Document and Entity Information - shares	3 Months Ended
Document and Entity Information - shares	Mar. 31, 2018	Apr. 19, 2018
Document and Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2018
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		32,758,139
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	Q1

Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Investments:
Fixed maturity securities at fair value (amortized cost $2,437.3 at March 31, 2018 and $2,421.0 at December 31, 2017)	$ 2,434,800	$ 2,463,400
Equity securities at fair value (cost $113.3 at March 31, 2018)	194,000
Equity securities, AFS, at fair value (cost $116.7 at December 31, 2017)		210,300
Equity securities at cost	4,700	0
Short-term investments at fair value (amortized cost $34.9 at March 31, 2018 and $4.0 at December 31, 2017)	34,900	4,000
Total investments	2,668,400	2,677,700
Cash and cash equivalents	56,300	73,300
Restricted cash and cash equivalents	900	1,000
Accrued investment income	18,900	19,600
Premiums receivable (less bad debt allowance of $10.0 at March 31, 2018 and December 31, 2017)	350,000	326,700
Reinsurance recoverable for:
Paid losses	6,900	7,200
Unpaid losses	531,100	537,000
Deferred policy acquisition costs	50,800	45,800
Deferred income taxes, net	26,500	28,700
Property and equipment, net	14,800	13,900
Intangible assets, net	7,800	7,900
Goodwill	36,200	36,200
Contingent commission receivable—LPT Agreement	31,400	31,400
Other assets	47,900	33,700
Total assets	3,847,900	3,840,100
Claims and policy liabilities:
Claims and policy liabilities:	2,258,100	2,266,100
Unearned premiums	351,900	318,300
Total claims and policy liabilities	2,610,000	2,584,400
Commissions and premium taxes payable	55,800	55,300
Accounts payable and accrued expenses	21,600	23,700
Deferred reinsurance gain—LPT Agreement	161,000	163,600
Notes payable	20,000	20,000
Other liabilities	49,200	45,400
Total liabilities	2,917,600	2,892,400
Commitments and contingencies
Stockholders’ equity:
Common stock, $0.01 par value; 150,000,000 shares authorized; 56,849,494 and 56,695,174 shares issued and 32,752,139 and 32,597,819 shares outstanding at March 31, 2018 and December 31, 2017, respectively	600	600
Preferred stock, $0.01 par value; 25,000,000 shares authorized; none issued	0	0
Additional paid-in capital	380,400	381,200
Retained earnings	935,000	842,200
Accumulated other comprehensive (loss) income, net of tax	(2,000)	107,400
Treasury stock, at cost (24,097,355 shares at March 31, 2018 and December 31, 2017)	(383,700)	(383,700)
Total liabilities and stockholders’ equity	930,300	947,700
Total liabilities and stockholders’ equity	$ 3,847,900	$ 3,840,100

Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Available for sale:
Amortized cost	$ 2,472,200	$ 2,541,700
Equity securities at fair value, cost	113,300
Available for sale, short-term investments, at amortized cost	34,900	4,000
Premiums receivable, bad debt allowance	10,000	10,000
Reinsurance Recoverables on Unpaid Losses, Allowance	$ 0	$ 0
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)	56,849,494	56,695,174
Common stock, shares outstanding (in shares)	32,752,139	32,597,819
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]
Available for sale:
Amortized cost	$ 2,437,300	$ 2,421,000
Equity Securities [Member]
Available for sale:
Amortized cost		116,700
Short-term Investments [Member]
Available for sale:
Amortized cost	$ 34,900	$ 4,000

Consolidated Statements of Income - USD ($) $ in Thousands	3 Months Ended
Consolidated Statements of Income - USD ($) $ in Thousands	Mar. 31, 2018	Mar. 31, 2017
Revenues
Net premiums earned	$ 176,600	$ 175,300
Net investment income	19,400	18,800
Net realized and unrealized (losses) gains on investments	(8,000)
Net realized (losses) gains on investments		2,200
Total revenues	188,000	196,300
Expenses
Losses and loss adjustment expenses	95,400	109,000
Commission expense	23,700	21,500
Underwriting and other operating expenses	39,200	35,900
Interest and financing expenses	300	400
Total expenses	158,600	166,800
Net income before income taxes	29,400	29,500
Income tax expense	3,800	6,300
Net income	25,600	23,200
Comprehensive (loss) income
Unrealized AFS investment (losses) gains arising during the period (net of taxes of $(9.6) and $5.1 for the three months ended March 31, 2018 and 2017, respectively)	(35,800)	9,400
Reclassification adjustment for realized AFS investment losses (gains) in net income (net of taxes of $0.1 and $(0.8) for the three months ended March 31, 2018 and 2017, respectively)	400	(1,400)
Other comprehensive (loss) income, net of tax	(35,400)	8,000
Total comprehensive (loss) income	(9,800)	31,200
Net realized and unrealized (losses) gains on investments
Net realized and unrealized (losses) gains on investments before impairments	(6,000)	2,400
Other than temporary impairment recognized in earnings	(2,000)	(200)
Net realized and unrealized (losses) gains on investments	$ (8,000)
Net realized (losses) gains on investments		$ 2,200
Earnings per common share (Note 11):
Basic	$ 0.78	$ 0.72
Diluted	0.77	0.70
Cash dividends declared per common share and eligible RSUs and PSUs	$ 0.20	$ 0.15

Conolidated Statements of Comprehensive Income (Parentheticals) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Income Statement Parenthetical [Abstract]
Other comprehensive income (loss), unrealized holding gain (loss) on securities arising during period, tax	$ (9,600)	$ 5,100
Other comprehensive income (loss), reclassification adjustment for sale of securities included in net income, tax	$ (100)	$ 800

Consolidated Statements of Stockholders Equity Statement - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income, Net	Treasury Stock [Member]
Stockholders' equity, shares at Dec. 31, 2016		56,226,277
Stockholders' equity, value at Dec. 31, 2016	$ 840,600	$ 600	$ 372,000	$ 777,200	$ 74,500	$ (383,700)
Stock-based obligations, shares		0
Stock-based obligations, value	$ 2,000	$ 0	2,000	0	0	0
Stock-options exercised, shares	37,005	37,005
Stock-options exercised, value	$ 600	$ 0	600	0	0	0
Vesting of RSUs and PSUs, net of shares withheld to satisfy minimum tax withholding, shares		110,286
Vesting of RSUs and PSUs, net of shares withheld to satisfy minimum tax withholding, value	(1,900)	$ 0	(1,900)	0	0	0
Dividends declared, shares		0
Dividends declared, value	(5,000)	$ 0	0	(5,000)	0	0
Net income	23,200	0	0	23,200	0	0
Change in net unrealized gains in investments, net of tax	8,000	$ 0	0	0	8,000	0
Stockholders' equity, shares at Mar. 31, 2017		56,373,568
Stockholders' equity, value at Mar. 31, 2017	867,500	$ 600	372,700	795,400	82,500	(383,700)
Stockholders' equity, shares at Dec. 31, 2016		56,226,277
Stockholders' equity, value at Dec. 31, 2016	$ 840,600	$ 600	372,000	777,200	74,500	(383,700)
Stock-options exercised, shares	307,076
Stockholders' equity, shares at Dec. 31, 2017	56,695,174	56,695,174
Stockholders' equity, value at Dec. 31, 2017	$ 947,700	$ 600	381,200	842,200	107,400	(383,700)
Stock-based obligations, shares		0
Stock-based obligations, value	$ 2,100	$ 0	2,100	0	0	0
Stock-options exercised, shares	275	275
Stock-options exercised, value	$ 0	$ 0	0	0	0	0
Vesting of RSUs and PSUs, net of shares withheld to satisfy minimum tax withholding, shares		154,045
Vesting of RSUs and PSUs, net of shares withheld to satisfy minimum tax withholding, value	(2,900)	$ 0	(2,900)	0	0	0
Dividends declared, shares		0
Dividends declared, value	(6,600)	$ 0	0	(6,600)	0	0
Net income	25,600	0	0	25,600	0	0
Change in net unrealized gains in investments, net of tax	$ (35,400)	$ 0	0	0	(35,400)	0
Stockholders' equity, shares at Mar. 31, 2018	56,849,494	56,849,494
Stockholders' equity, value at Mar. 31, 2018	$ 930,300	$ 600	380,400	935,000	(2,000)	(383,700)
Reclassification adjustment for adoption of ASU \| Accounting Standards Update 2016-01 [Member]	$ 0	$ 0	$ 0	$ 74,000	$ (74,000)	$ 0

