Allied World Assurance 10-K 22 Feb 16 2015 FY Annual report Financial data

Document And Entity Information

Document And Entity Information - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2015	Feb. 15, 2016	Jun. 30, 2015
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Entity Registrant Name	Allied World Assurance Co Holdings, AG
Entity Central Index Key	1,163,348
Document Period End Date	Dec. 31, 2015
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	FY
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		90,474,045
Entity Public Float			$ 3.9
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
ASSETS:
Fixed maturity investments trading, at fair value (amortized cost: 2015: $7,290.6; 2014: $6,035.2)	$ 7,201.5	$ 6,069
Equity securities trading, at fair value (cost: 2015: $395.3; 2014: $791.2)	403	844.2
Other invested assets	966.7	955.5
Total investments	8,571.2	7,868.7
Cash and cash equivalents	608	589.3
Restricted cash	60.6	81
Insurance balances receivable	745.9	664.8
Funds held	640.8	724
Prepaid reinsurance	392.3	360.7
Reinsurance recoverable	1,480	1,340.3
Reinsurance recoverable on paid losses	96.4	86.1
OSLR recoverable	254.6	232.6
Accrued investment income	38.3	28.5
Net deferred acquisition costs	165.2	151.5
Goodwill	388.1	278.3
Intangible assets	116.6	46.3
Balances receivable on sale of investments	36.9	47.1
Net deferred tax assets	24.4	33.6
Other assets	147.2	118.6
Total assets	13,511.9	12,418.8
LIABILITIES:
Reserve for losses and loss expenses	6,456.2	5,881.2
Unearned premiums	1,683.3	1,555.3
Reinsurance balances payable	214.4	180.1
Balances due on purchases of investments	125.1	5.4
Senior notes:
Principal amount	1,300	800
Less unamortized discount and debt issuance costs	7.1	3.9
Senior notes, net of unamortized discount and debt issuance costs	1,292.9	796.1
Other long-term debt	23	19.2
Dividends payable	0	21.7
Accounts payable and accrued liabilities	184.5	181.6
Total liabilities	9,979.4	8,640.6
SHAREHOLDERS’ EQUITY:
Common shares: 2015 and 2014: par value CHF 4.10 per share (2015: 95,523,230; 2014: 100,775,256 shares issued and 2015: 90,959,635; 2014: 96,195,482 shares outstanding)	386.7	408
Treasury shares, at cost (2015: 4,563,595; 2014: 4,579,774)	(155.1)	(143.1)
Accumulated other comprehensive loss	(9.3)	0
Retained earnings	3,310.2	3,513.3
Total shareholders’ equity	3,532.5	3,778.2
Total liabilities and shareholders’ equity	$ 13,511.9	$ 12,418.8

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) $ in Millions	Dec. 31, 2015USD ($)shares	Dec. 31, 2014USD ($)shares
Fixed maturity investments trading, amortized cost | $	$ 7,290.6	$ 6,035.2
Equity securities trading - cost | $	$ 395.3	$ 791.2
Common stock, shares issued	95,523,230	100,775,256
Common stock, shares outstanding	90,959,635	96,195,482
Treasury stock (shares)	4,563,595	4,579,774

