Document and Entity Information - shares	6 Months Ended
Document and Entity Information - shares	Jun. 30, 2017	Jul. 20, 2017
Document and Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2017
Entity Registrant Name	Employers Holdings, Inc.
Entity Central Index Key	0001379041
Current Fiscal Year End Date	--12-31
Entity Well Know Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Common Stock Shares Outstanding		32,414,995
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	Q2

Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Available for sale:
Fixed maturity securities at fair value (amortized cost $2,361.3 at June 30, 2017 and $2,305.9 at December 31, 2016)	$ 2,418,700	$ 2,344,400
Equity securities at fair value (cost $118.2 at June 30, 2017 and $116.1 at December 31, 2016)	199,700	192,200
Short-term investments at fair value (amortized cost $5.5 at June 30, 2017 and $16.0 at December 31, 2016)	5,500	16,000
Total investments	2,623,900	2,552,600
Cash and cash equivalents	42,600	67,200
Restricted cash and cash equivalents	400	3,600
Accrued investment income	20,500	20,600
Premiums receivable (less bad debt allowance of $9.9 at June 30, 2017 and $9.8 at December 31, 2016)	333,100	304,700
Reinsurance recoverable for:
Paid losses	8,400	8,700
Unpaid losses	559,800	580,000
Deferred policy acquisition costs	49,600	44,300
Deferred income taxes, net	44,900	59,400
Property and equipment, net	24,300	22,200
Intangible assets, net	8,000	8,200
Goodwill	36,200	36,200
Contingent commission receivable—LPT Agreement	31,100	31,100
Other assets	42,000	34,600
Total assets	3,824,800	3,773,400
Claims and policy liabilities:
Unpaid losses and loss adjustment expenses	2,284,900	2,301,000
Unearned premiums	341,100	310,300
Total claims and policy liabilities	2,626,000	2,611,300
Commissions and premium taxes payable	52,000	48,800
Accounts payable and accrued expenses	20,300	24,200
Deferred reinsurance gain—LPT Agreement	168,900	174,900
Notes payable	20,000	32,000
Other liabilities	38,400	41,600
Total liabilities	2,925,600	2,932,800
Commitments and contingencies
Stockholders’ equity:
Common stock, $0.01 par value; 150,000,000 shares authorized; 56,510,352 and 56,226,277 shares issued and 32,412,997 and 32,128,922 shares outstanding at June 30, 2017 and December 31, 2016, respectively	600	600
Preferred stock, $0.01 par value; 25,000,000 shares authorized; none issued	0	0
Additional paid-in capital	376,600	372,000
Retained earnings	815,400	777,200
Accumulated other comprehensive income, net of tax	90,300	74,500
Treasury stock, at cost (24,097,355 shares at June 30, 2017 and December 31, 2016)	(383,700)	(383,700)
Total stockholders’ equity	899,200	840,600
Total liabilities and stockholders’ equity	$ 3,824,800	$ 3,773,400

Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Available for sale:
Fixed maturity securities, amortized cost	$ 2,485,000	$ 2,438,000
Available for sale, short-term investments, at amortized cost	5,500	16,000
Premiums receivable, bad debt allowance	9,900	9,800
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)	56,510,352	56,226,277
Common stock, shares outstanding (in shares)	32,412,997	32,128,922
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	25,000,000	25,000,000
Preferred stock, shares issued (in shares)	0	0
Treasury stock, at cost (in shares)	24,097,355	24,097,355
Debt Securities [Member]
Available for sale:
Fixed maturity securities, amortized cost	$ 2,361,300	$ 2,305,900
Equity Securities [Member]
Available for sale:
Fixed maturity securities, amortized cost	118,200	116,100
Short-term Investments [Member]
Available for sale:
Fixed maturity securities, amortized cost	$ 5,500	$ 16,000

Consolidated Statements of Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
Consolidated Statements of Income - USD ($) $ in Thousands	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Revenues
Net premiums earned	$ 171,700	$ 176,900	$ 347,100	$ 349,500
Net investment income	18,200	18,400	36,900	36,200
Net realized gains on investments	1,100	6,000	3,300	7,500
Gain on redemption of notes payable	2,100	0	2,100	0
Other income	100	500	100	600
Total revenues	193,200	201,800	389,500	393,800
Expenses
Losses and loss adjustment expenses	106,100	111,700	215,000	219,000
Commission expense	21,500	21,900	43,000	42,200
Underwriting and other operating expenses	32,600	33,600	68,600	69,900
Interest expense	400	400	800	800
Total expenses	160,600	167,600	327,400	331,900
Net income before income taxes	32,600	34,200	62,100	61,900
Income tax expense	7,800	7,400	14,100	13,300
Net income	24,800	26,800	48,000	48,600
Comprehensive income
Unrealized gains arising during the period (net of taxes of $4.5 and $12.6 for the three months ended June 30, 2017 and 2016, respectively, and $9.7 and $23.8 for the six months ended June 30, 2017 and 2016, respectively)	8,400	23,300	17,900	44,100
Reclassification adjustment for realized gains in net income (net of taxes of $0.4 and $2.1 for the three months ended June 30, 2017 and 2016, respectively, and $1.2 and $2.6 for the six months ended June 30, 2017 and 2016, respectively)	(700)	(3,900)	(2,100)	(4,900)
Other comprehensive income, net of tax	7,700	19,400	15,800	39,200
Total comprehensive income	32,500	46,200	63,800	87,800
Net realized gains on investments
Net realized gains on investments before credit related impairments	1,100	6,000	3,500	12,800
Other than temporary impairment recognized in earnings	0	0	(200)	(5,300)
Net realized gains on investments	$ 1,100	$ 6,000	$ 3,300	$ 7,500
Earnings per common share (Note 11):
Basic	$ 0.76	$ 0.82	$ 1.48	$ 1.49
Diluted	0.75	0.81	1.46	1.47
Cash dividends declared per common share and eligible RSUs and PSUs	$ 0.15	$ 0.09	$ 0.30	$ 0.18

Conolidated Statements of Comprehensive Income (Parentheticals) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Income Statement Parenthetical [Abstract]
Other comprehensive income (loss), unrealized holding gain (loss) on securities arising during period, tax	$ 4,500	$ 12,600	$ 9,700	$ 23,800
Other comprehensive income (loss), reclassification adjustment for sale of securities included in net income, tax	$ 400	$ 2,100	$ 1,200	$ 2,600

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, 2015		55,589,454
Stockholders' equity, value at Dec. 31, 2015	$ 760,800	$ 600	$ 357,200	$ 682,000	$ 83,600	$ (362,600)
Stock-based compensation, shares		0
Stock-based compensation, value	$ 3,200	$ 0	3,200	0	0	0
Stock-options exercised, shares	438,774	438,774
Stock-options exercised, value	$ 6,800	$ 0	6,800	0	0	0
Vesting of restricted stock units, net of shares withheld to satisfy minimum tax withholding, shares		50,691
Vesting of restricted stock units, net of shares withheld to satisfy minimum tax withholding, value	(600)	$ 0	(600)	0	0	0
Acquisition of treasury stock, shares		0
Acquisition of treasury stock, value	(6,900)	$ 0	0	0	0	(6,900)
Dividends declared, shares		0
Dividends declared, value	(5,800)	$ 0	0	(5,800)	0	0
Net income	48,600	0	0	48,600	0	0
Change in net unrealized gains in investments, net of tax	39,200	$ 0	0	0	39,200	0
Stockholders' equity, shares at Jun. 30, 2016		56,078,919
Stockholders' equity, value at Jun. 30, 2016	845,300	$ 600	366,600	724,800	122,800	(369,500)
Stockholders' equity, shares at Dec. 31, 2015		55,589,454
Stockholders' equity, value at Dec. 31, 2015	$ 760,800	$ 600	357,200	682,000	83,600	(362,600)
Stock-options exercised, shares	586,132
Stockholders' equity, shares at Dec. 31, 2016	56,226,277	56,226,277
Stockholders' equity, value at Dec. 31, 2016	$ 840,600	$ 600	372,000	777,200	74,500	(383,700)
Stock-based compensation, shares		0
Stock-based compensation, value	$ 3,200	$ 0	3,200	0	0	0
Stock-options exercised, shares	167,026	167,026
Stock-options exercised, value	$ 3,300	$ 0	3,300	0	0	0
Vesting of restricted stock units, net of shares withheld to satisfy minimum tax withholding, shares		117,049
Vesting of restricted stock units, 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	(9,800)	$ 0	0	(9,800)	0	0
Net income	48,000	0	0	48,000	0	0
Change in net unrealized gains in investments, net of tax	$ 15,800	$ 0	0	0	15,800	0
Stockholders' equity, shares at Jun. 30, 2017	56,510,352	56,510,352
Stockholders' equity, value at Jun. 30, 2017	$ 899,200	$ 600	$ 376,600	$ 815,400	$ 90,300	$ (383,700)