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Operating activities
Net income	$ 25,600	$ 23,200
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	2,000	2,100
Stock-based compensation	2,100	1,900
Amortization of premium on investments, net	2,400	3,600
Allowance for doubtful accounts	0	(400)
Deferred income tax (benefit) expense	11,700	3,000
Net realized and unrealized losses (gains) on investments	8,000	(2,200)
Change in operating assets and liabilities:
Premiums receivable	(23,300)	(18,700)
Reinsurance recoverable on paid and unpaid losses	6,200	7,700
Current federal income taxes	(8,000)	3,200
Unpaid losses and loss adjustment expenses	8,000	2,800
Unearned premiums	33,600	20,500
Accounts payable, accrued expenses and other liabilities	700	(3,100)
Deferred reinsurance gain—LPT Agreement	(2,600)	(3,000)
Other	(4,200)	(4,300)
Net cash provided by operating activities	46,200	30,700
Investing activities
Purchases of fixed maturity securities	(231,900)	(138,300)
Purchases of equity securities	(6,800)	(5,600)
Purchases of short-term investments	(34,900)	(7,900)
Proceeds from sale of fixed maturity securities	133,700	27,300
Proceeds from sale of equity securities	10,900	5,800
Proceeds from maturities and redemptions of fixed maturity securities	78,900	63,300
Proceeds from maturities of short-term investments	4,000	8,500
Net change in unsettled investment purchases and sales	(4,700)	18,000
Capital expenditures and other	(2,900)	(3,500)
Net cash used in investing activities	(53,700)	(32,400)
Financing activities
Cash transactions related to stock-based compensation	(2,900)	(1,300)
Dividends paid to stockholders	(6,600)	(5,000)
Payments on capital leases	100	100
Net cash used in financing activities	(9,600)	(6,400)
Net decrease in cash, cash equivalents and restricted cash	(17,100)	(8,100)
Cash, cash equivalents, restricted cash and restricted cash equivalents at the beginning of the period	74,300	70,800
Cash, cash equivalents, restricted cash and restricted cash equivalents at the end of the period	57,200	62,700
Total cash, cash equivalents, restricted cash	$ 74,300	$ 70,800

Basis of Presentation	3 Months Ended
Basis of Presentation	Mar. 31, 2018
Basis of Presentation [Abstract]
Basis of Presentation	Basis of Presentation and Summary of Operations 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 Note 7). 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. The accompanying consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (GAAP) for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X of the Securities Exchange Act of 1934, as amended. Accordingly, they do not include all of the information and notes required by GAAP for complete financial statements. In the opinion of management, all adjustments (consisting of normal, recurring adjustments) necessary for a fair presentation of the Company’s consolidated financial position and results of operations for the periods presented have been included. The results of operations for an interim period are not necessarily indicative of the results for an entire year. These financial statements have been prepared consistent with the accounting policies described in the Company’s Form 10-K for the year ended December 31, 2017 (Annual Report). 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. Reclassifications Certain prior period information has been reclassified to conform to the current period presentation. 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.

New Accounting Standards Level 1 (Notes)	3 Months Ended
New Accounting Standards Level 1 (Notes)	Mar. 31, 2018
New Accounting Standards [Abstract]
New Accounting Standards	New Accounting Standards Recently Issued Accounting Standards 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 has identified lease contracts applicable to this update. Upon completion of these and other assessments, the Company will be able to identify the impact of adopting the new standard on its consolidated financial condition and results of operations. Recently Adopted Accounting Standards In March 2018, the FASB issued ASU Number 2018-04, Investments - Debt Securities (Topic 320) and Regulated Operations (Topic 980). This update amended the guidance for other than temporary impairment of equity securities at fair value upon a registrant's adoption of ASC Topic 320. The Company adopted Topic 320 concurrently with ASU Number 2016-01 in January 2018. Topic 980 is not applicable to the Company. In March 2018, the FASB issued ASU Number 2018-05, Income Taxes (Topic 740). This update provides guidance regarding the application of ASC Topic 740 for the income tax effects of the Tax Cuts and Jobs Act. This update allowed companies to report provisional amounts of the effects of the Tax Cuts and Jobs Act in their financial statements in the first reporting period they are able to determine a reasonable estimate and any adjustments to provisional amounts should be included in income from continuing operations as an adjustment to tax expense or benefit in the reporting period the amounts are determined. The Company adopted this update in the fourth quarter of 2017 and included an estimate of the income tax effects in its financial statements for the year ended December 31, 2017. The Company does not expect the amounts of any future income tax adjustments related to the effects of the Tax Cuts and Jobs Act to be material. 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 those 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 (AFS) securities is needed, in combination with an evaluation of other deferred tax assets, to determine if a valuation allowance is required. This update did not apply to the Company’s investment in Federal Home Loan Bank (FHLB) stock. Rather, it specified that FHLB stock shall be carried at cost and evaluated periodically for impairment; furthermore, it specified that, beginning January 1, 2018, FHLB stock shall not be shown with securities accounted for under ASC 321, which provides detailed guidance on, among other things, accounting and reporting of investments in equity securities that have readily determinable fair values. As a result, the Company’s investment in FHLB stock is presented within Equity securities at cost on the Company's Consolidated Balance Sheet at March 31, 2018. In all periods prior to January 1, 2018, the Company's investment in FHLB stock is presented within Equity securities at fair value on the Company's Consolidated Balance Sheets. This update became effective for fiscal years beginning after December 15, 2017, including interim periods within those fiscal years. The Company adopted this update effective January 1, 2018. Adoption of this accounting standard resulted in a $74.0 million reclassification adjustment, net of tax, from accumulated other comprehensive income to retained earnings.

Fair Value of Financial Instruments

3 Months Ended

Mar. 31, 2018

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 at fair value were as follows:



	March 31, 2018				December 31, 2017
	Carrying Value		Estimated Fair Value		Carrying Value		Estimated Fair Value
	(in millions)
Financial assets
Total investments at fair value	$	2,663.7	$	2,663.7	$	2,677.7	$	2,677.7
Cash and cash equivalents	56.3		56.3		73.3		73.3
Restricted cash and cash equivalents	0.9		0.9		1.0		1.0
Financial liabilities
Notes payable	$	20.0	$	24.3	$	20.0	$	23.6

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 it 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 non-binding 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 prices, when available, as they represent 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 speed assumptions. There were no material adjustments made to the prices obtained from third party pricing services as of March 31, 2018 and December 31, 2017.

These methods of valuation only produce an estimate of fair value if there is objectively verifiable information to produce a valuation. When objectively verifiable information is not available, the Company produces 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 notes payable 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 FHLB of San Francisco. Members are required to purchase stock in FHLB in addition to maintaining collateral deposits that back any funds advanced. The Company's 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.

The following table presents the Company's investments at fair value and the corresponding fair value measurements.



	March 31, 2018						December 31, 2017
	Level 1		Level 2		Level 3		Level 1		Level 2		Level 3
	(in millions)
Fixed maturity securities:
U.S. Treasuries	$	—	$	137.0	$	—	$	—	$	137.0	$	—
U.S. Agencies	—		11.6		—		—		11.8		—
States and municipalities	—		565.0		—		—		642.5		—
Corporate securities	—		1,127.3		—		—		1,118.0		—
Residential mortgage-backed securities	—		426.9		—		—		389.3		—
Commercial mortgage-backed securities	—		105.0		—		—		106.0		—
Asset-backed securities	—		62.0		—		—		58.8		—
Total fixed maturity securities	$	—	$	2,434.8	$	—	$	—	$	2,463.4	$	—
Equity securities at fair value:
Industrial and miscellaneous	$	170.9	$	—	$	—	$	181.7	$	—	$	—
Non-redeemable preferred stock (FHLB)	—		—		—		—		—		4.7
Other	23.1		—		—		23.9		—		—
Total equity securities at fair value	194.0		—		—		205.6		—		4.7
Short-term investments	—		34.9		—		—		4.0		—
Total investments at fair value	$	194.0	$	2,469.7	$	—	$	205.6	$	2,467.4	$	4.7

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.