Consolidated Statements Of Oper

Consolidated Statements Of Operations And Comprehensive Income - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
REVENUES:
Gross premiums written	$ 632.3	$ 754.1	$ 826	$ 880.6	$ 565.7	$ 707.9	$ 760.4	$ 901.4	$ 3,093	$ 2,935.4	$ 2,738.7
Premiums ceded	(167.5)	(147.1)	(222.3)	(108.1)	(137.9)	(139.2)	(206.5)	(129.8)	(645)	(613.4)	(618.2)
Net premiums written	464.8	607	603.7	772.5	427.8	568.7	553.9	771.6	2,448	2,322	2,120.5
Change in unearned premiums	158	43.7	42.7	(204)	145.7	(27)	(16.7)	(241.3)	40.4	(139.3)	(114.6)
Net premiums earned	622.8	650.7	646.4	568.5	573.5	541.7	537.2	530.3	2,488.4	2,182.7	2,005.9
Net investment income	49.1	45.7	42.8	44.5	49.1	43.4	36.8	47.6	182.1	176.9	157.6
Net realized investment (losses) gains	(38.8)	(113.6)	(20.2)	45	(15.4)	(35.1)	85.3	54.2	(127.6)	89	59.5
Other income	1	0.7	0.9	0.9	1.1	1	0	0	3.5	2.1	0
Total revenues	634.1	583.5	669.9	658.9	608.3	551	659.3	632.1	2,546.4	2,450.7	2,223
EXPENSES:
Net losses and loss expenses	412.7	416.9	431.5	325.2	273	336.1	314.9	275.3	1,586.3	1,199.2	1,123.2
Acquisition costs	96	100.1	100.6	78.7	80.7	72.4	74.3	67.7	375.4	295.1	252.7
General and administrative expenses	95	105.8	108.4	97.1	100.9	88.3	96.2	80.3	406.3	365.7	352.3
Other expense	1.9	1.3	1.2	1.8	2	6.6	0	0	6.2	8.6	0
Amortization and impairment of intangible assets	3.7	2.7	2.8	0.6	0.6	0.6	0.7	0.6	9.8	2.5	2.5
Interest expense	18.1	14.5	14.5	14.3	14.3	14.3	14.6	14.5	61.4	57.8	56.5
Foreign exchange loss	0.9	(0.8)	1.3	9.9	0	0.3	0.7	0	11.3	1	8
Total expenses	628.3	640.5	660.3	527.6	471.5	518.6	501.4	438.4	2,456.7	1,929.9	1,795.2
Income before income taxes	5.8	(57)	9.6	131.3	136.8	32.4	157.9	193.7	89.7	520.8	427.8
Income tax expense	4	(5.3)	0.1	7	6.2	1.5	6.2	16.6	5.8	30.5	9.8
NET INCOME	$ 1.8	$ (51.7)	$ 9.5	$ 124.3	$ 130.6	$ 30.9	$ 151.7	$ 177.1	83.9	490.3	418
Other comprehensive loss:
Other comprehensive loss: foreign currency translation adjustment, net of tax									(9.3)	0	0
COMPREHENSIVE INCOME									$ 74.6	$ 490.3	$ 418
PER SHARE DATA
Basic earnings per share	$ 0.02	$ (0.57)	$ 0.10	$ 1.30	$ 1.35	$ 0.32	$ 1.55	$ 1.78	$ 0.91	$ 5.03	$ 4.08
Diluted earnings per share	$ 0.02	$ (0.57)	$ 0.10	$ 1.27	$ 1.33	$ 0.31	$ 1.52	$ 1.74	$ 0.89	$ 4.92	$ 3.98
Weighted average common shares outstanding	90,934,107	90,882,511	92,441,730	95,935,551	96,386,796	96,458,231	97,809,639	99,545,187	92,530,208	97,538,319	102,464,715
Weighted average common shares and common share equivalents outstanding	92,422,422	90,882,511	93,984,226	97,577,029	98,394,432	98,444,238	99,724,802	101,584,662	94,174,460	99,591,773	104,865,834
Dividends paid per share									$ 1.23	$ 0.784	$ 0.458

Consolidated Statements Of Shar

Consolidated Statements Of Shareholders' Equity - USD ($) $ in Millions		Total	Share Capital	Treasury Shares	Accumulated Other Comprehensive Loss	Retained Earnings
Balance, at beginning of period at Dec. 31, 2012		$ 3,326.4	$ 455	$ (113.8)	$ 0	$ 2,985.2
Net income		418				418
Dividends — par value reduction		(13)	(13)
Dividends		(50.8)				(50.8)
Stock compensation	[1]	13.9		31.9		(18)
Share repurchases		(174.7)		(174.7)
Shares cancelled		0	(23)	176.6		(153.6)
Foreign currency translation adjustment		0
Balance, at end of period at Dec. 31, 2013		3,519.8	419	(80)	0	3,180.8
Net income		490.3				490.3
Dividends		(81.7)				(81.7)
Stock compensation	[1]	25.2		19.6		5.6
Share repurchases		(175.4)		(175.4)
Shares cancelled		0	(11)	92.7		(81.7)
Foreign currency translation adjustment		0
Balance, at end of period at Dec. 31, 2014		3,778.2	408	(143.1)	0	3,513.3
Net income		83.9				83.9
Dividends		(92.4)				(92.4)
Stock compensation	[1]	17.4		19.6		(2.2)
Share repurchases		(245.3)		(245.3)
Shares cancelled		0	(21.3)	213.7		(192.4)
Foreign currency translation adjustment		(9.3)			(9.3)
Balance, at end of period at Dec. 31, 2015		$ 3,532.5	$ 386.7	$ (155.1)	$ (9.3)	$ 3,310.2
[1]	Includes stock compensation expense for the period and shares issued out of treasury for awards exercised or vested. See note 2(o) to the notes to the consolidated financial statement