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Operating activities
Net income	$ 48,000	$ 48,600
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	4,200	4,300
Stock-based compensation	3,100	3,200
Amortization of premium on investments, net	7,500	7,400
Allowance for doubtful accounts	100	(2,300)
Deferred income tax expense	6,000	5,600
Net realized gains on investments	(3,300)	(7,500)
Gain on redemption of notes payable	(2,100)	0
Change in operating assets and liabilities:
Premiums receivable	(28,500)	(27,000)
Reinsurance recoverable on paid and unpaid losses	20,500	29,800
Current federal income taxes payable	(6,900)	1,500
Unpaid losses and loss adjustment expenses	16,100	15,200
Unearned premiums	30,800	27,200
Payables and other liabilities	(7,100)	(9,200)
Deferred reinsurance gain—LPT Agreement	(6,000)	(8,800)
Contingent commission receivable—LPT Agreement	0	(1,900)
Other	(7,600)	(13,000)
Net cash provided by operating activities	42,600	42,700
Investing activities
Purchase of fixed maturity securities	(202,100)	(196,400)
Purchase of equity securities	(10,700)	(34,900)
Purchase of short-term investments	(8,100)	0
Proceeds from sale of fixed maturity securities	43,000	111,700
Proceeds from sale of equity securities	11,400	65,600
Proceeds from maturities and redemptions of fixed maturity securities	96,800	91,900
Proceeds from maturities of short-term investments	18,600	0
Net change in unsettled investment purchases and sales	5,000	0
Capital expenditures and other	(5,900)	(2,400)
Change in restricted cash and cash equivalents	3,200	100
Net cash (used in) provided by investing activities	(48,800)	35,600
Financing activities
Acquisition of common stock	0	(6,900)
Cash transactions related to stock-based compensation	1,400	6,200
Stockholder dividends paid	(9,800)	(5,900)
Redemption of notes payable	(9,900)	0
Payments on capital leases	100	100
Net cash used in financing activities	(18,400)	(6,700)
Net (decrease) increase in cash and cash equivalents	(24,600)	71,600
Cash and cash equivalents at the beginning of the period	67,200	56,600
Cash and cash equivalents at the end of the period	$ 42,600	$ 128,200

Basis of Presentation	6 Months Ended
Basis of Presentation	Jun. 30, 2017
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 in the accompanying 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, 2016 (Annual Report). 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. Currently, the Company has one operating segment, workers’ compensation insurance and related services. 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. See Note 2.

New Accounting Standards Level 1 (Notes)	6 Months Ended
New Accounting Standards Level 1 (Notes)	Jun. 30, 2017
New Accounting Standards [Abstract]
New Accounting Standards	New Accounting Standards Recently Adopted Accounting Standards In March 2016, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) Number 2016-09, Compensation - Stock Compensation (Topic 718) that impacted the net tax benefits of the Company's stock-based compensation. The Company elected to early adopt this standard in the third quarter of 2016 with an effective date of January 1, 2016. Adoption of this standard resulted in a $0.5 million and $1.3 million reduction to Income tax expense and a corresponding increase to Net income for the three and six months ended June 30, 2016, respectively. Adoption of the standard also increased basic and diluted earnings per share by $0.01 for the three months ended June 30, 2016 and increased basic earnings per share by $0.04 and diluted earnings per share by $0.03 for the six months ended June 30, 2016. This standard also requires that assumed proceeds under the treasury stock method be modified to exclude the excess tax benefits that would have been recognized in Additional paid-in capital. Additionally, this standard requires that excess tax benefits from stock-based compensation be reported as cash flows from operating activities, as opposed to financing activities. This update resulted in a change in presentation in the Consolidated Statements of Cash Flows. Recently Issued Accounting Standards In January 2017, the FASB issued ASU Number 2017-04, Intangibles-Goodwill and Other (Topic 350). This update simplifies the measurement of goodwill by eliminating the performance of Step 2 in the goodwill impairment testing. This update allows the testing to be performed by comparing the fair value of a reporting unit with its carrying amount and recognize an impairment charge when the carrying amount exceeds fair value. Additionally, this update eliminated the requirements of any reporting unit with a zero or negative carrying value to perform Step 2, but requires disclosure of the amount of goodwill allocated to a reporting unit with zero or negative carrying amount of net assets. This update becomes effective for fiscal years beginning after December 15, 2019. The Company does not expect this update to have a material impact to its consolidated financial condition and results of operations. In March 2017, the FASB issued ASU Number 2017-08, Receivables - Nonrefundable Fees and Other Costs (Subtopic 310-20). This update shortens the amortization period on callable debt securities held at a premium to the earliest call date, which now closely aligns the amortization period of premiums and discounts to expectations incorporated in the market pricing on callable debt securities. This update becomes effective for fiscal years beginning after December 15, 2018 and interim periods within those fiscal years, and early adoption is permitted. The Company does not expect that adoption of this standard will have a material impact on its consolidated financial condition and results of operations.

Fair Value of Financial Instruments

6 Months Ended

Jun. 30, 2017

Fair Value of Financial Instruments [Abstract]

Fair Value of Financial Instruments

The carrying value and the estimated fair value of the Company’s financial instruments were as follows:



	June 30, 2017				December 31, 2016
	Carrying Value		Estimated Fair Value		Carrying Value		Estimated Fair Value
	(in millions)
Financial assets
Investments	$	2,623.9	$	2,623.9	$	2,552.6	$	2,552.6
Cash and cash equivalents	42.6		42.6		67.2		67.2
Restricted cash and cash equivalents	0.4		0.4		3.6		3.6
Financial liabilities
Notes payable	$	20.0	$	22.7	$	32.0	$	33.0

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


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


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


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

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

The Company bases all of its estimates of fair value for assets on the bid 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 adjustments to prices obtained from third party pricing services as of June 30, 2017 and December 31, 2016 that were material to the consolidated financial statements.

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

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

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

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

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



	June 30, 2017						December 31, 2016
	Level 1		Level 2		Level 3		Level 1		Level 2		Level 3
	(in millions)
Fixed maturity securities
U.S. Treasuries	$	—	$	136.0	$	—	$	—	$	127.4	$	—
U.S. Agencies	—		13.5		—		—		12.8		—
States and municipalities	—		817.1		—		—		851.6		—
Corporate securities	—		1,009.3		—		—		956.7		—
Residential mortgage-backed securities	—		305.8		—		—		258.0		—
Commercial mortgage-backed securities	—		91.3		—		—		95.5		—
Asset-backed securities	—		45.7		—		—		35.4		7.0
Total fixed maturity securities	$	—	$	2,418.7	$	—	$	—	$	2,337.4	$	7.0
Equity securities
Industrial and miscellaneous	$	172.7	$	—	$	—	$	167.2	$	—	$	—
Non-redeemable preferred (FHLB stock)	—		—		4.7		—		—		4.9
Other	22.3		—		—		20.1		—		—
Total equity securities	$	195.0	$	—	$	4.7	$	187.3	$	—	$	4.9
Short-term investments	$	—	$	5.5	$	—	$	—	$	16.0	$	—

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



	June 30, 2017		December 31, 2016
	(in millions)
Cash and cash equivalents at fair value	$	10.6	$	9.7
Cash equivalents measured at NAV, which approximates fair value	32.0		57.5
Total cash and cash equivalents	$	42.6	$	67.2

The following table provides a reconciliation of the beginning and ending balances that are measured using Level 3 inputs for the six months ended June 30, 2017 and 2016.