	March 31, 2018		December 31, 2017
	(in millions)
Cash and cash equivalents at fair value	$	30.3	$	34.3
Cash equivalents measured at NAV, which approximates fair value	26.0		39.0
Total cash and cash equivalents	$	56.3	$	73.3

The following table provides a reconciliation of the beginning and ending balances that are measured using Level 3 inputs for the three months ended March 31, 2018 and 2017.



	Level 3 Securities
	2018			2017
	(in millions)
Beginning balance, January 1	$	4.7		$	11.9
Transfers out of Level 3 ⁽¹⁾	(4.7		)	(1.4		)
Purchases and sales, net	—			(0.2		)
Ending balance, March 31	$	—		$	10.3


(1)	Transfers during the first quarter of 2017 were from Level 3 to Level 2 as observable market data became available for these securities. The transfer during the first quarter of 2018 was the result of adoption of ASU 2016-01, which specified that FHLB stock shall be carried at cost and is no longer measured at fair value.

- 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

3 Months Ended

Mar. 31, 2018

Investments [Abstract]

Investments

The Company's investments in fixed maturity securities, equity securities at fair value (prior to 2018), and short-term investments are classified as AFS 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 (loss) income (AOCI) on the Company’s Consolidated Balance Sheets. Beginning in 2018, with the adoption of ASU 2016-01, the Company's investments in equity securities at fair value are no longer classified as AFS and changes in fair value are included in Net realized and unrealized (losses) gains on investments on the Company's Consolidated Statements of Comprehensive Income. Effective January 1, 2018, the Company's investment in FHLB stock is presented within Equity securities at cost on the Company's Consolidated Balance Sheets.

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



	Cost or Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(in millions)
At March 31, 2018
Fixed maturity securities
U.S. Treasuries	$	137.5	$	1.1	$	(1.6	)	$	137.0
U.S. Agencies	11.3		0.3		—			11.6
States and municipalities	550.1		15.9		(1.0		)	565.0
Corporate securities	1,134.8		8.7		(16.2		)	1,127.3
Residential mortgage-backed securities	434.2		2.4		(9.7		)	426.9
Commercial mortgage-backed securities	107.3		0.1		(2.4		)	105.0
Asset-backed securities	62.1		0.2		(0.3		)	62.0
Total fixed maturity securities	2,437.3		28.7		(31.2		)	2,434.8
Short-term investments	34.9		—		—			34.9
Total AFS investments	$	2,472.2	$	28.7	$	(31.2	)	$	2,469.7



At December 31, 2017
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 at fair value
Industrial and miscellaneous	100.8		81.5		(0.6		)	181.7
Non-redeemable preferred stock (FHLB)	4.7		—		—			4.7
Other	11.2		12.7		—			23.9
Total equity securities at fair value	116.7		94.2		(0.6		)	210.3
Short-term investments	4.0		—		—			4.0
Total AFS investments	$	2,541.7	$	144.5	$	(8.5	)	$	2,677.7

The cost and estimated fair value of the Company’s equity securities recorded at fair value at March 31, 2018 were as follows:



	Cost		Estimated Fair Value
	(in millions)
At March 31, 2018
Equity securities at fair value
Industrial and miscellaneous	$	102.0	$	170.9
Other	11.3		23.1
Total equity securities at fair value	$	113.3	$	194.0

The amortized cost and estimated fair value of the Company's fixed maturity securities at March 31, 2018, 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	$	209.0	$	210.0
Due after one year through five years	777.5		782.9
Due after five years through ten years	716.4		712.4
Due after ten years	130.8		135.6
Mortgage and asset-backed securities	603.6		593.9
Total	$	2,437.3	$	2,434.8

The following is a summary of AFS 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 March 31, 2018 and December 31, 2017.



	March 31, 2018						December 31, 2017
	Estimated Fair Value		Gross Unrealized Losses			Number of Issues	Estimated Fair Value		Gross Unrealized Losses			Number of Issues
	(in millions, except number of issues data)
Less than 12 months:
Fixed maturity securities
U.S. Treasuries	$	91.7	$	(1.3	)	29	$	86.0	$	(0.5	)	28
States and municipalities	95.0		(1.0		)	23	—		—			—
Corporate securities	789.6		(14.4		)	254	307.6		(2.3		)	113
Residential mortgage-backed securities	273.7		(6.3		)	83	165.0		(0.8		)	45
Commercial mortgage-backed securities	77.6		(1.4		)	33	41.8		(0.2		)	19
Asset-backed securities	44.5		(0.3		)	31	29.3		(0.2		)	25
Total less than 12 months	$	1,372.1	$	(24.7	)	453	$	629.7	$	(4.0	)	230

12 months or greater:
Fixed maturity securities
U.S. Treasuries	$	23.3	$	(0.3	)	10	$	23.4	$	(0.3	)	10
Corporate securities	36.2		(1.8		)	15	53.2		(1.1		)	17
Residential mortgage-backed securities	72.9		(3.4		)	32	77.1		(1.8		)	32
Commercial mortgage-backed securities	20.7		(1.0		)	8	25.1		(0.7		)	8
Total 12 months or greater	$	153.1	$	(6.5	)	65	$	178.8	$	(3.9	)	67

At December 31, 2017, the Company also had $0.6 million of gross unrealized losses on 24 equity securities that were in a continuous loss position for less than 12 months.

The Company recognized impairments on fixed maturity securities of $2.0 million (consisting of 57 securities) during the three months ended March 31, 2018 as a result of the Company's intent to sell these securities. There were no other-than-temporary impairments on fixed maturity securities recognized during the three months ended March 31, 2017. The Company determined that the remaining unrealized losses on fixed maturity securities for the three months ended March 31, 2018 were primarily the result of changes in prevailing interest rates and not the credit quality of the issuers. The fixed maturity securities whose total 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 their amortized cost.

The adoption of ASU 2016-01 removed the impairment assessment for equity securities at fair value, and, beginning in 2018, changes in fair value are included in Net realized and unrealized (losses) gains on investments on the Company's Consolidated Statements of Comprehensive Income. Prior to the adoption of this standard, the Company recognized an impairment on equity securities of $0.2 million (consisting of one security) during the three months ended March 31, 2017. The other-than-temporary impairment recognized during this period was the result of the severity and duration of the change in fair value of this security. Certain unrealized losses on equity securities during the three months ended March 31, 2017 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.

Realized gains and losses on investments include the gain or loss on a security at the time of sale compared to its original or adjusted cost (equity securities) or amortized cost (fixed maturity securities). Realized losses on fixed maturity securities are also recognized when securities are written down as a result of an other-than-temporary impairment.

Net realized gains on investments and the change in unrealized gains (losses) on the Company's investments recorded at fair value are determined on a specific-identification basis and were as follows:



	Gross Realized Gains		Gross Realized Losses			Change in Net Unrealized Gains (Losses)			Changes in Fair Value Reflected in Earnings			Changes in Fair Value Reflected in AOCI, before tax
			(in millions)
Three Months Ended March 31, 2018
Fixed maturity securities	$	1.8	$	(2.3	)	$	(44.9	)	$	(0.5	)	$	(44.9	)
Equity securities	5.6		(0.2		)	(12.9		)	(7.5		)	—
Total investments	$	7.4	$	(2.5	)	$	(57.8	)	$	(8.0	)	$	(44.9	)



Three Months Ended March 31, 2017
Fixed maturity securities	$	0.5	$	—		$	6.2	$	0.5	$	6.2
Equity securities	1.9		(0.2		)	6.1		1.7		6.1
Total investments	$	2.4	$	(0.2	)	$	12.3	$	2.2	$	12.3

Net investment income was as follows:



	Three Months Ended
	March 31,
	2018			2017
	(in millions)
Fixed maturity securities	$	18.5		$	17.8
Equity securities	1.6			1.8
Cash equivalents and restricted cash	0.2			0.1
Gross investment income	20.3			19.7
Investment expenses	(0.9		)	(0.9		)
Net investment income	$	19.4		$	18.8

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 March 31, 2018 and December 31, 2017, securities having a fair value of $950.0 million and $1,009.7 million, respectively, were on deposit. Additionally, standby letters of credit from the FHLB were in place in lieu of $140.0 million of securities on deposit as of March 31, 2018 (See Note 8).

