comprehensive Income, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Net unrealized gain on investments, before taxes	$ 136,000	$ 114,600
Deferred tax expense	(28,600)	(40,100)
Total accumulated other comprehensive income, net	$ 107,400	$ 74,500

Employee Benefit and Retirement Plans Employee Benefit and Retirement Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Employee Benefit and Retirement Plans [Abstract]
Safe habor matching, 100%	100.00%
Employee contributions, 100% match, percentage	3.00%
Safe harbor matching 50%	50.00%
Employee contributions 50% match, percentage		3.00%
Employee contributions, maximum match, percentage		5.00%
Company's contributions to Employers 401(k)	$ 1.9	$ 1.9	$ 1.8

Earnings Per Share Earnings Per Share (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share, Basic and Diluted, by Common Class [Line Items]
Net income	$ 31.3	$ 21.9	$ 24.8	$ 23.2	$ 35.5	$ 22.6	$ 26.8	$ 21.8	$ 101.2	$ 106.7	$ 94.4
Weighted average number of shares outstanding - basic									32,501,576	32,434,580	32,070,911
Effect of diluted securities:									559,184	542,255	490,542
Weighted average number of shares outstanding - diluted									33,060,760	32,976,835	32,561,453
Employee Stock Option [Member]
Earnings Per Share, Basic and Diluted, by Common Class [Line Items]
Effect of diluted securities:									208,602	246,562	286,764
Performance shares units [Member]
Earnings Per Share, Basic and Diluted, by Common Class [Line Items]
Effect of diluted securities:									271,738	222,594	155,768
Restricted stock units (RSUs)
Earnings Per Share, Basic and Diluted, by Common Class [Line Items]
Effect of diluted securities:									78,844	73,099	48,010

Earnings Per Share Antidilutive Securities (Details) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of EPS	0	89,221	257,405
Employee Stock Option [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of EPS	0	0	20,200

Selected Quarterly Financial Data Selected Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Condensed Financial Statements, Captions [Line Items]
Net premiums earned	$ 181.6	$ 187.9	$ 171.7	$ 175.3	$ 172.0	$ 173.3	$ 176.9	$ 172.6	$ 716.5	$ 694.8	$ 690.4
Net realized gains (losses) on investments	0.0	4.1	1.1	2.2	2.1	1.6	6.0	1.5	7.4	11.2	(10.7)
Losses and loss adjustment expenses	85.2	116.9	106.1	109.0	89.9	109.0	111.7	107.3	417.2	417.9	429.4
Commission expense	24.7	23.7	21.5	21.5	20.0	21.3	21.9	20.3	91.4	83.5	85.4
Underwriting and other operating expenses	37.8	33.6	32.6	35.9	34.5	31.7	33.6	36.3	139.9	136.1	135.2
Other expenses	0.0	7.5	0.0	0.0					7.5	0.0	0.0
Income tax expense	21.7	7.0	7.8	6.3	12.9	7.8	7.4	5.9	42.8	34.0	5.0
Net income	$ 31.3	$ 21.9	$ 24.8	$ 23.2	$ 35.5	$ 22.6	$ 26.8	$ 21.8	$ 101.2	$ 106.7	$ 94.4
Earnings per common share (Note 18):
Basic	$ 0.96	$ 0.67	$ 0.76	$ 0.72	$ 1.10	$ 0.70	$ 0.82	$ 0.67	$ 3.11	$ 3.29	$ 2.94
Diluted	$ 0.94	$ 0.66	$ 0.75	$ 0.70	$ 1.08	$ 0.69	$ 0.81	$ 0.66	$ 3.06	$ 3.24	$ 2.90

Selected Quarterly Financial Data Significant Quarterly Adjustments (Details) - USD ($)
$ in Thousands

3 Months Ended

12 Months Ended

Dec. 31, 2017

Sep. 30, 2017

Jun. 30, 2017

Dec. 31, 2016

Jun. 30, 2016

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2015

Gain on redemption of notes payable

$ 2,100

$ 0

Notes payable

$ 20,000

$ 32,000

20,000

32,000

Asset impairment charges

$ 7,500

7,500

Prior years

(18,000)

(16,900)

(18,500)

^[1]

(18,400)

^[1]

(7,200)

^[1]

Reduction in Current Accident Year Losses and LAE Due Provision Rate

10,600

Revaluation of deferred tax asset

7,000

Losses and loss adjustment expense primarily due to four large losses

$ 6,500

ICONS Surpuls Note [Member]

Gain on redemption of notes payable

2,100

Notes payable

$ 0

$ 12,000

12,000

Voluntary risk business

Prior years

(17,400)

(17,000)

(9,000)

Involuntary assigned risk business

Prior years

$ (1,100)

$ (1,400)