	Level 3 Securities
	2017			2016
	(in millions)
Beginning balance, January 1	$	11.9		$	—
Transfers (out) of Level 3 ⁽¹⁾	(7.0		)	—
Purchases and sales, net	(0.2		)	4.9
Ending balance, June 30	$	4.7		$	4.9


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

- Definition

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

+ References + Details

Investments

6 Months Ended

Jun. 30, 2017

Investments [Abstract]

Investments

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



	Cost or Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(in millions)
At June 30, 2017
Fixed maturity securities
U.S. Treasuries	$	133.3	$	2.9	$	(0.2	)	$	136.0
U.S. Agencies	12.8		0.7		—			13.5
States and municipalities	785.9		33.9		(2.7		)	817.1
Corporate securities	989.4		22.1		(2.2		)	1,009.3
Residential mortgage-backed securities	303.1		4.6		(1.9		)	305.8
Commercial mortgage-backed securities	91.4		0.6		(0.7		)	91.3
Asset-backed securities	45.4		0.3		—			45.7
Total fixed maturity securities	2,361.3		65.1		(7.7		)	2,418.7
Equity securities
Industrial and miscellaneous	101.7		73.3		(2.3		)	172.7
Non-redeemable preferred (FHLB stock)	4.7		—		—			4.7
Other	11.8		10.5		—			22.3
Total equity securities	118.2		83.8		(2.3		)	199.7
Short-term investments	5.5		—		—			5.5
Total investments	$	2,485.0	$	148.9	$	(10.0	)	$	2,623.9



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

The amortized cost and estimated fair value of the Company's fixed maturity securities at June 30, 2017, by contractual maturity, are shown below. Expected maturities differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties.



	Amortized Cost		Estimated Fair Value
	(in millions)
Due in one year or less	$	228.0	$	228.9
Due after one year through five years	824.2		849.0
Due after five years through ten years	642.6		665.0
Due after ten years	226.6		233.0
Mortgage and asset-backed securities	439.9		442.8
Total	$	2,361.3	$	2,418.7

The following is a summary of investments that have been in a continuous unrealized loss position for less than 12 months and those that have been in a continuous unrealized loss position for 12 months or greater as of June 30, 2017 and December 31, 2016.



	June 30, 2017						December 31, 2016
	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	$	51.3	$	(0.2	)	22	$	33.3	$	(0.2	)	14
U.S. Agencies	—		—			—	—		—			—
States and municipalities	97.2		(2.5		)	26	200.9		(6.1		)	50
Corporate securities	206.7		(1.9		)	213	289.5		(4.1		)	101
Residential mortgage-backed securities	127.7		(1.9		)	49	137.5		(2.6		)	51
Commercial mortgage-backed securities	37.1		(0.7		)	15	48.0		(1.0		)	21
Asset-backed securities	—		—			—	30.1		(0.2		)	20
Total fixed maturity securities	520.0		(7.2		)	325	739.3		(14.2		)	257
Equity securities	19.3		(1.8		)	35	13.6		(0.6		)	28
Short-term investments	—		—			—	—		—			—
Total less than 12 months	$	539.3	$	(9.0	)	360	$	752.9	$	(14.8	)	285

12 months or greater:
Fixed maturity securities
States and municipalities	5.0		(0.2		)	1	—		—			—
Corporate securities	$	16.9	$	(0.3	)	7	$	15.2	$	(0.4	)	5
Total fixed maturity securities	21.9		(0.5		)	8	15.2		(0.4		)	5
Equity securities	3.9		(0.5		)	2	1.7		(0.1		)	5
Total 12 months or greater	$	25.8	$	(1.0	)	10	$	16.9	$	(0.5	)	10

Total available-for-sale:
Fixed maturity securities
U.S. Treasuries	$	51.3	$	(0.2	)	22	$	33.3	$	(0.2	)	14
U.S. Agencies	—		—			—	—		—			—
States and municipalities	102.2		(2.7		)	27	200.9		(6.1		)	50
Corporate securities	223.6		(2.2		)	220	304.7		(4.5		)	106
Residential mortgage-backed securities	127.7		(1.9		)	49	137.5		(2.6		)	51
Commercial mortgage-backed securities	37.1		(0.7		)	15	48.0		(1.0		)	21
Asset-backed securities	—		—			—	30.1		(0.2		)	20
Total fixed maturity securities	541.9		(7.7		)	333	754.5		(14.6		)	262
Equity securities	23.2		(2.3		)	37	15.3		(0.7		)	33
Short-term investments	—		—			—	—		—			—
Total available-for-sale	$	565.1	$	(10.0	)	370	$	769.8	$	(15.3	)	295

The Company determined that unrealized losses on fixed maturities for the six months ended June 30, 2017 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 until fair value recovers to above amortized cost, or principal value upon maturity.

The Company recognized an impairment of $0.2 million (from one equity security) during the six months ended June 30, 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 equity security. Certain unrealized losses on equity securities were not considered to be other-than-temporary due to the financial condition and near-term prospects of the issuers, and the Company's intent to hold the securities until fair value recovers to above cost.

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



	Three Months Ended						Six Months Ended
	June 30,						June 30,
	2017			2016			2017			2016
	(in millions)
Net realized gains on investments
Fixed maturity securities
Gross gains	$	—		$	1.1		$	0.5		$	1.3
Gross losses	—			(0.4		)	(0.1		)	(0.5		)
Net realized gains on fixed maturity securities	$	—		$	0.7		$	0.4		$	0.8
Equity securities
Gross gains	$	1.1		$	5.5		$	3.1		$	12.7
Gross losses	—			(0.2		)	(0.2		)	(6.0		)
Net realized gains on equity securities	$	1.1		$	5.3		$	2.9		$	6.7
Total	$	1.1		$	6.0		$	3.3		$	7.5

Change in unrealized gains
Fixed maturity securities	$	12.5		$	24.3		$	18.9		$	53.6
Equity securities	(0.7		)	5.6			5.4			6.8
Total	$	11.8		$	29.9		$	24.3		$	60.4

Net investment income was as follows:



	Three Months Ended						Six Months Ended
	June 30,						June 30,
	2017			2016			2017			2016
	(in millions)
Fixed maturity securities	$	17.3		$	17.2		$	35.0		$	33.9
Equity securities	1.7			1.8			3.5			3.7
Cash equivalents and restricted cash	0.1			0.1			0.2			0.1
Gross investment income	19.1			19.1			38.7			37.7
Investment expenses	(0.9		)	(0.7		)	(1.8		)	(1.5		)
Net investment income	$	18.2		$	18.4		$	36.9		$	36.2

The Company is required by various state laws and regulations to hold securities or letters of credit in depository accounts with certain states in which it does business. These laws and regulations govern not only the amount but also the types of securities that are eligible for deposit. As of June 30, 2017 and December 31, 2016, securities having a fair value of $1,176.4 million and $1,009.7 million, respectively, were on deposit.

Certain reinsurance contracts require the Company's funds to be held in trust for the benefit of the ceding reinsurer to secure the outstanding liabilities assumed by the Company. The fair value of fixed maturity securities and restricted cash and cash equivalents held in trust for the benefit of ceding reinsurers at June 30, 2017 and December 31, 2016 was $25.1 million and $27.2 million, respectively.

Income Taxes	6 Months Ended
Income Taxes	Jun. 30, 2017
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 22.7% and 21.5% for the six months ended June 30, 2017 and 2016, respectively. Tax-advantaged investment income, LPT Reserve Adjustments, Deferred Gain amortization, and certain other adjustments reduced the Company's effective income tax rate below the U.S. statutory rate of 35%.

