AmTrust Financial Services (AFSIP) 10-Q 9 Aug 18 2018 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2018	Aug. 03, 2018
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q2
Trading Symbol	AFSI
Entity Registrant Name	AMTRUST FINANCIAL SERVICES, INC.
Entity Central Index Key	1,365,555
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		197,577,246

Consolidated Balance Sheets (un

Consolidated Balance Sheets (unaudited) - USD ($) $ in Millions		Jun. 30, 2018	Dec. 31, 2017
Investments:
Fixed maturity securities, available-for-sale, at fair value (amortized cost $8,376.8; and $7,408.7)		$ 8,278.3	$ 7,488.3
Fixed maturity securities, trading, at fair value (amortized cost $150.0; and $52.2)		148.8	49.8
Equity securities, at fair value (cost $137.3; and $195.9)	[1]	154.3	211.7
Short-term investments		169.7	187.8
Other investments (related party $271.6; and $56.6)		441.5	212
Total investments		9,192.6	8,149.6
Cash and cash equivalents		668.8	763.1
Restricted cash and cash equivalents		532.2	480.1
Accrued interest and dividends		62.6	64.4
Premiums receivable, net (related party $165.7; and $0)		3,069.7	2,784.8
Reinsurance recoverable (related party $3,188.7; and $3,026.8)		6,053.2	6,131.4
Prepaid reinsurance premiums (related party $1,248.0; and $1,172.3)		2,304.1	2,137.3
Federal income tax receivable		69.8	73.9
Deferred policy acquisition costs		980.9	922.9
Assets held for sale		0	900.9
Property and equipment, net		421.1	453.4
Goodwill		529.5	552.9
Intangible assets		350.6	380.8
Other assets (related party $195.7; and $271.4; recorded at fair value $1.9; and $20.8)		1,526.2	1,423.1
Total assets		25,761.3	25,218.6
Liabilities:
Loss and loss adjustment expense reserves		12,345.3	12,138.8
Unearned premiums		5,703.4	5,279.2
Ceded reinsurance premiums payable (related party $412.8; and $402.4)		898.4	809.6
Funds held under reinsurance treaties		75.5	83.6
Note payable on collateral loan – related party		168	168
Securities sold but not yet purchased, at fair value		161.8	75.5
Securities sold under agreements to repurchase		214.8	0
Liabilities held for sale		0	761.7
Deferred gain on retroactive reinsurance		317.9	330
Debt (net of debt issuance cost of $14.4, and $15.0)		1,315.3	1,288.7
Accrued expenses and other liabilities (related party $55.3; and $0; recorded at fair value $34.4; and $78.6)		959.8	913.5
Total liabilities		22,160.2	21,848.6
Commitments and contingencies
Redeemable non-controlling interest		0	1.9
Stockholders’ equity:
Common stock, $0.01 par value; 500.0 shares authorized; 210.8 issued in 2018 and 2017; 197.5 and 196.1 outstanding in 2018 and 2017, respectively		2.1	2.1
Preferred stock, $0.01 par value; 10.0 shares authorized; 5.4 issued and outstanding in 2018 and 2017; $913.7 aggregated liquidation preference in 2018 and 2017		913.7	913.7
Additional paid-in capital		1,622.8	1,639.6
Treasury stock at cost; 13.2 and 14.7 shares in 2018 and 2017, respectively		(218.2)	(242.1)
Accumulated other comprehensive (loss) income, net of tax		(150.6)	15.5
Retained earnings		1,373.8	860.9
Total AmTrust Financial Services, Inc. equity		3,543.6	3,189.7
Non-controlling interest		57.5	178.4
Total stockholders’ equity		3,601.1	3,368.1
Total liabilities and stockholders' equity		$ 25,761.3	$ 25,218.6
[1]	In connection with the adoption of ASU 2016-01, the consolidated balance sheets as of December 31, 2017 have been recast for comparability. See Note 2. "Recent Accounting Pronouncements" for additional information on the adoption of ASU 2016-01.

Consolidated Balance Sheets (u3

Consolidated Balance Sheets (unaudited) (Parenthetical) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Fixed maturity securities, available-for-sale, amortized costs	$ 8,376.8	$ 7,408.7
Fixed maturities, trading, amortized cost	150	52.2
Equity securities, cost	137.3	195.9
Other investments	441.5	212
Reinsurance recoverable	6,053.2	6,131.4
Premiums receivable, net (related party $165.7; and $0)	3,069.7	2,784.8
Prepaid reinsurance premium	2,304.1	2,137.3
Other assets	1,526.2	1,423.1
Other assets, fair value	1.9	20.8
Ceded reinsurance premiums payable	898.4	809.6
Debt issuance costs	14.4	15
Accrued expenses and other liabilities	959.8	913.5
Accrued expenses and other liabilities, fair value	$ 34.4	$ 78.6
Common stock, par value (usd per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	500,000,000	500,000,000
Common stock, issued (in shares)	210,800,000	210,800,000
Common stock, outstanding (in shares)	197,500,000	196,100,000
Preferred stock, par value (usd per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock, shares issued (in shares)	5,400,000	5,400,000
Preferred stock, shares outstanding (in shares)	5,400,000	5,400,000
Liquidation preference	$ 913.7	$ 913.7
Treasury stock at cost (in shares)	13,200,000	14,700,000
Related Party Transactions
Other investments	$ 271.6	$ 56.6
Reinsurance recoverable	3,188.7	3,026.8
Premiums receivable, net (related party $165.7; and $0)	165.7	0
Prepaid reinsurance premium	1,248	1,172.3
Other assets	195.7	271.4
Ceded reinsurance premiums payable	412.8	402.4
Accrued expenses and other liabilities	$ 55.3	$ 0

Consolidated Statements of Oper

Consolidated Statements of Operations (unaudited) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Income Statement [Abstract]
Net earned premium	$ 1,286.2	$ 1,380.7	$ 2,641.1	$ 2,603.2
Service and fee income (related parties - three months $12.7; $35.6 and six months $27.2; $55.9)	49.3	168.4	165.4	305.9
Net investment income	68.3	49.3	136.5	112.6
Net realized gain on investments	5.4	23.5	7.7	32.1
Gain on sale of U.S.-based fee business	0	0	724.1	0
Other	(2.5)	(1.5)	5.2	7.2
Total revenues	1,406.7	1,620.4	3,680	3,061
Losses and expenses:
Loss and loss adjustment expenses	933.7	1,024.5	1,906.6	1,864.8
Amortization of deferred acquisition costs (net of ceding commission - related party - three months $156.0; $158.2 and six months $314.9; $311.9)	310.4	207.8	526	413.7
Underwriting, general and administrative expenses	121.1	165.4	333.7	287.7
Interest expense (net of interest income - related party - three months $1.2; $1.2 and six months $2.3; $2.3)	21.9	24.2	44.7	47.8
Foreign currency loss (gain)	11.6	58.9	(14.9)	76.9
Other	109.3	199.8	323.9	362.7
Total losses and expenses	1,508	1,680.6	3,120	3,053.6
(Loss) income before income taxes and equity in earnings of unconsolidated subsidiaries	(101.3)	(60.2)	560	7.4
(Benefit) provision for income taxes	(4.4)	(19.8)	(19)	1.6
(Loss) income before equity in earnings of unconsolidated subsidiaries	(96.9)	(40.4)	579	5.8
Equity in earnings of unconsolidated subsidiaries	0	69.5	0	73.5
Net (loss) income	(96.9)	29.1	579	79.3
Net income attributable to non-controlling interest and redeemable non-controlling interest of subsidiaries	(2.8)	(6.7)	(0.3)	(17.7)
Net (loss) income attributable to AmTrust stockholders	(99.7)	22.4	578.7	61.6
Dividends on preferred stock	(16.5)	(16.5)	(33.1)	(33.1)
Net (loss) income attributable to AmTrust common stockholders	$ (116.2)	$ 5.9	$ 545.6	$ 28.5
Earnings per common share: (usd per share)
Basic (loss) earnings per share (usd per share)	$ (0.59)	$ 0.03	$ 2.78	$ 0.16
Diluted (loss) earnings per share (usd per share)	(0.59)	0.03	2.77	0.16
Dividends declared per common share (usd per share)	$ 0	$ 0.17	$ 0.17	$ 0.34

Consolidated Statements of Inco

Consolidated Statements of Income (unaudited) (Parenthetical) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Service and fee income	$ 49.3	$ 168.4	$ 165.4	$ 305.9
Interest Income form related party	1.2	1.2	2.3	2.3
Related Party Transactions
Service and fee income	12.7	35.6	27.2	55.9
Ceding commission - earned	$ 156	$ 158.2	$ 314.9	$ 311.9

Consolidated Statement of Compr

Consolidated Statement of Comprehensive Income (unaudited) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement of Comprehensive Income [Abstract]
Net (loss) income		$ (96.9)	$ 29.1	$ 579	$ 79.3
Other comprehensive (loss) income, net of tax:
Foreign currency translation adjustments		(86.6)	62.7	(24.4)	76.6
Change in fair value of interest rate swap		0	0	0	0.1
Unrealized (loss) gain on debt securities:
Gross unrealized holding (loss) gain		(17.8)	66.1	(174.9)	98.1
Less tax (benefit) expense		(5.6)	16.6	(38)	23
Cumulative effect of change in accounting principles, net of taxes of $20.4 for the six months ended June 30, 2018 (1)	[1]	0	0	(0.7)	0
Net unrealized holding (loss) gain		(12.2)	49.5	(137.6)	75.1
Other net realized gain on investments		(2.5)	(19.3)	(4.1)	(30.9)
Reclassification adjustment for investment gain included in net (loss) income		(2.5)	(19.3)	(4.1)	(30.9)
Other comprehensive (loss) income, net of tax		(101.3)	92.9	(166.1)	120.9
Comprehensive (loss) income		(198.2)	122	412.9	200.2
Less: comprehensive income attributable to non-controlling and redeemable non-controlling interest		2.8	6.7	0.3	17.7
Comprehensive (loss) income attributable to AmTrust Financial Services, Inc.		$ (201)	$ 115.3	$ 412.6	$ 182.5
[1]	See Note 2. "Recent Accounting Pronouncements" for additional information on the adoptions of ASU 2016-01 and ASU 2018-02.

Consolidated Statement of Comp7

Consolidated Statement of Comprehensive Income (unaudited) (Parenthetical) $ in Millions	6 Months Ended
	Jun. 30, 2018USD ($)
Statement of Comprehensive Income [Abstract]
Cumulative effect of change in accounting principles, taxes	$ 20.4

Consolidated Statements of Cash

Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Millions		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017
Statement of Cash Flows [Abstract]
Net cash provided by operating activities		$ 323.9	$ 277.6	[1]
Purchases of:
Fixed maturity securities, available-for-sale		(2,125.3)	(1,112.4)	[1]
Fixed maturity securities, trading		(383.2)	(312.9)	[1]
Equity securities		(114.7)	(11.2)	[1]
Other investments		(13.5)	(15.6)	[1]
Subsidiaries, net of cash received		0.1	(97.8)	[1]
Property, equipment and software, net		(4.9)	(188.7)	[1]
Life settlement contracts		0	(16.5)	[1]
Sales of:
Fixed maturity securities, available-for-sale (includes maturities & paydowns)		1,079.1	988.3	[1]
Fixed maturity securities, trading		282.9	309.4	[1]
Equity securities		181.7	151.7	[1]
Other investments		4	65.7	[1]
Securities sold but not purchased, net		85.4	21.5	[1]
Equity method investment		0	211.3	[1]
Subsidiary, net of cash transferred	[2]	538.4	0	[1]
Short term investments, net		35.2	0	[1]
Receipt of life settlement contract proceeds		0	33.2	[1]
Net cash (used in) provided by investing activities		(434.8)	26	[1]
Cash flows from financing activities:
Securities sold under agreements to repurchase, net		214.8	(128.6)	[1]
Secured loan agreements borrowings		0	105.6	[1]
Secured loan agreements payments		(3.8)	(7.5)	[1]
Promissory notes and other proceeds (payments)		13.3
Promissory notes and other proceeds (payments)	[1]		(52.3)
Financing fees		0	(0.2)	[1]
Common stock issuance		0	298.7	[1]
Contingent consideration payments		(1.4)	(5)	[1]
Non-controlling interest capital (dividends) contributions from consolidated subsidiaries, net		(114.6)
Non-controlling interest capital (dividends) contributions from consolidated subsidiaries, net	[1]		12.4
Stock option exercise and other		(3.1)	(1.4)	[1]
Dividends distributed on common stock		(66.7)	(58.1)	[1]
Dividends distributed on preferred stock		(33.1)	(33.1)	[1]
Net cash (used in) provided by financing activities		5.4	130.5	[1]
Effect of exchange rate changes on cash		(26.6)	19.1	[1]
Cash, cash equivalents and restricted cash included in business classified as held for sale, beginning of the year		89.9	0	[1]
Net (decrease) increase in cash, cash equivalents and restricted cash and restricted cash equivalents		(42.2)	453.2	[1]
Cash, cash equivalents, restricted cash and restricted cash equivalents, beginning of the year		1,243.2	1,281.1	[1]
Cash, cash equivalents, restricted cash and restricted cash equivalents, end of the period		$ 1,201	$ 1,734.3	[1]
[1]	In connection with the adoption of ASU 2016-18, the disclosure for the six months ended June 30, 2017 has been recast for comparability. See Note 2. "Recent Accounting Pronouncements" for additional information on the adoption of ASU 2016-18.
[2]	Relates to the transfer of our U.S.-based fee business. See Note 13. "Divestiture" for additional information.

Basis of Reporting and Merger A

Basis of Reporting and Merger Agreement	6 Months Ended
	Jun. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Reporting and Merger Agreement	Basis of Reporting and Merger Agreement Basis of Reporting The accompanying unaudited interim consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) for interim financial statements and with the instructions to Form 10-Q and Article 10 of Regulation S-X and, therefore, do not include all of the information and footnotes required by GAAP for complete financial statements. These interim statements should be read in conjunction with the consolidated financial statements and notes thereto included in the AmTrust Financial Services, Inc. (“AmTrust” or the “Company”) Annual Report on Form 10-K for the year ended December 31, 2017 , previously filed with the Securities and Exchange Commission ("SEC") on March 16, 2018 ("Form 10-K"). These interim consolidated financial statements reflect all adjustments that are, in the opinion of management, necessary for a fair presentation of the results for the interim period and all such adjustments are of a normal recurring nature. The results of operations for the interim period are not necessarily indicative, if annualized, of those to be expected for the full year. The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Actual results could differ from those estimates. A detailed description of the Company’s significant accounting policies and management judgments is located in the audited consolidated financial statements for the year ended December 31, 2017 , included in the Company’s Form 10-K filed with the SEC. All material inter-company transactions and accounts have been eliminated in the consolidated financial statements. To facilitate period-to-period comparisons, certain reclassifications have been made to prior period consolidated financial statement amounts to conform to current period presentation. Merger Agreement On March 1, 2018, the Company entered into an agreement and plan of merger with Evergreen Parent, L.P. (“Evergreen Parent”), an entity formed by private equity funds managed by Stone Point Capital LLC (“Stone Point”), together with Barry D. Zyskind, the Company’s Chairman and CEO, George Karfunkel and Leah Karfunkel (such individuals, collectively, the “Karfunkel-Zyskind Family”) pursuant to which Evergreen Parent will acquire all of the Company’s outstanding common shares, par value $0.01 per share (the “Common Stock”) that are not currently owned or controlled by the Karfunkel-Zyskind Family and its affiliates and certain related parties (the “Merger Agreement”). The Karfunkel-Zyskind Family and its affiliates and certain related parties currently own or control approximately 55% of the Company's outstanding shares of Common Stock. On June 6, 2018, the parties entered into Amendment No. 1 to the Merger Agreement (the “Amended Merger Agreement”). Pursuant to the transactions contemplated by the Amended Merger Agreement, at the effective time of the merger, each outstanding share of the Company’s Common Stock (other than certain excluded shares) will be converted into the right to receive $14.75 per share of Common Stock in cash, without interest and less any required withholding taxes (the “Merger Consideration”). Common Stock owned by the Company, any wholly-owned subsidiary of the Company, a subsidiary formed to participate in the merger, Evergreen Parent (including the Rollover Shares (as defined below)) or holders who have properly exercised dissenters’ rights under Delaware law will not be converted into the right to receive the Merger Consideration. On June 21, 2018, the Amended Merger Agreement was adopted by the affirmative vote of (i) the holders of at least a majority of all outstanding shares of Common Stock and (ii) the holders of at least a majority of all outstanding shares of Common Stock held by the “Public Stockholders” (defined as stockholders other than Evergreen Parent and its affiliates, the Rollover Stockholders (as defined below) and their respective affiliates and certain related parties and the Company’s directors and officers as set forth on Schedule I to the Merger Agreement), in each case, entitled to vote on the merger at a meeting of stockholders duly called and held for such purpose (the “Requisite Stockholder Vote”). Consummation of the merger remains subject to certain customary closing conditions, including regulatory approvals. The Amended Merger Agreement contains customary termination rights for the Company and Evergreen Parent, which were described in the Company’s Current Report on Form 8-K filed with the SEC on March 1, 2018 and its Current Report on Form 8-K filed with the SEC on June 7, 2018. The Amended Merger Agreement also contains customary representations, warranties and covenants of the Company, including covenants to conduct its business in the ordinary course during the interim period between the execution of the Amended Merger Agreement and consummation of the merger and not to engage in certain types of transactions during this interim period without the prior written consent of Evergreen Parent. Evergreen Parent has obtained equity financing commitments for the transactions contemplated by the Amended Merger Agreement, the aggregate proceeds of which, when combined with available cash resources of the Company, will be sufficient for Evergreen Parent to pay the aggregate Merger Consideration and all related fees and expenses. On March 1, 2018, private equity funds managed by Stone Point and an investment entity controlled by the Karfunkel-Zyskind Family committed to capitalize Evergreen Parent, at or immediately prior to the effective time of the merger, with an aggregate equity contribution in an amount up to $800.0 and $400.0 , respectively, in exchange for equity interests in Evergreen Parent, subject to the terms and conditions set forth in certain equity financing commitment letters, dated as of March 1, 2018 . On July 23, 2018, Evergreen Parent entered into subscription agreements, subject to certain conditions, with Enstar Group Limited (“Enstar”), an entity controlled by Madison Dearborn Partners (“MDP”), and for certain limited purposes, a private equity fund controlled by Stone Point and the investment entity controlled by the Karfunkel-Zyskind Family, pursuant to which Enstar and MDP agreed to purchase equity in Evergreen Parent in an aggregate amount of $200.0 and $150.0 , respectively. This aggregate amount of equity financing provided to Evergreen Parent by Enstar and MDP will reduce, pro rata, the aggregate amount of equity financing provided to Evergreen Parent by the private equity funds managed by Stone Point and the investment entity controlled by the Karfunkel-Zyskind Family. In addition, the Karfunkel-Zyskind Family and its affiliates and certain related parties (the “Rollover Stockholders”) entered into a rollover agreement, dated as of March 1, 2018 , pursuant to which such Rollover Stockholders committed to contribute all of the shares of Common Stock that they own to Evergreen Parent immediately prior to the closing of the merger (the “Rollover Shares”). The Company incurred $36.6 of transaction expenses in connection with the merger during the six months ended June 30, 2018 , respectively.

Recent Accounting Pronouncement

Recent Accounting Pronouncements	6 Months Ended
	Jun. 30, 2018
Accounting Policies [Abstract]
Recent Accounting Pronouncements	Recent Accounting Pronouncements As compared to those described in the Company's Annual Report on Form 10-K for the fiscal year ended December 31, 2017 , the Company's significant accounting policies have been updated for the recent accounting pronouncements or changes in accounting pronouncements discussed below during the six months ended June 30, 2018 . Recent Accounting Standards, Adopted In February 2018, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") 2018-02, Income Statement-Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income . The amendments allow an entity to elect to reclassify the income tax effects of the United States of America ("U.S.") federal government enacted tax bill, the Tax Cuts and Jobs Act ("TCJA"), on items within accumulated other comprehensive income to retained earnings. If an entity elects to reclassify the income tax effects, the amount of that reclassification only includes the effect of the change in the U.S. federal corporate income tax rate on the gross deferred tax amounts and related valuation allowances, if any, at the date of enactment related to items remaining in accumulated other comprehensive income. An entity is not permitted to reclassify the effect of the change in the U.S. federal corporate income tax rate on gross valuation allowances that were originally charged to income from operations. An entity is required to disclose a description of the accounting policy for releasing income tax effects from accumulated other comprehensive income. An entity is permitted to apply the guidance either at the beginning of the period of adoption or retrospectively to each period (or periods) in which the income tax effects of the TCJA are recognized. This guidance is effective for fiscal years beginning after December 15, 2018, including interim reporting periods within that reporting period. Early adoption is permitted, including adoption in any interim period. The Company adopted the guidance early on January 1, 2018. The cumulative effect was an increase to accumulated other comprehensive income and a decrease to retained earnings of $16.0 . In February 2017, the FASB issued ASU 2017-05, Other Income-Gains and Losses from the Derecognition of Nonfinancial Assets (Subtopic 610-20): Clarifying the Scope of Asset Derecognition Guidance and Accounting for Partial Sales of Nonfinancial Assets, which clarifies that ASC 610-20 applies to the derecognition of nonfinancial assets and in substance nonfinancial assets unless other specific guidance applies. As a result, the new guidance does not apply to the derecognition of businesses, nonprofit activities, or financial assets (including equity method investments), or to certain revenue transactions accounted for as revenue from contracts with customers. The new guidance also clarifies that an in substance nonfinancial asset is an asset or group of assets for which substantially all of the fair value consists of nonfinancial assets and the group or subsidiary is not a business. In addition, transfers of nonfinancial assets to another entity in exchange for a noncontrolling ownership interest in that entity is accounted for under ASC 610-20, and the specific guidance on such partial exchanges from ASC 845, Nonmonetary Transactions is eliminated. As a result of the new guidance, the guidance specific to real estate sales in ASC 360-20, Property, Plant, and Equipment-Real Estate Sales is eliminated. As such, sales and partial sales of real estate assets are subject to the same derecognition model as all other nonfinancial assets. The Company adopted this guidance on a modified retrospective basis. The adoption of this guidance on January 1, 2018 did not have a material effect on the Company's financial position, results of operations or cash flows. In October 2016, the FASB issued ASU 2016-16, Accounting for Income Taxes: Intra-Entity Asset Transfers of Assets Other than Inventory . The ASU is part of the FASB’s simplification initiative aimed at reducing complexity in accounting standards. The new guidance eliminates the exception for all intra-entity sales of assets other than inventory. As a result, a reporting entity recognizes the tax expense from the sale of the asset in the seller’s tax jurisdiction when the transfer occurs, even though the pre-tax effects of that transaction are eliminated in consolidation. Any deferred tax asset that arises in the buyer’s jurisdiction is also recognized at the time of the transfer. The adoption of this guidance on January 1, 2018 did not have a material effect on the Company's financial position, results of operations or cash flows. In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments . The amendments provide guidance and clarification for eight specific cash flow issues, which include debt prepayment or debt extinguishment costs, settlement of zero-coupon debt instruments or other debt instruments with coupon interest rates that are insignificant in relation to the effective interest rate of the borrowing, contingent consideration payments made after a business combination, proceeds from the settlement of insurance claims, proceeds from the settlement of corporate and bank owned life insurance policies, distributions received from equity-method investees, beneficial interests in securitization transactions, and separately identifiable cash flows and application of the predominance principle. In November 2016, the FASB issued ASU 2016-18, Statement of Cash Flows (Topic 230) - Restricted Cash, which provides guidance on the presentation of restricted cash and restricted cash equivalents in the statement of cash flows. As a result, amounts generally described as restricted cash and restricted cash equivalents are required to be included with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts presented on the statement of cash flows. An entity is required to disclose the amounts of cash, cash equivalents, and restricted cash, disaggregated by related captions within the balance sheet, reconciled to the total amount cash, cash equivalents, and restricted cash presented in the statement of cash flows, and to disclose information on the nature of restrictions on its cash, cash equivalents, and restricted cash. The Company adopted both ASUs on January 1, 2018 using a retrospective transition method to each period presented. In January 2016, the FASB issued ASU 2016-01, Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities , which address certain aspects of recognition, measurement, presentation, and disclosure of financial instruments. Specifically, the guidance (a) requires equity investments to be measured at fair value with changes in fair value recognized in earnings. However, an entity may elect to measure equity investments that do not have readily determinable fair values at cost minus impairment, if any, plus or minus changes resulted from observable price changes in orderly transactions for identical or similar investments of the same issuer, (b) simplifies the impairment assessment of equity investments without readily determinable fair values by requiring a qualitative assessment to identify impairment, (c) eliminates the requirement to disclose the methods and significant assumptions used to estimate the fair value that is required to be disclosed for financial instruments measured at amortized cost, (d) requires the use of the exit price notion when measuring the fair value of financial instruments for disclosure purposes, (e) requires an entity to present separately in other comprehensive income the portion of the total change in fair value of a liability resulting from a change in the instrument-specific credit risk when the entity has elected to measure the liability at fair value in accordance with the fair value option, (f) requires separate presentation of financial assets and liabilities by measurement category and form on the balance sheet or the notes to the financial statements, and (g) clarifies that the need for a valuation allowance on a deferred tax asset related to an available for sale security should be evaluated with other deferred tax assets. The Company adopted the guidance on January 1, 2018. The cumulative effect was a decrease to accumulated other comprehensive income and an increase to retained earnings of $16.7 . The Company elected to measure its equity investments that do not have readily determinable fair values at cost minus impairment, if any, plus or minus changes resulting from observable price changes in orderly transactions for identical or similar investments of the same issuer, and applied the prospective transition method. In May 2014, the FASB issued ASU 2014-09, Revenue From Contracts With Customers . The new standard supersedes the revenue recognition requirements in Topic 605, Revenue Recognition , and eliminates industry-specific guidance. The core principle of the new standard is that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. To achieve the core principle, an entity should apply the following steps: identify the contract with a customer, identify the performance obligations in the contract, determine the transaction price, allocate the transaction price to the performance obligations in the contract, and recognize revenue when (or as) the entity satisfies a performance obligation. The new standard requires variable consideration to be estimated as part of the determination of the transaction price of a contract subject to a constraint based on a probability assessment of revenue reversal. The new standard also requires certain incremental costs incurred to obtain or fulfill a contract to be deferred and amortized on a systematic basis consistent with the transfer of goods or services to the customer. The guidance also requires additional disclosures about the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts, including significant judgments and changes in judgments in determining the timing of satisfaction of performance obligations (over time or at a point in time), determining transaction price and amounts allocated to performance obligations, and assets recognized from the costs incurred to obtain or fulfill a contract. ASU 2014-09 does not apply to insurance contracts, leases, financial instruments, and certain other agreements that are within the scope of other GAAP guidance. The Company adopted the standard on January 1, 2018 using the modified retrospective method. The adoption of this guidance on January 1, 2018 did not have a material effect on the Company's financial position, results of operations or cash flows. As a provider of property and casualty insurance products, the Company’s insurance contracts are accounted for as insurance which is not effected by the accounting policy changes. The accounting policy changes are applied to the Company’s contracts with customers related to the performance of services with no underlying insurance risk. The financial statement information reported for comparable prior periods is not adjusted for the accounting policy changes, and is reported in accordance with the accounting standards in effect under Topic 605, Revenue Recognition in accordance with the modified retrospective transition method applied under ASU 2014-09. For the three and six months ended June 30, 2018 , approximately $49.7 and $156.9 , respectively, of revenues, or less than 5% of the Company's total revenues, are affected by the accounting policy changes. Refer to Note 12. "Segments" for disclosure of revenues from contracts with customers by business segment. On February 28, 2018, the Company completed the transfer of a majority interest in the portion of the Company's U.S.-based fee businesses that (a) act as managing general agents for the distribution, underwriting and procurement of property and casualty insurance on behalf of certain of the Company's affiliates and other insurance carriers and (b) design, develop, market and act as third party administrators for programs for service contracts, limited warranties and replacement plans as further described in the Acquisition Agreement (the “U.S.-based fee business”), that reduces service and fee income subsequent to the transfer date. The Company’s revenues related to services provided to customers include, (i) product warranty registration and service, (ii) insurance-related services, broker and agency services, claims administration, management services, loss control and risk management services, and (iii) asset management services and other business services. The Company’s broker and commission revenues are recognized at the point in time when the insurance or reinsurance is effective and the Company has the right to receive contract consideration, net of an adjustment for cancellations. The Company’s revenues from the other services are recognized on a pro rata basis over the contract service periods by allocating estimated contract consideration to the performance obligations which are satisfied as the services are provided and transferred to its customers. The contract consideration amounts received or receivable at inception of the contract service periods are recognized as deferred revenue. The Company defers the incremental costs of obtaining contracts with customers and amortizes those costs over the contract service periods as services are transferred to the customers. The incremental costs incurred to obtain and fulfill contracts with customers are deferred when the costs a) relate directly to a specific contract or anticipated contract, b) generate or enhance resources that the Company will use in satisfying the performance obligation, and c) are expected to be recovered. Subsequent to the transfer of the U.S.-based fee business on February 28, 2018, the deferred contract costs are not significant. The Company expenses the incremental costs of obtaining contracts with customers as incurred if the amortization period of the asset that otherwise would have been recognized is one year or less as a permitted practical expedient. Recent Accounting Standards, Not Yet Adopted In March 2017, the FASB issued ASU 2017-08, Receivables-Nonrefundable Fees and Other Costs (Subtopic 310-20): Premium Amortization on Purchased Callable Debt Securities . The new guidance shortens the amortization period for the premium on callable debt securities to the earliest call date. The amortization period for the discount on callable debt securities is not changed by the new guidance, and continues to be amortized to maturity. The new guidance more closely aligns interest income recorded on debt securities held at a premium or a discount with the economics of the underlying instrument. The guidance is effective for fiscal years beginning after December 15, 2018, including interim periods within that reporting period. Early adoption is permitted, including adoption in an interim period. If an entity early adopts the guidance in an interim period, any adjustments should be reflected as of the beginning of the fiscal year that includes that interim period. The Company is currently evaluating the impact this standard will have on its financial position, results of operations or cash flows. In January 2017, the FASB issued ASU 2017-04, Intangibles-Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment , which simplifies the accounting for goodwill impairment charges. Under the current guidance, if the fair value of a reporting unit is lower than its carrying amount, an entity calculates any impairment charge by comparing the implied fair value of goodwill with its carrying amount. The implied fair value of goodwill is calculated by deducting the fair value of all assets and liabilities of the reporting unit from the reporting unit’s fair value. Under the new guidance, an entity will record an impairment charge based on the excess of a reporting unit’s carrying amount over its fair value not to exceed the amount of goodwill allocated to that reporting unit. The guidance is effective for fiscal years beginning after December 15, 2019, including interim periods within that reporting period. Early adoption is permitted for annual and interim goodwill impairment testing dates after January 1, 2017. The Company is currently evaluating the impact this standard will have on its financial position, results of operations or cash flows. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments . The new standard requires financial assets measured at amortized cost basis to be presented at the net amount expected to be collected by recording an allowance for credit losses, presented as a deduction from the amortized cost basis, with changes in the allowance recorded as credit loss expense based on management's current estimate of expected credit losses each period. The new standard also requires impairment relating to credit losses on available-for-sale debt securities to be presented through an allowance for credit losses with changes in the allowance recorded in the period of the change as credit loss expense or reversal of credit loss expense. Any impairment amount not recorded through an allowance for credit losses on available-for-sale debt securities is recorded through other comprehensive income. This new standard is effective for fiscal years beginning after December 15, 2019, including interim reporting periods within that reporting period. The Company is currently evaluating the impact this standard will have on its financial position, results of operations or cash flows. In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842). The new standard amends the guidance for leasing transactions. The guidance requires a lessee to classify lease contracts as finance or operating leases, and to recognize assets and liabilities for the rights and obligations created by leasing transactions with lease terms more than twelve months. The guidance substantially retains the criteria for classifying leasing transactions as finance or operating leases. For finance leases, a lessee recognizes a right-of-use asset and a lease liability initially measured at the present value of the lease payments, and recognizes interest expense on the lease liability separately from the amortization of the right-of-use asset. For operating leases, a lessee recognizes a right-of-use asset and a lease liability initially measured at the present value of the lease payments, and recognizes lease expense on a straight-line basis. The guidance requires a lessor to recognize lease income related to an operating lease generally on a straight-line basis over the lease term. Lessees and lessors are required to disclose qualitative and quantitative information about leasing arrangements to enable a user of the financial statements to assess the amount, timing and uncertainty of cash flows arising from leases. In January 2018, the FASB issued ASU 2018-01, Land Easement Practical Expedient for Transition to Topic 842 that provides a lessee or lessor the election to not assess whether land easements, not currently accounted for as leases under the current lease guidance, are leases under the new standard. On a prospective basis after adoption of the guidance, a lessee or lessor is required to apply the new standard to new or modified land easements. In July 2018, the FASB issued ASU 2018-11, Targeted Improvements that permits the initial application of the new standard as of the effective date and the recognition of a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption. ASU 2018-11 also provides lessors with an option, by class of underlying asset, to not separate nonlease components from the related lease component and, instead, to account for those components as a single component subject to certain criteria. The new standard is effective for fiscal years beginning after December 15, 2018, including interim periods within that period. Early adoption is permitted. The Company is implementing changes to its enterprise reporting systems and its processes in conjunction with the evaluation of the new standard on the existing lease agreements. The Company plans to adopt the new standard as of January 1, 2019, and to recognize any cumulative-effect adjustment to the opening balance of retained earnings as of the date of adoption. The Company is currently evaluating the impact this standard will have on its financial position, results of operations or cash flows.