Consolidated Statements Of Cash

Consolidated Statements Of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
CASH FLOWS PROVIDED BY OPERATING ACTIVITIES:
Net income	$ 83.9	$ 490.3	$ 418
Adjustments to reconcile net income to cash provided by operating activities:
Net realized gains on sales of investments	(73.9)	(145)	(109.1)
Mark to market adjustments	189.8	22	48.1
Stock compensation expense	15.8	14.2	14
Undistributed income of equity method investments	22.6	13.9	(11.9)
Changes in:
Reserve for losses and loss expenses, net of reinsurance recoverables	175.9	8.9	27.6
Unearned premiums, net of prepaid reinsurance	(43.9)	139.3	114.6
Insurance balances receivable	37	(76.8)	(108.4)
Reinsurance recoverable on paid losses	(10.4)	(8.5)	(45.8)
Funds held	83.2	(91.6)	(296.1)
Reinsurance balances payable	(5.6)	7	36.8
Net deferred acquisition costs	17	(24.9)	(18.7)
Net deferred tax assets	(2.7)	4.2	(11.9)
Accounts payable and accrued liabilities	(10.1)	8	22.9
Other items, net	34.2	55.9	34.4
Net cash provided by operating activities	512.8	416.9	114.5
CASH FLOWS USED IN INVESTING ACTIVITIES:
Purchases of trading securities	(5,863.2)	(7,630)	(7,527.7)
Purchases of other invested assets	(126.7)	(307.9)	(276.9)
Sales of trading securities	5,328.8	7,536.9	7,540.2
Sales of other invested assets	161.3	267.9	187.5
Purchases of fixed assets	(31.8)	(59.7)	(5.3)
Net cash paid for acquisitions	(124.4)	(2.6)	0
Change in restricted cash	20.3	68.4	34.1
Net cash used in investing activities	(635.7)	(127)	(48.1)
CASH FLOWS PROVIDED BY (USED IN) FINANCING ACTIVITIES:
Dividends paid — par value reduction	0	0	(13)
Dividends paid	(114.1)	(76.7)	(34)
Share repurchases	(246.4)	(175.9)	(173)
Proceeds from the exercise of stock options	10.1	10	12.1
Proceeds from senior notes	496.7	0	0
Proceeds from other long-term debt	4	19.2	0
Repayment of other long-term debt	(0.2)	0	0
Net cash provided by (used in) used in financing activities	150.1	(223.4)	(207.9)
Effect of exchange rate changes on foreign currency cash	(8.5)	(9.1)	(8.5)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	18.7	57.4	(150)
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD	589.3	531.9	681.9
CASH AND CASH EQUIVALENTS, END OF PERIOD	608	589.3	531.9
Supplemental disclosure of cash flow information:
Cash paid for income taxes	2.5	18.4	22.6
Cash paid for interest expense	$ 54	$ 54	$ 54

General

General	12 Months Ended
	Dec. 31, 2015
General [Abstract]
General	GENERAL Allied World Assurance Company Holdings, AG, a Swiss holding company (“Allied World Switzerland”), through its wholly-owned subsidiaries (collectively, the “Company”), provides property and casualty insurance and reinsurance on a worldwide basis. References to $ are to the lawful currency of the United States and to CHF are to the lawful currency of Switzerland.