$ 1,800

[1]

Schedule II. Condensed Financial Information of Registrant (Condensed Balance Sheets) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Investments
Fixed maturity securities at fair value (amortized cost $40.2 in 2017 and $14.7 in 2016)	$ 2,677,700	$ 2,552,600
Short-term investments at fair value (amortized cost $3.7 at December 31, 2017)	4,000	16,000
Total investments	2,677,700	2,552,600
Cash and cash equivalents	73,300	67,200	$ 56,600	$ 103,600
Accrued investment income	19,600	20,600
Deferred income taxes, net	28,700	59,400
Other assets	33,700	34,600
Total assets	3,840,100	3,773,400
Liabilities and stockholders’ equity
Accounts payable and accrued expenses	23,700	24,200
Total liabilities	2,892,400	2,932,800
Stockholders’ equity:
Common stock, $0.01 par value; 150,000,000 shares authorized; 56,695,174 and 56,226,277 shares issued and 32,597,819 and 32,128,922 shares outstanding at December 31, 2017 and 2016, respectively	600	600
Preferred stock, $0.01 par value; 25,000,000 shares authorized; none issued	0	0
Additional paid-in capital	381,200	372,000
Retained earnings	842,200	777,200
Accumulated other comprehensive income, net of tax	107,400	74,500
Treasury stock, at cost (24,097,355 shares at December 31, 2017 and December 31, 2016)	(383,700)	(383,700)
Total stockholders’ equity	947,700	840,600
Total liabilities and stockholders’ equity	3,840,100	3,773,400
Parent Company [Member]
Investments
Investment in subsidiaries	849,600	757,500
Fixed maturity securities at fair value (amortized cost $40.2 in 2017 and $14.7 in 2016)	41,400	16,000
Short-term investments at fair value (amortized cost $3.7 at December 31, 2017)	3,700	0
Total investments	894,700	773,500
Cash and cash equivalents	39,600	41,400	$ 1,400	$ 10,900
Accrued investment income	300	300
Federal income taxes recoverable	4,200	9,600
Deferred income taxes, net	14,500	20,000
Other assets	800	700
Total assets	954,100	845,500
Liabilities and stockholders’ equity
Accounts payable and accrued expenses	4,500	4,800
Intercompany payable	1,900	100
Total liabilities	6,400	4,900
Stockholders’ equity:
Common stock, $0.01 par value; 150,000,000 shares authorized; 56,695,174 and 56,226,277 shares issued and 32,597,819 and 32,128,922 shares outstanding at December 31, 2017 and 2016, respectively	600	600
Preferred stock, $0.01 par value; 25,000,000 shares authorized; none issued	0	0
Additional paid-in capital	381,200	372,000
Retained earnings	842,200	777,200
Accumulated other comprehensive income, net of tax	107,400	74,500
Treasury stock, at cost (24,097,355 shares at December 31, 2017 and December 31, 2016)	(383,700)	(383,700)
Total stockholders’ equity	947,700	840,600
Total liabilities and stockholders’ equity	$ 954,100	$ 845,500

Schedule II. Condensed Financial Information of Registrant (Condensed Statements of Income) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues
Net investment income									$ 74.6	$ 73.2	$ 72.2
Net realized gains on investments	$ 0.0	$ 4.1	$ 1.1	$ 2.2	$ 2.1	$ 1.6	$ 6.0	$ 1.5	7.4	11.2	(10.7)
Total revenues									801.4	779.8	752.1
Expenses
Other operating expenses	0.0	7.5	0.0	0.0					7.5	0.0	0.0
Interest expense									1.4	1.6	2.7
Total expenses									657.4	639.1	652.7
Income tax expense	21.7	7.0	7.8	6.3	12.9	7.8	7.4	5.9	42.8	34.0	5.0
Net income	$ 31.3	$ 21.9	$ 24.8	$ 23.2	$ 35.5	$ 22.6	$ 26.8	$ 21.8	$ 101.2	$ 106.7	$ 94.4
Earnings per common share for the stated periods (Note 18):
Basic	$ 0.96	$ 0.67	$ 0.76	$ 0.72	$ 1.10	$ 0.70	$ 0.82	$ 0.67	$ 3.11	$ 3.29	$ 2.94
Diluted	$ 0.94	$ 0.66	$ 0.75	$ 0.70	$ 1.08	$ 0.69	$ 0.81	$ 0.66	3.06	3.24	2.90
Cash dividends declared per common share									$ 0.60	$ 0.36	$ 0.24
Parent Company [Member]
Revenues
Net investment income									$ 1.3	$ 1.9	$ 4.0
Net realized gains on investments									0.0	8.0	2.4
Total revenues									1.3	9.9	6.4
Expenses
Other operating expenses									15.2	13.8	13.8
Interest expense									0.0	0.0	1.1
Total expenses									15.2	13.8	14.9
Income (loss) before income taxes and equity in earnings of subsidiaries									(13.9)	(3.9)	(8.5)
Income tax expense									(5.8)	(3.5)	(3.3)
Net income (loss) before equity in earnings of subsidiaries									(8.1)	(0.4)	(5.2)
Equity in earnings of subsidiary									109.3	107.1	99.6
Net income									$ 101.2	$ 106.7	$ 94.4
Earnings per common share for the stated periods (Note 18):
Basic									$ 3.11	$ 3.29	$ 2.94
Diluted									$ 3.06	$ 3.24	$ 2.90