Liability for Unpaid Losses and Loss Adjustment Expenses

6 Months Ended

Jun. 30, 2017

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						Six Months Ended
	June 30,						June 30,
	2017			2016			2017			2016
	(in millions)
Unpaid losses and LAE, gross of reinsurance, at beginning of period	$	2,298.2		$	2,341.9		$	2,301.0		$	2,347.5
Less reinsurance recoverable, excluding bad debt allowance, on unpaid losses and LAE	572.9			621.4			580.0			628.2
Net unpaid losses and LAE at beginning of period	1,725.3			1,720.5			1,721.0			1,719.3
Losses and LAE, net of reinsurance, incurred during the period related to:
Current period	109.4			121.3			221.3			232.0
Prior periods	(0.3		)	(2.0		)	(0.3		)	(2.3		)
Total net losses and LAE incurred during the period	109.1			119.3			221.0			229.7
Paid losses and LAE, net of reinsurance, related to:
Current period	17.0			14.4			21.7			19.1
Prior periods	92.3			91.9			195.2			196.4
Total net paid losses and LAE during the period	109.3			106.3			216.9			215.5
Ending unpaid losses and LAE, net of reinsurance	1,725.1			1,733.5			1,725.1			1,733.5
Reinsurance recoverable, excluding bad debt allowance, on unpaid losses and LAE	559.8			598.8			559.8			598.8
Unpaid losses and LAE, gross of reinsurance, at end of period	$	2,284.9		$	2,332.3		$	2,284.9		$	2,332.3

Total net losses and LAE included in the above table excludes the impact of the aggregate of amortization of the deferred reinsurance gain—LPT Agreement, LPT Reserve Adjustments, and LPT Contingent Commission Adjustments, which totaled $3.1 million and $7.6 million for the three months ended June 30, 2017 and 2016, respectively, and $6.0 million and $10.7 million for the six months ended June 30, 2017 and 2016, respectively (Note 7).

The change in incurred losses and LAE attributable to prior periods was related to the Company's assigned risk business for the six months ended June 30, 2016.

LPT Agreement	6 Months Ended
LPT Agreement	Jun. 30, 2017
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 $3.1 million and $2.7 million of the Deferred Gain for the three months ended June 30, 2017 and 2016, respectively, and $6.0 million and $5.8 million for the six months ended June 30, 2017 and 2016, respectively. Additionally, the Deferred Gain was reduced by a further $3.1 million and $1.8 million for the six months ended June 30, 2016, due to a favorable LPT Reserve Adjustment and a favorable LPT Contingent Commission Adjustment, respectively. The remaining Deferred Gain was $168.9 million and $174.9 million as of June 30, 2017 and December 31, 2016, respectively. The estimated remaining liabilities subject to the LPT Agreement were $451.5 million and $465.5 million as of June 30, 2017 and December 31, 2016, respectively. Losses and LAE paid with respect to the LPT Agreement totaled $736.7 million and $722.7 million from inception through June 30, 2017 and December 31, 2016, respectively.

Notes Payable Level 1 (Notes)

6 Months Ended

Jun. 30, 2017

Notes Payable [Abstract]

Debt Disclosure [Text Block]

Notes Payable

Notes payable is comprised of the following:



	June 30, 2017		December 31, 2016
	(in millions)
Dekania Surplus Note, due April 30, 2034	$	10.0	$	10.0
ICONS Surplus Note, due May 26, 2034	—		12.0
Alesco Surplus Note, due December 15, 2034	10.0		10.0
Balance	$	20.0	$	32.0

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

EPIC had a $12.0 million surplus note to ICONS, Inc. issued as part of a pooled transaction. This note was redeemed in May 2017 for $9.9 million, resulting in a $2.1 million gain.

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.

Accumulated Other Comprehensive Income

6 Months Ended

Jun. 30, 2017

Accumulated Other Comprehensive Income [Abstract]

Accumulated Other Comprehensive Income, Net

Accumulated Other Comprehensive Income

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



	June 30, 2017			December 31, 2016
	(in millions)
Net unrealized gains on investments, before taxes	$	138.9		$	114.6
Deferred tax expense on net unrealized gains	(48.6		)	(40.1		)
Total accumulated other comprehensive income	$	90.3		$	74.5

Stock-Based Compensation

6 Months Ended

Jun. 30, 2017

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		Weighted Average Exercise Price		Aggregate Fair Value on Date of Grant
						(in millions)
March 2017
RSUs⁽¹⁾	72,020	$	37.60	$	—	$	2.7
PSUs⁽²⁾	97,440	37.60		—		3.7

May 2017
RSUs⁽¹⁾	11,888	$	40.35	$	—	$	0.5


(1)	The RSUs awarded in March 2017 were awarded to certain employees of the Company and vest 25% on March 15, 2018, 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 change of control of the Company.

The RSUs awarded in May 2017 were awarded to non-employee Directors of the Company and have a vesting period of one year from the date of grant.


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

Commencing in 2017, employees who were awarded RSUs and PSUs are entitled to receive dividend equivalents for eligible awards, payable in cash, when the underlying award vests and becomes payable. If the underlying award does not vest or is forfeited, any dividend equivalents with respect to the underlying award will also fail to become payable and will be forfeited.

Stock options exercised totaled 167,026 for the six months ended June 30, 2017, 438,774 for the six months ended June 30, 2016, and 586,132 for the year ended December 31, 2016.

Earnings Per Share

6 Months Ended

Jun. 30, 2017

Earnings Per Share [Abstract]

Earnings Per Share

Basic earnings per share excludes dilution and is computed by dividing income applicable to stockholders by the weighted average number of shares outstanding for the period. Diluted earnings per share reflects the potential dilutive impact of all convertible securities 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. 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				Six Months Ended
	June 30,				June 30,
	2017		2016		2017		2016
	(in millions, except share data)
Net income available to stockholders—basic and diluted	$	24.8	$	26.8	$	48.0	$	48.6
Weighted average number of shares outstanding—basic	32,469,137		32,629,525		32,398,858		32,521,672
Effect of dilutive securities:
PSUs	235,617		201,029		272,754		170,031
Stock options	230,049		256,303		227,856		247,442
RSUs	57,795		57,091		83,460		64,304
Dilutive potential shares	523,461		514,423		584,070		481,777
Weighted average number of shares outstanding—diluted	32,992,598		33,143,948		32,982,928		33,003,449

Diluted earnings per share excludes outstanding options and other common stock equivalents in periods where the inclusion of such options and common stock equivalents would be anti-dilutive. The following table presents options that were excluded from diluted earnings per share.



	Three Months Ended		Six Months Ended
	June 30,		June 30,
	2017	2016	2017	2016
Options excluded under the treasury method as the potential proceeds on settlement or exercise price were greater than the value of shares acquired	—	145,831	—	113,316

Fair Value of Financial Instruments (Tables)

6 Months Ended

Jun. 30, 2017

Fair Value of Financial Instruments [Abstract]

Estimated fair value of financial instruments table

The carrying value and the estimated fair value of the Company’s financial instruments were as follows:



	June 30, 2017				December 31, 2016
	Carrying Value		Estimated Fair Value		Carrying Value		Estimated Fair Value
	(in millions)
Financial assets
Investments	$	2,623.9	$	2,623.9	$	2,552.6	$	2,552.6
Cash and cash equivalents	42.6		42.6		67.2		67.2
Restricted cash and cash equivalents	0.4		0.4		3.6		3.6
Financial liabilities
Notes payable	$	20.0	$	22.7	$	32.0	$	33.0

Fair value, assets and liabilities measured on recurring basis table

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



	June 30, 2017						December 31, 2016
	Level 1		Level 2		Level 3		Level 1		Level 2		Level 3
	(in millions)
Fixed maturity securities
U.S. Treasuries	$	—	$	136.0	$	—	$	—	$	127.4	$	—
U.S. Agencies	—		13.5		—		—		12.8		—
States and municipalities	—		817.1		—		—		851.6		—
Corporate securities	—		1,009.3		—		—		956.7		—
Residential mortgage-backed securities	—		305.8		—		—		258.0		—
Commercial mortgage-backed securities	—		91.3		—		—		95.5		—
Asset-backed securities	—		45.7		—		—		35.4		7.0
Total fixed maturity securities	$	—	$	2,418.7	$	—	$	—	$	2,337.4	$	7.0
Equity securities
Industrial and miscellaneous	$	172.7	$	—	$	—	$	167.2	$	—	$	—
Non-redeemable preferred (FHLB stock)	—		—		4.7		—		—		4.9
Other	22.3		—		—		20.1		—		—
Total equity securities	$	195.0	$	—	$	4.7	$	187.3	$	—	$	4.9
Short-term investments	$	—	$	5.5	$	—	$	—	$	16.0	$	—

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.