Investments

Investments	6 Months Ended
	Jun. 30, 2018
Investments, Debt and Equity Securities [Abstract]
Investments	Investments (a) Available-for-Sale Securities The amortized cost, gross unrealized gains and losses, and estimated fair value of securities classified as available-for-sale as of June 30, 2018 and December 31, 2017 , are presented below: As of June 30, 2018 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value U.S. treasury securities $ 299.7 $ 0.9 $ (3.0 ) $ 297.6 U.S. government agencies 131.4 0.8 (1.6 ) 130.6 Municipal bonds 822.5 7.6 (9.0 ) 821.1 Foreign government 286.5 1.3 (3.9 ) 283.9 Corporate bonds: Finance 1,909.8 13.9 (37.3 ) 1,886.4 Industrial 2,400.3 16.4 (55.5 ) 2,361.2 Utilities 325.6 4.5 (7.3 ) 322.8 Commercial mortgage-backed securities 397.2 1.6 (14.1 ) 384.7 Residential mortgage-backed securities: Agency backed 916.3 1.5 (16.8 ) 901.0 Non-agency backed 7.6 — — 7.6 Collateralized loan / debt obligation 822.6 4.4 (2.9 ) 824.1 Asset backed securities 57.3 0.1 (0.1 ) 57.3 Total available-for-sale securities $ 8,376.8 $ 53.0 $ (151.5 ) $ 8,278.3 As of December 31, 2017 (1) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value U.S. treasury securities $ 301.6 $ 0.9 $ (3.2 ) $ 299.3 U.S. government agencies 51.1 — (0.6 ) 50.5 Municipal bonds 1,035.5 15.9 (5.9 ) 1,045.5 Foreign government 151.4 3.5 (3.2 ) 151.7 Corporate bonds: Finance 1,733.2 48.1 (11.9 ) 1,769.4 Industrial 2,237.0 57.3 (26.1 ) 2,268.2 Utilities 323.8 10.7 (2.1 ) 332.4 Commercial mortgage-backed securities 419.3 3.8 (10.4 ) 412.7 Residential mortgage-backed securities: Agency backed 562.0 5.8 (11.4 ) 556.4 Non-agency backed 6.9 — (0.1 ) 6.8 Collateralized loan / debt obligation 591.2 9.7 (0.3 ) 600.6 Asset backed securities 30.1 0.1 (0.1 ) 30.1 Less: Assets classified as held for sale (See Note 13) (34.4 ) (0.9 ) — (35.3 ) Total available-for-sale securities $ 7,408.7 $ 154.9 $ (75.3 ) $ 7,488.3 (1) In connection with the adoption of ASU 2016-01, the disclosure for December 31, 2017 has been recast for comparability. See Note 2. "Recent Accounting Pronouncements" for additional information on the impact of the adoption of ASU 2016-01. Proceeds from the sales of investments in available-for-sale securities were $342.0 and $464.9 during the three months ended June 30, 2018 and 2017 , respectively, and $1,079.1 and $988.3 during the six months ended June 30, 2018 and 2017 , respectively. A summary of the Company’s available-for-sale securities as of June 30, 2018 and December 31, 2017 , by contractual maturity, is shown below. Expected maturities may differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties. June 30, 2018 December 31, 2017 Amortized Cost Fair Value Amortized Cost Fair Value Due in one year or less $ 319.8 $ 317.3 $ 228.1 $ 226.7 Due after one through five years 1,875.8 1,877.7 1,811.3 1,845.5 Due after five through ten years 3,455.4 3,383.4 3,199.7 3,239.8 Due after ten years 524.8 525.2 594.5 605.0 Mortgage and asset backed securities 2,201.0 2,174.7 1,609.5 1,606.6 Less: Assets classified as held for sale (See Note 13) — — (34.4 ) (35.3 ) Total $ 8,376.8 $ 8,278.3 $ 7,408.7 $ 7,488.3 The tables below summarize the gross unrealized losses of the Company's available-for-sale securities by length of time the security has continuously been in an unrealized loss position as of June 30, 2018 and December 31, 2017 : Less Than 12 Months 12 Months or More Total As of June 30, 2018 Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses U.S. treasury securities $ 40.6 $ (0.4 ) $ 233.9 $ (2.6 ) $ 274.5 $ (3.0 ) U.S. government agencies 94.6 (1.6 ) 1.5 — 96.1 (1.6 ) Municipal bonds 256.3 (4.6 ) 134.2 (4.4 ) 390.5 (9.0 ) Foreign government 182.5 (3.2 ) 14.6 (0.7 ) 197.1 (3.9 ) Corporate bonds: Finance 1,299.7 (34.0 ) 73.1 (3.3 ) 1,372.8 (37.3 ) Industrial 1,544.0 (43.2 ) 190.9 (12.3 ) 1,734.9 (55.5 ) Utilities 223.4 (7.0 ) 9.2 (0.3 ) 232.6 (7.3 ) Commercial mortgage-backed securities 164.0 (5.4 ) 127.4 (8.7 ) 291.4 (14.1 ) Residential mortgage-backed securities: Agency backed 557.5 (9.6 ) 120.4 (7.2 ) 677.9 (16.8 ) Collateralized loan / debt obligations 316.9 (2.9 ) — — 316.9 (2.9 ) Asset backed securities 4.0 — 0.7 (0.1 ) 4.7 (0.1 ) Total $ 4,683.5 $ (111.9 ) $ 905.9 $ (39.6 ) $ 5,589.4 $ (151.5 ) Less Than 12 Months 12 Months or More Total As of December 31, 2017 (1) Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses U.S. treasury securities $ 41.9 $ (0.5 ) $ 247.0 $ (2.7 ) $ 288.9 $ (3.2 ) U.S. government agencies 48.7 (0.6 ) 0.5 — 49.2 (0.6 ) Municipal bonds 171.3 (2.7 ) 178.7 (3.2 ) 350.0 (5.9 ) Foreign government 57.4 (2.2 ) 17.1 (1.0 ) 74.5 (3.2 ) Corporate bonds: Finance 419.3 (9.7 ) 91.5 (2.2 ) 510.8 (11.9 ) Industrial 437.1 (16.4 ) 255.4 (9.7 ) 692.5 (26.1 ) Utilities 72.5 (2.0 ) 11.9 (0.1 ) 84.4 (2.1 ) Commercial mortgage-backed securities 81.5 (4.1 ) 157.5 (6.3 ) 239.0 (10.4 ) Residential mortgage-backed securities: Agency backed 91.7 (4.7 ) 167.8 (6.7 ) 259.5 (11.4 ) Non-agency backed 2.9 — 0.8 (0.1 ) 3.7 (0.1 ) Collateralized loan / debt obligations 56.8 (0.2 ) 4.3 (0.1 ) 61.1 (0.3 ) Asset backed securities 7.1 — 3.1 (0.1 ) 10.2 (0.1 ) Total $ 1,488.2 $ (43.1 ) $ 1,135.6 $ (32.2 ) $ 2,623.8 $ (75.3 ) (1) In connection with the adoption of ASU 2016-01, the disclosure for December 31, 2017 has been recast for comparability. See Note 2. "Recent Accounting Pronouncements" for additional information on the impact of the adoption of ASU 2016-01. There were 3,596 and 2,086 individual security lots as of June 30, 2018 and December 31, 2017 , respectively, that account for the gross unrealized loss, none of which is deemed by the Company to be other-than-temporarily impaired ("OTTI"). The Company analyzes its fixed maturity securities in an unrealized loss position for OTTI each reporting period. Beginning January 1, 2018, the Company generally evaluates an investment for impairment when it has been in an unrealized loss position of 20% or more of amortized cost for twelve consecutive months. As of June 30, 2018 , the Company has determined that the unrealized losses on fixed maturity securities were primarily due to market interest rate movements since their date of purchase. As of June 30, 2018 , for the $39.6 of unrealized losses related to securities in unrealized loss positions for a period of twelve or more consecutive months, none were related to securities in unrealized loss positions greater than or equal to 20% of amortized cost or cost. There were no material credit-related OTTI charges for the three and six months ended June 30, 2018 and 2017 . (b) Trading Securities The amortized cost, gross unrealized gains and losses, and estimated fair value of securities classified as trading as of June 30, 2018 and December 31, 2017 are presented in the tables below: As of June 30, 2018 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Corporate bonds: Industrial $ 25.3 $ 0.6 $ (1.6 ) $ 24.3 Finance 1.0 — — 1.0 U.S. treasury securities 123.7 0.3 (0.5 ) 123.5 Total trading securities $ 150.0 $ 0.9 $ (2.1 ) $ 148.8 As of December 31, 2017 (1) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Corporate bonds: Industrial $ 26.7 $ 0.1 $ (2.4 ) $ 24.4 Finance 0.5 — — 0.5 U.S. treasury securities 25.0 — (0.1 ) 24.9 Total trading securities $ 52.2 $ 0.1 $ (2.5 ) $ 49.8 (1) In connection with the adoption of ASU 2016-01, the disclosure for December 31, 2017 has been recast for comparability. See Note 2. "Recent Accounting Pronouncements" for additional information on the impact of the adoption of ASU 2016-01. Proceeds from the sales of investments in trading securities were approximately $68.8 and $177.6 during the three months ended June 30, 2018 and 2017 , respectively, and $282.9 and $309.4 during the six months ended June 30, 2018 and 2017 , respectively. The table below shows the portion of trading gains and losses for the period related to trading securities still held during the three months ended June 30, 2018 and 2017 : Three Months Ended June 30, Six Months Ended June 30, 2018 2017 (1) 2018 2017 (1) Net losses recognized during the period on trading securities $ (1.9 ) $ (1.5 ) $ (5.0 ) $ (4.6 ) Less: Net (gains) losses recognized during the period on trading securities sold during the period (4.3 ) 0.6 (3.9 ) 2.4 Unrealized gains (losses) recognized during the reporting period on trading securities still held at the reporting date $ 2.4 $ (2.1 ) $ (1.1 ) $ (7.0 ) (1) In connection with the adoption of ASU 2016-01, the disclosure for the three and six months ended June 30, 2017 has been recast for comparability. See Note 2. "Recent Accounting Pronouncements" for additional information on the impact of the adoption of ASU 2016-01. (c) Equity Securities In accordance with the adoption of ASU 2016-01, the Company's equity securities are no longer bifurcated between available-for-sale and trading, but rather are measured at fair value with changes in fair value recognized in earnings. See Note 2. "Recent Accounting Pronouncements" for additional information on the impact of the adoption of ASU 2016-01. The original cost, gross unrealized gains and losses, and estimated fair value of the Company's equity securities as of June 30, 2018 and December 31, 2017 , are presented below: As of June 30, 2018 Original Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Preferred stock $ 0.5 $ — $ — $ 0.5 Common stock 136.8 37.3 (20.3 ) 153.8 Total equity securities $ 137.3 $ 37.3 $ (20.3 ) $ 154.3 As of December 31, 2017 Original Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Preferred stock $ 0.5 $ — $ — $ 0.5 Common stock 195.4 30.6 (14.8 ) 211.2 Total equity securities $ 195.9 $ 30.6 $ (14.8 ) $ 211.7 Proceeds from the sales of investments in equity securities were approximately $58.8 and $32.4 during the three months ended June 30, 2018 and 2017 , respectively, and $181.7 and $151.7 during the six months ended June 30, 2018 and 2017 , respectively. The table below shows the portion of gains and losses for the period related to equity securities still held during the three and six months ended June 30, 2018 and 2017 : Three Months Ended June 30, Six Months Ended June 30, 2018 2017 2018 2017 Net gains recognized during the period on equity securities $ 4.6 $ 11.9 $ 8.7 $ 17.0 Less: Net gains recognized during the period on equity securities sold during the period (6.4 ) (4.4 ) (1.4 ) (5.0 ) Unrealized gains recognized during the reporting period on equity securities still held at the reporting date $ 11.0 $ 16.3 $ 10.1 $ 22.0 (d) Investment Income Net investment income for the three and six months ended June 30, 2018 and 2017 was derived from the following sources: Three Months Ended June 30, Six Months Ended June 30, 2018 2017 2018 2017 Fixed maturity securities, available-for-sale $ 62.0 $ 69.4 $ 121.4 $ 126.7 Fixed maturity securities, trading 4.2 — 4.8 1.0 Equity securities (1) 0.4 0.2 0.7 1.6 Cash and short term investments 4.7 1.9 8.8 3.3 Other invested assets 0.3 (19.2 ) 6.7 (15.0 ) Total investment income 71.6 52.3 142.4 117.6 Investment expenses and interest expense on securities sold under agreement to repurchase (3.3 ) (3.0 ) (5.9 ) (5.0 ) Net investment income $ 68.3 $ 49.3 $ 136.5 $ 112.6 (1) In connection with the adoption of ASU 2016-01, the disclosure for the three and six months ended June 30, 2017 has been recast for comparability. See Note 2. "Recent Accounting Pronouncements" for additional information on the impact of the adoption of ASU 2016-01. (e) Realized Gains and Losses The tables below summarize the gross and net realized gains and (losses) for the three and six months ended June 30, 2018 and 2017 : Three Months Ended June 30, 2018 2017 Gross Gains Gross Losses Net Gains (Losses) Gross Gains Gross Losses Net Gains (Losses) Fixed maturity securities, available-for-sale $ 16.4 $ (13.9 ) $ 2.5 $ 14.1 $ (0.9 ) $ 13.2 Fixed maturity securities, trading — (1.9 ) (1.9 ) 2.8 (4.3 ) (1.5 ) Equity securities (1) 10.1 (5.5 ) 4.6 9.8 (13.7 ) (3.9 ) Other invested assets 0.2 — 0.2 15.7 — 15.7 Total $ 26.7 $ (21.3 ) $ 5.4 $ 42.4 $ (18.9 ) $ 23.5 Six Months Ended June 30, 2018 2017 Gross Gains Gross Losses Net Gains (Losses) Gross Gains Gross Losses Net Gains (Losses) Fixed maturity securities, available-for-sale $ 19.9 $ (15.8 ) $ 4.1 $ 22.4 $ (2.1 ) $ 20.3 Fixed maturity securities, trading 2.1 (7.1 ) (5.0 ) 5.2 (9.8 ) (4.6 ) Equity securities (1) 23.7 (15.0 ) 8.7 21.0 (20.6 ) 0.4 Other invested assets 0.2 — 0.2 16.0 — 16.0 Other-than-temporary impairment of fixed maturity securities, available-for-sale — (0.3 ) (0.3 ) — — — Total $ 45.9 $ (38.2 ) $ 7.7 $ 64.6 $ (32.5 ) $ 32.1 (1) In connection with the adoption of ASU 2016-01, the disclosure for the three and six months ended June 30, 2017 has been recast for comparability. See Note 2. "Recent Accounting Pronouncements" for additional information on the impact of the adoption of ASU 2016-01. (f) Restricted Cash and Investments The Company, in order to conduct business in certain states, is required to maintain letters of credit or assets on deposit to support state mandated regulatory requirements and certain third party agreements. The Company also utilizes trust accounts to collateralize business with its reinsurance counterparties. These assets are primarily in the form of cash and certain investment grade securities. The fair values of the Company's restricted assets as of June 30, 2018 and December 31, 2017 are as follows: June 30, 2018 December 31, 2017 Restricted cash and cash equivalents $ 532.2 $ 480.1 Restricted investments 3,062.2 3,193.8 Total restricted cash, cash equivalents and investments $ 3,594.4 $ 3,673.9 (g) Other Securities sold but not yet purchased are securities that the Company has sold, but does not own, in anticipation of a decline in the market value of the security. For more information related to these agreements, see Note 3. "Investments" to the consolidated financial statements included in the Company's Annual Report on Form 10-K for the year ended December 31, 2017 . The Company’s liability for securities to be delivered is measured at their fair value and was $161.8 and $75.5 as of June 30, 2018 and December 31, 2017 , respectively. From time to time, the Company enters into repurchase agreements that are subject to a master netting arrangement, which are accounted for as collateralized borrowing transactions and are recorded at contract amounts. The Company receives cash or securities that it invests or holds in short term or fixed maturity securities. For more information related to these agreements, see Note 2. "Significant Accounting Policies" to the consolidated financial statements included in the Company's Annual Report on Form 10-K for the year ended December 31, 2017 . As of June 30, 2018 , the Company had 16 individual repurchase agreements outstanding with a principal amount of $214.8 , which approximates fair value, at interest rates between 0.0% and 3.5% . The Company had approximately $227.5 of collateral pledged in support of these agreements as of June 30, 2018 . As of December 31, 2017 , the Company had no repurchase agreements outstanding.