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 March 31, 2018 and December 31, 2017 was $24.3 million and $24.5 million, respectively.

Income Taxes	3 Months Ended
Income Taxes	Mar. 31, 2018
Income Taxes [Abstract]
Income Taxes	Income Taxes Income tax expense for interim periods is measured using an estimated effective tax rate for the annual period. The Company's effective tax rate was 12.9% and 21.4% for the three months ended March 31, 2018 and 2017, respectively. Tax-advantaged investment income, Deferred Gain amortization, and certain other adjustments reduced the Company's effective income tax rate below the U.S. statutory rates of 21% and 35% for the three months ended March 31, 2018 and 2017, respectively.

Liability for Unpaid Losses and Loss Adjustment Expenses

3 Months Ended

Mar. 31, 2018

Liability for Unpaid Losses and Loss Adjustment Expenses [Abstract]

Liability for Unpaid Losses and Loss Adjustment Expenses

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



	Three Months Ended
	March 31,
	2018			2017
	(in millions)
Unpaid losses and LAE at beginning of period	$	2,266.1		$	2,301.0
Less reinsurance recoverable, excluding bad debt allowance, on unpaid losses and LAE	537.0			580.0
Net unpaid losses and LAE at beginning of period	1,729.1			1,721.0
Losses and LAE, net of reinsurance, incurred during the period related to:
Current period	110.4			111.9
Prior periods	(12.4		)	—
Total net losses and LAE incurred during the period	98.0			111.9
Paid losses and LAE, net of reinsurance, related to:
Current period	5.9			4.7
Prior periods	94.2			102.9
Total net paid losses and LAE during the period	100.1			107.6
Ending unpaid losses and LAE, net of reinsurance	1,727.0			1,725.3
Reinsurance recoverable, excluding bad debt allowance, on unpaid losses and LAE	531.1			572.9
Unpaid losses and LAE at end of period	$	2,258.1		$	2,298.2

Total net losses and LAE included in the above table exclude amortization of the deferred reinsurance gain—LPT Agreement, which totaled $2.6 million and $2.9 million for the three months ended March 31, 2018 and 2017, respectively (See Note 7).

The change in incurred losses and LAE attributable to prior periods included $12.0 million of favorable development on the Company's voluntary risk business and $0.4 million of favorable development on the Company's assigned risk business for the three months ended March 31, 2018.

LPT Agreement	3 Months Ended
LPT Agreement	Mar. 31, 2018
LPT Agreement [Abstract]
LPT Agreement	LPT Agreement The Company is party to the LPT Agreement under which $1.5 billion in liabilities for losses and LAE related to claims incurred by the Fund prior to July 1, 1995 were reinsured for consideration of $775.0 million. The LPT Agreement provides coverage up to $2.0 billion. The Company records its estimate of contingent profit commission in the accompanying Consolidated Balance Sheets as Contingent commission receivable–LPT Agreement and a corresponding liability is recorded in the accompanying Consolidated Balance Sheets in Deferred reinsurance gain–LPT Agreement. The Deferred Gain is being amortized using the recovery method. Amortization is determined by the proportion of actual reinsurance recoveries to total estimated recoveries over the life of the LPT Agreement, except for the contingent profit commission, which is amortized through June 30, 2024, the date through which the Company is entitled to receive a contingent profit commission under the LPT Agreement. The amortization is recorded in losses and LAE incurred in the accompanying consolidated statements of comprehensive income. Any adjustments to the Deferred Gain are recorded in losses and LAE incurred in the accompanying consolidated statements of comprehensive income. The Company amortized $2.6 million and $2.9 million of the Deferred Gain for the three months ended March 31, 2018 and 2017, respectively. The remaining Deferred Gain was $161.0 million and $163.6 million as of March 31, 2018 and December 31, 2017, respectively. The estimated remaining liabilities subject to the LPT Agreement were $432.8 million and $438.9 million as of March 31, 2018 and December 31, 2017, respectively. Losses and LAE paid with respect to the LPT Agreement totaled $755.4 million and $749.3 million from inception through March 31, 2018 and December 31, 2017, respectively.

Notes Payable Level 1 (Notes)

3 Months Ended

Mar. 31, 2018

Notes Payable [Abstract]

Debt Disclosure [Text Block]

Notes Payable and Other Financing Arrangements

Notes payable is comprised of the following:



	March 31, 2018		December 31, 2017
	(in millions)
Dekania Surplus Note, due April 29, 2034	$	10.0	$	10.0
Alesco Surplus Note, due December 15, 2034	10.0		10.0
Total	$	20.0	$	20.0

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 note described in the following paragraph are subject to the prior approval of the Florida Department of Financial Services.

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.

Other financing arrangements is comprised of the following:

Each of the Company's insurance subsidiaries is a member of the FHLB. Membership allows the insurance subsidiaries access to collateralized advances, which may be used to support and enhance liquidity management. The amount of advances that may be taken is dependent on statutory admitted assets on a per company basis. Currently, none of the Company's insurance subsidiaries has advances outstanding under the FHLB facility.

FHLB membership also allows the Company's insurance subsidiaries access to standby letters of credit. On March 9, 2018, ECIC, EPIC, and EAC entered into standby Letter of Credit Reimbursement Agreements (Letter of Credit Agreements) with the FHLB. The Letter of Credit Agreements are between FHLB and each of EAC, in the amount of $40.0 million, ECIC, in the amount of $50.0 million, and EPIC, in the amount of $50.0 million. The Letter of Credit Agreements became effective March 9, 2018 and expire March 31, 2019; however, the Letter of Credit Agreements will remain evergreen with automatic one-year extensions unless the FHLB notifies the beneficiary at least 60 days prior to the then applicable expiration date of its election not to renew. The Letter of Credit Agreements may only be used to satisfy, in whole or in part, insurance deposit requirements with the State of California and are fully secured with eligible collateral at all times. The Letter of Credit Agreements are subject to annual maintenance charges and a fee of 15 basis points on issued amounts. As of March 31, 2018, letters of credit totaling $140.0 million were issued in lieu of securities on deposit with the State of California under these Letter of Credit Agreements.

As of March 31, 2018, investment securities having a fair value of $241.2 million were pledged to FHLB by the Company's insurance subsidiaries in support of the collateralized advance facility and the Letter of Credit Agreements.

Accumulated Other Comprehensive Income

3 Months Ended

Mar. 31, 2018

Accumulated Other Comprehensive Income [Abstract]

Accumulated Other Comprehensive Income, Net

Accumulated Other Comprehensive Income

Accumulated other comprehensive income is comprised of unrealized (losses) gains on investments classified as AFS, net of deferred tax expense. Beginning in 2018, with the adoption of ASU No. 2016-01, the Company's investments in equity securities at fair value are no longer considered to be AFS and are reported at fair value with unrealized gains and losses included in Net realized and unrealized (losses) gains on investments on the Company's Consolidated Statements of Comprehensive Income. Prior to 2018, investments in equity securities at fair value were classified as AFS and changes in fair value were excluded from earnings and reported in accumulated other comprehensive income. The following table summarizes the components of accumulated other comprehensive (loss) income:



	March 31, 2018			December 31, 2017
	(in millions)
Net unrealized (losses) gains on investments, before taxes	$	(2.5	)	$	136.0
Deferred tax benefit (expense) on net unrealized (losses) gains	0.5			(28.6		)
Total accumulated other comprehensive (loss) income	$	(2.0	)	$	107.4

Stock-Based Compensation

3 Months Ended

Mar. 31, 2018

Stock-Based Compensation [Abstract]

Stock-Based compensation

Stock-Based Compensation

The Company awarded restricted stock units (RSUs) and performance share units (PSUs) to certain employees and non-employee Directors of the Company as follows:



	Number Awarded	Weighted Average Fair Value on Date of Grant		Aggregate Fair Value on Date of Grant
				(in millions)
March 2018
RSUs⁽¹⁾	71,400	$	40.30	$	2.9
RSUs⁽²⁾	736	40.50		—
PSUs⁽³⁾	96,940	40.30		3.9


(1)	The RSUs awarded in March 2018 were awarded to certain employees of the Company and vest 25% on March 15, 2019, and each of the subsequent three anniversaries of that date. The RSUs are subject to accelerated vesting in certain circumstances, including but not limited to: death, disability, retirement, or in connection with a change of control of the Company.