Schedule II. Condensed Financial Information of Registrant (Condensed Balance Sheets Parenthetical) (Details) - USD ($) $ / shares in Units, $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Fixed maturity securities, amortized cost	$ 2,541.7	$ 2,438.0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	150,000,000	150,000,000
Common stock, shares issued (in shares)	56,695,174	56,226,277
Common stock, shares outstanding (in shares)	32,597,819	32,128,922
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	25,000,000	25,000,000
Preferred stock, shares issued (in shares)	0	0
Treasury stock, at cost (in shares)	24,097,355	24,097,355
Parent Company [Member]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	150,000,000	150,000,000
Common stock, shares issued (in shares)	56,226,277	55,589,454
Common stock, shares outstanding (in shares)	32,128,922	32,216,480
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	25,000,000	25,000,000
Preferred stock, shares issued (in shares)	0	0
Treasury stock, at cost (in shares)	24,097,355	23,372,974
Debt Securities [Member]
Fixed maturity securities, amortized cost	$ 2,421.0	$ 2,305.9
Debt Securities [Member] \| Parent Company [Member]
Fixed maturity securities, amortized cost	14.7	40.2
Equity Securities [Member]
Fixed maturity securities, amortized cost	116.7	116.1
Equity Securities [Member] \| Parent Company [Member]
Fixed maturity securities, amortized cost	$ 0.0	$ 46.0

Schedule II. Condensed Financial Information of Registrant (Condensed Statements of Cash Flows) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating activities
Net income	$ 31.3	$ 21.9	$ 24.8	$ 23.2	$ 35.5	$ 22.6	$ 26.8	$ 21.8	$ 101.2	$ 106.7	$ 94.4
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Realized gains on investments									(7.4)	(11.2)	10.7
Stock-based compensation									6.8	5.8	4.6
Excess Tax Benefit from Share-based Compensation, Operating Activities									0.0	0.0	1.2
Amortization of premium on investments, net									14.3	14.6	12.8
Deferred income tax expense									24.2	13.4	(5.6)
Change in operating assets and liabilities:
Accounts payable, accrued expenses and other liabilities									(7.0)	(4.2)	8.6
Federal income taxes									(2.7)	7.7	(3.9)
Other									15.3	(0.5)	(6.9)
Net cash provided by operating activities									142.3	122.8	116.4
Investing activities
Purchases of fixed maturity securities									(592.3)	(466.8)	(476.9)
Purchase of equity securities									(36.8)	(49.1)	(85.1)
Purchases of short-term investments									(8.2)	(10.0)	0.0
Proceeds from sale of fixed maturity securities									249.8	132.4	105.4
Proceeds from maturities and redemptions of fixed maturity securities									215.7	230.6	323.9
Proceeds from sale of equity securities									41.2	80.4	34.7
Capital Contributions to subsidiary									(5.6)	(8.0)	0.0
Restricted cash used in investing activities									2.6	(1.1)	8.3
Net cash provided by investing activities									(110.2)	(88.6)	(101.2)
Financing activities
Acquisition of common stock									0.0	(21.1)	0.0
Cash transactions related to stock-based compensation									3.8	9.0	4.8
Dividends paid to stockholders									(19.7)	(11.5)	(7.7)
Excess tax benefits from stock-based compensation									0.0	0.0	1.2
Net cash used in financing activities									(26.0)	(23.6)	(62.2)
Net increase (decrease) in cash and cash equivalents									6.1	10.6	(47.0)
Cash and cash equivalents at the beginning of the period				67.2				56.6	67.2	56.6	103.6
Cash and cash equivalents at the end of the period	73.3				67.2				73.3	67.2	56.6
Parent Company [Member]
Operating activities
Net income									101.2	106.7	94.4
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Equity in net income of subsidiaries									71.5	107.1	99.6
Realized gains on investments									0.0	(8.0)	(2.4)
Stock-based compensation									6.8	5.8	4.6
Excess Tax Benefit from Share-based Compensation, Operating Activities									0.0	0.0	(1.2)
Amortization of premium on investments, net									0.1	0.4	0.9
Deferred income tax expense									5.3	2.9	(4.6)
Change in operating assets and liabilities:
Accounts payable, accrued expenses and other liabilities									(0.3)	(0.7)	1.7
Federal income taxes									5.4	(7.9)	4.9
Other assets									0.1	(0.8)	(0.4)
Intercompany payable/receivable									1.8	0.3	0.1
Other									0.0	0.4	(1.2)
Net cash provided by operating activities									48.7	(7.2)	0.4
Investing activities
Purchases of fixed maturity securities									(30.6)	(31.0)	(21.6)
Purchase of equity securities									0.0	(3.6)	(19.0)
Purchases of short-term investments									(7.9)	0.0	0.0
Proceeds from sale of fixed maturity securities									5.0	0.0	18.3
Proceeds from maturities and redemptions of fixed maturity securities									4.5	24.9	45.5
Proceeds from sale of equity securities									0.0	88.5	24.0
Restricted cash used in investing activities									0.0	0.0	4.6
Net cash provided by investing activities									(34.6)	70.8	51.8
Financing activities
Acquisition of common stock									0.0	(21.1)	0.0
Cash transactions related to stock-based compensation									3.8	9.0	4.8
Dividends paid to stockholders									(19.7)	(11.5)	(7.7)
Payments on notes payable and capital leases									0.0	0.0	(60.0)
Excess tax benefits from stock-based compensation									0.0	0.0	1.2
Net cash used in financing activities									(15.9)	(23.6)	(61.7)
Net increase (decrease) in cash and cash equivalents									(1.8)	40.0	(9.5)
Cash and cash equivalents at the beginning of the period				$ 41.4				$ 1.4	41.4	1.4	10.9
Cash and cash equivalents at the end of the period	$ 39.6				$ 41.4				$ 39.6	$ 41.4	$ 1.4