Fair Value of Financial Instrum

Fair Value of Financial Instruments	6 Months Ended
	Jun. 30, 2018
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	Fair Value of Financial Instruments The following tables present the level within the fair value hierarchy at which the Company’s financial assets and financial liabilities are measured on a recurring basis as of June 30, 2018 and December 31, 2017 : As of June 30, 2018 Total Level 1 Level 2 Level 3 Financial Assets U.S. treasury securities $ 421.1 $ 421.1 $ — $ — U.S. government agencies 130.6 — 130.6 — Municipal bonds 821.1 — 820.5 0.6 Foreign government 283.9 — 283.9 — Corporate bonds and other bonds: Finance 1,887.4 — 1,887.4 — Industrial 2,385.5 — 2,385.5 — Utilities 322.8 — 322.8 — Commercial mortgage-backed securities 384.7 — 362.6 22.1 Residential mortgage-backed securities: Agency backed 901.0 — 901.0 — Non-agency backed 7.6 — 7.6 — Collateralized loan / debt obligations 824.1 — 824.1 — Asset-backed securities 57.3 — 56.5 0.8 Equity securities 154.3 153.2 0.3 0.8 Short term investments 169.7 — 169.7 — Other investments 4.1 — — 4.1 Life settlement contracts 1.9 — — 1.9 Total financial assets $ 8,757.1 $ 574.3 $ 8,152.5 $ 30.3 Financial Liabilities Securities sold but not yet purchased $ 161.8 $ 153.9 $ 7.9 $ — Securities sold under agreements to repurchase 214.8 — 214.8 — Life settlement contract profit commission 3.2 — — 3.2 Contingent consideration 31.2 — — 31.2 Total financial liabilities $ 411.0 $ 153.9 $ 222.7 $ 34.4 As of December 31, 2017 Total Level 1 Level 2 Level 3 Financial Assets U.S. treasury securities $ 324.2 $ 324.2 $ — $ — U.S. government agencies 50.5 — 50.5 — Municipal bonds 1,045.5 — 1,045.1 0.4 Foreign government 151.7 — 151.7 — Corporate bonds and other bonds: Finance 1,769.9 — 1,769.9 — Industrial 2,292.6 — 2,292.6 — Utilities 332.4 — 332.4 — Commercial mortgage-backed securities 412.7 — 389.8 22.9 Residential mortgage-backed securities: Agency backed 556.4 — 556.4 — Non-agency backed 6.8 — 6.8 — Collateralized loan / debt obligations 600.6 — 600.6 — Asset-backed securities 30.1 — 29.3 0.8 Equity securities 211.7 210.7 0.5 0.5 Short term investments 187.8 — 187.8 — Other investments 5.0 — — 5.0 Life settlement contracts 20.8 — — 20.8 Less: Fixed maturity securities classified as held for sale (see note 13) (35.3 ) — (35.3 ) — Total financial assets (1) $ 7,963.4 $ 534.9 $ 7,378.1 $ 50.4 Financial Liabilities Securities sold but not yet purchased $ 75.5 $ 70.8 $ 4.7 $ — Life settlement contract profit commission 3.2 — — 3.2 Contingent consideration 75.4 — — 75.4 Total financial liabilities (2) $ 154.1 $ 70.8 $ 4.7 $ 78.6 (1) Does not include assets held for sale of $900.9 carried at fair value and classified as Level 2 within the fair value hierarchy as of December 31, 2017. See Note 13. "Divestiture" for additional information. (2) Does not include liabilities held for sale of $761.7 carried at fair value and classified as Level 2 within the fair value hierarchy as of December 31, 2017. See Note 13. "Divestiture" for additional information. Transfers between Level 1 and Level 2 for all periods presented are due to changes in the availability of observable market information and re-evaluation of the observability of pricing inputs. During the three and six months ended June 30, 2018 and 2017 , there were no significant transfers between Level 1 and Level 2. The following table provides a summary of changes in fair value of the Company’s Level 3 financial assets and liabilities for the three and six months ended June 30, 2018 and 2017 . The transfers into and out of Level 3 were due to changes in the availability of market observable inputs. All transfers are reflected in the table at fair value as of the end of the reporting period. Balance as of March 31, 2018 Net (loss) Other comprehensive income Purchases and issuances Sales and settlements Net transfers into Level 3 Balance as of June 30, Fixed maturities, available-for-sale $ 23.3 $ — $ 1.1 $ — $ (0.9 ) $ — $ 23.5 Equity securities 0.5 — 0.3 — — — 0.8 Other investments 4.5 — — — (0.4 ) — 4.1 Life settlement contracts 15.4 (2.3 ) — — (11.2 ) — 1.9 Life settlement contract profit commission (3.4 ) 0.2 — — — — (3.2 ) Contingent consideration (32.3 ) (0.9 ) — — 2.0 — (31.2 ) Total $ 8.0 $ (3.0 ) $ 1.4 $ — $ (10.5 ) $ — $ (4.1 ) Balance as of March 31, 2017 Net (loss) Other comprehensive income Purchases and issuances Sales and settlements Net transfers into Level 3 Balance as of June 30, Fixed maturities, available-for-sale $ 35.1 $ — $ 0.2 $ 5.2 $ (2.3 ) $ 3.3 $ 41.5 Equity securities 21.5 (0.1 ) 0.1 0.1 (16.7 ) 18.6 23.5 Life settlement contracts 397.5 13.1 — 1.3 (15.1 ) — 396.8 Life settlement contract profit commission (5.6 ) (0.1 ) — — — — (5.7 ) Contingent consideration (72.4 ) (3.1 ) — (27.2 ) 5.0 — (97.7 ) Total $ 376.1 $ 9.8 $ 0.3 $ (20.6 ) $ (29.1 ) $ 21.9 $ 358.4 Balance as of December 31, 2017 Net (loss) Other comprehensive income Purchases and issuances Sales and settlements Net transfers into Level 3 Balance as of June 30, Fixed maturities, available-for-sale $ 24.1 $ (0.3 ) $ 0.8 $ — $ (1.1 ) $ — $ 23.5 Equity securities 0.5 — 0.3 — — — 0.8 Other investments 5.0 (0.5 ) — — (0.4 ) — 4.1 Life settlement contracts 20.8 2.3 — — (21.2 ) — 1.9 Life settlement contract profit commission (3.2 ) — — — — — (3.2 ) Contingent consideration (75.4 ) (2.6 ) — — 46.8 — (31.2 ) Total $ (28.2 ) $ (1.1 ) $ 1.1 $ — $ 24.1 $ — $ (4.1 ) Balance as of December 31, 2016 Net (loss) Other comprehensive (loss) income Purchases and issuances Sales and settlements Net transfers into Level 3 Balance as of June 30, Fixed maturities, available-for-sale $ 46.9 $ — $ (0.5 ) $ 7.5 $ (2.8 ) $ (9.6 ) $ 41.5 Equity securities 24.4 (0.4 ) 0.3 4.6 (18.8 ) 13.4 23.5 Life settlement contracts 356.9 48.6 — 16.5 (25.2 ) — 396.8 Life settlement contract profit commission (4.9 ) (0.8 ) — — — — (5.7 ) Contingent consideration (71.7 ) (3.8 ) — (27.2 ) 5.0 — (97.7 ) Total $ 351.6 $ 43.6 $ (0.2 ) $ 1.4 $ (41.8 ) $ 3.8 $ 358.4 The Company uses the following methods and assumptions in estimating its fair value disclosures for financial instruments: • Equity and Fixed Maturity Investments: As of June 30, 2018 , the Company's Level 3 securities consisted primarily of a commercial mortgage-backed security. The fair value of this fixed maturity security as of June 30, 2018 was measured using valuation techniques involving unobservable inputs. • Cash and Cash Equivalents, Restricted Cash and Cash Equivalents, and Short Term Investments: The carrying value of cash and cash equivalents, restricted cash and cash equivalents, and short term investments approximate their respective fair value and are classified as Level 2 in the fair value hierarchy. • Premiums Receivable, Accrued Interest, Reinsurance Recoverables: The carrying values reported in the accompanying balance sheets for these financial instruments approximate their fair values due to the short term nature of the asset and are classified as Level 1 in the financial hierarchy. • Equity Investment in Unconsolidated Subsidiaries - Related Party: In June 2017, the Company sold 10,586,000 common shares of National General Holdings Corp, a publicly-held insurance holding company ("NGHC"). As a result of the sale, the Company ceased accounting for this investment under the equity method. The Company has classified its investment in NGHC common stock of $45.0 and $33.6 as of June 30, 2018 and December 31, 2017, respectively, as equity securities. • Subordinated Debentures and Debt: The fair value of the Company's debt arrangements as of June 30, 2018 was as follows: June 30, 2018 Carrying Value Fair Value Revolving credit facility $ 130.0 $ 130.0 5.5% Convertible senior notes due 2021 5.4 5.4 2.75% Convertible senior notes due 2044 176.4 218.8 6.125% Senior notes due 2023 248.6 242.5 Junior subordinated debentures due 2035-2037 122.2 112.1 Trust preferred securities due 2033-2037 92.8 87.3 7.25% Subordinated Notes due 2055 145.4 146.0 7.50% Subordinated Notes due 2055 130.9 134.7 Secured loan agreements 168.2 168.2 Promissory notes and other 95.4 95.4 Total debt $ 1,315.3 $ 1,340.4 The 7.25% subordinated notes due 2055, the 7.50% subordinated notes due 2055, the 2.75% convertible senior notes due 2044, and the 6.125% notes due 2023 are publicly traded instruments and are classified as Level 1 in the fair value hierarchy. The fair value of the junior subordinated debentures due 2035-2037 and trust preferred securities due 2033-2037 were determined using the Black-Derman-Toy interest rate lattice model and are classified as Level 3 in the fair value hierarchy. In determining the fair value of its remaining debt, the Company uses estimates based on rates currently available to the Company for debt with similar terms and remaining maturities. Accordingly, the fair value of the Republic promissory note and other debt is classified as Level 2 within the valuation hierarchy. The Company considers its other debt's carrying value to approximate fair value as their interest rates approximate current borrowing rates. • Securities sold but not yet purchased : The Company's securities sold but not yet purchased consist of equity and fixed maturity securities and are valued and classified within the fair value hierarchy accordingly. • Securities sold under agreements to repurchase : The Company's securities sold under agreements to repurchase are classified as Level 2 in the fair value hierarchy and approximate their fair values due to the short-term and secured nature of the liabilities. • Contingent consideration: The fair value of contingent consideration is based on a discounted cash flow methodology and is classified as Level 3 in the fair value hierarchy. The range of discount rates used for contingent consideration was primarily between 11% and 30% .

Loss and loss adjustment expens

Loss and loss adjustment expense reserves	6 Months Ended
	Jun. 30, 2018
Insurance [Abstract]
Loss and loss adjustment expense reserves	Loss and Loss Adjustment Expense Reserves The following table provides a reconciliation of the beginning and ending balances for loss and loss adjustment expense ("Loss and LAE") reserves for the six months ended June 30, 2018 , and 2017 , respectively: Six Months Ended June 30, 2018 2017 Loss and LAE reserves, gross of related reinsurance recoverables at beginning of year $ 12,138.8 $ 10,140.7 Less: Reinsurance recoverables at beginning of year 5,669.6 3,873.8 Net balance, beginning of year 6,469.2 6,266.9 Incurred related to: Current year 1,886.3 1,772.9 Prior year 20.3 91.9 Total incurred during the period 1,906.6 1,864.8 Paid related to: Current year (414.0 ) (366.2 ) Prior year (1,177.4 ) (1,148.3 ) Total paid during the period (1,591.4 ) (1,514.5 ) Acquired loss and loss adjustment reserves and other 9.2 200.8 Retroactive reinsurance adjustment 12.1 (698.0 ) Effect of foreign exchange rates (51.5 ) 87.4 Net balance, end of period 6,754.2 6,207.4 Plus reinsurance recoverables at end of period 5,591.1 4,942.1 Loss and LAE reserves, at end of period $ 12,345.3 $ 11,149.5 The Company's Loss and LAE reserves, gross of related reinsurance recoverables, increased $206.5 and $1,008.8 , respectively, during the six months ended June 30, 2018 and 2017 . The Company had adverse prior period reserve development of $20.3 during the six months ended June 30, 2018 after reflecting a $12.1 gain on an adverse development cover (ADC) obtained in 2017. Prior to the gain on the ADC, the Company's total six-month prior period reserve development is $32.4 . Consistent with prior periods, the actuarial process was driven by updated and new incurred and paid loss data, continued review of actuarial diagnostics, and actuarial analysis based on updated data for the period. For the six months ended June 30, 2018 , adverse development of approximately $49.0 was recognized in the Small Commercial Business and Specialty Program Commercial Auto Liability portfolio on accident years 2014 through 2017, driven by severity trends that exceeded prior expectations and actuarial analysis using updated data for the period. The Company is currently engaged in re-underwriting and devoting additional claims resources/focus to the existing auto liability portfolio to mitigate risks of future development. Additionally, $30.4 of adverse development was reflected in the Small Commercial Business General Liability portfolio, largely driven by severity trends being greater than expected in the regional New York/New Jersey policies and large loss development on Excess & Surplus policies. Additionally, $22.3 of adverse development was driven primarily by long-tailed terminated programs, particularly general liability programs, in the Company's Specialty Program segment. The Company's adverse prior period reserve development was $91.9 for the six months ended June 30, 2017 , primarily due to adverse loss experience in the Company's Specialty Program segment's general liability and auto liability portfolios, and the Company's Small Commercial Business segment's auto liability portfolio. In setting its reserves, the Company utilizes a combination of Company loss development factors and industry-wide loss development factors. In the event that the Company’s losses develop more favorably (adversely) than the industry, as a whole, the Company’s liabilities for unpaid losses and LAE may decrease (increase). Company management believes that its use of both its historical experience and industry-wide loss development factors provide a reasonable basis for estimating future losses. In either case, future events beyond the control of management, such as changes in or judicial interpretations of law and inflation, may favorably or unfavorably impact the ultimate settlement of the Company’s Loss and LAE reserves. The anticipated effect of inflation is implicitly considered when estimating Loss and LAE reserves. While the Company considers anticipated changes in claim costs due to inflation in estimating the ultimate claim costs, the increase in average severity of claims is caused by a number of factors that vary with the individual type of policy written. The Company projects future average severities based on historical trends adjusted for implemented changes in underwriting standards, policy provisions, and general economic trends. The Company monitors those anticipated trends based on actual development and makes modifications, if necessary.

Debt

Debt	6 Months Ended
	Jun. 30, 2018
Debt Disclosure [Abstract]
Debt	Debt The Company’s outstanding debt consisted of the following at June 30, 2018 and December 31, 2017 : June 30, 2018 December 31, 2017 Revolving credit facility $ 130.0 $ 130.0 5.5% Convertible senior notes due 2021 (the "2021 Notes") 5.4 5.4 2.75% Convertible senior notes due 2044 (the "2044 Notes") 176.4 173.0 6.125% Notes due 2023 (the "2023 Notes") 248.6 248.4 Junior subordinated debentures (the "2035-2037 Notes") 122.2 122.1 Trust preferred securities (the "2033-2037 TPS Notes") 92.8 92.8 7.25% Subordinated notes due 2055 (the "7.25% 2055 Notes") 145.4 145.3 7.50% Subordinated notes due 2055 (the "7.50% 2055 Notes") 130.9 130.8 Secured loan agreements 168.2 174.4 Promissory notes and other 95.4 66.5 Total debt $ 1,315.3 $ 1,288.7 Additionally, the Company utilizes various letters of credit in its operations. The following is a summary of the Company's letters of credit as of June 30, 2018 : Limit Outstanding Available Revolving credit facility $ 175.0 $ 173.4 $ 1.6 Funds at Lloyd's facility 600.9 567.7 33.2 ING Bank N.V., BHF Bank Aktiengesellschaft, and Deutsche Bank AG facilities 101.3 80.6 20.7 Comerica Bank facility 75.0 42.9 32.1 Other letters of credit, in aggregate 114.1 114.1 — On May 8, 2018, the Company, as Guarantor, and several of its wholly-owned subsidiaries, as Account Party and as Corporate Members, entered into a Second Amendment Agreement (the “FAL Amendment”) to its existing £455.0 million (or $600.9 million at June 30, 2018 ) Funds at Lloyd's facility agreement with ING Bank, N.V., London Branch, The Bank of Nova Scotia, London Branch and Bank of Montreal, London Branch (as amended from time to time, the “Lloyd’s Agreement”). The FAL Amendment revised the financial covenant related to realistic disaster scenario loss estimate calculations to exclude the Company's life syndicate, Syndicate 44, on a prospective basis, effective as of the date of the FAL Amendment. Additionally, the FAL Amendment revised the financial covenant related to forecast underwriting losses exceeding 25% of allocated capacity in respect of any one open year of account to now be calculated on the basis of aggregate forecast underwriting losses across the non-life syndicates (Syndicates 1861, 1206, 2526 and 5820) and a per syndicate basis for Syndicate 44. Under the financial covenant as included in the original Lloyd’s Agreement, forecast losses were calculated per syndicate rather than in the aggregate. This revised approach aligned the operation of the covenant with the consolidation of all non-life underwriting within Syndicate 1861 from January 1, 2018. The change to the forecast underwriting losses financial covenant is retroactively effective to the date of the Lloyd’s Agreement dated November 8, 2017. Interest expense, including amortization of original issue discount and deferred origination costs, as well as applicable bank fees, related to the Company's outstanding debt and letters of credit for the three and six months ended June 30, 2018 and 2017 was: Three Months Ended June 30, Six Months Ended June 30, 2018 2017 2018 2017 Revolving credit facility $ 1.6 $ 1.5 $ 3.4 $ 3.0 2021 Notes 0.1 0.1 0.2 0.2 2044 Notes 3.4 3.2 6.7 6.4 2023 Notes 4.0 4.0 7.8 7.8 2035-2037 Notes 1.8 1.4 3.3 2.9 2033-2037 TPS Notes 1.3 1.1 2.5 2.1 7.25% 2055 Notes 2.7 2.7 5.5 5.5 7.50% 2055 Notes 2.5 2.5 5.1 5.1 Secured loan agreements 1.7 1.5 3.3 2.8 Promissory notes 0.8 1.0 1.7 2.7 Funds at Lloyd's facility 1.2 1.2 2.8 2.7 Other, including interest income 0.8 4.0 2.4 6.6 Total $ 21.9 $ 24.2 $ 44.7 $ 47.8 A detailed description of the Company's various debt arrangements is located in Note 13 to the consolidated financial statements included in the Company's Annual Report on Form 10-K for the year ended December 31, 2017 .

Earnings Per Share

Earnings Per Share	6 Months Ended
	Jun. 30, 2018
Earnings Per Share [Abstract]
Earnings Per Share	Earnings Per Share The following table is a summary of the elements used in calculating basic and diluted earnings per share for the three and six months ended June 30, 2018 and 2017 : Three Months Ended June 30, Six Months Ended June 30, 2018 2017 2018 2017 Numerator: Net (loss) income attributable to AmTrust common stockholders $ (116.2 ) $ 5.9 $ 545.6 $ 28.5 Denominator: Weighted average common shares outstanding – basic 196.9 180.7 196.6 175.8 Plus: Dilutive effect of stock options, convertible debt, other (1) — 0.8 0.3 1.1 Weighted average common shares outstanding – dilutive 196.9 181.5 196.9 176.9 Net (loss) income per AmTrust common share – basic $ (0.59 ) $ 0.03 $ 2.78 $ 0.16 Net (loss) income per AmTrust common share – diluted $ (0.59 ) $ 0.03 $ 2.77 $ 0.16 (1) In accordance with ASC 260, Earnings Per Share, no potential common shares are included in the computation of diluted per share amounts as the effect would be antidilutive for the three months ended June 30, 2018.

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2018
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes Income tax benefit for the six months ended June 30, 2018 was $19.0 , which resulted in an effective tax rate of (3.4)% , compared to an income tax provision of $1.6 for the six months ended June 30, 2017 , which resulted in an effective tax rate of 21.8% . The decrease in the effective tax rate during the six months ended June 30, 2018 compared to the six months ended June 30, 2017 resulted from a lower U.S. statutory tax rate as a result of tax reform under the Tax Cuts and Jobs Act, which went into effect December 22, 2017, and an estimated permanent favorable tax adjustment on the gain related to the transfer of the Company's U.S.-based fee business on February 28, 2018. Income tax benefit for the three months ended June 30, 2018 was $4.4 , which resulted in an effective tax rate of 4.3% , compared to an income tax benefit of $19.8 for the three months ended June 30, 2017 , which resulted in an effective tax rate of 32.9% . The decrease in the effective tax rate during the three months ended June 30, 2018 compared to the three months ended June 30, 2017 resulted from a lower U.S. statutory tax rate as a result of tax reform under the Tax Cuts and Jobs Act, which went into effect December 22, 2017, and a shift in the Company's foreign operations from higher taxing jurisdictions to lower taxing jurisdictions, partially offset by an estimated permanent favorable tax adjustment on the gain related to the transfer of the Company's U.S.-based fee business on February 28, 2018. As of June 30, 2018 , the Company has U.S. Net Operating Losses ("NOLs") of $82.0 that expire beginning in 2019 through 2038 . In addition, these NOLs are subject to certain limitations under Section 382 of the Internal Revenue Code due to changes in ownership of $9.1 per year. The Company also has foreign NOLs of $948.6 , the majority of which have no expiration. The Company’s management believes that as of June 30, 2018 , except for a portion of the NOLs, it will realize the benefits of its deferred tax assets, which are included as a component of other assets on the condensed consolidated balance sheet, due to the Company having an overall deferred tax asset position. As a result, the Company recorded a valuation allowance of $169.2 and $195.1 as of June 30, 2018 and December 31, 2017 , respectively. The decrease in the valuation allowance from December 31, 2017 to June 30, 2018 was driven primarily by the tax rate decrease in Luxembourg, which reduced the Luxembourg NOLs, thereby requiring a reduction in the valuation allowance because the Luxembourg NOLs are in a full valuation allowance position. The Company did not utilize any equalization reserves attributed to its Luxembourg reinsurance companies during the six months ended June 30, 2018 and 2017 , respectively. In accordance with the adoption of ASU 2018-02, the Company reclassed certain tax effects from accumulated other comprehensive (loss) income. See Note 2. "Recent Accounting Pronouncements" for additional information on the impact of the adoption of ASU 2018-02. For additional information relating to Income Taxes, see Note 18 to the Consolidated Financial Statements included in the Company's Annual Report on Form 10-K for the year ended December 31, 2017 .

Related Party Transactions

Related Party Transactions	6 Months Ended
	Jun. 30, 2018
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions The Company has various reinsurance and service agreements with Maiden Holdings, Ltd. ("Maiden") and NGHC. With the exception of the agreement discussed below, there were no material changes to these agreements during the six months ended June 30, 2018 . For more information related to these agreements, see Note 15. "Related Party Transactions" to the consolidated financial statements included in the Company's Annual Report on Form 10-K for the year ended December 31, 2017. In addition, a related party transaction entered into by the Company and a Karfunkel-Zyskind Family affiliated entity is described in Note 1. "Basis of Reporting and Merger Agreement". Effective May 1, 2018, NGHC's subsidiaries terminated their asset management agreements with the Company.

Stockholders' Equity

Stockholders' Equity	6 Months Ended
	Jun. 30, 2018
Equity [Abstract]
Stockholders' Equity	Stockholders' Equity Stockholders' Equity The following table summarizes the ownership components of total stockholders' equity: Six Months Ended June 30, 2018 2017 AmTrust Non-Controlling Interest Total AmTrust Non-Controlling Interest Total Beginning balance $ 3,189.7 $ 178.4 $ 3,368.1 $ 3,269.1 $ 196.5 $ 3,465.6 Net income (loss) 578.7 (6.3 ) 572.4 61.6 17.1 78.7 Unrealized holding gain, net of tax (136.9 ) — (136.9 ) 75.1 — 75.1 Reclassification adjustment (4.1 ) — (4.1 ) (30.9 ) — (30.9 ) Foreign currency translation (24.4 ) — (24.4 ) 76.6 — 76.6 Unrealized gain on interest rate swap — — — 0.1 — 0.1 Distribution of non-controlling interest — (114.6 ) (114.6 ) — — — Share exercises, compensation and other 7.0 — 7.0 9.7 — 9.7 Common stock issuance — — — 298.7 — 298.7 Common stock dividends (33.3 ) — (33.3 ) (63.3 ) — (63.3 ) Preferred stock dividends (33.1 ) — (33.1 ) (33.1 ) — (33.1 ) Capital distributions, net — — — — 19.3 19.3 Balance, June 30, $ 3,543.6 $ 57.5 $ 3,601.1 $ 3,663.6 $ 232.9 $ 3,896.5 During the six months ended June 30, 2017 , net income attributable to non-controlling interest was $17.1 , and net income attributable to non-controlling interest and redeemable non-controlling interest of subsidiaries was $17.7 . During the six months ended June 30, 2018 , net loss attributable to non-controlling interest was $6.3 , and net income attributable to non-controlling interest and redeemable non-controlling interest of subsidiaries was $0.3 . Redeemable non-controlling interest of subsidiaries was extinguished with the transfer of the U.S.-based fee business during the six months ended June 30, 2018 . Each share of the Company's preferred stock will remain outstanding in accordance with its terms through consummation of the proposed merger transaction. Accumulated Other Comprehensive Income (Loss) The following table summarizes the activities and components of accumulated other comprehensive income (loss) for the three and six months ended June 30, 2018 and 2017: Foreign Currency Items Unrealized Gains (Losses) on Investments Interest Rate Swap Hedge Net Benefit Plan Assets and Obligations Recognized in Stockholders' Equity Accumulated Other Comprehensive Income (Loss) Balance, March 31, 2018 $ 17.4 $ (64.4 ) $ — $ (2.3 ) $ (49.3 ) Other comprehensive income (loss) before reclassification (86.6 ) (17.8 ) — — (104.4 ) Amounts reclassed out of accumulated other comprehensive (loss) income — (2.5 ) — — (2.5 ) Income tax benefit — 5.6 — — 5.6 Net current-period other comprehensive loss (86.6 ) (14.7 ) — — (101.3 ) Balance, June 30, 2018 $ (69.2 ) $ (79.1 ) $ — $ (2.3 ) $ (150.6 ) Balance, March 31, 2017 $ (174.3 ) $ 79.8 $ (0.1 ) $ (3.2 ) $ (97.8 ) Other comprehensive income before reclassification 62.7 66.1 — — 128.8 Amounts reclassed out of accumulated other comprehensive (loss) income — (19.3 ) — — (19.3 ) Income tax expense — (16.6 ) — — (16.6 ) Net current-period other comprehensive income 62.7 30.2 — — 92.9 Balance, June 30, 2017 $ (111.6 ) $ 110.0 $ (0.1 ) $ (3.2 ) $ (4.9 ) Foreign Currency Items Unrealized Gains (Losses) on Investments Interest Rate Swap Hedge Net Benefit Plan Assets and Obligations Recognized in Stockholders' Equity Accumulated Other Comprehensive Income (Loss) Balance, December 31, 2017 $ (44.8 ) $ 62.6 $ — $ (2.3 ) $ 15.5 Net cumulative effect adjustments (1) — (0.7 ) — — (0.7 ) Other comprehensive income (loss) before reclassification (24.4 ) (174.9 ) — — (199.3 ) Amounts reclassed out of accumulated other comprehensive (loss) income — (4.1 ) — — (4.1 ) Income tax benefit — 38.0 — — 38.0 Net current-period other comprehensive loss (24.4 ) (141.7 ) — — (166.1 ) Balance, June 30, 2018 $ (69.2 ) $ (79.1 ) $ — $ (2.3 ) $ (150.6 ) Balance, December 31, 2016 $ (188.2 ) $ 65.8 $ (0.2 ) $ (3.2 ) $ (125.8 ) Other comprehensive income before reclassification 76.6 98.1 0.1 — 174.8 Amounts reclassed out of accumulated other comprehensive (loss) income — (30.9 ) — — (30.9 ) Income tax expense — (23.0 ) — — (23.0 ) Net current-period other comprehensive income 76.6 44.2 0.1 — 120.9 Balance, June 30, 2017 $ (111.6 ) $ 110.0 $ (0.1 ) $ (3.2 ) $ (4.9 ) (1) See Note 2. "Recent Accounting Pronouncements" for additional information on the adoptions of ASU 2016-01 and ASU 2018-02.