(2)	The RSUs awarded in March 2018 were awarded to non-employee Directors of the Company and vest in full on May 25, 2018.


(3)	The PSUs awarded in March 2018 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 value shown in the table represents the aggregate number of PSUs awarded at the target level.

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, any dividend equivalents with respect to the underlying award will also fail to become payable and will be forfeited.

Stock options exercised totaled 275 for the three months ended March 31, 2018, 37,005 for the three months ended March 31, 2017, and 307,076 for the year ended December 31, 2017.

As of March 31, 2018, the Company had 247,072 options, 303,194 RSUs, and 266,535 PSUs (based on target number awarded) outstanding.

Earnings Per Share

3 Months Ended

Mar. 31, 2018

Earnings Per Share [Abstract]

Earnings Per Share

Basic earnings per share is computed by dividing net income by the weighted average number of shares outstanding for the period. Diluted earnings per share reflects the potential dilutive impact of all common stock equivalents on earnings per share. Diluted earnings per share includes shares that are assumed to be issued under the “treasury stock method,” which reflects the potential dilution that would occur if outstanding RSUs and PSUs had vested and 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. The dividend equivalents are reflected in the Company's net income; therefore, 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 number of shares outstanding used in the earnings per common share calculations.



	Three Months Ended
	March 31,
	2018		2017
	(in millions, except share data)
Net income—basic and diluted	$	25.6	$	23.2
Weighted average number of shares outstanding—basic	32,830,481		32,327,784
Effect of dilutive securities:
PSUs	304,047		309,891
Stock options	100,914		225,664
RSUs	84,978		102,028
Dilutive potential shares	489,939		637,583
Weighted average number of shares outstanding—diluted	33,320,420		32,965,367

Fair Value of Financial Instruments (Tables)

3 Months Ended

Mar. 31, 2018

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 at fair value were as follows:



	March 31, 2018				December 31, 2017
	Carrying Value		Estimated Fair Value		Carrying Value		Estimated Fair Value
	(in millions)
Financial assets
Total investments at fair value	$	2,663.7	$	2,663.7	$	2,677.7	$	2,677.7
Cash and cash equivalents	56.3		56.3		73.3		73.3
Restricted cash and cash equivalents	0.9		0.9		1.0		1.0
Financial liabilities
Notes payable	$	20.0	$	24.3	$	20.0	$	23.6

Fair value, assets and liabilities measured on recurring basis table

The following table presents the Company's investments at fair value and the corresponding fair value measurements.



	March 31, 2018						December 31, 2017
	Level 1		Level 2		Level 3		Level 1		Level 2		Level 3
	(in millions)
Fixed maturity securities:
U.S. Treasuries	$	—	$	137.0	$	—	$	—	$	137.0	$	—
U.S. Agencies	—		11.6		—		—		11.8		—
States and municipalities	—		565.0		—		—		642.5		—
Corporate securities	—		1,127.3		—		—		1,118.0		—
Residential mortgage-backed securities	—		426.9		—		—		389.3		—
Commercial mortgage-backed securities	—		105.0		—		—		106.0		—
Asset-backed securities	—		62.0		—		—		58.8		—
Total fixed maturity securities	$	—	$	2,434.8	$	—	$	—	$	2,463.4	$	—
Equity securities at fair value:
Industrial and miscellaneous	$	170.9	$	—	$	—	$	181.7	$	—	$	—
Non-redeemable preferred stock (FHLB)	—		—		—		—		—		4.7
Other	23.1		—		—		23.9		—		—
Total equity securities at fair value	194.0		—		—		205.6		—		4.7
Short-term investments	—		34.9		—		—		4.0		—
Total investments at fair value	$	194.0	$	2,469.7	$	—	$	205.6	$	2,467.4	$	4.7

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.



	March 31, 2018		December 31, 2017
	(in millions)
Cash and cash equivalents at fair value	$	30.3	$	34.3
Cash equivalents measured at NAV, which approximates fair value	26.0		39.0
Total cash and cash equivalents	$	56.3	$	73.3

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 three months ended March 31, 2018 and 2017.



	Level 3 Securities
	2018			2017
	(in millions)
Beginning balance, January 1	$	4.7		$	11.9
Transfers out of Level 3 ⁽¹⁾	(4.7		)	(1.4		)
Purchases and sales, net	—			(0.2		)
Ending balance, March 31	$	—		$	10.3


(1)	Transfers during the first quarter of 2017 were from Level 3 to Level 2 as observable market data became available for these securities. The transfer during the first quarter of 2018 was the result of adoption of ASU 2016-01, which specified that FHLB stock shall be carried at cost and is no longer measured at fair value.

- 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)

3 Months Ended

Mar. 31, 2018

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 AFS investments were as follows:



	Cost or Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(in millions)
At March 31, 2018
Fixed maturity securities
U.S. Treasuries	$	137.5	$	1.1	$	(1.6	)	$	137.0
U.S. Agencies	11.3		0.3		—			11.6
States and municipalities	550.1		15.9		(1.0		)	565.0
Corporate securities	1,134.8		8.7		(16.2		)	1,127.3
Residential mortgage-backed securities	434.2		2.4		(9.7		)	426.9
Commercial mortgage-backed securities	107.3		0.1		(2.4		)	105.0
Asset-backed securities	62.1		0.2		(0.3		)	62.0
Total fixed maturity securities	2,437.3		28.7		(31.2		)	2,434.8
Short-term investments	34.9		—		—			34.9
Total AFS investments	$	2,472.2	$	28.7	$	(31.2	)	$	2,469.7



At December 31, 2017
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 at fair value
Industrial and miscellaneous	100.8		81.5		(0.6		)	181.7
Non-redeemable preferred stock (FHLB)	4.7		—		—			4.7
Other	11.2		12.7		—			23.9
Total equity securities at fair value	116.7		94.2		(0.6		)	210.3
Short-term investments	4.0		—		—			4.0
Total AFS investments	$	2,541.7	$	144.5	$	(8.5	)	$	2,677.7

Equity securities table

The cost and estimated fair value of the Company’s equity securities recorded at fair value at March 31, 2018 were as follows:



	Cost		Estimated Fair Value
	(in millions)
At March 31, 2018
Equity securities at fair value
Industrial and miscellaneous	$	102.0	$	170.9
Other	11.3		23.1
Total equity securities at fair value	$	113.3	$	194.0

Investments classified by contractual maturity date table



	Amortized Cost		Estimated Fair Value
	(in millions)
Due in one year or less	$	209.0	$	210.0
Due after one year through five years	777.5		782.9
Due after five years through ten years	716.4		712.4
Due after ten years	130.8		135.6
Mortgage and asset-backed securities	603.6		593.9
Total	$	2,437.3	$	2,434.8

Unrealized loss on investments table



	March 31, 2018						December 31, 2017
	Estimated Fair Value		Gross Unrealized Losses			Number of Issues	Estimated Fair Value		Gross Unrealized Losses			Number of Issues
	(in millions, except number of issues data)
Less than 12 months:
Fixed maturity securities
U.S. Treasuries	$	91.7	$	(1.3	)	29	$	86.0	$	(0.5	)	28
States and municipalities	95.0		(1.0		)	23	—		—			—
Corporate securities	789.6		(14.4		)	254	307.6		(2.3		)	113
Residential mortgage-backed securities	273.7		(6.3		)	83	165.0		(0.8		)	45
Commercial mortgage-backed securities	77.6		(1.4		)	33	41.8		(0.2		)	19
Asset-backed securities	44.5		(0.3		)	31	29.3		(0.2		)	25
Total less than 12 months	$	1,372.1	$	(24.7	)	453	$	629.7	$	(4.0	)	230

12 months or greater:
Fixed maturity securities
U.S. Treasuries	$	23.3	$	(0.3	)	10	$	23.4	$	(0.3	)	10
Corporate securities	36.2		(1.8		)	15	53.2		(1.1		)	17
Residential mortgage-backed securities	72.9		(3.4		)	32	77.1		(1.8		)	32
Commercial mortgage-backed securities	20.7		(1.0		)	8	25.1		(0.7		)	8
Total 12 months or greater	$	153.1	$	(6.5	)	65	$	178.8	$	(3.9	)	67