	June 30, 2017		December 31, 2016
	(in millions)
Cash and cash equivalents at fair value	$	10.6	$	9.7
Cash equivalents measured at NAV, which approximates fair value	32.0		57.5
Total cash and cash equivalents	$	42.6	$	67.2

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 six months ended June 30, 2017 and 2016.



	Level 3 Securities
	2017			2016
	(in millions)
Beginning balance, January 1	$	11.9		$	—
Transfers (out) of Level 3 ⁽¹⁾	(7.0		)	—
Purchases and sales, net	(0.2		)	4.9
Ending balance, June 30	$	4.7		$	4.9


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

- 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)

6 Months Ended

Jun. 30, 2017

Investments [Abstract]

Available-for-sale securities table

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



	Cost or Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(in millions)
At June 30, 2017
Fixed maturity securities
U.S. Treasuries	$	133.3	$	2.9	$	(0.2	)	$	136.0
U.S. Agencies	12.8		0.7		—			13.5
States and municipalities	785.9		33.9		(2.7		)	817.1
Corporate securities	989.4		22.1		(2.2		)	1,009.3
Residential mortgage-backed securities	303.1		4.6		(1.9		)	305.8
Commercial mortgage-backed securities	91.4		0.6		(0.7		)	91.3
Asset-backed securities	45.4		0.3		—			45.7
Total fixed maturity securities	2,361.3		65.1		(7.7		)	2,418.7
Equity securities
Industrial and miscellaneous	101.7		73.3		(2.3		)	172.7
Non-redeemable preferred (FHLB stock)	4.7		—		—			4.7
Other	11.8		10.5		—			22.3
Total equity securities	118.2		83.8		(2.3		)	199.7
Short-term investments	5.5		—		—			5.5
Total investments	$	2,485.0	$	148.9	$	(10.0	)	$	2,623.9



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

Investments classified by contractual maturity date table



	Amortized Cost		Estimated Fair Value
	(in millions)
Due in one year or less	$	228.0	$	228.9
Due after one year through five years	824.2		849.0
Due after five years through ten years	642.6		665.0
Due after ten years	226.6		233.0
Mortgage and asset-backed securities	439.9		442.8
Total	$	2,361.3	$	2,418.7

Unrealized loss on investments table



	June 30, 2017						December 31, 2016
	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	$	51.3	$	(0.2	)	22	$	33.3	$	(0.2	)	14
U.S. Agencies	—		—			—	—		—			—
States and municipalities	97.2		(2.5		)	26	200.9		(6.1		)	50
Corporate securities	206.7		(1.9		)	213	289.5		(4.1		)	101
Residential mortgage-backed securities	127.7		(1.9		)	49	137.5		(2.6		)	51
Commercial mortgage-backed securities	37.1		(0.7		)	15	48.0		(1.0		)	21
Asset-backed securities	—		—			—	30.1		(0.2		)	20
Total fixed maturity securities	520.0		(7.2		)	325	739.3		(14.2		)	257
Equity securities	19.3		(1.8		)	35	13.6		(0.6		)	28
Short-term investments	—		—			—	—		—			—
Total less than 12 months	$	539.3	$	(9.0	)	360	$	752.9	$	(14.8	)	285

12 months or greater:
Fixed maturity securities
States and municipalities	5.0		(0.2		)	1	—		—			—
Corporate securities	$	16.9	$	(0.3	)	7	$	15.2	$	(0.4	)	5
Total fixed maturity securities	21.9		(0.5		)	8	15.2		(0.4		)	5
Equity securities	3.9		(0.5		)	2	1.7		(0.1		)	5
Total 12 months or greater	$	25.8	$	(1.0	)	10	$	16.9	$	(0.5	)	10

Total available-for-sale:
Fixed maturity securities
U.S. Treasuries	$	51.3	$	(0.2	)	22	$	33.3	$	(0.2	)	14
U.S. Agencies	—		—			—	—		—			—
States and municipalities	102.2		(2.7		)	27	200.9		(6.1		)	50
Corporate securities	223.6		(2.2		)	220	304.7		(4.5		)	106
Residential mortgage-backed securities	127.7		(1.9		)	49	137.5		(2.6		)	51
Commercial mortgage-backed securities	37.1		(0.7		)	15	48.0		(1.0		)	21
Asset-backed securities	—		—			—	30.1		(0.2		)	20
Total fixed maturity securities	541.9		(7.7		)	333	754.5		(14.6		)	262
Equity securities	23.2		(2.3		)	37	15.3		(0.7		)	33
Short-term investments	—		—			—	—		—			—
Total available-for-sale	$	565.1	$	(10.0	)	370	$	769.8	$	(15.3	)	295

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

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



	Three Months Ended						Six Months Ended
	June 30,						June 30,
	2017			2016			2017			2016
	(in millions)
Net realized gains on investments
Fixed maturity securities
Gross gains	$	—		$	1.1		$	0.5		$	1.3
Gross losses	—			(0.4		)	(0.1		)	(0.5		)
Net realized gains on fixed maturity securities	$	—		$	0.7		$	0.4		$	0.8
Equity securities
Gross gains	$	1.1		$	5.5		$	3.1		$	12.7
Gross losses	—			(0.2		)	(0.2		)	(6.0		)
Net realized gains on equity securities	$	1.1		$	5.3		$	2.9		$	6.7
Total	$	1.1		$	6.0		$	3.3		$	7.5

Change in unrealized gains
Fixed maturity securities	$	12.5		$	24.3		$	18.9		$	53.6
Equity securities	(0.7		)	5.6			5.4			6.8
Total	$	11.8		$	29.9		$	24.3		$	60.4

Investment income table

Net investment income was as follows:



	Three Months Ended						Six Months Ended
	June 30,						June 30,
	2017			2016			2017			2016
	(in millions)
Fixed maturity securities	$	17.3		$	17.2		$	35.0		$	33.9
Equity securities	1.7			1.8			3.5			3.7
Cash equivalents and restricted cash	0.1			0.1			0.2			0.1
Gross investment income	19.1			19.1			38.7			37.7
Investment expenses	(0.9		)	(0.7		)	(1.8		)	(1.5		)
Net investment income	$	18.2		$	18.4		$	36.9		$	36.2

- Definition

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

+ References + Details

Liability for Unpaid Losses and Loss Adjustment Expenses (Tables)

6 Months Ended

Jun. 30, 2017

Liability for Unpaid Losses and Loss Adjustment Expenses [Abstract]

Changes in the liability for unpaid losses and LAE table

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



	Three Months Ended						Six Months Ended
	June 30,						June 30,
	2017			2016			2017			2016
	(in millions)
Unpaid losses and LAE, gross of reinsurance, at beginning of period	$	2,298.2		$	2,341.9		$	2,301.0		$	2,347.5
Less reinsurance recoverable, excluding bad debt allowance, on unpaid losses and LAE	572.9			621.4			580.0			628.2
Net unpaid losses and LAE at beginning of period	1,725.3			1,720.5			1,721.0			1,719.3
Losses and LAE, net of reinsurance, incurred during the period related to:
Current period	109.4			121.3			221.3			232.0
Prior periods	(0.3		)	(2.0		)	(0.3		)	(2.3		)
Total net losses and LAE incurred during the period	109.1			119.3			221.0			229.7
Paid losses and LAE, net of reinsurance, related to:
Current period	17.0			14.4			21.7			19.1
Prior periods	92.3			91.9			195.2			196.4
Total net paid losses and LAE during the period	109.3			106.3			216.9			215.5
Ending unpaid losses and LAE, net of reinsurance	1,725.1			1,733.5			1,725.1			1,733.5
Reinsurance recoverable, excluding bad debt allowance, on unpaid losses and LAE	559.8			598.8			559.8			598.8
Unpaid losses and LAE, gross of reinsurance, at end of period	$	2,284.9		$	2,332.3		$	2,284.9		$	2,332.3

Notes Payable (Tables)

6 Months Ended

Jun. 30, 2017

Notes Payable [Abstract]

Schedule of long-term debt instruments table

Notes payable is comprised of the following:



	June 30, 2017		December 31, 2016
	(in millions)
Dekania Surplus Note, due April 30, 2034	$	10.0	$	10.0
ICONS Surplus Note, due May 26, 2034	—		12.0
Alesco Surplus Note, due December 15, 2034	10.0		10.0
Balance	$	20.0	$	32.0

- 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)

6 Months Ended

Jun. 30, 2017

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		Weighted Average Exercise Price		Aggregate Fair Value on Date of Grant
						(in millions)
March 2017
RSUs⁽¹⁾	72,020	$	37.60	$	—	$	2.7
PSUs⁽²⁾	97,440	37.60		—		3.7

May 2017
RSUs⁽¹⁾	11,888	$	40.35	$	—	$	0.5


(1)	The RSUs awarded in March 2017 were awarded to certain employees of the Company and vest 25% on March 15, 2018, 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 change of control of the Company.