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Litigation The Company’s insurance subsidiaries are named as defendants in various legal actions arising principally from claims made under insurance policies and contracts. The Company considers these actions in estimating its Loss and LAE reserves. The Company is also a party to various commercial and employment disputes, including claims made both by and against the Company. The Company’s management believes the resolution of these actions will not have a material adverse effect on the Company’s financial position or results of operations. In view of the inherent difficulty of assessing the potential outcome of legal proceedings, governmental, regulatory and legislative investigations and inquiries, claims and litigation and similar matters and contingencies, the Company generally cannot predict what the eventual outcome of the pending matters will be or the timing of any resolution of such matters. Unless specified below, the Company cannot reasonably estimate a potential range of loss, if any, with respect to the matters disclosed below due to, among other factors, the complexity of the matters involved and in many instances, the relatively early stage of the proceedings. The Company also is not able to predict at this time the impact, if any, that any such matters might have on how its business is conducted, on its competitive position or on its financial position, results of operations or cash flows. As the process to resolve any pending matters progresses, management will continue to review the latest information available and assess its ability to predict the outcome of such matters and the effects, if any, on its operations and financial condition and to accrue for and disclose such matters as and when required. Derivative Litigation On April 7, 2015, one of the Company's stockholders, Cambridge Retirement System ("Cambridge"), filed a derivative action in the Court of Chancery of the State of Delaware against the Company, as nominal defendant, and against the Company's board of directors, Leah Karfunkel, and ACP Re, as defendants. Cambridge amended its complaint on November 3, 2015 to add NGHC as a defendant. Cambridge purports to bring the derivative action on the Company's behalf, alleging breaches of the duties of loyalty and care on the part of the Company's board of directors and majority stockholders related to the Company's transactions involving Tower Group International, Ltd. Cambridge's claim against NGHC and ACP Re is for unjust enrichment. The amended complaint seeks damages, disgorgement and reform of the Company's governance practices. On April 27, 2017, one of the Company's stockholders, David Shaev Profit Sharing Plan, filed a derivative action in the Supreme Court of the State of New York for the County of New York ( Shaev v. DeCarlo et al. ). Two derivative suits have also been filed in the U.S. District Court for the District of Delaware. On May 11, 2017, one of the Company's stockholders, West Palm Beach Police Pension Fund, filed suit ( West Palm Beach Police Pension Fund v. Zyskind et al .), and on June 28, 2017, two of the Company's stockholders, City of Lauderhill Police Officers Retirement Plan and Pompano Beach Police & Firefighters Retirement System, filed suit ( City of Lauderhill Police Officers Retirement Plan and Pompano Beach Police & Firefighters Retirement System et al. v. Zyskind et al .). These two Delaware derivative actions have been consolidated under the case name In re AmTrust Financial Services, Inc. Derivative Litigation . Plaintiffs in this proceeding filed a Verified Amended Stockholder Derivative Complaint on November 7, 2017 and a Verified Second Amended Stockholder Derivative Complaint on December 11, 2017. The Verified Second Amended Stockholder Derivative Complaint alleges violations of Sections 10(b), 20A, and 29(b) of the Exchange Act, breaches of fiduciary duties, unjust enrichment, and corporate waste. Such stockholders purport to bring the derivative action on the Company's behalf and raise claims that primarily involve the Company's recent restatement of its financial statements, the identification of material weaknesses in the Company's internal control over financial reporting and recent increases in the Company's loss reserves. The In re AmTrust Financial Services, Inc. Derivative Litigation second amended complaint also seeks reform of the Company's governance practices and damages. The Company believes that the allegations in these pending derivative actions are unfounded and is vigorously pursuing its defenses. Securities Litigation The Company and certain of its officers and directors are also defendants in three putative securities class action lawsuits filed in March and April of 2017 in the U.S. District Court for the Southern District of New York. Another putative class action, filed in February 2017 in the U.S. District Court for the Central District of California, was voluntarily dismissed ( Miller v. AmTrust, Zyskind, and Pipoly ). The three cases in the Southern District of New York have been consolidated under the case name In re AmTrust Financial Services, Inc. Securities Litigation. Plaintiffs in this proceeding filed a consolidated, amended complaint on August 21, 2017 . Plaintiffs assert in the consolidated, amended complaint claims under Sections 10(b) and 20(a) of the Exchange Act, and Rule 10b-5 promulgated thereunder and Sections 11, 12(a)(2) and 15 of the Securities Act of 1933, as amended. The consolidated, amended complaint adds as defendants BDO USA LLP, Citigroup Global Markets Inc., Keefe, Bruyette & Woods, Inc., Morgan Stanley & Co. LLC, RBC Capital Markets, LLC, and UBS Securities LLC. Plaintiffs seek an unspecified amount in damages, attorneys’ fees, and other relief. The Company believes the allegations are unfounded and is vigorously pursuing its defenses. Section 220 Demands and Related Legal Proceedings Additionally, between April 2017 and May 2018, the Company received demands for the inspection of books and records pursuant to Section 220 of the Delaware General Corporation Law, from purported stockholders Rikhard Dauber, Pompano Beach Police & Firefighters Retirement System, Nestor Shust, the City of Lauderhill Police Officers’ Retirement Plan, the West Palm Beach Police Pension Fund, Cambridge, the Lislois Family Trust, Arca Capital Group ("Arca") and Gabriel McLure (“McLure”). In May and June 2018, Arca and McLure, respectively, commenced legal proceedings against the Company in the Court of Chancery of the State of Delaware over the scope of the Company’s proposed production of documents in response to the Section 220 demands of Arca and McLure. The lawsuits are entitled Arca Investments, A.S., Arca Capital Bohemia, S.A., and Arca Venture Capital A.S. v AmTrust Financial Services, Inc. (Case No. 2018-0381) and Gabriel McLure v AmTrust Financial Services, Inc. (Case No. 2018-0400). The Arca Section 220 demand lawsuit was dismissed voluntarily on August 6, 2018. SEC Investigation Since June 2013, the Company has been responding to an investigation by the SEC, which in its course has included a review of the Company's investment in life settlement contracts, acquisition of Luxembourg captives, certain accounting practices, including accounting for loss and loss adjustment expense reserve estimates for the Company’s major business lines and segments, internal controls and other related matters. The Company cannot predict the eventual scope, duration or outcome of such inquiry or whether it could have a material impact on the Company’s financial condition, results of operations or cash flow. The Company has been responsive to this ongoing inquiry and will continue to be cooperative with regards to any governmental or regulatory inquiries or investigations. Litigation Related to the Merger Following the filing by the Company of its definitive proxy statement with the SEC on May 4, 2018 in connection with the special meeting of the stockholders of the Company to consider and vote upon a proposal to adopt the Amended Merger Agreement by and among Evergreen Parent, Evergreen Merger Sub, Inc., a Delaware corporation and wholly owned subsidiary of Evergreen Parent (“Merger Sub”), and the Company, on May 9, 2018, purported stockholders of the Company filed putative class action lawsuits against the Company and members of the Board (other than Mr. Serock) in the United States District Court for the Southern District of New York, captioned Bartholomew v. AmTrust Fin’l Services, Inc., et al. , Case No. 1:18-cv-04178 (S.D.N.Y.) and Myhre v. AmTrust Fin’l Services, Inc., et al. , Case No. 1:18-cv-04175 (S.D.N.Y.), respectively. The complaints are substantially identical and allege that the defendants violated Sections 14(a) and 20(a) of the Exchange Act because the preliminary proxy statement filed with the SEC on April 9, 2018 allegedly omitted material information with respect to the merger, thus rendering the preliminary proxy statement false and misleading. The complaints seek, among other things, injunctive relief preventing the consummation of the merger and costs of the applicable action, including reasonable allowance for plaintiff attorneys’ and experts’ fees. On May 15, 2018, a purported stockholder of the Company filed a putative class action lawsuit against the Company and members of the Board in the United States District Court for the Northern District of Ohio, captioned Shust v. AmTrust Fin’l Services, Inc., et al. , Case No. 1:18-cv-01129 (N.D. Ohio). On May 18, 2018, a purported stockholder of the Company filed a putative class action lawsuit against the Company and members of the Board in the United States District Court for the Southern District of New York, captioned Raul v. AmTrust Fin’l Services, Inc., et al. , Case No. 1:18-cv-04440 (S.D.N.Y.). On May 21, 2018, a purported stockholder of the Company filed a putative class action lawsuit against the Company, members of the Board, Evergreen Parent, Merger Sub and Stone Point in the United States District Court for the Southern District of New York, captioned Rabinowitz v. AmTrust Fin’l Services, Inc. , et al., Case No. 1:18-cv-04484 (S.D.N.Y.). Similar to the complaints described above, the complaints allege that the defendants violated Sections 14(a) and 20(a) of the Exchange Act because the definitive proxy statement, in the case of the Shust complaint and the Rabinowitz complaint, and the preliminary proxy statement, in the case of the Raul complaint, omitted or misrepresented material information concerning the merger. The complaints seek, among other things, injunctive relief preventing the consummation of the merger unless additional disclosure is provided and costs of the applicable action, including for plaintiff attorneys’ and experts’ fees. On May 31, 2018, Pompano Beach Police & Firefighters’ Retirement System, City of Lauderhill Police Officers’ Retirement System and West Palm Beach Police Pension Fund filed a putative class action lawsuit against the Company’s board of directors, Stone Point, Trident Pine Acquisition ("Trident Pine"), Trident VII Professionals Fund, Trident VII, Trident VII DE Parallel Fund, and Trident VII Parallel Fund (collectively, the "Trident Funds") in the Court of Chancery of the State of Delaware, Case No. 2018-0396-AGB. The complaint alleges that defendants Zyskind, G. Karfunkel. L. Karfunkel, Gulkowitz, Fisch, DeCarlo, and Rivera breached their fiduciary duties, which resulted in an unfair merger stock price through an unfair process. The complaint alleges additional claims for breaches of fiduciary duty against Zyskind, G. Karfunkel and L. Karfunkel in their capacity as officers and directors of the Company and as controlling stockholders of the Company. The complaint alleges that Stone Point, Trident Pine and the Trident Funds aided and abetted the breaches of fiduciary duties. On June 4, 2018, Cambridge filed a putative class action lawsuit against the Company’s board of directors, the Estate of Michael Karfunkel, Evergreen Parent, K-Z Evergreen, LLC, Merger Sub, Trident Pine Acquisition LP and Stone Point in the Court of Chancery of the State of Delaware, Case No. 2018-0402-AGB. Similar to the 2018 Pompano Beach action, the complaint alleges that the director defendants breached their fiduciary duties, which resulted in an unfair merger stock price through an unfair process. The complaint alleges an additional claim for breach of fiduciary duty against Zyskind, G. Karfunkel, L. Karfunkel, and M. Karfunkel in their capacity as controlling shareholders of the Company and alleges that Evergreen Parent, Stone Point, and Trident Pine aided and abetted the foregoing breaches of fiduciary duties. The Company believes the allegations in the merger litigation described above are without merit and is vigorously pursuing its defenses. Other than as discussed above, the Company is not involved presently in any material litigation nor, to the Company’s knowledge, is any material litigation threatened against the Company or its properties.

Segments

Segments	6 Months Ended
	Jun. 30, 2018
Segment Reporting [Abstract]
Segments	Segments The Company operates three business segments: Small Commercial Business; Specialty Risk and Extended Warranty; and Specialty Program. The Corporate and Other segment represents the activities of the holding company as well as a portion of service and fee income. Investment income and realized gains (losses) on investments are determined by calculating an overall annual return on cash and invested assets and applying that overall return to the cash and invested assets by segment. Ceding commission is allocated to each segment based on that segment’s proportionate share of the Company’s overall acquisition costs. Interest expense is allocated based on gross written premiums by segment. Income taxes are allocated on a pro-rata basis based on the Company’s effective tax rate. Additionally, management reviews the performance of underwriting results in assessing the performance of and making decisions regarding the allocation of resources to the segments. Underwriting results excludes, primarily, service and fee income, investment income and other revenues, other expenses, interest expense and income taxes. Management believes that providing information in this manner is essential to providing the Company’s stockholders with an understanding of the Company’s business and operating performance. During the three and six months ended June 30, 2018 , neither Small Commercial Business nor Specialty Risk and Extended Warranty derived over ten percent of its total revenue from one customer. Specialty Program derived over ten percent of its total revenue during the three and six months ended June 30, 2018 from a customer that was formally a consolidated entity and was included in the transfer of the U.S.-based fee businesses completed on February 28, 2018 . See Note 13. "Divestiture" for additional information on the transfer. The following tables summarize the results of operations of the business segments for the three and six months ended June 30, 2018 and 2017 : Three Months Ended June 30, 2018 Small Commercial Business Specialty Risk and Extended Warranty Specialty Program Corporate and Other Total Revenues: Net earned premiums $ 622.9 $ 560.5 $ 102.8 $ — $ 1,286.2 Losses and expenses: Loss and loss adjustment expenses 478.0 356.9 98.8 — 933.7 Amortization of deferred acquisition costs 105.8 146.7 57.9 — 310.4 Underwriting, general and administrative expenses 31.9 62.5 26.7 — 121.1 Total losses and expenses 615.7 566.1 183.4 — 1,365.2 Underwriting gain (loss) 7.2 (5.6 ) (80.6 ) — (79.0 ) Other income (losses and expenses): Service and fee income 6.4 25.8 0.3 16.8 49.3 Investment income and realized gain on investments 32.8 29.5 11.4 — 73.7 Other expenses (26.8 ) (22.6 ) (4.7 ) (55.2 ) (109.3 ) Interest expense (11.3 ) (8.7 ) (1.9 ) — (21.9 ) Foreign currency loss — (11.6 ) — — (11.6 ) Other revenues (1.6 ) (0.8 ) (0.2 ) 0.1 (2.5 ) (Provision) benefit for income taxes (0.6 ) 1.6 (2.8 ) 6.2 4.4 Net income (loss) $ 6.1 $ 7.6 $ (78.5 ) $ (32.1 ) $ (96.9 ) Three Months Ended June 30, 2017 Small Commercial Business Specialty Risk and Extended Warranty Specialty Program Corporate and Other Total Revenues: Net earned premiums $ 631.9 $ 539.0 $ 209.8 $ — $ 1,380.7 Losses and expenses: Loss and loss adjustment expenses 466.9 370.9 186.7 — 1,024.5 Amortization of deferred acquisition costs 94.8 78.1 34.9 — 207.8 Underwriting, general and administrative expenses 75.4 62.2 27.8 — 165.4 Total losses and expenses 637.1 511.2 249.4 — 1,397.7 Underwriting (loss) income (5.2 ) 27.8 (39.6 ) — (17.0 ) Other income (losses and expenses): Service and fee income 30.9 98.2 0.5 38.8 168.4 Investment income and realized gain on investments 32.5 27.8 12.5 — 72.8 Other expenses (51.4 ) (35.8 ) (12.7 ) (99.9 ) (199.8 ) Interest expense (12.4 ) (8.7 ) (3.1 ) — (24.2 ) Foreign currency loss — (58.9 ) — — (58.9 ) Other revenues (0.9 ) (0.4 ) (0.2 ) — (1.5 ) Benefit (provision) for income taxes 7.5 28.6 (0.3 ) (16.0 ) 19.8 Equity in earnings of unconsolidated subsidiary – related party — — — 69.5 69.5 Net income (loss) $ 1.0 $ 78.6 $ (42.9 ) $ (7.6 ) $ 29.1 Six Months Ended June 30, 2018 Small Commercial Business Specialty Risk and Extended Warranty Specialty Program Corporate and Other Total Revenues: Net earned premiums $ 1,266.9 $ 1,155.2 $ 219.0 $ — $ 2,641.1 Losses and expenses: Loss and loss adjustment expenses 976.7 749.2 180.7 — 1,906.6 Amortization of deferred acquisition costs 205.2 234.5 86.3 — 526.0 Underwriting, general and administrative expenses 130.1 148.9 54.7 — 333.7 Total losses and expenses 1,312.0 1,132.6 321.7 — 2,766.3 Underwriting (loss) gain (45.1 ) 22.6 (102.7 ) — (125.2 ) Other income (losses and expenses): Service and fee income 25.9 102.5 1.3 35.7 165.4 Investment income and realized gain on investments 63.5 57.5 23.2 — 144.2 Other expenses (85.6 ) (62.0 ) (13.8 ) (162.5 ) (323.9 ) Interest expense (23.8 ) (17.1 ) (3.8 ) — (44.7 ) Foreign currency gain — 14.9 — — 14.9 Other revenues 2.7 2.0 0.4 724.2 729.3 (Provision) benefit for income taxes (2.1 ) 4.1 (3.2 ) 20.2 19.0 Net (loss) income $ (64.5 ) $ 124.5 $ (98.6 ) $ 617.6 $ 579.0 Six Months Ended June 30, 2017 Small Commercial Business Specialty Risk and Extended Warranty Specialty Program Corporate and Other Total Revenues: Net earned premiums $ 1,185.5 $ 1,012.5 $ 405.2 $ — $ 2,603.2 Losses and expenses: Loss and loss adjustment expenses 844.3 683.5 337.0 — 1,864.8 Amortization of deferred acquisition costs 191.8 152.4 69.5 — 413.7 Underwriting, general and administrative expenses 133.1 106.3 48.3 — 287.7 Total losses and expenses 1,169.2 942.2 454.8 — 2,566.2 Underwriting gain (loss) 16.3 70.3 (49.6 ) — 37.0 Other income (losses and expenses): Service and fee income 59.6 185.1 2.0 59.2 305.9 Investment income and realized gain on investments 62.2 53.9 28.6 — 144.7 Other expenses (96.7 ) (62.1 ) (22.6 ) (181.3 ) (362.7 ) Interest expense (25.5 ) (16.3 ) (6.0 ) — (47.8 ) Foreign currency gain — (76.9 ) — — (76.9 ) Other revenues 3.9 2.4 0.9 — 7.2 (Provision) benefit for income taxes (0.4 ) (3.1 ) 0.9 1.0 (1.6 ) Equity in earnings of unconsolidated subsidiary – related party — — — 73.5 73.5 Net income (loss) $ 19.4 $ 153.3 $ (45.8 ) $ (47.6 ) $ 79.3 The following table summarizes net earned premiums by major line of business, by segment, for the three and six months ended June 30, 2018 and 2017 : Small Commercial Business Specialty Risk and Extended Warranty Specialty Program Total Three Months Ended June 30, 2018: Workers' compensation $ 376.6 $ — $ 46.3 $ 422.9 Warranty — 232.0 — 232.0 Commercial auto and liability, physical damage 125.0 — 24.0 149.0 Commercial multiple-peril 84.2 15.7 9.3 109.2 Other liabilities — 66.4 9.8 76.2 Medical malpractice — 41.7 — 41.7 Accident and health — 39.8 — 39.8 Surety 16.1 17.3 — 33.4 Homeowners multiple-peril 6.6 32.7 2.5 41.8 Fire 1.9 27.9 — 29.8 Inland Marine 1.8 27.4 — 29.2 Other 10.7 59.6 10.9 81.2 Total net earned premiums $ 622.9 $ 560.5 $ 102.8 $ 1,286.2 Small Commercial Business Specialty Risk and Extended Warranty Specialty Program Total Three Months Ended June 30, 2017: Workers' compensation $ 373.1 $ — $ 114.6 $ 487.7 Warranty — 255.8 — 255.8 Commercial auto and liability, physical damage 95.6 — 28.5 124.1 Commercial multiple-peril 66.4 — 16.0 82.4 Other liabilities — 46.2 52.2 98.4 Medical malpractice — 53.9 — 53.9 Accident and health — 46.9 — 46.9 Surety 13.9 27.4 — 41.3 Homeowners multiple-peril 14.1 1.1 2.7 17.9 Fire 8.3 54.8 — 63.1 Inland Marine 3.0 (3.8 ) — (0.8 ) Other 57.5 56.7 (4.2 ) 110.0 Total net earned premiums $ 631.9 $ 539.0 $ 209.8 $ 1,380.7 Small Commercial Business Specialty Risk and Extended Warranty Specialty Program Total Six Months Ended June 30, 2018: Workers' compensation $ 754.9 $ — $ 110.8 $ 865.7 Warranty — 531.8 — 531.8 Commercial auto and liability, physical damage 238.6 — 54.6 293.2 Commercial multiple-peril 164.7 25.9 20.8 211.4 Other liabilities — 136.0 19.4 155.4 Medical malpractice — 104.4 — 104.4 Accident and health — 83.4 — 83.4 Surety 29.5 42.5 — 72.0 Homeowners multiple-peril 13.1 56.5 2.5 72.1 Fire 3.4 53.3 — 56.7 Inland Marine 3.3 38.5 — 41.8 Other 59.4 82.9 10.9 153.2 Total net earned premiums $ 1,266.9 $ 1,155.2 $ 219.0 $ 2,641.1 Small Commercial Business Specialty Risk and Extended Warranty Specialty Program Total Six Months Ended June 30, 2017: Workers' compensation $ 709.4 $ — $ 223.6 $ 933.0 Warranty — 470.3 — 470.3 Commercial auto and liability, physical damage 196.7 — 54.5 251.2 Commercial multiple-peril 98.2 — 16.0 114.2 Other liabilities — 89.5 106.7 196.2 Medical malpractice — 106.7 — 106.7 Accident and health — 80.0 — 80.0 Surety 26.1 52.3 — 78.4 Homeowners multiple-peril 25.6 1.1 2.7 29.4 Fire 20.1 115.0 — 135.1 Inland Marine 3.0 14.2 — 17.2 Other 106.4 83.4 1.7 191.5 Total net earned premiums $ 1,185.5 $ 1,012.5 $ 405.2 $ 2,603.2 The following table presents the Company's revenues from contracts with customers disaggregated by major business activity and primary geographic regions for the three and six months ended June 30, 2018 : Three Months Ended June 30, 2018 Small Commercial Business Specialty Risk and Extended Warranty Specialty Program Corporate and Other Total Major service lines Product warranty registration and service $ — $ 22.5 $ — $ — $ 22.5 Broker and agency services, and insurance-related services 4.3 10.6 0.3 — 15.2 Asset management, and business services — — — 12.0 12.0 Total $ 4.3 $ 33.1 $ 0.3 $ 12.0 $ 49.7 Primary Geographic Market United States $ 4.3 $ 9.7 $ 0.3 $ 3.0 $ 17.3 International — 23.4 — 9.0 32.4 Total $ 4.3 $ 33.1 $ 0.3 $ 12.0 $ 49.7 Six Months Ended June 30, 2018 Small Commercial Business Specialty Risk and Extended Warranty Specialty Program Corporate and Other Total Major service lines Product warranty registration and service $ — $ 74.9 $ — $ — $ 74.9 Broker and agency services, and insurance-related services 21.8 33.7 1.3 — 56.8 Asset management, and business services — — — 25.2 25.2 Total $ 21.8 $ 108.6 $ 1.3 $ 25.2 $ 156.9 Primary Geographic Market United States $ 21.8 $ 64.9 $ 1.3 $ 7.0 $ 95.0 International — 43.7 — 18.2 61.9 Total $ 21.8 $ 108.6 $ 1.3 $ 25.2 $ 156.9

Divestitures

Divestitures	6 Months Ended
	Jun. 30, 2018
Discontinued Operations and Disposal Groups [Abstract]
Divestitures	Divestiture On November 3, 2017 , the Company and Mayfield Holdings LLC (“Mayfield”), entered into a Contribution and Stock Purchase Agreement (the “Acquisition Agreement”) with MH JV Holdings L.P. (“Investor”), a newly-formed investment vehicle owned by affiliates of Madison Dearborn Partners, related to the Investor’s acquisition of a majority interest in a portion of the Company's U.S.-based fee business. On February 28, 2018 , the Company completed the transfer of the U.S.-based fee businesses to Mayfield and the Investor's acquisition of a majority interest in Mayfield. Under the terms of the Acquisition Agreement, as amended, (1) Investor contributed to Mayfield approximately $225.8 in cash in exchange for approximately 51% of the common units of Mayfield, (2) the Company contributed into Mayfield equity interests in certain of the entities comprising the U.S.-based fee businesses with an implied value of approximately $217.0 in exchange for approximately 49% of the common units of Mayfield, and (3) one or more subsidiaries of Mayfield acquired from the Company the remaining portion of the entities comprising the U.S.-based fee businesses in exchange for a base cash purchase price of approximately $933.0 , subject to post-closing purchase price adjustments based upon the amount of cash, indebtedness, other non-cash adjustments and transaction expenses of Mayfield and its subsidiaries at the closing of the transaction. The company recognized a $724.1 gain on the sale based on the base cash purchase price during the six months ended June 30, 2018 . There were no post-closing purchase price adjustments made during the six months ended June 30, 2018. Now that the transaction has closed, the Company will cease consolidating the results of the U.S.-based fee businesses within its consolidated financial statements and will report its ownership interest in Mayfield using the equity method of accounting and include it in other investments on the consolidated balance sheets. The assets and liabilities related to this transaction were classified as held for sale in the consolidated balance sheets as of December 31, 2017. The Company determined the estimated fair value of the net assets held for sale based on the estimated selling price less costs to sell and was classified as Level 2 within the fair value hierarchy as of December 31, 2017. The classes of assets and liabilities to be sold and classified as held for sale as of December 31, 2017 consisted of the following: December 31, 2017 Fixed maturity securities, available for sale $ 35.3 Other investments 0.2 Cash and cash equivalents 56.1 Restricted cash and cash equivalents 33.8 Accrued interest and dividends 0.3 Premiums receivable, net 33.9 Deferred policy acquisition costs 211.5 Property, equipment and software, net 4.2 Goodwill 188.3 Intangible assets 171.9 Other assets 165.4 Total assets held for sale $ 900.9 Funds held under reinsurance treaties $ 1.3 Accrued expenses and other liabilities 760.4 Total liabilities held for sale $ 761.7

Investments (Tables)