Unrealized gain (loss) on investments



	Gross Realized Gains		Gross Realized Losses			Change in Net Unrealized Gains (Losses)			Changes in Fair Value Reflected in Earnings			Changes in Fair Value Reflected in AOCI, before tax
			(in millions)
Three Months Ended March 31, 2018
Fixed maturity securities	$	1.8	$	(2.3	)	$	(44.9	)	$	(0.5	)	$	(44.9	)
Equity securities	5.6		(0.2		)	(12.9		)	(7.5		)	—
Total investments	$	7.4	$	(2.5	)	$	(57.8	)	$	(8.0	)	$	(44.9	)



Three Months Ended March 31, 2017
Fixed maturity securities	$	0.5	$	—		$	6.2	$	0.5	$	6.2
Equity securities	1.9		(0.2		)	6.1		1.7		6.1
Total investments	$	2.4	$	(0.2	)	$	12.3	$	2.2	$	12.3

Investment income table

Net investment income was as follows:



	Three Months Ended
	March 31,
	2018			2017
	(in millions)
Fixed maturity securities	$	18.5		$	17.8
Equity securities	1.6			1.8
Cash equivalents and restricted cash	0.2			0.1
Gross investment income	20.3			19.7
Investment expenses	(0.9		)	(0.9		)
Net investment income	$	19.4		$	18.8

- 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

Liability for Unpaid Losses and Loss Adjustment Expenses (Tables)

3 Months Ended

Mar. 31, 2018

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.



	Three Months Ended
	March 31,
	2018			2017
	(in millions)
Unpaid losses and LAE at beginning of period	$	2,266.1		$	2,301.0
Less reinsurance recoverable, excluding bad debt allowance, on unpaid losses and LAE	537.0			580.0
Net unpaid losses and LAE at beginning of period	1,729.1			1,721.0
Losses and LAE, net of reinsurance, incurred during the period related to:
Current period	110.4			111.9
Prior periods	(12.4		)	—
Total net losses and LAE incurred during the period	98.0			111.9
Paid losses and LAE, net of reinsurance, related to:
Current period	5.9			4.7
Prior periods	94.2			102.9
Total net paid losses and LAE during the period	100.1			107.6
Ending unpaid losses and LAE, net of reinsurance	1,727.0			1,725.3
Reinsurance recoverable, excluding bad debt allowance, on unpaid losses and LAE	531.1			572.9
Unpaid losses and LAE at end of period	$	2,258.1		$	2,298.2

Notes Payable (Tables)

3 Months Ended

Mar. 31, 2018

Notes Payable [Abstract]

Schedule of long-term debt instruments table

Notes payable is comprised of the following:



	March 31, 2018		December 31, 2017
	(in millions)
Dekania Surplus Note, due April 29, 2034	$	10.0	$	10.0
Alesco Surplus Note, due December 15, 2034	10.0		10.0
Total	$	20.0	$	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

Stock-Based Compensation Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2018

Stock-Based Compensation [Abstract]

Share-based compensation arrangements by share-based payment award table

The Company awarded restricted stock units (RSUs) and performance share units (PSUs) to certain employees and non-employee Directors of the Company as follows:



	Number Awarded	Weighted Average Fair Value on Date of Grant		Aggregate Fair Value on Date of Grant
				(in millions)
March 2018
RSUs⁽¹⁾	71,400	$	40.30	$	2.9
RSUs⁽²⁾	736	40.50		—
PSUs⁽³⁾	96,940	40.30		3.9


(1)	The RSUs awarded in March 2018 were awarded to certain employees of the Company and vest 25% on March 15, 2019, and each of the subsequent three anniversaries of that date. The RSUs are subject to accelerated vesting in certain circumstances, including but not limited to: death, disability, retirement, or in connection with a change of control of the Company.


(2)	The RSUs awarded in March 2018 were awarded to non-employee Directors of the Company and vest in full on May 25, 2018.


(3)	The PSUs awarded in March 2018 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 value shown in the table represents the aggregate number of PSUs awarded at the target level.

Earnings Per Share (Tables)

3 Months Ended

Mar. 31, 2018

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 number of shares outstanding used in the earnings per common share calculations.



	Three Months Ended
	March 31,
	2018		2017
	(in millions, except share data)
Net income—basic and diluted	$	25.6	$	23.2
Weighted average number of shares outstanding—basic	32,830,481		32,327,784
Effect of dilutive securities:
PSUs	304,047		309,891
Stock options	100,914		225,664
RSUs	84,978		102,028
Dilutive potential shares	489,939		637,583
Weighted average number of shares outstanding—diluted	33,320,420		32,965,367

Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at fair value	$ 2,663,700	$ 2,677,700
Total Investments at fair value, estimated fair value	2,663,700	2,677,700
Cash and cash equivalents	56,300	73,300
Cash and cash equivalents, estimated fair value	56,300	73,300
Equity securities at cost	4,700	0
Restricted cash and cash equivalents	900	1,000
Notes payable	20,000	20,000
Notes Payable, estimated fair value	24,300	23,600
Estimate of Fair Value, Fair Value Disclosure [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Restricted cash and cash equivalents	$ 900	$ 1,000

Fair Value of Financial Instruments Cash Equivalents at NAV and Total Cash and Cash Equivalents Carried at Fair Value (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents at fair value	$ 30.3	$ 34.3
Cash equivalents measured at NAV, which approximates fair value	26.0	39.0
Total cash and cash equivalents	$ 56.3	$ 73.3

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

3 Months Ended

Mar. 31, 2018

Mar. 31, 2017

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

Beginning balance, January 1

$ 2,677,700

Ending balance, March 31

2,668,400

Fair Value, Inputs, Level 3 [Member]

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

Beginning balance, January 1

4,700

$ 11,900

Transfers out of Level 3 (1)

(4,700)

^[1]

(1,400)

Purchases and sales, net

(200)

Ending balance, March 31

$ 0

$ 10,300

[1]

(1)Transfers during the first quarter of 2017 were from Level 3 to Level 2 as observable market data became available for these securities. The transfer during the first quarter of 2018 was the result of adoption of ASU 2016-01, which specified that FHLB stock shall be carried at cost and is no longer measured at fair value.

Investments Available for Sale Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	$ 2,472,200	$ 2,541,700
Gross unrealized gain	28,700	144,500
Gross unrealized loss	(31,200)	(8,500)
Investments	2,469,700	2,677,700
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	2,437,300	2,421,000
Gross unrealized gain	28,700	50,300
Gross unrealized loss	(31,200)	(7,900)
Investments	2,434,800	2,463,400
US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	137,500	135,800
Gross unrealized gain	1,100	2,000
Gross unrealized loss	(1,600)	(800)
Investments	137,000	137,000
US Government Agencies Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	11,300	11,300
Gross unrealized gain	300	500
Gross unrealized loss	0	0
Investments	11,600	11,800
US States and Political Subdivisions Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	550,100	617,000
Gross unrealized gain	15,900	25,500
Gross unrealized loss	(1,000)	0
Investments	565,000	642,500
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	1,134,800	1,103,400
Gross unrealized gain	8,700	18,000
Gross unrealized loss	(16,200)	(3,400)
Investments	1,127,300	1,118,000
Residential Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	434,200	388,300
Gross unrealized gain	2,400	3,600
Gross unrealized loss	(9,700)	(2,600)
Investments	426,900	389,300
Commercial Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	107,300	106,500
Gross unrealized gain	100	400
Gross unrealized loss	(2,400)	(900)
Investments	105,000	106,000
Asset-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	62,100	58,700
Gross unrealized gain	200	300
Gross unrealized loss	(300)	(200)
Investments	62,000	58,800
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost		116,700
Gross unrealized gain		94,200
Gross unrealized loss		(600)
Investments		210,300
Industrial and Miscellaneous [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost		100,800
Gross unrealized gain		81,500
Gross unrealized loss		(600)
Investments		181,700
Non-redeemable preferred (FHLB stock) [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost		4,700
Gross unrealized gain		0
Gross unrealized loss		0
Investments		4,700
Other [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost		11,200
Gross unrealized gain		12,700
Gross unrealized loss		0
Investments		23,900
Short-term Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	34,900	4,000
Gross unrealized gain	0	0
Gross unrealized loss	0	0
Investments	$ 34,900	$ 4,000