The RSUs awarded in May 2017 were awarded to non-employee Directors of the Company and have a vesting period of one year from the date of grant.


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

Earnings Per Share (Tables)

6 Months Ended

Jun. 30, 2017

Earnings Per Share [Abstract]

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

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



	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2017		2016		2017		2016
	(in millions, except share data)
Net income available to stockholders—basic and diluted	$	24.8	$	26.8	$	48.0	$	48.6
Weighted average number of shares outstanding—basic	32,469,137		32,629,525		32,398,858		32,521,672
Effect of dilutive securities:
PSUs	235,617		201,029		272,754		170,031
Stock options	230,049		256,303		227,856		247,442
RSUs	57,795		57,091		83,460		64,304
Dilutive potential shares	523,461		514,423		584,070		481,777
Weighted average number of shares outstanding—diluted	32,992,598		33,143,948		32,982,928		33,003,449

Antidilutive securities excluded from computation of earnings per share table

The following table presents options that were excluded from diluted earnings per share.



	Three Months Ended		Six Months Ended
	June 30,		June 30,
	2017	2016	2017	2016
Options excluded under the treasury method as the potential proceeds on settlement or exercise price were greater than the value of shares acquired	—	145,831	—	113,316

New Accounting Standards Adopted ASU (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Income Tax Expense (Benefit)	$ (7,800)	$ (7,400)	$ (14,100)	$ (13,300)
Net income	$ 24,800	$ 26,800	$ 48,000	$ 48,600
Basic	$ 0.76	$ 0.82	$ 1.48	$ 1.49
Diluted	$ 0.75	$ 0.81	$ 1.46	$ 1.47
Accounting Standards Update No 2016-09 [Member]
Income Tax Expense (Benefit)		$ 500		$ 1,300
Net income		$ 500		$ 1,300
Basic and Diluted		$ 0.01
Basic				$ 0.04
Diluted				$ 0.03

Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2016	Dec. 31, 2015
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments	$ 2,623,900	$ 2,552,600
Investments, fair value	2,623,900	2,552,600
Cash and cash equivalents	42,600	67,200	$ 128,200	$ 56,600
Cash and cash equivalents, estimated fair value	42,600	67,200
Restricted cash and cash equivalents	400	3,600
Notes payable	20,000	32,000
Notes Payable, fair value	22,700	33,000
Estimate of Fair Value, Fair Value Disclosure [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Restricted cash and cash equivalents	$ 400	$ 3,600

- Definition

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

+ References + Details

Fair Value of Financial Instruments Cash Equivalents at NAV and Total Cash and Cash Equivalents Carried at Fair Value (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents at fair value	$ 10.6	$ 9.7
Cash equivalents measured at NAV, which approximates fair value	32.0	57.5
Total cash and cash equivalents	$ 42.6	$ 67.2

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

6 Months Ended

Jun. 30, 2017

Jun. 30, 2016

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

Beginning balance, January 1, 2017

$ 2,552,600

Transfers (out) of Level 3 (1)

(7,000)

^[1]

$ 0

Purchases and sales, net

(200)

4,900

Ending balance, March 31, 2017

2,623,900

Fair Value, Inputs, Level 3 [Member]

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

Beginning balance, January 1, 2017

11,900

Ending balance, March 31, 2017

$ 4,700

$ 4,900

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

Investments (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	$ 2,485,000	$ 2,438,000
Gross unrealized gain	148,900	129,900
Gross unrealized loss	(10,000)	(15,300)
Investments	2,623,900	2,552,600
Deposit Assets
Investments	2,623,900	2,552,600
Assets Held-in-trust
Investments	2,623,900	2,552,600
Funds Held under Reinsurance Agreements, Asset	25,100	27,200
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	2,361,300	2,305,900
Gross unrealized gain	65,100	53,100
Gross unrealized loss	(7,700)	(14,600)
Investments	2,418,700	2,344,400
Deposit Assets
Investments	2,418,700	2,344,400
Assets Held-in-trust
Investments	2,418,700	2,344,400
US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	133,300	124,100
Gross unrealized gain	2,900	3,500
Gross unrealized loss	(200)	(200)
Investments	136,000	127,400
Deposit Assets
Investments	136,000	127,400
Assets Held-in-trust
Investments	136,000	127,400
US Government Agencies Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	12,800	11,900
Gross unrealized gain	700	900
Gross unrealized loss	0	0
Investments	13,500	12,800
Deposit Assets
Investments	13,500	12,800
Assets Held-in-trust
Investments	13,500	12,800
US States and Political Subdivisions Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	785,900	833,000
Gross unrealized gain	33,900	24,700
Gross unrealized loss	(2,700)	(6,100)
Investments	817,100	851,600
Deposit Assets
Investments	817,100	851,600
Assets Held-in-trust
Investments	817,100	851,600
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	989,400	942,300
Gross unrealized gain	22,100	18,900
Gross unrealized loss	(2,200)	(4,500)
Investments	1,009,300	956,700
Deposit Assets
Investments	1,009,300	956,700
Assets Held-in-trust
Investments	1,009,300	956,700
Residential Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	303,100	255,900
Gross unrealized gain	4,600	4,700
Gross unrealized loss	(1,900)	(2,600)
Investments	305,800	258,000
Deposit Assets
Investments	305,800	258,000
Assets Held-in-trust
Investments	305,800	258,000
Commercial Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	91,400	96,100
Gross unrealized gain	600	400
Gross unrealized loss	(700)	(1,000)
Investments	91,300	95,500
Deposit Assets
Investments	91,300	95,500
Assets Held-in-trust
Investments	91,300	95,500
Asset-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	45,400	42,600
Gross unrealized gain	300	0
Gross unrealized loss	0	(200)
Investments	45,700	42,400
Deposit Assets
Investments	45,700	42,400
Assets Held-in-trust
Investments	45,700	42,400
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	118,200	116,100
Gross unrealized gain	83,800	76,800
Gross unrealized loss	(2,300)	(700)
Investments	199,700	192,200
Deposit Assets
Investments	199,700	192,200
Assets Held-in-trust
Investments	199,700	192,200
Industrial and Miscellaneous [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	101,700	100,500
Gross unrealized gain	73,300	67,400
Gross unrealized loss	(2,300)	(700)
Investments	172,700	167,200
Deposit Assets
Investments	172,700	167,200
Assets Held-in-trust
Investments	172,700	167,200
Non-redeemable preferred (FHLB stock) [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	4,700	4,900
Gross unrealized gain	0	0
Gross unrealized loss	0	0
Investments	4,700	4,900
Deposit Assets
Investments	4,700	4,900
Assets Held-in-trust
Investments	4,700	4,900
Other [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	11,800	10,700
Gross unrealized gain	10,500	9,400
Gross unrealized loss	0	0
Investments	22,300	20,100
Deposit Assets
Investments	22,300	20,100
Assets Held-in-trust
Investments	22,300	20,100
Short-term Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	5,500	16,000
Gross unrealized gain	0	0
Gross unrealized loss	0	0
Investments	5,500	16,000
Deposit Assets
Investments	5,500	16,000
Assets Held-in-trust
Investments	5,500	16,000
Required by various state laws and regulations to hold securities or letters of credit in depository account [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments	1,176,400	1,009,700
Deposit Assets
Investments	1,176,400	1,009,700
Assets Held-in-trust
Investments	$ 1,176,400	$ 1,009,700