Significant Accounting Policies

Significant Accounting Policies	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Significant accounting policies	SIGNIFICANT ACCOUNTING POLICIES These consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States (“U.S. GAAP”). The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. The significant estimates reflected in the Company’s financial statements include, but are not limited to: • The premium estimates for certain reinsurance agreements, • Recoverability of deferred acquisition costs, • The reserve for outstanding losses and loss expenses, • Valuation of ceded reinsurance recoverables, • Determination of impairment of goodwill and other intangible assets, and • Valuation of financial instruments. Intercompany accounts and transactions have been eliminated on consolidation and all entities meeting consolidation requirements have been included in the consolidated financial statements. To facilitate comparison of information across periods, certain reclassifications have been made to prior year amounts to conform to the current year's presentation. The significant accounting policies are as follows: a) Premiums and Acquisition Costs Premiums are recorded as written on the inception date of the policy. For certain types of business written by the Company, notably assumed reinsurance, the exact premium income may not be known at the policy inception date. In the case of quota share reinsurance treaties assumed by the Company, the underwriter makes an estimate of premium income at inception. The underwriter’s estimate is based on statistical data provided by reinsureds and the underwriter’s judgment and experience. Such estimations are refined over the reporting period of each treaty as actual written premium information is reported by ceding companies and intermediaries. Premiums resulting from changes in the estimate of the premium income are recorded in the period the estimate is changed. Certain insurance and reinsurance contracts may require that the premium be adjusted at the expiry of the contract to reflect the change in exposure or loss experience of the insured or reinsured. Premiums are recognized as earned over the period of policy coverage in proportion to the risks to which they relate. Reinsurance premiums under a losses-occurring reinsurance contract are earned over the coverage period. Reinsurance premiums under a risks-attaching reinsurance contract are earned over the same period as the underlying policies, or risks, covered by the contract. As a result, the earning pattern of a risks-attaching reinsurance contract may extend up to 24 months, reflecting the inception dates of the underlying policies. Premiums relating to the unexpired periods of coverage are recorded on the consolidated balance sheets as “unearned premiums”. Acquisition costs, comprised of commissions, brokerage fees and insurance taxes, are costs that are directly related to the successful acquisition of new and renewal business and are deferred. While permitted under U.S. GAAP to defer certain internal costs that are directly related to the successful acquisition of new and renewal business, the Company does not defer such costs. Acquisition costs that are deferred, and carried on the balance sheets as an asset, are expensed as the premiums to which they relate are earned. Expected losses and loss expenses, other costs and anticipated investment income related to these unearned premiums are considered in determining the recoverability or deficiency of deferred acquisition costs. If it is determined that deferred acquisition costs are not recoverable, they are expensed. Further analysis is performed to determine if a liability is required to provide for losses which may exceed the related unearned premiums. Acquisition costs recorded in the consolidated statements of operations and comprehensive income (“consolidated income statements”) includes other acquisition-related costs such as profit commissions that are expensed as incurred and the amortization of insurance-related intangible assets. b) Reserve for Losses and Loss Expenses The reserve for losses and loss expenses is comprised of two main elements: outstanding loss reserves (“OSLR,” also known as case reserves) and reserves for losses incurred but not reported (“IBNR”). OSLR relate to known claims and represent management’s best estimate of the likely loss payment. Reserves for IBNR relates to reserves established by the Company for claims that have occurred but have not yet been reported to us as well as for changes in the values of claims that have been reported to us but are not yet settled. The reserve for IBNR is estimated by management for each line of business based on various factors including underwriters’ expectations about loss experience, actuarial analysis, comparisons with the results of industry benchmarks and loss experience to date. The Company’s actuaries employ generally accepted actuarial methodologies to determine estimated ultimate loss reserves. The adequacy of the reserves is re-evaluated quarterly by the Company’s actuaries. At the completion of each quarterly review of the reserves, a reserve analysis is prepared and reviewed with the Company’s loss reserve committee. This committee determines management’s best estimate for loss and loss expense reserves based upon the reserve analysis. While management believes that OSLR and the reserves for IBNR are sufficient to cover losses assumed by the Company, there can be no assurance that losses will not deviate from the Company’s reserves, possibly by material amounts. The methodology of estimating loss reserves is periodically reviewed to ensure that the assumptions made continue to be appropriate. The Company recognizes any changes in its loss reserve estimates, including prior year loss reserve development, and the related reinsurance recoverables are recorded in “net losses and loss expenses” in the consolidated income statements in the periods in which they are determined. c) Ceded Reinsurance In the ordinary course of business, the Company uses both treaty and facultative reinsurance to minimize its net loss exposure to any one catastrophic loss event or to an accumulation of losses from a number of smaller events. Reinsurance premiums ceded are expensed and any