Investments (Tables)	6 Months Ended
	Jun. 30, 2018
Investments, Debt and Equity Securities [Abstract]
Schedule of Available-for-sale Securities	The amortized cost, gross unrealized gains and losses, and estimated fair value of securities classified as available-for-sale as of June 30, 2018 and December 31, 2017 , are presented below: As of June 30, 2018 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value U.S. treasury securities $ 299.7 $ 0.9 $ (3.0 ) $ 297.6 U.S. government agencies 131.4 0.8 (1.6 ) 130.6 Municipal bonds 822.5 7.6 (9.0 ) 821.1 Foreign government 286.5 1.3 (3.9 ) 283.9 Corporate bonds: Finance 1,909.8 13.9 (37.3 ) 1,886.4 Industrial 2,400.3 16.4 (55.5 ) 2,361.2 Utilities 325.6 4.5 (7.3 ) 322.8 Commercial mortgage-backed securities 397.2 1.6 (14.1 ) 384.7 Residential mortgage-backed securities: Agency backed 916.3 1.5 (16.8 ) 901.0 Non-agency backed 7.6 — — 7.6 Collateralized loan / debt obligation 822.6 4.4 (2.9 ) 824.1 Asset backed securities 57.3 0.1 (0.1 ) 57.3 Total available-for-sale securities $ 8,376.8 $ 53.0 $ (151.5 ) $ 8,278.3 As of December 31, 2017 (1) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value U.S. treasury securities $ 301.6 $ 0.9 $ (3.2 ) $ 299.3 U.S. government agencies 51.1 — (0.6 ) 50.5 Municipal bonds 1,035.5 15.9 (5.9 ) 1,045.5 Foreign government 151.4 3.5 (3.2 ) 151.7 Corporate bonds: Finance 1,733.2 48.1 (11.9 ) 1,769.4 Industrial 2,237.0 57.3 (26.1 ) 2,268.2 Utilities 323.8 10.7 (2.1 ) 332.4 Commercial mortgage-backed securities 419.3 3.8 (10.4 ) 412.7 Residential mortgage-backed securities: Agency backed 562.0 5.8 (11.4 ) 556.4 Non-agency backed 6.9 — (0.1 ) 6.8 Collateralized loan / debt obligation 591.2 9.7 (0.3 ) 600.6 Asset backed securities 30.1 0.1 (0.1 ) 30.1 Less: Assets classified as held for sale (See Note 13) (34.4 ) (0.9 ) — (35.3 ) Total available-for-sale securities $ 7,408.7 $ 154.9 $ (75.3 ) $ 7,488.3 (1) In connection with the adoption of ASU 2016-01, the disclosure for December 31, 2017 has been recast for comparability. See Note 2. "Recent Accounting Pronouncements" for additional information on the impact of the adoption of ASU 2016-01.
Summary of Available for Sale Fixed Securities by Contractual Maturity	A summary of the Company’s available-for-sale securities as of June 30, 2018 and December 31, 2017 , by contractual maturity, is shown below. Expected maturities may differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties. June 30, 2018 December 31, 2017 Amortized Cost Fair Value Amortized Cost Fair Value Due in one year or less $ 319.8 $ 317.3 $ 228.1 $ 226.7 Due after one through five years 1,875.8 1,877.7 1,811.3 1,845.5 Due after five through ten years 3,455.4 3,383.4 3,199.7 3,239.8 Due after ten years 524.8 525.2 594.5 605.0 Mortgage and asset backed securities 2,201.0 2,174.7 1,609.5 1,606.6 Less: Assets classified as held for sale (See Note 13) — — (34.4 ) (35.3 ) Total $ 8,376.8 $ 8,278.3 $ 7,408.7 $ 7,488.3
Summary of Gross Unrealized Losses of Fixed-maturities and Equity Securities	The tables below summarize the gross unrealized losses of the Company's available-for-sale securities by length of time the security has continuously been in an unrealized loss position as of June 30, 2018 and December 31, 2017 : Less Than 12 Months 12 Months or More Total As of June 30, 2018 Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses U.S. treasury securities $ 40.6 $ (0.4 ) $ 233.9 $ (2.6 ) $ 274.5 $ (3.0 ) U.S. government agencies 94.6 (1.6 ) 1.5 — 96.1 (1.6 ) Municipal bonds 256.3 (4.6 ) 134.2 (4.4 ) 390.5 (9.0 ) Foreign government 182.5 (3.2 ) 14.6 (0.7 ) 197.1 (3.9 ) Corporate bonds: Finance 1,299.7 (34.0 ) 73.1 (3.3 ) 1,372.8 (37.3 ) Industrial 1,544.0 (43.2 ) 190.9 (12.3 ) 1,734.9 (55.5 ) Utilities 223.4 (7.0 ) 9.2 (0.3 ) 232.6 (7.3 ) Commercial mortgage-backed securities 164.0 (5.4 ) 127.4 (8.7 ) 291.4 (14.1 ) Residential mortgage-backed securities: Agency backed 557.5 (9.6 ) 120.4 (7.2 ) 677.9 (16.8 ) Collateralized loan / debt obligations 316.9 (2.9 ) — — 316.9 (2.9 ) Asset backed securities 4.0 — 0.7 (0.1 ) 4.7 (0.1 ) Total $ 4,683.5 $ (111.9 ) $ 905.9 $ (39.6 ) $ 5,589.4 $ (151.5 ) Less Than 12 Months 12 Months or More Total As of December 31, 2017 (1) Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses U.S. treasury securities $ 41.9 $ (0.5 ) $ 247.0 $ (2.7 ) $ 288.9 $ (3.2 ) U.S. government agencies 48.7 (0.6 ) 0.5 — 49.2 (0.6 ) Municipal bonds 171.3 (2.7 ) 178.7 (3.2 ) 350.0 (5.9 ) Foreign government 57.4 (2.2 ) 17.1 (1.0 ) 74.5 (3.2 ) Corporate bonds: Finance 419.3 (9.7 ) 91.5 (2.2 ) 510.8 (11.9 ) Industrial 437.1 (16.4 ) 255.4 (9.7 ) 692.5 (26.1 ) Utilities 72.5 (2.0 ) 11.9 (0.1 ) 84.4 (2.1 ) Commercial mortgage-backed securities 81.5 (4.1 ) 157.5 (6.3 ) 239.0 (10.4 ) Residential mortgage-backed securities: Agency backed 91.7 (4.7 ) 167.8 (6.7 ) 259.5 (11.4 ) Non-agency backed 2.9 — 0.8 (0.1 ) 3.7 (0.1 ) Collateralized loan / debt obligations 56.8 (0.2 ) 4.3 (0.1 ) 61.1 (0.3 ) Asset backed securities 7.1 — 3.1 (0.1 ) 10.2 (0.1 ) Total $ 1,488.2 $ (43.1 ) $ 1,135.6 $ (32.2 ) $ 2,623.8 $ (75.3 ) (1) In connection with the adoption of ASU 2016-01, the disclosure for December 31, 2017 has been recast for comparability. See Note 2. "Recent Accounting Pronouncements" for additional information on the impact of the adoption of ASU 2016-01.
Amortized Cost, Estimated Market Value and Gross Unrealized Appreciation and Depreciation of Trading Securities	The table below shows the portion of gains and losses for the period related to equity securities still held during the three and six months ended June 30, 2018 and 2017 : Three Months Ended June 30, Six Months Ended June 30, 2018 2017 2018 2017 Net gains recognized during the period on equity securities $ 4.6 $ 11.9 $ 8.7 $ 17.0 Less: Net gains recognized during the period on equity securities sold during the period (6.4 ) (4.4 ) (1.4 ) (5.0 ) Unrealized gains recognized during the reporting period on equity securities still held at the reporting date $ 11.0 $ 16.3 $ 10.1 $ 22.0 The table below shows the portion of trading gains and losses for the period related to trading securities still held during the three months ended June 30, 2018 and 2017 : Three Months Ended June 30, Six Months Ended June 30, 2018 2017 (1) 2018 2017 (1) Net losses recognized during the period on trading securities $ (1.9 ) $ (1.5 ) $ (5.0 ) $ (4.6 ) Less: Net (gains) losses recognized during the period on trading securities sold during the period (4.3 ) 0.6 (3.9 ) 2.4 Unrealized gains (losses) recognized during the reporting period on trading securities still held at the reporting date $ 2.4 $ (2.1 ) $ (1.1 ) $ (7.0 ) (1) In connection with the adoption of ASU 2016-01, the disclosure for the three and six months ended June 30, 2017 has been recast for comparability. See Note 2. "Recent Accounting Pronouncements" for additional information on the impact of the adoption of ASU 2016-01. The original cost, gross unrealized gains and losses, and estimated fair value of the Company's equity securities as of June 30, 2018 and December 31, 2017 , are presented below: As of June 30, 2018 Original Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Preferred stock $ 0.5 $ — $ — $ 0.5 Common stock 136.8 37.3 (20.3 ) 153.8 Total equity securities $ 137.3 $ 37.3 $ (20.3 ) $ 154.3 As of December 31, 2017 Original Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Preferred stock $ 0.5 $ — $ — $ 0.5 Common stock 195.4 30.6 (14.8 ) 211.2 Total equity securities $ 195.9 $ 30.6 $ (14.8 ) $ 211.7 The amortized cost, gross unrealized gains and losses, and estimated fair value of securities classified as trading as of June 30, 2018 and December 31, 2017 are presented in the tables below: As of June 30, 2018 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Corporate bonds: Industrial $ 25.3 $ 0.6 $ (1.6 ) $ 24.3 Finance 1.0 — — 1.0 U.S. treasury securities 123.7 0.3 (0.5 ) 123.5 Total trading securities $ 150.0 $ 0.9 $ (2.1 ) $ 148.8 As of December 31, 2017 (1) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Corporate bonds: Industrial $ 26.7 $ 0.1 $ (2.4 ) $ 24.4 Finance 0.5 — — 0.5 U.S. treasury securities 25.0 — (0.1 ) 24.9 Total trading securities $ 52.2 $ 0.1 $ (2.5 ) $ 49.8 (1) In connection with the adoption of ASU 2016-01, the disclosure for December 31, 2017 has been recast for comparability. See Note 2. "Recent Accounting Pronouncements" for additional information on the impact of the adoption of ASU 2016-01.
Net Investment Income	Net investment income for the three and six months ended June 30, 2018 and 2017 was derived from the following sources: Three Months Ended June 30, Six Months Ended June 30, 2018 2017 2018 2017 Fixed maturity securities, available-for-sale $ 62.0 $ 69.4 $ 121.4 $ 126.7 Fixed maturity securities, trading 4.2 — 4.8 1.0 Equity securities (1) 0.4 0.2 0.7 1.6 Cash and short term investments 4.7 1.9 8.8 3.3 Other invested assets 0.3 (19.2 ) 6.7 (15.0 ) Total investment income 71.6 52.3 142.4 117.6 Investment expenses and interest expense on securities sold under agreement to repurchase (3.3 ) (3.0 ) (5.9 ) (5.0 ) Net investment income $ 68.3 $ 49.3 $ 136.5 $ 112.6 (1) In connection with the adoption of ASU 2016-01, the disclosure for the three and six months ended June 30, 2017 has been recast for comparability. See Note 2. "Recent Accounting Pronouncements" for additional information on the impact of the adoption of ASU 2016-01.
Realized Gain (Loss) on Investments	The tables below summarize the gross and net realized gains and (losses) for the three and six months ended June 30, 2018 and 2017 : Three Months Ended June 30, 2018 2017 Gross Gains Gross Losses Net Gains (Losses) Gross Gains Gross Losses Net Gains (Losses) Fixed maturity securities, available-for-sale $ 16.4 $ (13.9 ) $ 2.5 $ 14.1 $ (0.9 ) $ 13.2 Fixed maturity securities, trading — (1.9 ) (1.9 ) 2.8 (4.3 ) (1.5 ) Equity securities (1) 10.1 (5.5 ) 4.6 9.8 (13.7 ) (3.9 ) Other invested assets 0.2 — 0.2 15.7 — 15.7 Total $ 26.7 $ (21.3 ) $ 5.4 $ 42.4 $ (18.9 ) $ 23.5 Six Months Ended June 30, 2018 2017 Gross Gains Gross Losses Net Gains (Losses) Gross Gains Gross Losses Net Gains (Losses) Fixed maturity securities, available-for-sale $ 19.9 $ (15.8 ) $ 4.1 $ 22.4 $ (2.1 ) $ 20.3 Fixed maturity securities, trading 2.1 (7.1 ) (5.0 ) 5.2 (9.8 ) (4.6 ) Equity securities (1) 23.7 (15.0 ) 8.7 21.0 (20.6 ) 0.4 Other invested assets 0.2 — 0.2 16.0 — 16.0 Other-than-temporary impairment of fixed maturity securities, available-for-sale — (0.3 ) (0.3 ) — — — Total $ 45.9 $ (38.2 ) $ 7.7 $ 64.6 $ (32.5 ) $ 32.1 (1) In connection with the adoption of ASU 2016-01, the disclosure for the three and six months ended June 30, 2017 has been recast for comparability. See Note 2. "Recent Accounting Pronouncements" for additional information on the impact of the adoption of ASU 2016-01.
Fair Values of Restricted Assets	The fair values of the Company's restricted assets as of June 30, 2018 and December 31, 2017 are as follows: June 30, 2018 December 31, 2017 Restricted cash and cash equivalents $ 532.2 $ 480.1 Restricted investments 3,062.2 3,193.8 Total restricted cash, cash equivalents and investments $ 3,594.4 $ 3,673.9
Investments	Investments (a) Available-for-Sale Securities The amortized cost, gross unrealized gains and losses, and estimated fair value of securities classified as available-for-sale as of June 30, 2018 and December 31, 2017 , are presented below: As of June 30, 2018 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value U.S. treasury securities $ 299.7 $ 0.9 $ (3.0 ) $ 297.6 U.S. government agencies 131.4 0.8 (1.6 ) 130.6 Municipal bonds 822.5 7.6 (9.0 ) 821.1 Foreign government 286.5 1.3 (3.9 ) 283.9 Corporate bonds: Finance 1,909.8 13.9 (37.3 ) 1,886.4 Industrial 2,400.3 16.4 (55.5 ) 2,361.2 Utilities 325.6 4.5 (7.3 ) 322.8 Commercial mortgage-backed securities 397.2 1.6 (14.1 ) 384.7 Residential mortgage-backed securities: Agency backed 916.3 1.5 (16.8 ) 901.0 Non-agency backed 7.6 — — 7.6 Collateralized loan / debt obligation 822.6 4.4 (2.9 ) 824.1 Asset backed securities 57.3 0.1 (0.1 ) 57.3 Total available-for-sale securities $ 8,376.8 $ 53.0 $ (151.5 ) $ 8,278.3 As of December 31, 2017 (1) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value U.S. treasury securities $ 301.6 $ 0.9 $ (3.2 ) $ 299.3 U.S. government agencies 51.1 — (0.6 ) 50.5 Municipal bonds 1,035.5 15.9 (5.9 ) 1,045.5 Foreign government 151.4 3.5 (3.2 ) 151.7 Corporate bonds: Finance 1,733.2 48.1 (11.9 ) 1,769.4 Industrial 2,237.0 57.3 (26.1 ) 2,268.2 Utilities 323.8 10.7 (2.1 ) 332.4 Commercial mortgage-backed securities 419.3 3.8 (10.4 ) 412.7 Residential mortgage-backed securities: Agency backed 562.0 5.8 (11.4 ) 556.4 Non-agency backed 6.9 — (0.1 ) 6.8 Collateralized loan / debt obligation 591.2 9.7 (0.3 ) 600.6 Asset backed securities 30.1 0.1 (0.1 ) 30.1 Less: Assets classified as held for sale (See Note 13) (34.4 ) (0.9 ) — (35.3 ) Total available-for-sale securities $ 7,408.7 $ 154.9 $ (75.3 ) $ 7,488.3 (1) In connection with the adoption of ASU 2016-01, the disclosure for December 31, 2017 has been recast for comparability. See Note 2. "Recent Accounting Pronouncements" for additional information on the impact of the adoption of ASU 2016-01. Proceeds from the sales of investments in available-for-sale securities were $342.0 and $464.9 during the three months ended June 30, 2018 and 2017 , respectively, and $1,079.1 and $988.3 during the six months ended June 30, 2018 and 2017 , respectively. A summary of the Company’s available-for-sale securities as of June 30, 2018 and December 31, 2017 , by contractual maturity, is shown below. Expected maturities may differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties. June 30, 2018 December 31, 2017 Amortized Cost Fair Value Amortized Cost Fair Value Due in one year or less $ 319.8 $ 317.3 $ 228.1 $ 226.7 Due after one through five years 1,875.8 1,877.7 1,811.3 1,845.5 Due after five through ten years 3,455.4 3,383.4 3,199.7 3,239.8 Due after ten years 524.8 525.2 594.5 605.0 Mortgage and asset backed securities 2,201.0 2,174.7 1,609.5 1,606.6 Less: Assets classified as held for sale (See Note 13) — — (34.4 ) (35.3 ) Total $ 8,376.8 $ 8,278.3 $ 7,408.7 $ 7,488.3 The tables below summarize the gross unrealized losses of the Company's available-for-sale securities by length of time the security has continuously been in an unrealized loss position as of June 30, 2018 and December 31, 2017 : Less Than 12 Months 12 Months or More Total As of June 30, 2018 Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses U.S. treasury securities $ 40.6 $ (0.4 ) $ 233.9 $ (2.6 ) $ 274.5 $ (3.0 ) U.S. government agencies 94.6 (1.6 ) 1.5 — 96.1 (1.6 ) Municipal bonds 256.3 (4.6 ) 134.2 (4.4 ) 390.5 (9.0 ) Foreign government 182.5 (3.2 ) 14.6 (0.7 ) 197.1 (3.9 ) Corporate bonds: Finance 1,299.7 (34.0 ) 73.1 (3.3 ) 1,372.8 (37.3 ) Industrial 1,544.0 (43.2 ) 190.9 (12.3 ) 1,734.9 (55.5 ) Utilities 223.4 (7.0 ) 9.2 (0.3 ) 232.6 (7.3 ) Commercial mortgage-backed securities 164.0 (5.4 ) 127.4 (8.7 ) 291.4 (14.1 ) Residential mortgage-backed securities: Agency backed 557.5 (9.6 ) 120.4 (7.2 ) 677.9 (16.8 ) Collateralized loan / debt obligations 316.9 (2.9 ) — — 316.9 (2.9 ) Asset backed securities 4.0 — 0.7 (0.1 ) 4.7 (0.1 ) Total $ 4,683.5 $ (111.9 ) $ 905.9 $ (39.6 ) $ 5,589.4 $ (151.5 ) Less Than 12 Months 12 Months or More Total As of December 31, 2017 (1) Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses U.S. treasury securities $ 41.9 $ (0.5 ) $ 247.0 $ (2.7 ) $ 288.9 $ (3.2 ) U.S. government agencies 48.7 (0.6 ) 0.5 — 49.2 (0.6 ) Municipal bonds 171.3 (2.7 ) 178.7 (3.2 ) 350.0 (5.9 ) Foreign government 57.4 (2.2 ) 17.1 (1.0 ) 74.5 (3.2 ) Corporate bonds: Finance 419.3 (9.7 ) 91.5 (2.2 ) 510.8 (11.9 ) Industrial 437.1 (16.4 ) 255.4 (9.7 ) 692.5 (26.1 ) Utilities 72.5 (2.0 ) 11.9 (0.1 ) 84.4 (2.1 ) Commercial mortgage-backed securities 81.5 (4.1 ) 157.5 (6.3 ) 239.0 (10.4 ) Residential mortgage-backed securities: Agency backed 91.7 (4.7 ) 167.8 (6.7 ) 259.5 (11.4 ) Non-agency backed 2.9 — 0.8 (0.1 ) 3.7 (0.1 ) Collateralized loan / debt obligations 56.8 (0.2 ) 4.3 (0.1 ) 61.1 (0.3 ) Asset backed securities 7.1 — 3.1 (0.1 ) 10.2 (0.1 ) Total $ 1,488.2 $ (43.1 ) $ 1,135.6 $ (32.2 ) $ 2,623.8 $ (75.3 ) (1) In connection with the adoption of ASU 2016-01, the disclosure for December 31, 2017 has been recast for comparability. See Note 2. "Recent Accounting Pronouncements" for additional information on the impact of the adoption of ASU 2016-01. There were 3,596 and 2,086 individual security lots as of June 30, 2018 and December 31, 2017 , respectively, that account for the gross unrealized loss, none of which is deemed by the Company to be other-than-temporarily impaired ("OTTI"). The Company analyzes its fixed maturity securities in an unrealized loss position for OTTI each reporting period. Beginning January 1, 2018, the Company generally evaluates an investment for impairment when it has been in an unrealized loss position of 20% or more of amortized cost for twelve consecutive months. As of June 30, 2018 , the Company has determined that the unrealized losses on fixed maturity securities were primarily due to market interest rate movements since their date of purchase. As of June 30, 2018 , for the $39.6 of unrealized losses related to securities in unrealized loss positions for a period of twelve or more consecutive months, none were related to securities in unrealized loss positions greater than or equal to 20% of amortized cost or cost. There were no material credit-related OTTI charges for the three and six months ended June 30, 2018 and 2017 . (b) Trading Securities The amortized cost, gross unrealized gains and losses, and estimated fair value of securities classified as trading as of June 30, 2018 and December 31, 2017 are presented in the tables below: As of June 30, 2018 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Corporate bonds: Industrial $ 25.3 $ 0.6 $ (1.6 ) $ 24.3 Finance 1.0 — — 1.0 U.S. treasury securities 123.7 0.3 (0.5 ) 123.5 Total trading securities $ 150.0 $ 0.9 $ (2.1 ) $ 148.8 As of December 31, 2017 (1) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Corporate bonds: Industrial $ 26.7 $ 0.1 $ (2.4 ) $ 24.4 Finance 0.5 — — 0.5 U.S. treasury securities 25.0 — (0.1 ) 24.9 Total trading securities $ 52.2 $ 0.1 $ (2.5 ) $ 49.8 (1) In connection with the adoption of ASU 2016-01, the disclosure for December 31, 2017 has been recast for comparability. See Note 2. "Recent Accounting Pronouncements" for additional information on the impact of the adoption of ASU 2016-01. Proceeds from the sales of investments in trading securities were approximately $68.8 and $177.6 during the three months ended June 30, 2018 and 2017 , respectively, and $282.9 and $309.4 during the six months ended June 30, 2018 and 2017 , respectively. The table below shows the portion of trading gains and losses for the period related to trading securities still held during the three months ended June 30, 2018 and 2017 : Three Months Ended June 30, Six Months Ended June 30, 2018 2017 (1) 2018 2017 (1) Net losses recognized during the period on trading securities $ (1.9 ) $ (1.5 ) $ (5.0 ) $ (4.6 ) Less: Net (gains) losses recognized during the period on trading securities sold during the period (4.3 ) 0.6 (3.9 ) 2.4 Unrealized gains (losses) recognized during the reporting period on trading securities still held at the reporting date $ 2.4 $ (2.1 ) $ (1.1 ) $ (7.0 ) (1) In connection with the adoption of ASU 2016-01, the disclosure for the three and six months ended June 30, 2017 has been recast for comparability. See Note 2. "Recent Accounting Pronouncements" for additional information on the impact of the adoption of ASU 2016-01. (c) Equity Securities In accordance with the adoption of ASU 2016-01, the Company's equity securities are no longer bifurcated between available-for-sale and trading, but rather are measured at fair value with changes in fair value recognized in earnings. See Note 2. "Recent Accounting Pronouncements" for additional information on the impact of the adoption of ASU 2016-01. The original cost, gross unrealized gains and losses, and estimated fair value of the Company's equity securities as of June 30, 2018 and December 31, 2017 , are presented below: As of June 30, 2018 Original Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Preferred stock $ 0.5 $ — $ — $ 0.5 Common stock 136.8 37.3 (20.3 ) 153.8 Total equity securities $ 137.3 $ 37.3 $ (20.3 ) $ 154.3 As of December 31, 2017 Original Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Preferred stock $ 0.5 $ — $ — $ 0.5 Common stock 195.4 30.6 (14.8 ) 211.2 Total equity securities $ 195.9 $ 30.6 $ (14.8 ) $ 211.7 Proceeds from the sales of investments in equity securities were approximately $58.8 and $32.4 during the three months ended June 30, 2018 and 2017 , respectively, and $181.7 and $151.7 during the six months ended June 30, 2018 and 2017 , respectively. The table below shows the portion of gains and losses for the period related to equity securities still held during the three and six months ended June 30, 2018 and 2017 : Three Months Ended June 30, Six Months Ended June 30, 2018 2017 2018 2017 Net gains recognized during the period on equity securities $ 4.6 $ 11.9 $ 8.7 $ 17.0 Less: Net gains recognized during the period on equity securities sold during the period (6.4 ) (4.4 ) (1.4 ) (5.0 ) Unrealized gains recognized during the reporting period on equity securities still held at the reporting date $ 11.0 $ 16.3 $ 10.1 $ 22.0 (d) Investment Income Net investment income for the three and six months ended June 30, 2018 and 2017 was derived from the following sources: Three Months Ended June 30, Six Months Ended June 30, 2018 2017 2018 2017 Fixed maturity securities, available-for-sale $ 62.0 $ 69.4 $ 121.4 $ 126.7 Fixed maturity securities, trading 4.2 — 4.8 1.0 Equity securities (1) 0.4 0.2 0.7 1.6 Cash and short term investments 4.7 1.9 8.8 3.3 Other invested assets 0.3 (19.2 ) 6.7 (15.0 ) Total investment income 71.6 52.3 142.4 117.6 Investment expenses and interest expense on securities sold under agreement to repurchase (3.3 ) (3.0 ) (5.9 ) (5.0 ) Net investment income $ 68.3 $ 49.3 $ 136.5 $ 112.6 (1) In connection with the adoption of ASU 2016-01, the disclosure for the three and six months ended June 30, 2017 has been recast for comparability. See Note 2. "Recent Accounting Pronouncements" for additional information on the impact of the adoption of ASU 2016-01. (e) Realized Gains and Losses The tables below summarize the gross and net realized gains and (losses) for the three and six months ended June 30, 2018 and 2017 : Three Months Ended June 30, 2018 2017 Gross Gains Gross Losses Net Gains (Losses) Gross Gains Gross Losses Net Gains (Losses) Fixed maturity securities, available-for-sale $ 16.4 $ (13.9 ) $ 2.5 $ 14.1 $ (0.9 ) $ 13.2 Fixed maturity securities, trading — (1.9 ) (1.9 ) 2.8 (4.3 ) (1.5 ) Equity securities (1) 10.1 (5.5 ) 4.6 9.8 (13.7 ) (3.9 ) Other invested assets 0.2 — 0.2 15.7 — 15.7 Total $ 26.7 $ (21.3 ) $ 5.4 $ 42.4 $ (18.9 ) $ 23.5 Six Months Ended June 30, 2018 2017 Gross Gains Gross Losses Net Gains (Losses) Gross Gains Gross Losses Net Gains (Losses) Fixed maturity securities, available-for-sale $ 19.9 $ (15.8 ) $ 4.1 $ 22.4 $ (2.1 ) $ 20.3 Fixed maturity securities, trading 2.1 (7.1 ) (5.0 ) 5.2 (9.8 ) (4.6 ) Equity securities (1) 23.7 (15.0 ) 8.7 21.0 (20.6 ) 0.4 Other invested assets 0.2 — 0.2 16.0 — 16.0 Other-than-temporary impairment of fixed maturity securities, available-for-sale — (0.3 ) (0.3 ) — — — Total $ 45.9 $ (38.2 ) $ 7.7 $ 64.6 $ (32.5 ) $ 32.1 (1) In connection with the adoption of ASU 2016-01, the disclosure for the three and six months ended June 30, 2017 has been recast for comparability. See Note 2. "Recent Accounting Pronouncements" for additional information on the impact of the adoption of ASU 2016-01. (f) Restricted Cash and Investments The Company, in order to conduct business in certain states, is required to maintain letters of credit or assets on deposit to support state mandated regulatory requirements and certain third party agreements. The Company also utilizes trust accounts to collateralize business with its reinsurance counterparties. These assets are primarily in the form of cash and certain investment grade securities. The fair values of the Company's restricted assets as of June 30, 2018 and December 31, 2017 are as follows: June 30, 2018 December 31, 2017 Restricted cash and cash equivalents $ 532.2 $ 480.1 Restricted investments 3,062.2 3,193.8 Total restricted cash, cash equivalents and investments $ 3,594.4 $ 3,673.9 (g) Other Securities sold but not yet purchased are securities that the Company has sold, but does not own, in anticipation of a decline in the market value of the security. For more information related to these agreements, see Note 3. "Investments" to the consolidated financial statements included in the Company's Annual Report on Form 10-K for the year ended December 31, 2017 . The Company’s liability for securities to be delivered is measured at their fair value and was $161.8 and $75.5 as of June 30, 2018 and December 31, 2017 , respectively. From time to time, the Company enters into repurchase agreements that are subject to a master netting arrangement, which are accounted for as collateralized borrowing transactions and are recorded at contract amounts. The Company receives cash or securities that it invests or holds in short term or fixed maturity securities. For more information related to these agreements, see Note 2. "Significant Accounting Policies" to the consolidated financial statements included in the Company's Annual Report on Form 10-K for the year ended December 31, 2017 . As of June 30, 2018 , the Company had 16 individual repurchase agreements outstanding with a principal amount of $214.8 , which approximates fair value, at interest rates between 0.0% and 3.5% . The Company had approximately $227.5 of collateral pledged in support of these agreements as of June 30, 2018 . As of December 31, 2017 , the Company had no repurchase agreements outstanding.

Fair Value of Financial Instr23

Fair Value of Financial Instruments (Tables)	6 Months Ended
	Jun. 30, 2018
Fair Value Disclosures [Abstract]
Fair Value Measurement of Financial Assets and Financial Liabilities on Recurring Basis	The following tables present the level within the fair value hierarchy at which the Company’s financial assets and financial liabilities are measured on a recurring basis as of June 30, 2018 and December 31, 2017 : As of June 30, 2018 Total Level 1 Level 2 Level 3 Financial Assets U.S. treasury securities $ 421.1 $ 421.1 $ — $ — U.S. government agencies 130.6 — 130.6 — Municipal bonds 821.1 — 820.5 0.6 Foreign government 283.9 — 283.9 — Corporate bonds and other bonds: Finance 1,887.4 — 1,887.4 — Industrial 2,385.5 — 2,385.5 — Utilities 322.8 — 322.8 — Commercial mortgage-backed securities 384.7 — 362.6 22.1 Residential mortgage-backed securities: Agency backed 901.0 — 901.0 — Non-agency backed 7.6 — 7.6 — Collateralized loan / debt obligations 824.1 — 824.1 — Asset-backed securities 57.3 — 56.5 0.8 Equity securities 154.3 153.2 0.3 0.8 Short term investments 169.7 — 169.7 — Other investments 4.1 — — 4.1 Life settlement contracts 1.9 — — 1.9 Total financial assets $ 8,757.1 $ 574.3 $ 8,152.5 $ 30.3 Financial Liabilities Securities sold but not yet purchased $ 161.8 $ 153.9 $ 7.9 $ — Securities sold under agreements to repurchase 214.8 — 214.8 — Life settlement contract profit commission 3.2 — — 3.2 Contingent consideration 31.2 — — 31.2 Total financial liabilities $ 411.0 $ 153.9 $ 222.7 $ 34.4 As of December 31, 2017 Total Level 1 Level 2 Level 3 Financial Assets U.S. treasury securities $ 324.2 $ 324.2 $ — $ — U.S. government agencies 50.5 — 50.5 — Municipal bonds 1,045.5 — 1,045.1 0.4 Foreign government 151.7 — 151.7 — Corporate bonds and other bonds: Finance 1,769.9 — 1,769.9 — Industrial 2,292.6 — 2,292.6 — Utilities 332.4 — 332.4 — Commercial mortgage-backed securities 412.7 — 389.8 22.9 Residential mortgage-backed securities: Agency backed 556.4 — 556.4 — Non-agency backed 6.8 — 6.8 — Collateralized loan / debt obligations 600.6 — 600.6 — Asset-backed securities 30.1 — 29.3 0.8 Equity securities 211.7 210.7 0.5 0.5 Short term investments 187.8 — 187.8 — Other investments 5.0 — — 5.0 Life settlement contracts 20.8 — — 20.8 Less: Fixed maturity securities classified as held for sale (see note 13) (35.3 ) — (35.3 ) — Total financial assets (1) $ 7,963.4 $ 534.9 $ 7,378.1 $ 50.4 Financial Liabilities Securities sold but not yet purchased $ 75.5 $ 70.8 $ 4.7 $ — Life settlement contract profit commission 3.2 — — 3.2 Contingent consideration 75.4 — — 75.4 Total financial liabilities (2) $ 154.1 $ 70.8 $ 4.7 $ 78.6 (1) Does not include assets held for sale of $900.9 carried at fair value and classified as Level 2 within the fair value hierarchy as of December 31, 2017. See Note 13. "Divestiture" for additional information. (2) Does not include liabilities held for sale of $761.7 carried at fair value and classified as Level 2 within the fair value hierarchy as of December 31, 2017. See Note 13. "Divestiture" for additional information.
Changes in Fair Value of Level 3 Financial Assets And Liabilities	The following table provides a summary of changes in fair value of the Company’s Level 3 financial assets and liabilities for the three and six months ended June 30, 2018 and 2017 . The transfers into and out of Level 3 were due to changes in the availability of market observable inputs. All transfers are reflected in the table at fair value as of the end of the reporting period. Balance as of March 31, 2018 Net (loss) Other comprehensive income Purchases and issuances Sales and settlements Net transfers into Level 3 Balance as of June 30, Fixed maturities, available-for-sale $ 23.3 $ — $ 1.1 $ — $ (0.9 ) $ — $ 23.5 Equity securities 0.5 — 0.3 — — — 0.8 Other investments 4.5 — — — (0.4 ) — 4.1 Life settlement contracts 15.4 (2.3 ) — — (11.2 ) — 1.9 Life settlement contract profit commission (3.4 ) 0.2 — — — — (3.2 ) Contingent consideration (32.3 ) (0.9 ) — — 2.0 — (31.2 ) Total $ 8.0 $ (3.0 ) $ 1.4 $ — $ (10.5 ) $ — $ (4.1 ) Balance as of March 31, 2017 Net (loss) Other comprehensive income Purchases and issuances Sales and settlements Net transfers into Level 3 Balance as of June 30, Fixed maturities, available-for-sale $ 35.1 $ — $ 0.2 $ 5.2 $ (2.3 ) $ 3.3 $ 41.5 Equity securities 21.5 (0.1 ) 0.1 0.1 (16.7 ) 18.6 23.5 Life settlement contracts 397.5 13.1 — 1.3 (15.1 ) — 396.8 Life settlement contract profit commission (5.6 ) (0.1 ) — — — — (5.7 ) Contingent consideration (72.4 ) (3.1 ) — (27.2 ) 5.0 — (97.7 ) Total $ 376.1 $ 9.8 $ 0.3 $ (20.6 ) $ (29.1 ) $ 21.9 $ 358.4 Balance as of December 31, 2017 Net (loss) Other comprehensive income Purchases and issuances Sales and settlements Net transfers into Level 3 Balance as of June 30, Fixed maturities, available-for-sale $ 24.1 $ (0.3 ) $ 0.8 $ — $ (1.1 ) $ — $ 23.5 Equity securities 0.5 — 0.3 — — — 0.8 Other investments 5.0 (0.5 ) — — (0.4 ) — 4.1 Life settlement contracts 20.8 2.3 — — (21.2 ) — 1.9 Life settlement contract profit commission (3.2 ) — — — — — (3.2 ) Contingent consideration (75.4 ) (2.6 ) — — 46.8 — (31.2 ) Total $ (28.2 ) $ (1.1 ) $ 1.1 $ — $ 24.1 $ — $ (4.1 ) Balance as of December 31, 2016 Net (loss) Other comprehensive (loss) income Purchases and issuances Sales and settlements Net transfers into Level 3 Balance as of June 30, Fixed maturities, available-for-sale $ 46.9 $ — $ (0.5 ) $ 7.5 $ (2.8 ) $ (9.6 ) $ 41.5 Equity securities 24.4 (0.4 ) 0.3 4.6 (18.8 ) 13.4 23.5 Life settlement contracts 356.9 48.6 — 16.5 (25.2 ) — 396.8 Life settlement contract profit commission (4.9 ) (0.8 ) — — — — (5.7 ) Contingent consideration (71.7 ) (3.8 ) — (27.2 ) 5.0 — (97.7 ) Total $ 351.6 $ 43.6 $ (0.2 ) $ 1.4 $ (41.8 ) $ 3.8 $ 358.4
Fair Value Measurements, Recurring and Nonrecurring	The fair value of the Company's debt arrangements as of June 30, 2018 was as follows: June 30, 2018 Carrying Value Fair Value Revolving credit facility $ 130.0 $ 130.0 5.5% Convertible senior notes due 2021 5.4 5.4 2.75% Convertible senior notes due 2044 176.4 218.8 6.125% Senior notes due 2023 248.6 242.5 Junior subordinated debentures due 2035-2037 122.2 112.1 Trust preferred securities due 2033-2037 92.8 87.3 7.25% Subordinated Notes due 2055 145.4 146.0 7.50% Subordinated Notes due 2055 130.9 134.7 Secured loan agreements 168.2 168.2 Promissory notes and other 95.4 95.4 Total debt $ 1,315.3 $ 1,340.4