Investments, Amortized Cost and Estimated Fair Value (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Amortized Cost
Due in one year or less, amortized cost	$ 228,000
Due after one year through five years, amortized cost	824,200
Due after five years through ten years, amortized cost	642,600
Due after ten years, amortized cost	226,600
Mortgage and asset-backed securities, amortized cost	439,900
Total, amortized cost	2,361,300
Estimated Fair Value
Due in one year or less, fair value	228,900
Due after one year through five years, fair value	849,000
Due after five years through ten years, fair value	665,000
Due after ten years, fair value	233,000
Mortgage and asset-backed securities, fair value	442,800
Total, fair value	$ 2,418,700	$ 2,344,400

Investments, Continuous Loss Position (Details)	3 Months Ended		6 Months Ended
Investments, Continuous Loss Position (Details)	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)
Estimated Fair Value
Estimated fair value, less than 12 months	$ 539,300,000		$ 539,300,000		$ 752,900,000
Estimated fair value, 12 months or greater	25,800,000		25,800,000		16,900,000
Estimated fair value, total	565,100,000		565,100,000		769,800,000
Gross Unrealized Losses
Gross unrealized losses, less than 12 months	(9,000,000)		(9,000,000)		(14,800,000)
Gross unrealized losses, 12 months or greater	1,000,000		1,000,000		500,000
Estimated unrealized losses, total	$ (10,000,000)		$ (10,000,000)		$ (15,300,000)
Number of issues in loss position, less than 12 months	360		360		285
Number of Issues in loss position, 12 months or greater	10		10		10
Number of issues loss position, aggregate	370		370		295
Other than temporary impairment, credit losses recognized in earnings	$ 0	$ 0	$ 200,000	$ 5,300,000
Total impairments, number of securities	1		1
Debt Securities [Member]
Estimated Fair Value
Estimated fair value, less than 12 months	$ 520,000,000		$ 520,000,000		$ 739,300,000
Estimated fair value, 12 months or greater	21,900,000		21,900,000		15,200,000
Estimated fair value, total	541,900,000		541,900,000		754,500,000
Gross Unrealized Losses
Gross unrealized losses, less than 12 months	(7,200,000)		(7,200,000)		(14,200,000)
Gross unrealized losses, 12 months or greater	500,000		500,000		400,000
Estimated unrealized losses, total	$ (7,700,000)		$ (7,700,000)		$ (14,600,000)
Number of issues in loss position, less than 12 months	325		325		257
Number of Issues in loss position, 12 months or greater	8		8		5
Number of issues loss position, aggregate	333		333		262
US Treasury Securities [Member]
Estimated Fair Value
Estimated fair value, less than 12 months	$ 51,300,000		$ 51,300,000		$ 33,300,000
Estimated fair value, total	51,300,000		51,300,000		33,300,000
Gross Unrealized Losses
Gross unrealized losses, less than 12 months	(200,000)		(200,000)		(200,000)
Estimated unrealized losses, total	$ (200,000)		$ (200,000)		$ (200,000)
Number of issues in loss position, less than 12 months	22		22		14
Number of issues loss position, aggregate	22		22		14
US States and Political Subdivisions Debt Securities [Member]
Estimated Fair Value
Estimated fair value, less than 12 months	$ 97,200,000		$ 97,200,000		$ 200,900,000
Estimated fair value, total	102,200,000		102,200,000		200,900,000
Gross Unrealized Losses
Gross unrealized losses, less than 12 months	(2,500,000)		(2,500,000)		(6,100,000)
Estimated unrealized losses, total	$ (2,700,000)		$ (2,700,000)		$ (6,100,000)
Number of issues in loss position, less than 12 months	26		26		50
Number of issues loss position, aggregate	27		27		50
Corporate Debt Securities [Member]
Estimated Fair Value
Estimated fair value, less than 12 months	$ 206,700,000		$ 206,700,000		$ 289,500,000
Estimated fair value, 12 months or greater	16,900,000		16,900,000		15,200,000
Estimated fair value, total	223,600,000		223,600,000		304,700,000
Gross Unrealized Losses
Gross unrealized losses, less than 12 months	(1,900,000)		(1,900,000)		(4,100,000)
Gross unrealized losses, 12 months or greater	300,000		300,000		400,000
Estimated unrealized losses, total	$ (2,200,000)		$ (2,200,000)		$ (4,500,000)
Number of issues in loss position, less than 12 months	213		213		101
Number of Issues in loss position, 12 months or greater	7		7		5
Number of issues loss position, aggregate	220		220		106
Residential Mortgage Backed Securities [Member]
Estimated Fair Value
Estimated fair value, less than 12 months	$ 127,700,000		$ 127,700,000		$ 137,500,000
Estimated fair value, total	127,700,000		127,700,000		137,500,000
Gross Unrealized Losses
Gross unrealized losses, less than 12 months	(1,900,000)		(1,900,000)		(2,600,000)
Estimated unrealized losses, total	$ (1,900,000)		$ (1,900,000)		$ (2,600,000)
Number of issues in loss position, less than 12 months	49		49		51
Number of issues loss position, aggregate	49		49		51
Commercial Mortgage Backed Securities [Member]
Estimated Fair Value
Estimated fair value, less than 12 months	$ 37,100,000		$ 37,100,000		$ 48,000,000
Estimated fair value, total	37,100,000		37,100,000		48,000,000
Gross Unrealized Losses
Gross unrealized losses, less than 12 months	(700,000)		(700,000)		(1,000,000)
Estimated unrealized losses, total	$ (700,000)		$ (700,000)		$ (1,000,000)
Number of issues in loss position, less than 12 months	15		15		21
Number of issues loss position, aggregate	15		15		21
Asset-backed Securities [Member]
Estimated Fair Value
Estimated fair value, less than 12 months	$ 0		$ 0		$ 30,100,000
Estimated fair value, total	0		0		30,100,000
Gross Unrealized Losses
Gross unrealized losses, less than 12 months	0		0		(200,000)
Estimated unrealized losses, total	$ 0		$ 0		$ (200,000)
Number of issues in loss position, less than 12 months	0		0		0
Number of issues loss position, aggregate	0		0		0
Equity Securities [Member]
Estimated Fair Value
Estimated fair value, less than 12 months	$ 19,300,000		$ 19,300,000		$ 13,600,000
Estimated fair value, 12 months or greater	3,900,000		3,900,000		1,700,000
Estimated fair value, total	23,200,000		23,200,000		15,300,000
Gross Unrealized Losses
Gross unrealized losses, less than 12 months	(1,800,000)		(1,800,000)		(600,000)
Gross unrealized losses, 12 months or greater	500,000		500,000		100,000
Estimated unrealized losses, total	$ (2,300,000)		$ (2,300,000)		$ (700,000)
Number of issues in loss position, less than 12 months	35		35		28
Number of Issues in loss position, 12 months or greater	2		2		5
Number of issues loss position, aggregate	37		37		33

Investments, Net Realized Gains (Losses) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Net realized gains (losses)
Net realized gains (losses) on fixed maturity and equity securities	$ 1.1	$ 6.0	$ 3.3	$ 7.5
Change in unrealized gains (losses)
Change in unrealized gains (losses) on fixed maturity and equity securities	11.8	29.9	24.3	60.4
Debt Securities [Member]
Net realized gains (losses)
Gross gains from sales	0.0	1.1	0.5	1.3
Gross losses from sales	0.0	0.4	0.1	0.5
Net realized gains (losses) on fixed maturity and equity securities	0.0	0.7	0.4	0.8
Change in unrealized gains (losses)
Change in unrealized gains (losses) on fixed maturity and equity securities	12.5	24.3	18.9	53.6
Equity Securities [Member]
Net realized gains (losses)
Gross gains from sales	1.1	5.5	3.1	12.7
Gross losses from sales	0.0	0.2	0.2	6.0
Net realized gains (losses) on fixed maturity and equity securities	1.1	5.3	2.9	6.7
Change in unrealized gains (losses)
Change in unrealized gains (losses) on fixed maturity and equity securities	$ (0.7)	$ 5.6	$ 5.4	$ 6.8