commissions recorded thereon are earned over the period the reinsurance coverage is provided in proportion to the risks to which they relate. For reinsurance treaties that have contractual minimum premium provisions, premiums ceded are recorded at the inception of the treaty based on the minimum premiums. Prepaid reinsurance represents unearned premiums ceded to reinsurance companies. Any unearned ceding commission is included in “net deferred acquisitions costs” on the consolidated balance sheets and is recorded as a reduction to the overall net deferred acquisition cost balance. Reinsurance recoverable includes the balances due from those reinsurance companies under the terms of the Company’s reinsurance agreements for unpaid losses and loss reserves, including IBNR, and is presented net of a provision for uncollectible reinsurance. Amounts recoverable from reinsurers are estimated in a manner consistent with the estimated claim liability associated with the reinsured policy. The Company determines the portion of the IBNR liability that will be recoverable under its reinsurance contracts by reference to the terms of the reinsurance protection purchased. This determination is necessarily based on the estimate of IBNR and accordingly, is subject to the same uncertainties as the estimate of IBNR. The Company remains liable to the extent that its reinsurers do not meet their obligations under the reinsurance contracts; therefore, the Company regularly evaluates the financial condition of its reinsurers and monitors concentration of credit risk. d) Investments All fixed maturity investments and equity securities are classified as trading securities as the Company has elected the fair value option permitted under U.S. GAAP for these investments. Trading securities are carried at fair value with any change in unrealized gains or losses recognized in the consolidated income statements and included in “net realized investment (losses) gains”. As a result of this investment classification, the Company does not record any change in unrealized gains or losses on investments as a separate component of accumulated other comprehensive income on the consolidated balance sheets. Other invested assets consist primarily of investments in hedge funds and private equity funds, which have been accounted for as trading securities as the Company has elected the fair value option as permitted under U.S. GAAP. In addition, included in the Company’s other invested assets are various investments which are accounted for using the equity method of accounting. Generally, the Company uses the equity method where it does not have a controlling interest and is not the primary beneficiary. Equity method investments are recorded at cost and adjusted for the Company’s proportionate share of earnings or losses on a quarterly lag basis. An other-than-temporary impairment charge related to the equity method investments is assessed when facts and circumstances exists that indicate an impairment may exist. An other-than-temporary impairment charge is recorded when it is determined that the carrying value of the equity method investment is below its fair value and the Company does not have the intent and ability to hold to recovery. See note 4(c) for additional information regarding an other-than-temporary impairment charge recorded related to one of the Company's equity method investments. No equity method investment, individually or in the aggregate, was deemed significant to disclose summarized financial data. Other investments are recorded based on valuation techniques depending on the nature of the individual assets. At each measurement date, the Company estimates the fair value of the financial instruments using various valuation techniques. The Company utilizes, to the extent available, quoted market prices in active markets or observable market inputs in estimating the fair value of financial instruments. When quoted market prices or observable market inputs are not available, the Company may utilize valuation techniques that rely on unobservable inputs to estimate the fair value of financial instruments. The Company bases its determination of whether a market is active or inactive on the spread between what a seller is asking for a security and what a buyer is bidding for that security. Spreads that are significantly above historical spreads are considered inactive markets. The Company also considers the volume of trading activity in the determination of whether a market is active or inactive. See note 6 for additional information regarding the fair value of financial instruments. The Company utilizes independent pricing sources to obtain market quotations for securities that have quoted prices in active markets. In general, the independent pricing sources use observable market inputs including, but not limited to, investment yields, credit risks and spreads, benchmarking of like securities, reported trades and sector groupings to determine the fair value. For a majority of the portfolio, the Company obtained two or more prices per security as of December 31, 2015 . When multiple prices are obtained, a price source hierarchy is utilized to determine which price source is the best estimate of the fair value of the security. The price source hierarchy emphasizes more weighting to significant observable inputs such as index pricing and less weighting towards non-binding broker-dealer quotes. In addition, to validate all prices obtained from these pricing sources including non-binding broker-dealer quotes, the Company also obtains prices from its investment portfolio managers and other sources ( e.g. , another pricing vendor), and compares the prices obtained from the independent pricing sources to those obtained from the Company’s investment portfolio managers and other sources. The Company investigates any material differences between the multiple sources and determines which price best reflects the fair value of the individual security. There were no material differences between the prices obtained from the independent pricing sources and the prices obtained from the Company’s investment portfolio managers and other sources as of December 31, 2015 and 2014 . Investment securities are recorded on a trade date basis. Investment income is recognized when earned