Loss and loss adjustment expe24

Loss and loss adjustment expense reserves (Tables)	6 Months Ended
	Jun. 30, 2018
Insurance [Abstract]
Schedule of Liability for Unpaid Claims and Claims Adjustment Expense	The following table provides a reconciliation of the beginning and ending balances for loss and loss adjustment expense ("Loss and LAE") reserves for the six months ended June 30, 2018 , and 2017 , respectively: Six Months Ended June 30, 2018 2017 Loss and LAE reserves, gross of related reinsurance recoverables at beginning of year $ 12,138.8 $ 10,140.7 Less: Reinsurance recoverables at beginning of year 5,669.6 3,873.8 Net balance, beginning of year 6,469.2 6,266.9 Incurred related to: Current year 1,886.3 1,772.9 Prior year 20.3 91.9 Total incurred during the period 1,906.6 1,864.8 Paid related to: Current year (414.0 ) (366.2 ) Prior year (1,177.4 ) (1,148.3 ) Total paid during the period (1,591.4 ) (1,514.5 ) Acquired loss and loss adjustment reserves and other 9.2 200.8 Retroactive reinsurance adjustment 12.1 (698.0 ) Effect of foreign exchange rates (51.5 ) 87.4 Net balance, end of period 6,754.2 6,207.4 Plus reinsurance recoverables at end of period 5,591.1 4,942.1 Loss and LAE reserves, at end of period $ 12,345.3 $ 11,149.5

Debt (Tables)

Debt (Tables)	6 Months Ended
	Jun. 30, 2018
Debt Disclosure [Abstract]
Borrowings	The Company’s outstanding debt consisted of the following at June 30, 2018 and December 31, 2017 : June 30, 2018 December 31, 2017 Revolving credit facility $ 130.0 $ 130.0 5.5% Convertible senior notes due 2021 (the "2021 Notes") 5.4 5.4 2.75% Convertible senior notes due 2044 (the "2044 Notes") 176.4 173.0 6.125% Notes due 2023 (the "2023 Notes") 248.6 248.4 Junior subordinated debentures (the "2035-2037 Notes") 122.2 122.1 Trust preferred securities (the "2033-2037 TPS Notes") 92.8 92.8 7.25% Subordinated notes due 2055 (the "7.25% 2055 Notes") 145.4 145.3 7.50% Subordinated notes due 2055 (the "7.50% 2055 Notes") 130.9 130.8 Secured loan agreements 168.2 174.4 Promissory notes and other 95.4 66.5 Total debt $ 1,315.3 $ 1,288.7
Schedule of Line of Credit Facilities	Additionally, the Company utilizes various letters of credit in its operations. The following is a summary of the Company's letters of credit as of June 30, 2018 : Limit Outstanding Available Revolving credit facility $ 175.0 $ 173.4 $ 1.6 Funds at Lloyd's facility 600.9 567.7 33.2 ING Bank N.V., BHF Bank Aktiengesellschaft, and Deutsche Bank AG facilities 101.3 80.6 20.7 Comerica Bank facility 75.0 42.9 32.1 Other letters of credit, in aggregate 114.1 114.1 —
Interest Income and Interest Expense Disclosure	Interest expense, including amortization of original issue discount and deferred origination costs, as well as applicable bank fees, related to the Company's outstanding debt and letters of credit for the three and six months ended June 30, 2018 and 2017 was: Three Months Ended June 30, Six Months Ended June 30, 2018 2017 2018 2017 Revolving credit facility $ 1.6 $ 1.5 $ 3.4 $ 3.0 2021 Notes 0.1 0.1 0.2 0.2 2044 Notes 3.4 3.2 6.7 6.4 2023 Notes 4.0 4.0 7.8 7.8 2035-2037 Notes 1.8 1.4 3.3 2.9 2033-2037 TPS Notes 1.3 1.1 2.5 2.1 7.25% 2055 Notes 2.7 2.7 5.5 5.5 7.50% 2055 Notes 2.5 2.5 5.1 5.1 Secured loan agreements 1.7 1.5 3.3 2.8 Promissory notes 0.8 1.0 1.7 2.7 Funds at Lloyd's facility 1.2 1.2 2.8 2.7 Other, including interest income 0.8 4.0 2.4 6.6 Total $ 21.9 $ 24.2 $ 44.7 $ 47.8

Earnings Per Share (Tables)

Earnings Per Share (Tables)	6 Months Ended
	Jun. 30, 2018
Earnings Per Share [Abstract]
Summary of elements used in calculating basic and diluted earnings per share	The following table is a summary of the elements used in calculating basic and diluted earnings per share for the three and six months ended June 30, 2018 and 2017 : Three Months Ended June 30, Six Months Ended June 30, 2018 2017 2018 2017 Numerator: Net (loss) income attributable to AmTrust common stockholders $ (116.2 ) $ 5.9 $ 545.6 $ 28.5 Denominator: Weighted average common shares outstanding – basic 196.9 180.7 196.6 175.8 Plus: Dilutive effect of stock options, convertible debt, other (1) — 0.8 0.3 1.1 Weighted average common shares outstanding – dilutive 196.9 181.5 196.9 176.9 Net (loss) income per AmTrust common share – basic $ (0.59 ) $ 0.03 $ 2.78 $ 0.16 Net (loss) income per AmTrust common share – diluted $ (0.59 ) $ 0.03 $ 2.77 $ 0.16 (1) In accordance with ASC 260, Earnings Per Share, no potential common shares are included in the computation of diluted per share amounts as the effect would be antidilutive for the three months ended June 30, 2018.

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	6 Months Ended
	Jun. 30, 2018
Equity [Abstract]
Ownership components of total equity	The following table summarizes the ownership components of total stockholders' equity: Six Months Ended June 30, 2018 2017 AmTrust Non-Controlling Interest Total AmTrust Non-Controlling Interest Total Beginning balance $ 3,189.7 $ 178.4 $ 3,368.1 $ 3,269.1 $ 196.5 $ 3,465.6 Net income (loss) 578.7 (6.3 ) 572.4 61.6 17.1 78.7 Unrealized holding gain, net of tax (136.9 ) — (136.9 ) 75.1 — 75.1 Reclassification adjustment (4.1 ) — (4.1 ) (30.9 ) — (30.9 ) Foreign currency translation (24.4 ) — (24.4 ) 76.6 — 76.6 Unrealized gain on interest rate swap — — — 0.1 — 0.1 Distribution of non-controlling interest — (114.6 ) (114.6 ) — — — Share exercises, compensation and other 7.0 — 7.0 9.7 — 9.7 Common stock issuance — — — 298.7 — 298.7 Common stock dividends (33.3 ) — (33.3 ) (63.3 ) — (63.3 ) Preferred stock dividends (33.1 ) — (33.1 ) (33.1 ) — (33.1 ) Capital distributions, net — — — — 19.3 19.3 Balance, June 30, $ 3,543.6 $ 57.5 $ 3,601.1 $ 3,663.6 $ 232.9 $ 3,896.5
Schedule of AOCI	The following table summarizes the activities and components of accumulated other comprehensive income (loss) for the three and six months ended June 30, 2018 and 2017: Foreign Currency Items Unrealized Gains (Losses) on Investments Interest Rate Swap Hedge Net Benefit Plan Assets and Obligations Recognized in Stockholders' Equity Accumulated Other Comprehensive Income (Loss) Balance, March 31, 2018 $ 17.4 $ (64.4 ) $ — $ (2.3 ) $ (49.3 ) Other comprehensive income (loss) before reclassification (86.6 ) (17.8 ) — — (104.4 ) Amounts reclassed out of accumulated other comprehensive (loss) income — (2.5 ) — — (2.5 ) Income tax benefit — 5.6 — — 5.6 Net current-period other comprehensive loss (86.6 ) (14.7 ) — — (101.3 ) Balance, June 30, 2018 $ (69.2 ) $ (79.1 ) $ — $ (2.3 ) $ (150.6 ) Balance, March 31, 2017 $ (174.3 ) $ 79.8 $ (0.1 ) $ (3.2 ) $ (97.8 ) Other comprehensive income before reclassification 62.7 66.1 — — 128.8 Amounts reclassed out of accumulated other comprehensive (loss) income — (19.3 ) — — (19.3 ) Income tax expense — (16.6 ) — — (16.6 ) Net current-period other comprehensive income 62.7 30.2 — — 92.9 Balance, June 30, 2017 $ (111.6 ) $ 110.0 $ (0.1 ) $ (3.2 ) $ (4.9 ) Foreign Currency Items Unrealized Gains (Losses) on Investments Interest Rate Swap Hedge Net Benefit Plan Assets and Obligations Recognized in Stockholders' Equity Accumulated Other Comprehensive Income (Loss) Balance, December 31, 2017 $ (44.8 ) $ 62.6 $ — $ (2.3 ) $ 15.5 Net cumulative effect adjustments (1) — (0.7 ) — — (0.7 ) Other comprehensive income (loss) before reclassification (24.4 ) (174.9 ) — — (199.3 ) Amounts reclassed out of accumulated other comprehensive (loss) income — (4.1 ) — — (4.1 ) Income tax benefit — 38.0 — — 38.0 Net current-period other comprehensive loss (24.4 ) (141.7 ) — — (166.1 ) Balance, June 30, 2018 $ (69.2 ) $ (79.1 ) $ — $ (2.3 ) $ (150.6 ) Balance, December 31, 2016 $ (188.2 ) $ 65.8 $ (0.2 ) $ (3.2 ) $ (125.8 ) Other comprehensive income before reclassification 76.6 98.1 0.1 — 174.8 Amounts reclassed out of accumulated other comprehensive (loss) income — (30.9 ) — — (30.9 ) Income tax expense — (23.0 ) — — (23.0 ) Net current-period other comprehensive income 76.6 44.2 0.1 — 120.9 Balance, June 30, 2017 $ (111.6 ) $ 110.0 $ (0.1 ) $ (3.2 ) $ (4.9 ) (1) See Note 2. "Recent Accounting Pronouncements" for additional information on the adoptions of ASU 2016-01 and ASU 2018-02.

Segments (Tables)

Segments (Tables)	6 Months Ended
	Jun. 30, 2018
Segment Reporting [Abstract]
Summary of results of the operations	The following tables summarize the results of operations of the business segments for the three and six months ended June 30, 2018 and 2017 : Three Months Ended June 30, 2018 Small Commercial Business Specialty Risk and Extended Warranty Specialty Program Corporate and Other Total Revenues: Net earned premiums $ 622.9 $ 560.5 $ 102.8 $ — $ 1,286.2 Losses and expenses: Loss and loss adjustment expenses 478.0 356.9 98.8 — 933.7 Amortization of deferred acquisition costs 105.8 146.7 57.9 — 310.4 Underwriting, general and administrative expenses 31.9 62.5 26.7 — 121.1 Total losses and expenses 615.7 566.1 183.4 — 1,365.2 Underwriting gain (loss) 7.2 (5.6 ) (80.6 ) — (79.0 ) Other income (losses and expenses): Service and fee income 6.4 25.8 0.3 16.8 49.3 Investment income and realized gain on investments 32.8 29.5 11.4 — 73.7 Other expenses (26.8 ) (22.6 ) (4.7 ) (55.2 ) (109.3 ) Interest expense (11.3 ) (8.7 ) (1.9 ) — (21.9 ) Foreign currency loss — (11.6 ) — — (11.6 ) Other revenues (1.6 ) (0.8 ) (0.2 ) 0.1 (2.5 ) (Provision) benefit for income taxes (0.6 ) 1.6 (2.8 ) 6.2 4.4 Net income (loss) $ 6.1 $ 7.6 $ (78.5 ) $ (32.1 ) $ (96.9 ) Three Months Ended June 30, 2017 Small Commercial Business Specialty Risk and Extended Warranty Specialty Program Corporate and Other Total Revenues: Net earned premiums $ 631.9 $ 539.0 $ 209.8 $ — $ 1,380.7 Losses and expenses: Loss and loss adjustment expenses 466.9 370.9 186.7 — 1,024.5 Amortization of deferred acquisition costs 94.8 78.1 34.9 — 207.8 Underwriting, general and administrative expenses 75.4 62.2 27.8 — 165.4 Total losses and expenses 637.1 511.2 249.4 — 1,397.7 Underwriting (loss) income (5.2 ) 27.8 (39.6 ) — (17.0 ) Other income (losses and expenses): Service and fee income 30.9 98.2 0.5 38.8 168.4 Investment income and realized gain on investments 32.5 27.8 12.5 — 72.8 Other expenses (51.4 ) (35.8 ) (12.7 ) (99.9 ) (199.8 ) Interest expense (12.4 ) (8.7 ) (3.1 ) — (24.2 ) Foreign currency loss — (58.9 ) — — (58.9 ) Other revenues (0.9 ) (0.4 ) (0.2 ) — (1.5 ) Benefit (provision) for income taxes 7.5 28.6 (0.3 ) (16.0 ) 19.8 Equity in earnings of unconsolidated subsidiary – related party — — — 69.5 69.5 Net income (loss) $ 1.0 $ 78.6 $ (42.9 ) $ (7.6 ) $ 29.1 Six Months Ended June 30, 2018 Small Commercial Business Specialty Risk and Extended Warranty Specialty Program Corporate and Other Total Revenues: Net earned premiums $ 1,266.9 $ 1,155.2 $ 219.0 $ — $ 2,641.1 Losses and expenses: Loss and loss adjustment expenses 976.7 749.2 180.7 — 1,906.6 Amortization of deferred acquisition costs 205.2 234.5 86.3 — 526.0 Underwriting, general and administrative expenses 130.1 148.9 54.7 — 333.7 Total losses and expenses 1,312.0 1,132.6 321.7 — 2,766.3 Underwriting (loss) gain (45.1 ) 22.6 (102.7 ) — (125.2 ) Other income (losses and expenses): Service and fee income 25.9 102.5 1.3 35.7 165.4 Investment income and realized gain on investments 63.5 57.5 23.2 — 144.2 Other expenses (85.6 ) (62.0 ) (13.8 ) (162.5 ) (323.9 ) Interest expense (23.8 ) (17.1 ) (3.8 ) — (44.7 ) Foreign currency gain — 14.9 — — 14.9 Other revenues 2.7 2.0 0.4 724.2 729.3 (Provision) benefit for income taxes (2.1 ) 4.1 (3.2 ) 20.2 19.0 Net (loss) income $ (64.5 ) $ 124.5 $ (98.6 ) $ 617.6 $ 579.0 Six Months Ended June 30, 2017 Small Commercial Business Specialty Risk and Extended Warranty Specialty Program Corporate and Other Total Revenues: Net earned premiums $ 1,185.5 $ 1,012.5 $ 405.2 $ — $ 2,603.2 Losses and expenses: Loss and loss adjustment expenses 844.3 683.5 337.0 — 1,864.8 Amortization of deferred acquisition costs 191.8 152.4 69.5 — 413.7 Underwriting, general and administrative expenses 133.1 106.3 48.3 — 287.7 Total losses and expenses 1,169.2 942.2 454.8 — 2,566.2 Underwriting gain (loss) 16.3 70.3 (49.6 ) — 37.0 Other income (losses and expenses): Service and fee income 59.6 185.1 2.0 59.2 305.9 Investment income and realized gain on investments 62.2 53.9 28.6 — 144.7 Other expenses (96.7 ) (62.1 ) (22.6 ) (181.3 ) (362.7 ) Interest expense (25.5 ) (16.3 ) (6.0 ) — (47.8 ) Foreign currency gain — (76.9 ) — — (76.9 ) Other revenues 3.9 2.4 0.9 — 7.2 (Provision) benefit for income taxes (0.4 ) (3.1 ) 0.9 1.0 (1.6 ) Equity in earnings of unconsolidated subsidiary – related party — — — 73.5 73.5 Net income (loss) $ 19.4 $ 153.3 $ (45.8 ) $ (47.6 ) $ 79.3 The following table summarizes net earned premiums by major line of business, by segment, for the three and six months ended June 30, 2018 and 2017 : Small Commercial Business Specialty Risk and Extended Warranty Specialty Program Total Three Months Ended June 30, 2018: Workers' compensation $ 376.6 $ — $ 46.3 $ 422.9 Warranty — 232.0 — 232.0 Commercial auto and liability, physical damage 125.0 — 24.0 149.0 Commercial multiple-peril 84.2 15.7 9.3 109.2 Other liabilities — 66.4 9.8 76.2 Medical malpractice — 41.7 — 41.7 Accident and health — 39.8 — 39.8 Surety 16.1 17.3 — 33.4 Homeowners multiple-peril 6.6 32.7 2.5 41.8 Fire 1.9 27.9 — 29.8 Inland Marine 1.8 27.4 — 29.2 Other 10.7 59.6 10.9 81.2 Total net earned premiums $ 622.9 $ 560.5 $ 102.8 $ 1,286.2 Small Commercial Business Specialty Risk and Extended Warranty Specialty Program Total Three Months Ended June 30, 2017: Workers' compensation $ 373.1 $ — $ 114.6 $ 487.7 Warranty — 255.8 — 255.8 Commercial auto and liability, physical damage 95.6 — 28.5 124.1 Commercial multiple-peril 66.4 — 16.0 82.4 Other liabilities — 46.2 52.2 98.4 Medical malpractice — 53.9 — 53.9 Accident and health — 46.9 — 46.9 Surety 13.9 27.4 — 41.3 Homeowners multiple-peril 14.1 1.1 2.7 17.9 Fire 8.3 54.8 — 63.1 Inland Marine 3.0 (3.8 ) — (0.8 ) Other 57.5 56.7 (4.2 ) 110.0 Total net earned premiums $ 631.9 $ 539.0 $ 209.8 $ 1,380.7 Small Commercial Business Specialty Risk and Extended Warranty Specialty Program Total Six Months Ended June 30, 2018: Workers' compensation $ 754.9 $ — $ 110.8 $ 865.7 Warranty — 531.8 — 531.8 Commercial auto and liability, physical damage 238.6 — 54.6 293.2 Commercial multiple-peril 164.7 25.9 20.8 211.4 Other liabilities — 136.0 19.4 155.4 Medical malpractice — 104.4 — 104.4 Accident and health — 83.4 — 83.4 Surety 29.5 42.5 — 72.0 Homeowners multiple-peril 13.1 56.5 2.5 72.1 Fire 3.4 53.3 — 56.7 Inland Marine 3.3 38.5 — 41.8 Other 59.4 82.9 10.9 153.2 Total net earned premiums $ 1,266.9 $ 1,155.2 $ 219.0 $ 2,641.1 Small Commercial Business Specialty Risk and Extended Warranty Specialty Program Total Six Months Ended June 30, 2017: Workers' compensation $ 709.4 $ — $ 223.6 $ 933.0 Warranty — 470.3 — 470.3 Commercial auto and liability, physical damage 196.7 — 54.5 251.2 Commercial multiple-peril 98.2 — 16.0 114.2 Other liabilities — 89.5 106.7 196.2 Medical malpractice — 106.7 — 106.7 Accident and health — 80.0 — 80.0 Surety 26.1 52.3 — 78.4 Homeowners multiple-peril 25.6 1.1 2.7 29.4 Fire 20.1 115.0 — 135.1 Inland Marine 3.0 14.2 — 17.2 Other 106.4 83.4 1.7 191.5 Total net earned premiums $ 1,185.5 $ 1,012.5 $ 405.2 $ 2,603.2
Disaggregation of revenue	The following table presents the Company's revenues from contracts with customers disaggregated by major business activity and primary geographic regions for the three and six months ended June 30, 2018 : Three Months Ended June 30, 2018 Small Commercial Business Specialty Risk and Extended Warranty Specialty Program Corporate and Other Total Major service lines Product warranty registration and service $ — $ 22.5 $ — $ — $ 22.5 Broker and agency services, and insurance-related services 4.3 10.6 0.3 — 15.2 Asset management, and business services — — — 12.0 12.0 Total $ 4.3 $ 33.1 $ 0.3 $ 12.0 $ 49.7 Primary Geographic Market United States $ 4.3 $ 9.7 $ 0.3 $ 3.0 $ 17.3 International — 23.4 — 9.0 32.4 Total $ 4.3 $ 33.1 $ 0.3 $ 12.0 $ 49.7 Six Months Ended June 30, 2018 Small Commercial Business Specialty Risk and Extended Warranty Specialty Program Corporate and Other Total Major service lines Product warranty registration and service $ — $ 74.9 $ — $ — $ 74.9 Broker and agency services, and insurance-related services 21.8 33.7 1.3 — 56.8 Asset management, and business services — — — 25.2 25.2 Total $ 21.8 $ 108.6 $ 1.3 $ 25.2 $ 156.9 Primary Geographic Market United States $ 21.8 $ 64.9 $ 1.3 $ 7.0 $ 95.0 International — 43.7 — 18.2 61.9 Total $ 21.8 $ 108.6 $ 1.3 $ 25.2 $ 156.9

Divestitures (Tables)

Divestitures (Tables)	6 Months Ended
	Jun. 30, 2018
Discontinued Operations and Disposal Groups [Abstract]
Schedule of Classes of Assets and Liabilities to be Sold and Classified as Held for Sale	The classes of assets and liabilities to be sold and classified as held for sale as of December 31, 2017 consisted of the following: December 31, 2017 Fixed maturity securities, available for sale $ 35.3 Other investments 0.2 Cash and cash equivalents 56.1 Restricted cash and cash equivalents 33.8 Accrued interest and dividends 0.3 Premiums receivable, net 33.9 Deferred policy acquisition costs 211.5 Property, equipment and software, net 4.2 Goodwill 188.3 Intangible assets 171.9 Other assets 165.4 Total assets held for sale $ 900.9 Funds held under reinsurance treaties $ 1.3 Accrued expenses and other liabilities 760.4 Total liabilities held for sale $ 761.7

Basis of Reporting and Merger30

Basis of Reporting and Merger Agreement - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	Mar. 01, 2018	Jun. 30, 2018	Jun. 30, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Common stock, par value (usd per share)	$ 0.01	$ 0.01	$ 0.01	$ 0.01
Karfunkel-Zyskind Family
Business Acquisition [Line Items]
Ownership interest	55.00%
Evergreen Parent
Business Acquisition [Line Items]
Merger consideration share price (usd per share)	$ 14.75
Transaction expenses			$ 36.6
Stone Point | Evergreen Parent
Business Acquisition [Line Items]
Equity interest exchanged in acquisition	$ 800
Entity Controlled By Karfunkel-Zyskind Family | Evergreen Parent
Business Acquisition [Line Items]
Equity interest exchanged in acquisition	$ 400
Enstar | Evergreen Parent
Business Acquisition [Line Items]
Equity interest exchanged in acquisition		$ 200
MDP | Evergreen Parent
Business Acquisition [Line Items]
Equity interest exchanged in acquisition		$ 150

Recent Accounting Pronounceme31

Recent Accounting Pronouncements - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue from contracts with customers	$ 49.7	$ 156.9
Revenue from contracts with customers, percentage of total revenues	5.00%	5.00%
Accumulated Other Comprehensive Income (Loss) | Accounting Standards Update 2018-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net cumulative effect adjustments			$ 16
Accumulated Other Comprehensive Income (Loss) | Accounting Standards Update 2016-01
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net cumulative effect adjustments			(16.7)
Retained Earnings | Accounting Standards Update 2018-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net cumulative effect adjustments			(16)
Retained Earnings | Accounting Standards Update 2016-01
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net cumulative effect adjustments			$ 16.7

Investments - Available-for-sal

Investments - Available-for-sale (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Total	$ 8,376.8	$ 7,408.7
Gross Unrealized Gains	53	154.9
Gross Unrealized Losses	(151.5)	(75.3)
Fair Value	8,278.3	7,488.3
U.S. treasury securities
Debt Securities, Available-for-sale [Line Items]
Total	299.7	301.6
Gross Unrealized Gains	0.9	0.9
Gross Unrealized Losses	(3)	(3.2)
Fair Value	297.6	299.3
U.S. government agencies
Debt Securities, Available-for-sale [Line Items]
Total	131.4	51.1
Gross Unrealized Gains	0.8	0
Gross Unrealized Losses	(1.6)	(0.6)
Fair Value	130.6	50.5
Municipal bonds
Debt Securities, Available-for-sale [Line Items]
Total	822.5	1,035.5
Gross Unrealized Gains	7.6	15.9
Gross Unrealized Losses	(9)	(5.9)
Fair Value	821.1	1,045.5
Foreign government
Debt Securities, Available-for-sale [Line Items]
Total	286.5	151.4
Gross Unrealized Gains	1.3	3.5
Gross Unrealized Losses	(3.9)	(3.2)
Fair Value	283.9	151.7
Finance | Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Total	1,909.8	1,733.2
Gross Unrealized Gains	13.9	48.1
Gross Unrealized Losses	(37.3)	(11.9)
Fair Value	1,886.4	1,769.4
Industrial | Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Total	2,400.3	2,237
Gross Unrealized Gains	16.4	57.3
Gross Unrealized Losses	(55.5)	(26.1)
Fair Value	2,361.2	2,268.2
Utilities | Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Total	325.6	323.8
Gross Unrealized Gains	4.5	10.7
Gross Unrealized Losses	(7.3)	(2.1)
Fair Value	322.8	332.4
Commercial mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Total	397.2	419.3
Gross Unrealized Gains	1.6	3.8
Gross Unrealized Losses	(14.1)	(10.4)
Fair Value	384.7	412.7
Agency backed | Residential mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Total	916.3	562
Gross Unrealized Gains	1.5	5.8
Gross Unrealized Losses	(16.8)	(11.4)
Fair Value	901	556.4
Non-agency backed | Residential mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Total	7.6	6.9
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	(0.1)
Fair Value	7.6	6.8
Collateralized loan / debt obligation
Debt Securities, Available-for-sale [Line Items]
Total	822.6	591.2
Gross Unrealized Gains	4.4	9.7
Gross Unrealized Losses	(2.9)	(0.3)
Fair Value	824.1	600.6
Asset backed securities
Debt Securities, Available-for-sale [Line Items]
Total	57.3	30.1
Gross Unrealized Gains	0.1	0.1
Gross Unrealized Losses	(0.1)	(0.1)
Fair Value	57.3	30.1
Disposal Group, Held-for-sale, Not Discontinued Operations | US Based Fee Businesses
Debt Securities, Available-for-sale [Line Items]
Total	0	34.4
Gross Unrealized Gains		0.9
Gross Unrealized Losses		0
Fair Value	$ 0	$ 35.3

Investments - Additional Inform

Investments - Additional Information (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2018USD ($)agreementInvestment	Jun. 30, 2017USD ($)	Jun. 30, 2018USD ($)agreementInvestment	Jun. 30, 2017USD ($)		Dec. 31, 2017USD ($)Investment
Investment [Line Items]
Fixed maturity securities, available-for-sale (includes maturities & paydowns)	$ 342,000,000	$ 464,900,000	$ 1,079,100,000	$ 988,300,000	[1]
Number of securities | Investment	3,596		3,596			2,086
Continuous unrealized loss position, 12 months or longer, accumulated loss	$ 39,600,000		$ 39,600,000			$ 32,200,000
Continuous unrealized loss position, 12 months or longer, accumulated loss, greater or equal to 20% of amortized cost			0
Proceeds from sale of trading securities	68,800,000	177,600,000	282,900,000	309,400,000
Equity securities	58,800,000	$ 32,400,000	181,700,000	$ 151,700,000	[1]
Securities sold but not yet purchased, at fair value	$ 161,800,000		$ 161,800,000			75,500,000
Number of repurchase agreements outstanding | agreement	16		16
Collateral pledged	$ 227,500,000		$ 227,500,000
Securities sold under agreements to repurchase	214,800,000		214,800,000			0
Equity securities
Investment [Line Items]
Securities sold but not yet purchased, at fair value	$ 161,800,000		$ 161,800,000			$ 75,500,000
Minimum
Investment [Line Items]
Securities sold under agreements to repurchase, interest rate	0.00%		0.00%
Maximum
Investment [Line Items]
Securities sold under agreements to repurchase, interest rate	3.50%		3.50%
[1]	In connection with the adoption of ASU 2016-18, the disclosure for the six months ended June 30, 2017 has been recast for comparability. See Note 2. "Recent Accounting Pronouncements" for additional information on the adoption of ASU 2016-18.