Investments Equity Securities (Details) $ in Thousands	Mar. 31, 2018 USD ($)
Schedule of Equity Securities and Other [Line Items]
Equity securities at fair value, cost	$ 113,300
Equity securities, estimated fair value	194,000
Industrial and Miscellaneous [Member]
Schedule of Equity Securities and Other [Line Items]
Equity securities at fair value, cost	102,000
Equity securities, estimated fair value	170,900
Other [Member]
Schedule of Equity Securities and Other [Line Items]
Equity securities at fair value, cost	11,300
Equity securities, estimated fair value	$ 23,100

Investments, Amortized Cost and Estimated Fair Value (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Amortized Cost
Due in one year or less, amortized cost	$ 209,000
Due after one year through five years, amortized cost	777,500
Due after five years through ten years, amortized cost	716,400
Due after ten years, amortized cost	130,800
Mortgage and asset-backed securities, amortized cost	603,600
Total, amortized cost	2,437,300
Estimated Fair Value
Due in one year or less, fair value	210,000
Due after one year through five years, fair value	782,900
Due after five years through ten years, fair value	712,400
Due after ten years, fair value	135,600
Mortgage and asset-backed securities, fair value	593,900
Total, fair value	$ 2,434,800	$ 2,463,400

Investments, Continuous Loss Position (Details)	3 Months Ended
Investments, Continuous Loss Position (Details)	Mar. 31, 2018 USD ($) shares	Mar. 31, 2017 USD ($) shares	Dec. 31, 2017 USD ($) shares
Estimated Fair Value
Estimated fair value, less than 12 months	$ 1,372,100,000		$ 629,700,000
Estimated fair value, 12 months or greater	153,100,000		178,800,000
Gross Unrealized Losses
Gross unrealized losses, less than 12 months	(24,700,000)		(4,000,000)
Gross unrealized losses, 12 months or greater	$ (6,500,000)		$ (3,900,000)
Number of issues in loss position, less than 12 months	453		230
Number of Issues in loss position, 12 months or greater	65		67
Other than temporary impairment, credit losses recognized in earnings	$ 2,000,000	$ 200,000
Debt Securities [Member]
Gross Unrealized Losses
Other than temporary impairment, credit losses recognized in earnings	$ 2,000,000
Total impairments, number of securities \| shares	57	0
US Treasury Securities [Member]
Estimated Fair Value
Estimated fair value, less than 12 months	$ 91,700,000		$ 86,000,000
Estimated fair value, 12 months or greater	23,300,000		23,400,000
Gross Unrealized Losses
Gross unrealized losses, less than 12 months	(1,300,000)		(500,000)
Gross unrealized losses, 12 months or greater	$ (300,000)		$ (300,000)
Number of issues in loss position, less than 12 months	29		28
Number of Issues in loss position, 12 months or greater	10		10
US States and Political Subdivisions Debt Securities [Member]
Estimated Fair Value
Estimated fair value, less than 12 months	$ 95,000,000		$ 0
Gross Unrealized Losses
Gross unrealized losses, less than 12 months	$ (1,000,000)		$ 0
Number of issues in loss position, less than 12 months	23		0
Corporate Debt Securities [Member]
Estimated Fair Value
Estimated fair value, less than 12 months	$ 789,600,000		$ 307,600,000
Estimated fair value, 12 months or greater	36,200,000		53,200,000
Gross Unrealized Losses
Gross unrealized losses, less than 12 months	(14,400,000)		(2,300,000)
Gross unrealized losses, 12 months or greater	$ (1,800,000)		$ (1,100,000)
Number of issues in loss position, less than 12 months	254		113
Number of Issues in loss position, 12 months or greater	15		17
Residential Mortgage Backed Securities [Member]
Estimated Fair Value
Estimated fair value, less than 12 months	$ 273,700,000		$ 165,000,000
Estimated fair value, 12 months or greater	72,900,000		77,100,000
Gross Unrealized Losses
Gross unrealized losses, less than 12 months	(6,300,000)		(800,000)
Gross unrealized losses, 12 months or greater	$ (3,400,000)		$ (1,800,000)
Number of issues in loss position, less than 12 months	83		45
Number of Issues in loss position, 12 months or greater	32		32
Commercial Mortgage Backed Securities [Member]
Estimated Fair Value
Estimated fair value, less than 12 months	$ 77,600,000		$ 41,800,000
Estimated fair value, 12 months or greater	20,700,000		25,100,000
Gross Unrealized Losses
Gross unrealized losses, less than 12 months	(1,400,000)		(200,000)
Gross unrealized losses, 12 months or greater	$ (1,000,000)		$ (700,000)
Number of issues in loss position, less than 12 months	33		19
Number of Issues in loss position, 12 months or greater	8		8
Asset-backed Securities [Member]
Estimated Fair Value
Estimated fair value, less than 12 months	$ 44,500,000		$ 29,300,000
Gross Unrealized Losses
Gross unrealized losses, less than 12 months	$ (300,000)		$ (200,000)
Number of issues in loss position, less than 12 months	31		25
Equity Securities [Member]
Gross Unrealized Losses
Gross unrealized losses, less than 12 months			$ (600,000)
Number of issues in loss position, less than 12 months \| shares			24
Other than temporary impairment, credit losses recognized in earnings		$ 200,000
Total impairments, number of securities \| shares		1

Investments Investments, Net Realized Gains and Losses (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
AFS, change in unrealized gains (losses)
AFS, change unrealized gains (losses) on fixed maturity and equity securities reflected in AOCI	$ (44,900)	$ 12,300
AFS, net realized gains (losses)
AFS, Gross gains from sales		2,400
AFS, Gross losses from sales		(200)
Net realized (losses) gains on investments		2,200
Net realized and unrealized (losses) gains on investments	(8,000)
Total gross realized gains	7,400
Total gross realized losses	(2,500)
Total change in net unrealized gains (losses)	(57,800)
Debt Securities [Member]
AFS, change in unrealized gains (losses)
AFS, change unrealized gains (losses) on fixed maturity and equity securities reflected in AOCI	(44,900)	6,200
AFS, net realized gains (losses)
AFS, Gross gains from sales	1,800	500
AFS, Gross losses from sales	(2,300)	0
Net realized (losses) gains on investments		500
Net realized and unrealized (losses) gains on investments	(500)
Equity Securities [Member]
Equity securities:
Equity securities, gross realized gain	5,600
Equity securities, gross realized loss	(200)
Equity securities, change in unrealized gains (losses)	(12,900)
AFS, change in unrealized gains (losses)
AFS, change unrealized gains (losses) on fixed maturity and equity securities reflected in AOCI	0	6,100
AFS, net realized gains (losses)
AFS, Gross gains from sales		1,900
AFS, Gross losses from sales		(200)
Net realized (losses) gains on investments		$ 1,700
Net realized and unrealized (losses) gains on investments	$ (7,500)

Net Investment Income (Details) - USD ($) $ in Millions	3 Months Ended
Net Investment Income (Details) - USD ($) $ in Millions	Mar. 31, 2018	Mar. 31, 2017
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	$ 20.3	$ 19.7
Investment expenses	0.9	0.9
Net investment income	19.4	18.8
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	18.5	17.8
Equity Securities [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income related to equity securities	1.6	1.8
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	$ 0.2	$ 0.1

Investments Investments, Held in Trust or on Deposit (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Deposit Assets [Abstract]
Investments	$ 2,668,400	$ 2,677,700
Assets Held-in-trust [Abstract]
Funds Held under Reinsurance Agreements, Asset	24,300	24,500
Federal Home Loan Bank [Member]
Deposit Assets [Abstract]
Investments	140,000
Required by various state laws and regulations to hold securities or letters of credit in depository account [Member]
Deposit Assets [Abstract]
Investments	$ 950,000	$ 1,009,700

Income Taxes (Details)	3 Months Ended
Income Taxes (Details)	Mar. 31, 2018	Mar. 31, 2017
Effective Income Tax Rate, Continuing Operations, Tax Rate Reconciliation [Abstract]
Statutory tax rate	21.00%	35.00%
Effective tax rate	12.90%	21.40%