Net Investment Income (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
Net Investment Income (Details) - USD ($) $ in Millions	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income	$ 19.1	$ 19.1	$ 38.7	$ 37.7
Investment expenses	0.9	0.7	1.8	1.5
Net investment income	18.2	18.4	36.9	36.2
Debt Securities [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income related to fixed maturity securities and short-term investments and cash equivalents	17.3	17.2	35.0	33.9
Equity Securities [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income related to equity securities	1.7	1.8	3.5	3.7
Short-term Investments [Member]
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Investment income related to fixed maturity securities and short-term investments and cash equivalents	$ 0.1	$ 0.1	$ 0.2	$ 0.1

Income Taxes (Details)	6 Months Ended
Income Taxes (Details)	Jun. 30, 2017	Jun. 30, 2016
Effective Income Tax Rate, Continuing Operations, Tax Rate Reconciliation [Abstract]
Statutory tax rate	35.00%
Effective tax rate	22.70%	21.50%

Liability for Unpaid Losses and Loss Adjustment Expenses (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Unpaid losses and LAE, gross of reinsurance, at beginning of period	$ 2,298,200	$ 2,341,900	$ 2,301,000	$ 2,347,500
Less reinsurance recoverable, excluding bad debt allowance, on unpaid losses and LAE	572,900	621,400	580,000	628,200
Net unpaid losses and LAE at beginning of period	1,725,300	1,720,500	1,721,000	1,719,300
Losses and LAE, net of reinsurance, incurred during the period related to:
Current period	109,400	121,300	221,300	232,000
Prior periods	(300)	(2,000)	(300)	(2,300)
Total net losses and LAE incurred during the period	109,100	119,300	221,000	229,700
Deduct payments for losses and LAE, net of reinsurance, related to:
Current period	17,000	14,400	21,700	19,100
Prior periods	92,300	91,900	195,200	196,400
Total net paid losses and LAE during the period	109,300	106,300	216,900	215,500
Ending unpaid losses and LAE, net of reinsurance	1,725,100	1,733,500	1,725,100	1,733,500
Reinsurance recoverable, excluding bad debt allowance, on unpaid losses and LAE	559,800	598,800	559,800	598,800
Unpaid losses and LAE, gross of reinsurance, at end of period	2,284,900	2,332,300	2,284,900	2,332,300
LPT Agreement [Abstract]
Impact of the LPT Agreement	$ 3,100	$ 7,600	$ 6,000	$ 10,700

LPT Agreement LPT Agreement (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Reinsurance Agreement [Line Items]
Liabilities for the incurred but unpaid losses and LAE related to claims prior to July 1, 1995	$ 1,500,000		$ 1,500,000
Ceded premiums written			775,000
Amortization of deferred gain	3,100	$ 2,700	6,000	$ 5,800
LPT reserve adjustment				3,100
LPT contingent commission adjustment				$ 1,800
Deferred reinsurance gain—LPT Agreement	168,900		168,900		$ 174,900
Estimated remaining liabilities - LPT Agreement	451,500		451,500		465,500
Paid losses and LAE claims related to LPT	736,700		736,700		$ 722,700
Indemnification Agreement [Member]
Reinsurance Agreement [Line Items]
Coverage provided under LPT Agreement	$ 2,000,000		$ 2,000,000

Notes Payable Notes Payable Outstanding(Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Debt Instrument [Line Items]
Notes payable	$ 20,000		$ 20,000		$ 32,000
Gain on redemption of notes payable	2,100	$ 0	2,100	$ 0
Redemption of notes payable			9,900	$ 0
Dekania Surplus Note [Member]
Debt Instrument [Line Items]
Notes payable	10,000		$ 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
ICONS Surplus Note [Member]
Debt Instrument [Line Items]
Notes payable	0		$ 0		12,000
Date notes payable was redeemed			May 01, 2017
Gain on redemption of notes payable			$ 2,100
Redemption of notes payable			9,900
Alesco Surplus Note [Member]
Debt Instrument [Line Items]
Notes payable	$ 10,000		$ 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

Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Net unrealized gain on investments, before taxes	$ 138,900	$ 114,600
Deferred tax expense on net unrealized gains	(48,600)	(40,100)
Accumulated other comprehensive income, net	$ 90,300	$ 74,500

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

1 Months Ended

3 Months Ended

6 Months Ended

12 Months Ended

May 31, 2017

Mar. 31, 2017

Jun. 30, 2017

Jun. 30, 2016

Dec. 31, 2016

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

Stock-options exercised

167,026

438,774

586,132

Officer [Member]

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

Vesting rights for options awarded

vest 25% on March 15, 2018, 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%

Stock Option [Member]

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

Number of outstanding options or share units

395,945

Restricted Stock Units (RSUs) [Member]

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

Share-based compensation award, shares issued

^[1]

11,888

72,020

Share-based compensation options, exercise price on grant date

$ 40.35

^[1]

$ 37.60

^[2]

Share-based compensation award, fair value assumptions, exercise price

$ 0

Fair value of awards awarded on grant date

^[1]

$ 0.5

$ 2.7

Number of outstanding options or share units

337,007

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

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

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

1 year

Performance Shares [Member]

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

Share-based compensation award, shares issued

^[2]

97,440

Share-based compensation options, exercise price on grant date

^[2]

$ 37.60

Share-based compensation award, fair value assumptions, exercise price

$ 0

Fair value of awards awarded on grant date

^[2]

$ 3.7

Number of outstanding options or share units

304,676

Performance Shares [Member] | Officer [Member]

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

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

1 year

[1]	The RSUs awarded in March 2017 were awarded to certain employees of the Company and vest 25% on March 15, 2018, 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 change of control of the Company.
[2]	RSUs awarded in May 2017 were awarded to non-employee Directors of the Company and have a vesting period of one year from the date of grant.(2)The PSUs awarded in March 2017 were awarded to certain employees of the Company and have a performance period of two years followed by an additional one year vesting period. The PSU awards are subject to certain performance goals with payouts tha

Earnings Per Share (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
Earnings Per Share (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Earnings Per Share, Basic and Diluted, by Common Class [Line Items]
Net income available to stockholders - basic and diluted	$ 24,800	$ 26,800	$ 48,000	$ 48,600
Weighted average number of shares outstanding - basic	32,469,137	32,629,525	32,398,858	32,521,672
Effect of dilutive securities:
Dilutive securities	523,461	514,423	584,070	481,777
Weighted average number of shares outstanding - diluted	32,992,598	33,143,948	32,982,928	33,003,449
Antidilutive securites excluded under the treasury method from computation of earnings per share	0	145,831	0	113,316
Employee Stock Option [Member]
Effect of dilutive securities:
Dilutive securities	230,049	256,303	227,856	247,442
Restricted Stock Units (RSUs) [Member]
Effect of dilutive securities:
Dilutive securities	57,795	57,091	83,460	64,304
Performance Shares [Member]
Effect of dilutive securities:
Dilutive securities	235,617	201,029	272,754	170,031

Conslidated Stockholders Equity (Parentheticals) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Statement of Stockholders' Equity Parenthetical [Abstract]
Change in net unrealized gains on investments, net of tax	$ 8.5	$ 21.2

Basis of Presentation (Details)	6 Months Ended
Basis of Presentation (Details)	Jun. 30, 2017
Basis of Presentation [Abstract]
Number of Operating Segments	1

Fair Value of Financial Instruments, Fair Value Inputs (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	$ 2,623.9	$ 2,552.6
Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	2,418.7	2,344.4
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	2,418.7	2,337.4
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	7.0
US Treasury Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	136.0	127.4
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	136.0	127.4
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	13.5	12.8
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	13.5	12.8
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	817.1	851.6
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	817.1	851.6
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	1,009.3	956.7
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	1,009.3	956.7
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	305.8	258.0
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	305.8	258.0
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	91.3	95.5
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	91.3	95.5
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	45.7	42.4
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	45.7	35.4
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	7.0
Equity Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	199.7	192.2
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	195.0	187.3
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	4.7	4.9
Industrial and Miscellaneous [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	172.7	167.2
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	172.7	167.2
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	4.9
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	4.7	4.9
Other [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	22.3	20.1
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	22.3	20.1
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	5.5	16.0
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		16.0
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