Investments - Summary of Availa

Investments - Summary of Available for Sale Fixed Securities by Contractual Maturity (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Amortized Cost, Rolling Maturity [Abstract]
Due in one year or less	$ 319.8	$ 228.1
Due after one through five years	1,875.8	1,811.3
Due after five through ten years	3,455.4	3,199.7
Due after ten years	524.8	594.5
Mortgage and asset backed securities	2,201	1,609.5
Total	8,376.8	7,408.7
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Fair Value [Abstract]
Due in one year or less	317.3	226.7
Due after one through five years	1,877.7	1,845.5
Due after five through ten years	3,383.4	3,239.8
Due after ten years	525.2	605
Mortgage and asset backed securities	2,174.7	1,606.6
Total	8,278.3	7,488.3
Disposal Group, Held-for-sale, Not Discontinued Operations | US Based Fee Businesses
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Amortized Cost, Rolling Maturity [Abstract]
Total	0	34.4
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Fair Value [Abstract]
Total	$ 0	$ 35.3

Investments - Summary of Gross

Investments - Summary of Gross Unrealized Losses of Fixed-maturities and Equity Securities (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Fair Value
Less Than 12 Months	$ 4,683.5	$ 1,488.2
12 Months or More	905.9	1,135.6
Total	5,589.4	2,623.8
Unrealized Losses
Less Than 12 Months	(111.9)	(43.1)
12 Months or More	(39.6)	(32.2)
Total	(151.5)	(75.3)
U.S. treasury securities
Fair Value
Less Than 12 Months	40.6	41.9
12 Months or More	233.9	247
Total	274.5	288.9
Unrealized Losses
Less Than 12 Months	(0.4)	(0.5)
12 Months or More	(2.6)	(2.7)
Total	(3)	(3.2)
U.S. government agencies
Fair Value
Less Than 12 Months	94.6	48.7
12 Months or More	1.5	0.5
Total	96.1	49.2
Unrealized Losses
Less Than 12 Months	(1.6)	(0.6)
12 Months or More	0	0
Total	(1.6)	(0.6)
Municipal bonds
Fair Value
Less Than 12 Months	256.3	171.3
12 Months or More	134.2	178.7
Total	390.5	350
Unrealized Losses
Less Than 12 Months	(4.6)	(2.7)
12 Months or More	(4.4)	(3.2)
Total	(9)	(5.9)
Foreign government
Fair Value
Less Than 12 Months	182.5	57.4
12 Months or More	14.6	17.1
Total	197.1	74.5
Unrealized Losses
Less Than 12 Months	(3.2)	(2.2)
12 Months or More	(0.7)	(1)
Total	(3.9)	(3.2)
Finance | Corporate bonds
Fair Value
Less Than 12 Months	1,299.7	419.3
12 Months or More	73.1	91.5
Total	1,372.8	510.8
Unrealized Losses
Less Than 12 Months	(34)	(9.7)
12 Months or More	(3.3)	(2.2)
Total	(37.3)	(11.9)
Industrial | Corporate bonds
Fair Value
Less Than 12 Months	1,544	437.1
12 Months or More	190.9	255.4
Total	1,734.9	692.5
Unrealized Losses
Less Than 12 Months	(43.2)	(16.4)
12 Months or More	(12.3)	(9.7)
Total	(55.5)	(26.1)
Utilities | Corporate bonds
Fair Value
Less Than 12 Months	223.4	72.5
12 Months or More	9.2	11.9
Total	232.6	84.4
Unrealized Losses
Less Than 12 Months	(7)	(2)
12 Months or More	(0.3)	(0.1)
Total	(7.3)	(2.1)
Commercial mortgage-backed securities
Fair Value
Less Than 12 Months	164	81.5
12 Months or More	127.4	157.5
Total	291.4	239
Unrealized Losses
Less Than 12 Months	(5.4)	(4.1)
12 Months or More	(8.7)	(6.3)
Total	(14.1)	(10.4)
Agency backed | Residential mortgage-backed securities
Fair Value
Less Than 12 Months	557.5	91.7
12 Months or More	120.4	167.8
Total	677.9	259.5
Unrealized Losses
Less Than 12 Months	(9.6)	(4.7)
12 Months or More	(7.2)	(6.7)
Total	(16.8)	(11.4)
Non-agency backed | Residential mortgage-backed securities
Fair Value
Less Than 12 Months		2.9
12 Months or More		0.8
Total		3.7
Unrealized Losses
Less Than 12 Months		0
12 Months or More		(0.1)
Total		(0.1)
Collateralized loan / debt obligations
Fair Value
Less Than 12 Months	316.9	56.8
12 Months or More	0	4.3
Total	316.9	61.1
Unrealized Losses
Less Than 12 Months	(2.9)	(0.2)
12 Months or More	0	(0.1)
Total	(2.9)	(0.3)
Asset backed securities
Fair Value
Less Than 12 Months	4	7.1
12 Months or More	0.7	3.1
Total	4.7	10.2
Unrealized Losses
Less Than 12 Months	0	0
12 Months or More	(0.1)	(0.1)
Total	$ (0.1)	$ (0.1)

Investments - Trading Securitie

Investments - Trading Securities (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Debt and Equity Securities, FV-NI [Line Items]
Amortized Cost	$ 150		$ 150		$ 52.2
Gross Unrealized Gains	0.9		0.9		0.1
Gross Unrealized Losses	(2.1)		(2.1)		(2.5)
Fair Value	148.8		148.8		49.8
Proceeds from sale of trading securities	68.8	$ 177.6	282.9	$ 309.4
Net losses recognized during the period on trading securities	(1.9)	(1.5)	(5)	(4.6)
Less: Net (gains) losses recognized during the period on trading securities sold during the period	(4.3)	0.6	(3.9)	2.4
Unrealized gains (losses) recognized during the reporting period on trading securities still held at the reporting date	2.4	$ (2.1)	(1.1)	$ (7)
U.S. treasury securities
Debt and Equity Securities, FV-NI [Line Items]
Amortized Cost	123.7		123.7		25
Gross Unrealized Gains	0.3		0.3		0
Gross Unrealized Losses	(0.5)		(0.5)		(0.1)
Fair Value	123.5		123.5		24.9
Corporate bonds | Industrial
Debt and Equity Securities, FV-NI [Line Items]
Amortized Cost	25.3		25.3		26.7
Gross Unrealized Gains	0.6		0.6		0.1
Gross Unrealized Losses	(1.6)		(1.6)		(2.4)
Fair Value	24.3		24.3		24.4
Corporate bonds | Finance
Debt and Equity Securities, FV-NI [Line Items]
Amortized Cost	1		1		0.5
Gross Unrealized Gains	0		0		0
Gross Unrealized Losses	0		0		0
Fair Value	$ 1		$ 1		$ 0.5

Investments - Equity Investment

Investments - Equity Investments (Details) - USD ($) $ in Millions		Jun. 30, 2018	Dec. 31, 2017
Debt Securities, Trading, and Equity Securities, FV-NI [Table] [Line Items]
Original Cost		$ 137.3	$ 195.9
Gross Unrealized Gains		37.3	30.6
Gross Unrealized Losses		(20.3)	(14.8)
Fair Value	[1]	154.3	211.7
Preferred stock
Debt Securities, Trading, and Equity Securities, FV-NI [Table] [Line Items]
Original Cost		0.5	0.5
Gross Unrealized Gains		0	0
Gross Unrealized Losses		0	0
Fair Value		0.5	0.5
Common stock
Debt Securities, Trading, and Equity Securities, FV-NI [Table] [Line Items]
Original Cost		136.8	195.4
Gross Unrealized Gains		37.3	30.6
Gross Unrealized Losses		(20.3)	(14.8)
Fair Value		$ 153.8	$ 211.2
[1]	In connection with the adoption of ASU 2016-01, the consolidated balance sheets as of December 31, 2017 have been recast for comparability. See Note 2. "Recent Accounting Pronouncements" for additional information on the adoption of ASU 2016-01.

Investments - Unrealized Gain (

Investments - Unrealized Gain (Loss) on Equity Securities (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Investments, Debt and Equity Securities [Abstract]
Net gains recognized during the period on equity securities	$ 4.6	$ 11.9	$ 8.7	$ 17
Less: Net gains recognized during the period on equity securities sold during the period	(6.4)	(4.4)	(1.4)	(5)
Unrealized gains recognized during the reporting period on equity securities still held at the reporting date	$ 11	$ 16.3	$ 10.1	$ 22

Investments - Net Investment In

Investments - Net Investment Income (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	$ 71.6	$ 52.3	$ 142.4	$ 117.6
Investment expenses and interest expense on securities sold under agreement to repurchase	(3.3)	(3)	(5.9)	(5)
Net investment income	68.3	49.3	136.5	112.6
Fixed maturity securities, available-for-sale
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	62	69.4	121.4	126.7
Debt Securities
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	4.2	0	4.8	1
Equity securities
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	0.4	0.2	0.7	1.6
Cash and short term investments
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	4.7	1.9	8.8	3.3
Other invested assets
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Gross investment income	$ 0.3	$ (19.2)	$ 6.7	$ (15)

Investments - Realized Gains an

Investments - Realized Gains and Losses (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Gross Gains
Fixed maturity securities, available-for-sale	$ 16.4	$ 14.1	$ 19.9	$ 22.4
Fixed maturity securities, trading	0	2.8	2.1	5.2
Equity securities	10.1		23.7
Other invested assets	0.2	15.7	0.2	16
Total	26.7	42.4	45.9	64.6
Gross Losses [Abstract]
Fixed maturity securities, available-for-sale	(13.9)	(0.9)	(15.8)	(2.1)
Fixed maturity securities, trading	(1.9)	(4.3)	(7.1)	(9.8)
Equity securities	(5.5)		(15)
Other invested assets	0	0	0	0
Other-than-temporary impairment of fixed maturity securities, available-for-sale			(0.3)	0
Total	(21.3)	(18.9)	(38.2)	(32.5)
Net Gains (Losses) [Abstract]
Fixed maturity securities, available-for-sale	2.5	13.2	4.1	20.3
Net losses recognized during the period on trading securities	(1.9)	(1.5)	(5)	(4.6)
Net gains recognized during the period on equity securities	4.6	11.9	8.7	17
Other invested assets	0.2	15.7	0.2	16
Total	$ 5.4	23.5	$ 7.7	32.1
Pro Forma
Gross Gains
Equity securities		9.8		21
Gross Losses [Abstract]
Equity securities		(13.7)		(20.6)
Net Gains (Losses) [Abstract]
Net gains recognized during the period on equity securities		$ (3.9)		$ 0.4

Investments - Fair Values of Re

Investments - Fair Values of Restricted Assets (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Restricted cash and cash equivalents	$ 532.2	$ 480.1
Restricted investments	3,062.2	3,193.8
Total restricted cash, cash equivalents and investments	$ 3,594.4	$ 3,673.9

Fair Value of Financial Instr42

Fair Value of Financial Instruments - Assets and Financial Liabilities on Recurring Basis (Detail) - USD ($) $ in Millions		Jun. 30, 2018	Dec. 31, 2017
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Equity securities, at fair value	[1]	$ 154.3	$ 211.7
Short term investments		169.7	187.8
Other investments		4.1	5
Life settlement contracts		1.9	20.8
Less: Fixed maturity securities classified as held for sale (see note 13)			(35.3)
Total financial assets		8,757.1	7,963.4
Financial Liabilities Fair Value Disclosure [Abstract]
Securities sold but not yet purchased, at fair value		161.8	75.5
Securities sold under agreements to repurchase		214.8
Life settlement contract profit commission		3.2	3.2
Contingent consideration		31.2	75.4
Total financial liabilities		411	154.1
Level 1
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Equity securities, at fair value		153.2	210.7
Short term investments		0	0
Other investments		0	0
Life settlement contracts		0	0
Less: Fixed maturity securities classified as held for sale (see note 13)			0
Total financial assets		574.3	534.9
Financial Liabilities Fair Value Disclosure [Abstract]
Securities sold but not yet purchased, at fair value		153.9	70.8
Securities sold under agreements to repurchase		0
Life settlement contract profit commission		0	0
Contingent consideration		0	0
Total financial liabilities		153.9	70.8
Level 2
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Equity securities, at fair value		0.3	0.5
Short term investments		169.7	187.8
Other investments		0	0
Life settlement contracts		0	0
Less: Fixed maturity securities classified as held for sale (see note 13)			(35.3)
Total financial assets		8,152.5	7,378.1
Financial Liabilities Fair Value Disclosure [Abstract]
Securities sold but not yet purchased, at fair value		7.9	4.7
Securities sold under agreements to repurchase		214.8
Life settlement contract profit commission		0	0
Contingent consideration		0	0
Total financial liabilities		222.7	4.7
Level 3
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Equity securities, at fair value		0.8	0.5
Short term investments		0	0
Other investments		4.1	5
Life settlement contracts		1.9	20.8
Less: Fixed maturity securities classified as held for sale (see note 13)			0
Total financial assets		30.3	50.4
Financial Liabilities Fair Value Disclosure [Abstract]
Securities sold but not yet purchased, at fair value		0	0
Securities sold under agreements to repurchase		0
Life settlement contract profit commission		3.2	3.2
Contingent consideration		31.2	75.4
Total financial liabilities		34.4	78.6
U.S. treasury securities
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt securities		421.1	324.2
U.S. treasury securities | Level 1
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt securities		421.1	324.2
U.S. treasury securities | Level 2
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt securities		0	0
U.S. treasury securities | Level 3
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt securities		0	0
U.S. government agencies
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt securities		130.6	50.5
U.S. government agencies | Level 1
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt securities		0	0
U.S. government agencies | Level 2
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt securities		130.6	50.5
U.S. government agencies | Level 3
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt securities		0	0
Municipal bonds
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt securities		821.1	1,045.5
Municipal bonds | Level 1
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt securities		0	0
Municipal bonds | Level 2
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt securities		820.5	1,045.1
Municipal bonds | Level 3
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt securities		0.6	0.4
Foreign government
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt securities		283.9	151.7
Foreign government | Level 1
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt securities		0	0
Foreign government | Level 2
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt securities		283.9	151.7
Foreign government | Level 3
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt securities		0	0
Finance | Corporate bonds
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt securities		1,887.4	1,769.9
Finance | Level 1 | Corporate bonds
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt securities		0	0
Finance | Level 2 | Corporate bonds
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt securities		1,887.4	1,769.9
Finance | Level 3 | Corporate bonds
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt securities		0	0
Industrial | Corporate bonds
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt securities		2,385.5	2,292.6
Industrial | Level 1 | Corporate bonds
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt securities		0	0
Industrial | Level 2 | Corporate bonds
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt securities		2,385.5	2,292.6
Industrial | Level 3 | Corporate bonds
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt securities		0	0
Utilities | Corporate bonds
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt securities		322.8	332.4
Utilities | Level 1 | Corporate bonds
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt securities		0	0
Utilities | Level 2 | Corporate bonds
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt securities		322.8	332.4
Utilities | Level 3 | Corporate bonds
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt securities		0	0
Commercial mortgage-backed securities
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt securities		384.7	412.7
Commercial mortgage-backed securities | Level 1
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt securities		0	0
Commercial mortgage-backed securities | Level 2
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt securities		362.6	389.8
Commercial mortgage-backed securities | Level 3
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt securities		22.1	22.9
Agency backed
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt securities		901	556.4
Agency backed | Level 1
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt securities		0	0
Agency backed | Level 2
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt securities		901	556.4
Agency backed | Level 3
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt securities		0	0
Non-agency backed
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt securities		7.6	6.8
Non-agency backed | Level 1
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt securities		0	0
Non-agency backed | Level 2
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt securities		7.6	6.8
Non-agency backed | Level 3
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt securities		0	0
Collateralized loan / debt obligations
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt securities		824.1	600.6
Collateralized loan / debt obligations | Level 1
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt securities		0	0
Collateralized loan / debt obligations | Level 2
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt securities		824.1	600.6
Collateralized loan / debt obligations | Level 3
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt securities		0	0
Asset backed securities
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt securities		57.3	30.1
Asset backed securities | Level 1
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt securities		0	0
Asset backed securities | Level 2
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt securities		56.5	29.3
Asset backed securities | Level 3
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Debt securities		$ 0.8	$ 0.8
[1]	In connection with the adoption of ASU 2016-01, the consolidated balance sheets as of December 31, 2017 have been recast for comparability. See Note 2. "Recent Accounting Pronouncements" for additional information on the adoption of ASU 2016-01.

Fair Value of Financial Instr43

Fair Value of Financial Instruments - Changes in Fair Value of Level 3 Financial Assets And Liabilities (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Fair Value, Net Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning Balance	$ 8	$ 376.1	$ (28.2)	$ 351.6
Net income	(3)	9.8	(1.1)	43.6
Other comprehensive income	1.4	0.3	1.1	(0.2)
Purchases and issuances	0	(20.6)	0	1.4
Sales and settlements	(10.5)	(29.1)	24.1	(41.8)
Net transfers into Level 3	0	21.9	0	3.8
Ending Balance	(4.1)	358.4	(4.1)	358.4
Life settlement contract profit commission
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	(3.4)	5.6	(3.2)	(4.9)
Net (loss) income	0.2	(0.1)	0	(0.8)
Other comprehensive income	0	0	0	0
Purchases and issuances	0	0	0	0
Sales and settlements	0	0	0	0
Net transfers into Level 3	0	0	0	0
Ending balance	(3.2)	(5.7)	(3.2)	(5.7)
Contingent consideration
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	(32.3)	72.4	(75.4)	(71.7)
Net (loss) income	(0.9)	(3.1)	(2.6)	(3.8)
Other comprehensive income	0	0	0	0
Purchases and issuances	0	27.2	0	27.2
Sales and settlements	2	5	46.8	5
Net transfers into Level 3	0	0	0	0
Ending balance	(31.2)	(97.7)	(31.2)	(97.7)
Fixed maturities, available-for-sale
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	23.3	35.1	24.1	46.9
Net (loss) income	0	0	(0.3)	0
Other comprehensive income	1.1	0.2	0.8	(0.5)
Purchases and issuances	0	5.2	0	7.5
Sales and settlements	(0.9)	2.3	(1.1)	2.8
Net transfers into Level 3	0	3.3	0	(9.6)
Ending balance	23.5	41.5	23.5	41.5
Equity securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	0.5	21.5	0.5	24.4
Net (loss) income	0	(0.1)	0	(0.4)
Other comprehensive income	0.3	0.1	0.3	0.3
Purchases and issuances	0	0.1	0	4.6
Sales and settlements	0	16.7	0	18.8
Net transfers into Level 3	0	18.6	0	13.4
Ending balance	0.8	23.5	0.8	23.5
Other investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	4.5		5
Net (loss) income	0		(0.5)
Other comprehensive income	0		0
Purchases and issuances	0		0
Sales and settlements	(0.4)		(0.4)
Net transfers into Level 3	0		0
Ending balance	4.1		4.1
Life settlement contracts
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	15.4	397.5	20.8	356.9
Net (loss) income	(2.3)	13.1	2.3	48.6
Other comprehensive income	0	0	0	0
Purchases and issuances	0	1.3	0	16.5
Sales and settlements	(11.2)	15.1	(21.2)	25.2
Net transfers into Level 3	0	0	0	0
Ending balance	$ 1.9	$ 396.8	$ 1.9	$ 396.8

Fair Value of Financial Instr44

Fair Value of Financial Instruments - Fair Value of Debt (Details) $ in Millions	Jun. 30, 2018USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument, stated interest rate	6.125%
5.5% Convertible senior notes due 2021 (the 2021 Notes)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument, stated interest rate	5.50%
2.75% Convertible senior notes due 2044 (the 2044 Notes)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument, stated interest rate	2.75%
7.25% Subordinated Notes due 2055
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument, stated interest rate	7.25%
7.50% Subordinated Notes due 2055
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument, stated interest rate	7.50%
Carrying Value
Fair Value
Revolving credit facility	$ 130
6.125% Notes due 2023	248.6
Secured loan agreements	168.2
Promissory notes and other	95.4
Total debt	1,315.3
Carrying Value | 5.5% Convertible senior notes due 2021 (the 2021 Notes)
Fair Value
Convertible senior notes due 2044	5.4
Carrying Value | 2.75% Convertible senior notes due 2044 (the 2044 Notes)
Fair Value
Convertible senior notes due 2044	176.4
Carrying Value | Junior subordinated debentures (the 2035-2037 Notes)
Fair Value
Junior subordinated debentures	122.2
Carrying Value | Trust preferred securities (the 2033-2037 TPS Notes)
Fair Value
Junior subordinated debentures	92.8
Carrying Value | 7.25% Subordinated Notes due 2055
Fair Value
Subordinated Notes due 2055	145.4
Carrying Value | 7.50% Subordinated Notes due 2055
Fair Value
Subordinated Notes due 2055	130.9
Fair Value
Fair Value
Revolving credit facility	130
6.125% Notes due 2023	242.5
Secured loan agreements	168.2
Promissory notes and other	95.4
Total debt	1,340.4
Fair Value | 5.5% Convertible senior notes due 2021 (the 2021 Notes)
Fair Value
Convertible senior notes due 2044	5.4
Fair Value | 2.75% Convertible senior notes due 2044 (the 2044 Notes)
Fair Value
Convertible senior notes due 2044	218.8
Fair Value | Junior subordinated debentures (the 2035-2037 Notes)
Fair Value
Junior subordinated debentures	112.1
Fair Value | Trust preferred securities (the 2033-2037 TPS Notes)
Fair Value
Junior subordinated debentures	87.3
Fair Value | 7.25% Subordinated Notes due 2055
Fair Value
Subordinated Notes due 2055	146
Fair Value | 7.50% Subordinated Notes due 2055
Fair Value
Subordinated Notes due 2055	$ 134.7

Fair Value of Financial Instr45

Fair Value of Financial Instruments - Additional Information (Details) - USD ($) $ in Millions	1 Months Ended
	Jun. 30, 2017	Jun. 30, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value disclosure		$ 8,757.1	$ 7,963.4
Financial liabilities		$ 411	154.1
Debt instrument, stated interest rate		6.125%
7.25% Subordinated Notes due 2055
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument, stated interest rate		7.25%
7.25% Subordinated Notes due 2055 | Subordinated Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument, stated interest rate		7.25%
7.50% Subordinated Notes due 2055
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument, stated interest rate		7.50%
2.75% Convertible senior notes due 2044 (the 2044 Notes)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument, stated interest rate		2.75%
2.75% Convertible senior notes due 2044 (the 2044 Notes) | Convertible Notes Payable
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument, stated interest rate		2.75%
6.125% Notes due 2023 | Promissory Note
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument, stated interest rate		6.125%
Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of investment in NGHC		$ 45	33.6
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value disclosure		8,152.5	7,378.1
Financial liabilities		222.7	4.7
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value disclosure		30.3	50.4
Financial liabilities		$ 34.4	78.6
NGHC
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Sale of stock (in shares)	10,586,000
Disposal Group, Held-for-sale, Not Discontinued Operations | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value disclosure			900.9
Financial liabilities			$ 761.7
Measurement Input, Discount Rate [Member] | Discounted Cash Flow Technique | Level 3 | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Business Combination, Contingent Consideration, Liability, Measurement Input, Percentage		11.00%
Measurement Input, Discount Rate [Member] | Discounted Cash Flow Technique | Level 3 | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Business Combination, Contingent Consideration, Liability, Measurement Input, Percentage		30.00%