and includes the accrual of discount or amortization of premium on fixed maturity investments using the effective yield method and is net of related expenses. Interest income for fixed maturity investments is accrued and recognized based on the contractual terms of the fixed maturity investments and is included in “net investment income” in the consolidated income statements. The Company’s share of distributed and undistributed net income from equity method investments is included in net investment income. The return on investments is managed on a total financial statement portfolio return basis, which includes the distributed and undistributed net income from equity method investments, and as such have classified these amounts in net investment income. Realized gains and losses on the disposition of investments, which are based upon the first-in first-out method of identification, are included in “net realized investment (losses) gains” in the consolidated income statements. For mortgage-backed and asset-backed securities and any other holdings for which there is a prepayment risk, prepayment assumptions are evaluated and revised on a regular basis. Revised prepayment assumptions are applied to securities on a retrospective basis to the date of acquisition. The cumulative adjustments to amortized cost required due to these changes in effective yields and maturities are recognized in net investment income in the same period as the revision of the assumptions. e) Variable Interest Entities The Company is involved in the normal course of business with variable interest entities (“VIEs”) as a passive investor in certain asset-backed securities issued by third-party VIEs and affiliated VIEs. The Company performs a qualitative assessment at the date when it becomes initially involved in the VIE, followed by ongoing reassessments related to its involvement in VIEs. The Company’s maximum exposure to loss with respect to these investments is limited to the investment carrying amounts reported in the Company’s consolidated balance sheets and any unfunded commitments. f) Translation of Foreign Currencies Transactions in currencies other than a foreign operation's functional currency are translated into the functional currency of the foreign operation. Foreign currency transaction gains and losses, including those arising from forward exchange contracts, are included in “foreign exchange loss” in the consolidated income statements. Functional currency assets and liabilities are translated into the reporting currency, U.S. dollars, using period-end exchange rates, and functional currency income statements are translated using average exchange rates with the related foreign currency translation adjustment recorded as a separate component of accumulated other comprehensive income or loss. g) Cash and Cash Equivalents Cash and cash equivalents include amounts held in banks, time deposits, commercial paper, discount notes and U.S. Treasury Bills with maturities of less than three months from the date of purchase. h) Income Taxes Allied World Switzerland and certain of its subsidiaries operate in jurisdictions where they are subject to income taxation. Current and deferred income taxes are charged or credited to operations, or to shareholders' equity in certain cases, based upon enacted tax laws and rates applicable in the relevant jurisdiction in the period in which the tax becomes payable. Deferred income taxes are provided for all temporary differences between the bases of assets and liabilities used in the financial statements and those used in the various jurisdictional tax returns. It is the Company’s policy to recognize interest accrued related to unrecognized tax benefits in “interest expense” and penalties in “general and administrative expenses” in the consolidated income statements. The Company has not recorded any interest or penalties during the years ended December 31, 2015 , 2014 and 2013 and the Company has not accrued any payment of interest and penalties as of December 31, 2015 and 2014 . i) Employee Stock Option Compensation Plan The Company has an employee stock option plan, which is in run-off, in which the amount of Allied World Switzerland's common shares received as compensation through the issuance of stock options is determined by reference to the value of the shares. Compensation expense for stock options granted to employees is recorded on a straight-line basis over the option vesting period and is based on the fair value of the stock options on the grant date. The fair value of each stock option on the grant date is determined by using the Black-Scholes option-pricing model. j) Restricted Stock Units The Company has granted restricted stock units (“RSUs”) to certain employees. The compensation expense for the RSUs is based on the market value of Allied World Switzerland’s common shares on the grant date, and is recognized on a straight-line basis over the applicable vesting period. The Company has also granted cash-equivalent RSUs to certain employees that vest on a straight-line basis over the applicable vesting period. The amount payable per unit awarded will be equal to the price per share of Allied World Switzerland’s common shares and as such the Company measures the value of the award each reporting period based on the period ending share price. The effects of changes in the share price at each period end during the service period are recognized as increases or decreases in compensation expense over the service period. k) Performance-Based Equity Awards The Company has granted performance-based equity awards to key employees in order to promote the long-term growth and profitability of the Company. Each award represents the right to receive a number of common shares in the future, based upon the achievement of established performance criteria during the applicable performance period. These performance-based equity awards vest after a three-year performance period. The compensation expense for these awards is based on the market value of Allied World Switzerland’s common shares on the grant date, and is recognized on a straight-line basis over the applicable performance and vesting period. The Company will also adjust the compensation expense, as a cumulative adjustment, to the extent the Company's performance