Consolidated Stockholders Equity (Parentheticals) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Stockholders Equity Parenthetical [Abstract]
Change in net unrealized gains on investments, net of tax of	$ 6.3	$ (4.9)	$ (12.6)

Basis of Presentation Pending Purchase of PRUS (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($)
Business Acquisition [Line Items]
Estimated statutory capital and surplus of pending acquisition	$ 40,000
Net cash payment to acquire business	$ 5,800

Fair Value of Financial Instruments, Fair Value Inputs (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	$ 2,677,700	$ 2,552,600
Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	2,463,400	2,344,400
Debt Securities [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	0	0
Debt Securities [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	2,463,400	2,337,400
Debt Securities [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	0	7,000
US Treasury Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	137,000	127,400
US Treasury Securities [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	0	0
US Treasury Securities [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	137,000	127,400
US Treasury Securities [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	0	0
US Government Agencies Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	11,800	12,800
US Government Agencies Debt Securities [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	0	0
US Government Agencies Debt Securities [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	11,800	12,800
US Government Agencies Debt Securities [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	0	0
US States and Political Subdivisions Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	642,500	851,600
US States and Political Subdivisions Debt Securities [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	0	0
US States and Political Subdivisions Debt Securities [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	642,500	851,600
US States and Political Subdivisions Debt Securities [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	0	0
Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	1,118,000	956,700
Corporate Debt Securities [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	0	0
Corporate Debt Securities [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	1,118,000	956,700
Corporate Debt Securities [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	0	0
Residential Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	389,300	258,000
Residential Mortgage Backed Securities [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	0	0
Residential Mortgage Backed Securities [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	389,300	258,000
Residential Mortgage Backed Securities [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	0	0
Commercial Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	106,000	95,500
Commercial Mortgage Backed Securities [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	0	0
Commercial Mortgage Backed Securities [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	106,000	95,500
Commercial Mortgage Backed Securities [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	0	0
Asset-backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	58,800	42,400
Asset-backed Securities [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	0	0
Asset-backed Securities [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	58,800	35,400
Asset-backed Securities [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	0	7,000
Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	210,300	192,200
Equity Securities [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	205,600	187,300
Equity Securities [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	0	0
Equity Securities [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	4,700	4,900
Industrial and miscellaneous
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	181,700	167,200
Industrial and miscellaneous \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	181,700	167,200
Industrial and miscellaneous \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	0	0
Industrial and miscellaneous \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	0	0
Federal home loan bank stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	4,700	4,900
Federal home loan bank stock \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	0	0
Federal home loan bank stock \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	0	0
Federal home loan bank stock \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	4,700	4,900
Other equities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	23,900	20,100
Other equities \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	23,900	20,100
Other equities \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	0	0
Other equities \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	0	0
Short-term Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	4,000	16,000
Short-term Investments [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	0	0
Short-term Investments [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	4,000	16,000
Short-term Investments [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	$ 0	$ 0