Loss and loss adjustment expe46

Loss and loss adjustment expense reserves - Reconciliation of the beginning and ending balances for unpaid losses and LAE (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Loss and LAE, gross of related reinsurance recoverables at beginning of year	$ 12,138.8	$ 10,140.7
Less: Reinsurance recoverables at beginning of year	5,669.6	3,873.8
Net balance, beginning of year			$ 6,469.2	$ 6,266.9
Incurred related to:
Current year	1,886.3	1,772.9
Prior year	20.3	91.9
Total incurred during the year	1,906.6	1,864.8
Paid related to:
Current year	(414)	(366.2)
Prior year	(1,177.4)	(1,148.3)
Total paid during the year	(1,591.4)	(1,514.5)
Acquired outstanding loss and loss adjustment reserves	9.2	200.8
Retroactive reinsurance adjustment	12.1	(698)
Effect of foreign exchange rates	51.5	(87.4)
Net balance, end of year	6,754.2	6,207.4
Plus reinsurance recoverables at end of year	5,591.1	4,942.1
Loss and LAE reserves, at end of period	12,345.3	11,149.5
Loss and LAE, gross of related reinsurance recoverables at end of period	$ 206.5	$ 1,008.8

Loss and loss adjustment expe47

Loss and loss adjustment expense reserves (Narrative) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Liability for Claims and Claims Adjustment Expense [Line Items]
Prior year	$ 20.3	$ 91.9
Adverse development cover, gain	12.1
Prior period adjustment gross	32.4
Small Commercial Business and Specialty Program | Commercial auto and liability, physical damage
Liability for Claims and Claims Adjustment Expense [Line Items]
Adverse adjustment	49
Small Commercial Business | General liability
Liability for Claims and Claims Adjustment Expense [Line Items]
Adverse adjustment	30.4
Specialty Program | General liability
Liability for Claims and Claims Adjustment Expense [Line Items]
Adverse adjustment	$ 22.3

Debt - Borrowings (Detail)

Debt - Borrowings (Detail) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Debt instrument, stated interest rate	6.125%
Revolving credit facility	$ 130	$ 130
Secured loan agreements	168.2	174.4
Promissory notes	95.4	66.5
Total debt	$ 1,315.3	1,288.7
5.5% Convertible senior notes due 2021 (the 2021 Notes)
Debt Instrument [Line Items]
Debt instrument, stated interest rate	5.50%
Convertible senior notes	$ 5.4	5.4
2.75% Convertible senior notes due 2044 (the 2044 Notes)
Debt Instrument [Line Items]
Debt instrument, stated interest rate	2.75%
Convertible senior notes	$ 176.4	173
6.125% Notes due 2023 (the 2023 Notes)
Debt Instrument [Line Items]
Debt instrument, stated interest rate	6.125%
6.125% Notes due 2023 (the 2023 Notes)	$ 248.6	248.4
Junior subordinated debentures (the 2035-2037 Notes)
Debt Instrument [Line Items]
Junior subordinated debentures (the 2035-2037 Notes)	122.2	122.1
Trust preferred securities (the 2033-2037 TPS Notes)
Debt Instrument [Line Items]
Junior subordinated debentures (the 2035-2037 Notes)	$ 92.8	92.8
7.25% Subordinated Notes due 2055
Debt Instrument [Line Items]
Debt instrument, stated interest rate	7.25%
Subordinate Notes due 2055	$ 145.4	145.3
7.50% Subordinated Notes due 2055
Debt Instrument [Line Items]
Debt instrument, stated interest rate	7.50%
Subordinate Notes due 2055	$ 130.9	$ 130.8

Debt - Credit Facilities (Detai

Debt - Credit Facilities (Details) - 6 months ended Jun. 30, 2018 - Line of Credit	USD ($)	GBP (£)
Revolving credit facility
Line of Credit Facility [Line Items]
Limit	$ 175,000,000
Outstanding	173,400,000
Available	1,600,000
Lloyds | Letter of Credit
Line of Credit Facility [Line Items]
Limit	600,900,000	£ 455,000,000
Outstanding	567,700,000
Available	$ 33,200,000
Debt covenant, forecast underwriting losses threshold	25.00%
ING Bank N.V. and Deutsche Bank Netherlands N.V. | Letter of Credit
Line of Credit Facility [Line Items]
Limit	$ 101,300,000
Outstanding	80,600,000
Available	20,700,000
Comerica Bank | Letter of Credit
Line of Credit Facility [Line Items]
Limit	75,000,000
Outstanding	42,900,000
Available	32,100,000
Other Letters of Credit | Letter of Credit
Line of Credit Facility [Line Items]
Limit	114,100,000
Outstanding	114,100,000
Available	$ 0

Debt - Interest Expense (Detail

Debt - Interest Expense (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Debt Instrument [Line Items]
Interest expense	$ 21.9	$ 24.2	$ 44.7	$ 47.8
Convertible Notes Payable | 2021 Notes
Debt Instrument [Line Items]
Interest expense	0.1	0.1	0.2	0.2
Convertible Notes Payable | 2044 Notes
Debt Instrument [Line Items]
Interest expense	3.4	3.2	6.7	6.4
Senior Notes | 2023 Notes
Debt Instrument [Line Items]
Interest expense	4	4	7.8	7.8
Convertible Debt | 2035-2037 Notes
Debt Instrument [Line Items]
Interest expense	1.8	1.4	3.3	2.9
Junior Subordinated Debt | 2033-2037 TPS Notes
Debt Instrument [Line Items]
Interest expense	1.3	1.1	2.5	2.1
Subordinated Debt | 7.25% 2055 Notes
Debt Instrument [Line Items]
Interest expense	2.7	2.7	5.5	5.5
Subordinated Debt | 7.50% 2055 Notes
Debt Instrument [Line Items]
Interest expense	2.5	2.5	5.1	5.1
Secured loan agreements
Debt Instrument [Line Items]
Interest expense	1.7	1.5	3.3	2.8
Promissory notes
Debt Instrument [Line Items]
Interest expense	0.8	1	1.7	2.7
Other
Debt Instrument [Line Items]
Interest expense	0.8	4	2.4	6.6
Revolving credit facility | Line of Credit
Debt Instrument [Line Items]
Interest expense	1.6	1.5	3.4	3
Lloyds | Funds at Lloyd's facility | Line of Credit
Debt Instrument [Line Items]
Interest expense	$ 1.2	$ 1.2	$ 2.8	$ 2.7

Earnings Per Share - Summary of

Earnings Per Share - Summary of Elements Used in Calculating Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Numerator:
Net (loss) income attributable to AmTrust common stockholders	$ (116.2)	$ 5.9	$ 545.6	$ 28.5
Denominator:
Weighted average common shares outstanding - basic (in shares)	196.9	180.7	196.6	175.8
Plus: Dilutive effect of stock options, convertible debt, other (in shares)	0	0.8	0.3	1.1
Weighted average common shares outstanding - dilutive (in shares)	196.9	181.5	196.9	176.9
Net income per AmTrust common share - basic (usd per share)	$ (0.59)	$ 0.03	$ 2.78	$ 0.16
Net income per AmTrust common shares – diluted (usd per share)	$ (0.59)	$ 0.03	$ 2.77	$ 0.16

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Operating Loss Carryforwards [Line Items]
(Benefit) provision for income taxes	$ (4,400,000)	$ (19,800,000)	$ (19,000,000)	$ 1,600,000
Effective tax rate	4.30%	32.90%	(3.40%)	21.80%
Operating loss carryforwards, limitation on use per year	$ 9,123,000		$ 9,123,000
Operating loss carryforwards, valuation allowance	169,200,000		169,200,000		$ 195,100,000
Domestic Tax Authority
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	82,000,000		82,000,000
Foreign Tax Authority
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	$ 948,600,000		$ 948,600,000

Stockholders' Equity - Narrativ

Stockholders' Equity - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Class of Stock [Line Items]
Net income (loss)			$ 572.4	$ 78.7
Net income (loss) attributable to non-controlling interest and redeemable non-controlling interest of subsidiaries	$ 2.8	$ 6.7	0.3	17.7
Non-Controlling Interest
Class of Stock [Line Items]
Net income (loss)			$ (6.3)	$ 17.1

Stockholders' Equity - Ownershi

Stockholders' Equity - Ownership Components of Total Equity (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			$ 3,368.1	$ 3,465.6
Net income (loss)			572.4	78.7
Unrealized holding gain, net of tax			(136.9)	75.1
Reclassification adjustment	$ (2.5)	$ (19.3)	(4.1)	(30.9)
Foreign currency translation	(86.6)	62.7	(24.4)	76.6
Unrealized gain on interest rate swap	0	0	0	0.1
Distribution of non-controlling interest			(114.6)
Share exercises, compensation and other			7	9.7
Common stock issuance			0	298.7
Common stock dividends			(33.3)	(63.3)
Preferred stock dividends	(16.5)	(16.5)	(33.1)	(33.1)
Capital distributions, net			0	19.3
Ending Balance	3,601.1	3,896.5	3,601.1	3,896.5
AmTrust
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			3,189.7	3,269.1
Net income (loss)			578.7	61.6
Unrealized holding gain, net of tax			(136.9)	75.1
Reclassification adjustment			(4.1)	(30.9)
Foreign currency translation			(24.4)	76.6
Unrealized gain on interest rate swap			0	0.1
Share exercises, compensation and other			7	9.7
Common stock issuance			0	298.7
Common stock dividends			(33.3)	(63.3)
Preferred stock dividends			(33.1)	(33.1)
Ending Balance	3,543.6	3,663.6	3,543.6	3,663.6
Non-Controlling Interest
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance			178.4	196.5
Net income (loss)			(6.3)	17.1
Distribution of non-controlling interest			(114.6)
Capital distributions, net			0	19.3
Ending Balance	$ 57.5	$ 232.9	$ 57.5	$ 232.9

Stockholders' Equity - AOCI (De

Stockholders' Equity - AOCI (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance			$ 3,368.1	$ 3,465.6
Other comprehensive (loss) income, net of tax	$ (101.3)	$ 92.9	(166.1)	120.9
Ending Balance	3,601.1	3,896.5	3,601.1	3,896.5
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	(49.3)	(97.8)	15.5	(125.8)
Net cumulative effect adjustments					$ (0.7)
Other comprehensive income (loss) before reclassifications	(104.4)	128.8	(199.3)	174.8
Amounts reclassed from accumulated other comprehensive loss	(2.5)	(19.3)	(4.1)	(30.9)
Income tax expense	5.6	(16.6)	38	(23)
Other comprehensive (loss) income, net of tax	(101.3)	92.9	(166.1)	120.9
Ending Balance	(150.6)	(4.9)	(150.6)	(4.9)
Foreign Currency Items
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	17.4	(174.3)	(44.8)	(188.2)
Net cumulative effect adjustments					0
Other comprehensive income (loss) before reclassifications	(86.6)	62.7	(24.4)	76.6
Amounts reclassed from accumulated other comprehensive loss	0	0	0	0
Income tax expense	0	0	0	0
Other comprehensive (loss) income, net of tax	(86.6)	62.7	(24.4)	76.6
Ending Balance	(69.2)	(111.6)	(69.2)	(111.6)
Unrealized Gains (Losses) on Investments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	(64.4)	79.8	62.6	65.8
Net cumulative effect adjustments					(0.7)
Other comprehensive income (loss) before reclassifications	(17.8)	66.1	(174.9)	98.1
Amounts reclassed from accumulated other comprehensive loss	(2.5)	(19.3)	(4.1)	(30.9)
Income tax expense	5.6	(16.6)	38	(23)
Other comprehensive (loss) income, net of tax	(14.7)	30.2	(141.7)	44.2
Ending Balance	(79.1)	110	(79.1)	110
Interest Rate Swap Hedge
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	0	(0.1)	0	(0.2)
Net cumulative effect adjustments					0
Other comprehensive income (loss) before reclassifications	0	0	0	0.1
Amounts reclassed from accumulated other comprehensive loss	0	0	0	0
Income tax expense	0	0	0	0
Other comprehensive (loss) income, net of tax	0	0	0	0.1
Ending Balance	0	(0.1)	0	(0.1)
Net Benefit Plan Assets and Obligations Recognized in Stockholders' Equity
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	(2.3)	(3.2)	(2.3)	(3.2)
Net cumulative effect adjustments					$ 0
Other comprehensive income (loss) before reclassifications	0	0	0	0
Amounts reclassed from accumulated other comprehensive loss	0	0	0	0
Income tax expense	0	0	0	0
Other comprehensive (loss) income, net of tax	0	0	0	0
Ending Balance	$ (2.3)	$ (3.2)	$ (2.3)	$ (3.2)

Commitments and Contingencies (

Commitments and Contingencies (Narrative) (Details)	Jun. 28, 2017shareholder	May 11, 2017shareholder	Apr. 27, 2017suitshareholder	Apr. 07, 2015shareholder	Apr. 30, 2017case	Apr. 30, 2017suit
Commitments and Contingencies Disclosure [Abstract]
Number of stockholders	2	1	1	1
Number of claims filed			2		3	3

Segments - Results of Operation

Segments - Results of Operations of Business Segments (Detail) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018USD ($)	Jun. 30, 2017USD ($)	Jun. 30, 2018USD ($)segment	Jun. 30, 2017USD ($)
Segment Reporting Information [Line Items]
Number of operating segments | segment			3
Revenues:
Net earned premium	$ 1,286.2	$ 1,380.7	$ 2,641.1	$ 2,603.2
Losses and expenses:
Loss and loss adjustment expense	933.7	1,024.5	1,906.6	1,864.8
Amortization of deferred acquisition costs	310.4	207.8	526	413.7
Underwriting, general and administrative expenses	121.1	165.4	333.7	287.7
Total losses and expenses	1,365.2	1,397.7	2,766.3	2,566.2
Underwriting (loss) income	(79)	(17)	(125.2)	37
Other income (losses and expenses):
Service and fee income	49.3	168.4	165.4	305.9
Investment income and realized gain on investments	73.7	72.8	144.2	144.7
Other expenses	(109.3)	(199.8)	(323.9)	(362.7)
Interest expense	(21.9)	(24.2)	(44.7)	(47.8)
Foreign currency gain (loss)	(11.6)	(58.9)	14.9	(76.9)
Other revenues	(2.5)	(1.5)	729.3	7.2
Benefit (provision) for income taxes	4.4	19.8	19	(1.6)
Equity in earnings of unconsolidated subsidiary – related parties	0	69.5	0	73.5
Net (loss) income	(96.9)	29.1	579	79.3
Small Commercial Business
Revenues:
Net earned premium	622.9	631.9	1,266.9	1,185.5
Specialty Risk and Extended Warranty
Revenues:
Net earned premium	560.5	539	1,155.2	1,012.5
Specialty Program
Revenues:
Net earned premium	102.8	209.8	219	405.2
Operating Segments
Other income (losses and expenses):
Net (loss) income
Operating Segments | Small Commercial Business
Revenues:
Net earned premium	622.9	631.9	1,266.9	1,185.5
Losses and expenses:
Loss and loss adjustment expense	478	466.9	976.7	844.3
Amortization of deferred acquisition costs	105.8	94.8	205.2	191.8
Underwriting, general and administrative expenses	31.9	75.4	130.1	133.1
Total losses and expenses	615.7	637.1	1,312	1,169.2
Underwriting (loss) income	7.2	(5.2)	(45.1)	16.3
Other income (losses and expenses):
Service and fee income	6.4	30.9	25.9	59.6
Investment income and realized gain on investments	32.8	32.5	63.5	62.2
Other expenses	(26.8)	(51.4)	(85.6)	(96.7)
Interest expense	(11.3)	(12.4)	(23.8)	(25.5)
Foreign currency gain (loss)	0	0	0	0
Other revenues	(1.6)	(0.9)	2.7	3.9
Benefit (provision) for income taxes	(0.6)	7.5	(2.1)	(0.4)
Equity in earnings of unconsolidated subsidiary – related parties		0		0
Net (loss) income	6.1	1	(64.5)	19.4
Operating Segments | Specialty Risk and Extended Warranty
Revenues:
Net earned premium	560.5	539	1,155.2	1,012.5
Losses and expenses:
Loss and loss adjustment expense	356.9	370.9	749.2	683.5
Amortization of deferred acquisition costs	146.7	78.1	234.5	152.4
Underwriting, general and administrative expenses	62.5	62.2	148.9	106.3
Total losses and expenses	566.1	511.2	1,132.6	942.2
Underwriting (loss) income	(5.6)	27.8	22.6	70.3
Other income (losses and expenses):
Service and fee income	25.8	98.2	102.5	185.1
Investment income and realized gain on investments	29.5	27.8	57.5	53.9
Other expenses	(22.6)	(35.8)	(62)	(62.1)
Interest expense	(8.7)	(8.7)	(17.1)	(16.3)
Foreign currency gain (loss)	(11.6)	(58.9)	14.9	(76.9)
Other revenues	(0.8)	(0.4)	2	2.4
Benefit (provision) for income taxes	1.6	28.6	4.1	(3.1)
Equity in earnings of unconsolidated subsidiary – related parties		0		0
Net (loss) income	7.6	78.6	124.5	153.3
Operating Segments | Specialty Program
Revenues:
Net earned premium	102.8	209.8	219	405.2
Losses and expenses:
Loss and loss adjustment expense	98.8	186.7	180.7	337
Amortization of deferred acquisition costs	57.9	34.9	86.3	69.5
Underwriting, general and administrative expenses	26.7	27.8	54.7	48.3
Total losses and expenses	183.4	249.4	321.7	454.8
Underwriting (loss) income	(80.6)	(39.6)	(102.7)	(49.6)
Other income (losses and expenses):
Service and fee income	0.3	0.5	1.3	2
Investment income and realized gain on investments	11.4	12.5	23.2	28.6
Other expenses	(4.7)	(12.7)	(13.8)	(22.6)
Interest expense	(1.9)	(3.1)	(3.8)	(6)
Foreign currency gain (loss)	0	0	0	0
Other revenues	(0.2)	(0.2)	0.4	0.9
Benefit (provision) for income taxes	(2.8)	(0.3)	(3.2)	0.9
Equity in earnings of unconsolidated subsidiary – related parties		0		0
Net (loss) income	(78.5)	(42.9)	(98.6)	(45.8)
Corporate and Other
Revenues:
Net earned premium	0	0	0	0
Losses and expenses:
Loss and loss adjustment expense	0	0	0	0
Amortization of deferred acquisition costs	0	0	0	0
Underwriting, general and administrative expenses	0	0	0	0
Total losses and expenses	0	0	0	0
Underwriting (loss) income	0	0	0	0
Other income (losses and expenses):
Service and fee income	16.8	38.8	35.7	59.2
Investment income and realized gain on investments	0	0	0	0
Other expenses	(55.2)	(99.9)	(162.5)	(181.3)
Interest expense	0	0	0	0
Foreign currency gain (loss)	0	0	0	0
Other revenues	0.1	0	724.2	0
Benefit (provision) for income taxes	6.2	(16)	20.2	1
Equity in earnings of unconsolidated subsidiary – related parties		69.5		73.5
Net (loss) income	(32.1)	(7.6)	617.6	(47.6)
Workers' compensation
Revenues:
Net earned premium	422.9	487.7	865.7	933
Workers' compensation | Small Commercial Business
Revenues:
Net earned premium	376.6	373.1	754.9	709.4
Workers' compensation | Specialty Risk and Extended Warranty
Revenues:
Net earned premium	0	0	0	0
Workers' compensation | Specialty Program
Revenues:
Net earned premium	46.3	114.6	110.8	223.6
Warranty
Revenues:
Net earned premium	232	255.8	531.8	470.3
Warranty | Small Commercial Business
Revenues:
Net earned premium	0	0	0	0
Warranty | Specialty Risk and Extended Warranty
Revenues:
Net earned premium	232	255.8	531.8	470.3
Warranty | Specialty Program
Revenues:
Net earned premium	0	0	0	0
Commercial auto and liability, physical damage
Revenues:
Net earned premium	149	124.1	293.2	251.2
Commercial auto and liability, physical damage | Small Commercial Business
Revenues:
Net earned premium	125	95.6	238.6	196.7
Commercial auto and liability, physical damage | Specialty Risk and Extended Warranty
Revenues:
Net earned premium	0	0	0	0
Commercial auto and liability, physical damage | Specialty Program
Revenues:
Net earned premium	24	28.5	54.6	54.5
Commercial multiple-peril
Revenues:
Net earned premium	109.2	82.4	211.4	114.2
Commercial multiple-peril | Small Commercial Business
Revenues:
Net earned premium	84.2	66.4	164.7	98.2
Commercial multiple-peril | Specialty Risk and Extended Warranty
Revenues:
Net earned premium	15.7	0	25.9	0
Commercial multiple-peril | Specialty Program
Revenues:
Net earned premium	9.3	16	20.8	16
Other liabilities
Revenues:
Net earned premium	76.2	98.4	155.4	196.2
Other liabilities | Small Commercial Business
Revenues:
Net earned premium	0	0	0	0
Other liabilities | Specialty Risk and Extended Warranty
Revenues:
Net earned premium	66.4	46.2	136	89.5
Other liabilities | Specialty Program
Revenues:
Net earned premium	9.8	52.2	19.4	106.7
Medical malpractice
Revenues:
Net earned premium	41.7	53.9	104.4	106.7
Medical malpractice | Small Commercial Business
Revenues:
Net earned premium	0	0	0	0
Medical malpractice | Specialty Risk and Extended Warranty
Revenues:
Net earned premium	41.7	53.9	104.4	106.7
Medical malpractice | Specialty Program
Revenues:
Net earned premium	0	0	0	0
Accident and health
Revenues:
Net earned premium	39.8	46.9	83.4	80
Accident and health | Small Commercial Business
Revenues:
Net earned premium	0	0	0	0
Accident and health | Specialty Risk and Extended Warranty
Revenues:
Net earned premium	39.8	46.9	83.4	80
Accident and health | Specialty Program
Revenues:
Net earned premium	0	0	0	0
Surety
Revenues:
Net earned premium	33.4	41.3	72	78.4
Surety | Small Commercial Business
Revenues:
Net earned premium	16.1	13.9	29.5	26.1
Surety | Specialty Risk and Extended Warranty
Revenues:
Net earned premium	17.3	27.4	42.5	52.3
Surety | Specialty Program
Revenues:
Net earned premium	0	0	0	0
Homeowners multiple-peril
Revenues:
Net earned premium	41.8	17.9	72.1	29.4
Homeowners multiple-peril | Small Commercial Business
Revenues:
Net earned premium	6.6	14.1	13.1	25.6
Homeowners multiple-peril | Specialty Risk and Extended Warranty
Revenues:
Net earned premium	32.7	1.1	56.5	1.1
Homeowners multiple-peril | Specialty Program
Revenues:
Net earned premium	2.5	2.7	2.5	2.7
Fire
Revenues:
Net earned premium	29.8	63.1	56.7	135.1
Fire | Small Commercial Business
Revenues:
Net earned premium	1.9	8.3	3.4	20.1
Fire | Specialty Risk and Extended Warranty
Revenues:
Net earned premium	27.9	54.8	53.3	115
Fire | Specialty Program
Revenues:
Net earned premium	0	0	0	0
Inland Marine
Revenues:
Net earned premium	29.2	(0.8)	41.8	17.2
Inland Marine | Small Commercial Business
Revenues:
Net earned premium	1.8	3	3.3	3
Inland Marine | Specialty Risk and Extended Warranty
Revenues:
Net earned premium	27.4	(3.8)	38.5	14.2
Inland Marine | Specialty Program
Revenues:
Net earned premium	0	0	0	0
Other
Revenues:
Net earned premium	81.2	110	153.2	191.5
Other | Small Commercial Business
Revenues:
Net earned premium	10.7	57.5	59.4	106.4
Other | Specialty Risk and Extended Warranty
Revenues:
Net earned premium	59.6	56.7	82.9	83.4
Other | Specialty Program
Revenues:
Net earned premium	$ 10.9	$ (4.2)	$ 10.9	$ 1.7

Segments (Disaggregation of rev

Segments (Disaggregation of revenue) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Revenue	$ 49.7	$ 156.9
Corporate and Other
Disaggregation of Revenue [Line Items]
Revenue	12	25.2
Small Commercial Business | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	4.3	21.8
Specialty Risk and Extended Warranty | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	33.1	108.6
Specialty Program | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	0.3	1.3
Product warranty registration and service
Disaggregation of Revenue [Line Items]
Revenue	22.5	74.9
Product warranty registration and service | Corporate and Other
Disaggregation of Revenue [Line Items]
Revenue	0	0
Product warranty registration and service | Small Commercial Business | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	0	0
Product warranty registration and service | Specialty Risk and Extended Warranty | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	22.5	74.9
Product warranty registration and service | Specialty Program | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	0	0
Broker and agency services, and insurance-related services
Disaggregation of Revenue [Line Items]
Revenue	15.2	56.8
Broker and agency services, and insurance-related services | Corporate and Other
Disaggregation of Revenue [Line Items]
Revenue	0	0
Broker and agency services, and insurance-related services | Small Commercial Business | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	4.3	21.8
Broker and agency services, and insurance-related services | Specialty Risk and Extended Warranty | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	10.6	33.7
Broker and agency services, and insurance-related services | Specialty Program | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	0.3	1.3
Asset management, and business services
Disaggregation of Revenue [Line Items]
Revenue	12	25.2
Asset management, and business services | Corporate and Other
Disaggregation of Revenue [Line Items]
Revenue	12	25.2
Asset management, and business services | Small Commercial Business | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	0	0
Asset management, and business services | Specialty Risk and Extended Warranty | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	0	0
Asset management, and business services | Specialty Program | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	0	0
United States
Disaggregation of Revenue [Line Items]
Revenue	17.3	95
United States | Corporate and Other
Disaggregation of Revenue [Line Items]
Revenue	3	7
United States | Small Commercial Business | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	4.3	21.8
United States | Specialty Risk and Extended Warranty | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	9.7	64.9
United States | Specialty Program | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	0.3	1.3
International
Disaggregation of Revenue [Line Items]
Revenue	32.4	61.9
International | Corporate and Other
Disaggregation of Revenue [Line Items]
Revenue	9	18.2
International | Small Commercial Business | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	0	0
International | Specialty Risk and Extended Warranty | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	23.4	43.7
International | Specialty Program | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue	$ 0	$ 0

Divestitures (Net Assets) (Deta

Divestitures (Net Assets) (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Disposal Group, Including Discontinued Operation, Assets [Abstract]
Total assets held for sale	$ 0	$ 900.9
Disposal Group, Including Discontinued Operation, Liabilities [Abstract]
Total liabilities held for sale	$ 0	761.7
US Based Fee Businesses | Disposal Group, Held-for-sale, Not Discontinued Operations
Disposal Group, Including Discontinued Operation, Assets [Abstract]
Fixed maturity securities, available for sale		35.3
Other investments		0.2
Cash and cash equivalents		56.1
Restricted cash and cash equivalents		33.8
Accrued interest and dividends		0.3
Premiums receivable, net		33.9
Deferred policy acquisition costs		211.5
Property, equipment and software, net		4.2
Goodwill		188.3
Intangible assets		171.9
Other assets		165.4
Total assets held for sale		900.9
Disposal Group, Including Discontinued Operation, Liabilities [Abstract]
Funds held under reinsurance treaties		1.3
Accrued expenses and other liabilities		760.4
Total liabilities held for sale		$ 761.7

Divestitures (Narrative) (Detai

Divestitures (Narrative) (Details) - USD ($) $ in Millions	Feb. 28, 2018	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on sale of U.S.-based fee business		$ 0	$ 0	$ 724.1	$ 0
Mayfield Holdings LLC
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Payments to acquire businesses	$ 933
Percentage of voting Interests acquired (in percentage)	49.00%
Consideration transferred, equity interests issued and issuable	$ 217
MH JV Holdings L.P. | Mayfield Holdings LLC
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Payments to acquire businesses	$ 225.8
Percentage of voting Interests acquired (in percentage)	51.00%