Liability for Unpaid Losses and Loss Adjustment Expenses (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Unpaid losses and LAE at beginning of period	$ 2,266,100	$ 2,301,000
Less reinsurance recoverable, excluding bad debt allowance, on unpaid losses and LAE	537,000	580,000
Net unpaid losses and LAE at beginning of period	1,729,100	1,721,000
Losses and LAE, net of reinsurance, incurred during the period related to:
Current period	110,400	111,900
Prior periods	(12,400)	0
Total net losses and LAE incurred during the period	98,000	111,900
Deduct payments for losses and LAE, net of reinsurance, related to:
Current period	5,900	4,700
Prior periods	94,200	102,900
Total net paid losses and LAE during the period	100,100	107,600
Ending unpaid losses and LAE, net of reinsurance	1,727,000	1,725,300
Reinsurance recoverable, excluding bad debt allowance, on unpaid losses and LAE	531,100	572,900
Unpaid losses and LAE at end of period	2,258,100	2,298,200
LPT Agreement [Abstract]
Impact of the LPT Agreement	2,600	$ 2,900
Involuntary Assigned Risk Business [Member]
Losses and LAE, net of reinsurance, incurred during the period related to:
Prior periods	(400)
Voluntary Risk Business [Member]
Losses and LAE, net of reinsurance, incurred during the period related to:
Prior periods	$ (12,000)

LPT Agreement LPT Agreement (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
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
Amortization of deferred gain	2,600	$ 2,900
Deferred reinsurance gain—LPT Agreement	161,000		$ 163,600
Estimated remaining liabilities - LPT Agreement	432,800		438,900
Paid losses and LAE claims related to LPT	755,400		$ 749,300
Indemnification Agreement [Member]
Reinsurance Agreement [Line Items]
Coverage provided under LPT Agreement	$ 2,000,000

Notes Payable Notes Payable Outstanding(Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Notes payable	$ 20,000	$ 20,000
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
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

Notes Payable Letters of Credit (Details) $ in Millions	3 Months Ended
Notes Payable Letters of Credit (Details) $ in Millions	Mar. 31, 2018 USD ($)
Letters of Credit Facilities [Line Items]
Letters of credit, unused capacity, commitment fee percentage	0.15%
Federal Home Loan Bank [Member]
Letters of Credit Facilities [Line Items]
Letters of credit facilities, maximum borrowing capacity	$ 140.0
Letters of credit collateral amount	241.2
Federal Home Loan Bank [Member] \| EAC
Letters of Credit Facilities [Line Items]
Letters of credit facilities, maximum borrowing capacity	40.0
Federal Home Loan Bank [Member] \| ECIC
Letters of Credit Facilities [Line Items]
Letters of credit facilities, maximum borrowing capacity	50.0
Federal Home Loan Bank [Member] \| EPIC
Letters of Credit Facilities [Line Items]
Letters of credit facilities, maximum borrowing capacity	$ 50.0

Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Net unrealized gain on investments, before taxes	$ (2,500)	$ 136,000
Deferred tax expense on net unrealized gains	500	(28,600)
Accumulated other comprehensive income, net	$ (2,000)	$ 107,400

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

3 Months Ended

12 Months Ended

Mar. 31, 2018

Mar. 31, 2017

Dec. 31, 2017

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

Stock-options exercised

275

37,005

307,076

Officer [Member]

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

Vesting rights for RSUs awarded

vest 25% on March 15, 2019, and each of the subsequent three anniversaries of that date

Performance share awards performance period

two years

Performance share awards, minimum payout

0.00%

Performance share awards, maximum payout

200.00%

Director [Member]

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

Vesting rights for RSUs awarded

vest in full on May 25, 2018

Stock Option [Member]

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

Number of outstanding options or share units

247,072

Restricted Stock Units (RSUs) [Member]

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

Number of outstanding options or share units

303,194

Restricted Stock Units (RSUs) [Member] | Officer [Member]

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

Share-based compensation award, shares issued

^[1]

71,400

Share-based compensation options, exercise price on grant date

^[1]

$ 40.30

Fair value of awards awarded on grant date

^[1]

$ 2.9

Restricted Stock Units (RSUs) [Member] | Director [Member]

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

Share-based compensation award, shares issued

^[2]

736

Share-based compensation options, exercise price on grant date

^[2]

$ 40.50

Fair value of awards awarded on grant date

^[2]

$ 0.0

Performance Shares [Member]

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

Number of outstanding options or share units

266,535

Performance Shares [Member] | Officer [Member]

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

Share-based compensation award, shares issued

^[3]

96,940

Share-based compensation options, exercise price on grant date

^[3]

$ 40.30

Fair value of awards awarded on grant date

^[3]

$ 3.9

Share-based compensation arrangement by share-based payment award, award vesting period

1 year

[1]	The RSUs awarded in March 2018 were awarded to certain employees of the Company and vest 25% on March 15, 2019, and each of the subsequent three anniversaries of that date. The RSUs are subject to accelerated vesting in certain circumstances, including but not limited to: death, disability, retirement, or in connection with a change of control of the Company.
[2]	The RSUs awarded in March 2018 were awarded to non-employee Directors of the Company and vest in full on May 25, 2018
[3]	The PSUs awarded in March 2018 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 value shown in the table represents the aggregate number of PSUs awarded at the target level.

Earnings Per Share (Details) - USD ($) $ in Thousands	3 Months Ended
Earnings Per Share (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Mar. 31, 2017
Earnings Per Share, Basic and Diluted, by Common Class [Line Items]
Net income available to stockholders - basic and diluted	$ 25,600	$ 23,200
Weighted average number of shares outstanding - basic	32,830,481	32,327,784
Effect of dilutive securities:
Dilutive securities	489,939	637,583
Weighted average number of shares outstanding - diluted	33,320,420	32,965,367
Performance Shares [Member]
Effect of dilutive securities:
Dilutive securities	304,047	309,891
Employee Stock Option [Member]
Effect of dilutive securities:
Dilutive securities	100,914	225,664
Restricted Stock Units (RSUs) [Member]
Effect of dilutive securities:
Dilutive securities	84,978	102,028

Conslidated Stockholders Equity (Parentheticals) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Stockholders' Equity Parenthetical [Abstract]
Change in net unrealized gains on investments, net of tax	$ (9.5)	$ 4.3

Basis of Presentation Pending Purchase of PRUS (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018 USD ($)
Business Acquisition [Line Items]
Estimated statutory capital and surplus of pending acquisition	$ 40.0
Net cash payment to acquire business	$ 5.8

Fair Value of Financial Instruments, Fair Value Inputs (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	$ 2,469.7	$ 2,677.7
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	194.0	205.6
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	2,469.7	2,467.4
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	4.7
Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	2,434.8	2,463.4
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	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	2,434.8	2,463.4
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	0.0
US Treasury Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	137.0	137.0
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	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	137.0	137.0
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	0.0
US Government Agencies Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	11.6	11.8
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	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	11.6	11.8
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	0.0
US States and Political Subdivisions Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	565.0	642.5
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	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	565.0	642.5
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	0.0
Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	1,127.3	1,118.0
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	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	1,127.3	1,118.0
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	0.0
Residential Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	426.9	389.3
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	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	426.9	389.3
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	0.0
Commercial Mortgage Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	105.0	106.0
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	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	105.0	106.0
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	0.0
Asset-backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	62.0	58.8
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	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	62.0	58.8
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	0.0	0.0
Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments		210.3
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	194.0	205.6
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	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	0.0	4.7
Industrial and Miscellaneous [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments		181.7
Industrial and Miscellaneous [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	170.9	181.7
Industrial and Miscellaneous [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	0.0
Industrial and Miscellaneous [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	0.0
Non-redeemable preferred (FHLB stock) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments		4.7
Non-redeemable preferred (FHLB stock) [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	0.0
Non-redeemable preferred (FHLB stock) [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	0.0
Non-redeemable preferred (FHLB stock) [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	4.7
Other [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments		23.9
Other [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	23.1	23.9
Other [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	0.0
Other [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	0.0
Short-term Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	34.9	4.0
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	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		4.0
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	$ 0.0