is above or below the targeted performance criteria. The Company has also granted cash-equivalent, performance-based awards to certain employees that vest based upon the achievement of established performance criteria during the applicable performance period. These cash-equivalent, performance-based awards vest after a three-year performance period. The amount payable per unit awarded will be equal to the price per share of Allied World Switzerland’s common shares, and as such the Company measures the value of the award each reporting period based on the period-ending share price. The effects of changes in the share price at each period end during the service period are recognized as changes in compensation expense over the service period. The Company will also adjust the compensation expense, as a cumulative adjustment, to the extent the Company's performance is above or below the targeted performance criteria. l) Goodwill and Intangible Assets The Company classifies its intangible assets into three categories: (1) intangible assets with finite lives subject to amortization, (2) intangible assets with indefinite lives not subject to amortization, and (3) goodwill. Intangible assets, other than goodwill, generally consist of customer renewal rights, distribution channels, internally generated software, non-compete covenants, trademarks, and insurance licenses. For intangible assets with finite lives, the value of the assets is amortized over their expected useful lives and the expense is included in “amortization and impairment of intangible assets” in the consolidated income statements. The Company tests assets for impairment if conditions exist that indicate the carrying value may not be recoverable. If, as a result of the evaluation, the Company determines that the value of the intangible assets is impaired, then the value of the assets will be written-down in the period in which the determination of the impairment is made. See note 10 for additional information regarding an impairment recorded for one of the Company's intangible assets with finite lives. For indefinite lived intangible assets the Company does not amortize the intangible asset but evaluates and compares the fair value of the assets to their carrying values on an annual basis or more frequently if circumstances warrant. If, as a result of the evaluation, the Company determines that the value of the intangible assets is impaired, then the value of the assets will be written-down in the period in which the determination of the impairment is made. Goodwill represents the excess of the cost of acquisitions over the fair value of net assets acquired and is not amortized. Goodwill is assigned at acquisition to the applicable reporting unit(s) based on the expected benefit to be received by the reporting units from the business combination. The Company determines the expected benefit based on several factors including the purpose of the business combination, the strategy of the Company subsequent to the business combination and structure of the acquired company subsequent to the business combination. A reporting unit is a component of the Company’s business that has discrete financial information that is reviewed by management. In determining the reporting unit, the Company analyzes the inputs, processes, outputs and overall operating performance of the reporting unit. The Company has several reporting units to which the goodwill is allocated to. For goodwill, the Company performs an annual impairment test, or more frequently if circumstances are warranted. The Company may first assess qualitative factors to determine whether it is more likely than not that the fair value of a reporting unit is less than its carrying amount. The results of the qualitative assessment will determine if an entity needs to proceed with the two-step goodwill impairment test. For the year ended December 31, 2015 , the Company elected to bypass the qualitative assessment and performed the first step of the goodwill impairment test. During the fourth quarter of 2015, the Company changed its annual impairment test date from September 30th to October 1st. The Company believes the change in impairment test date is preferable as it aligns to the quarter in which the Company performs the impairment test, which is during the fourth quarter of each year. This change does not result in any delay, acceleration or avoidance of impairment. The first step of the goodwill impairment test is to compare the fair value of the reporting unit with its carrying value, including goodwill. If the carrying amount of the reporting unit exceeds its fair value then the second step of the goodwill impairment test is performed. The second step of the goodwill impairment test compares the implied fair value of the reporting unit’s goodwill with the carrying amount of that goodwill in order to determine the amount of impairment to be recognized. The implied fair value of goodwill is determined by deducting the fair value of a reporting unit’s identifiable assets and liabilities from the fair value of the reporting unit as a whole. The excess of the carrying value of goodwill above the implied goodwill, if any, would be recognized as an impairment charge in the consolidated income statements. We recorded no goodwill impairments during the years ended December 31, 2015 , 2014 and 2013 . m) Derivative Instruments The Company utilizes derivative financial instruments as part of its overall risk management strategy. The Company recognizes all derivative financial instruments at fair value as either assets or liabilities on the consolidated balance sheets. The accounting for gains and losses associated with changes in the fair value of a derivative and the effect on the consolidated financial statements depends on its hedge designation and whether the hedge is highly effective in achieving offsetting changes in the fair value of the asset or liability hedged. The Company uses currency forward contracts and foreign currency swaps to manage currency exposure. The Company also utilizes various derivative instruments such as interest rate futures, interest rate swaps and index options, for the purpose of managing market exposures, interest rate volatility, portfolio duration, hedging certain investments, or enhancing investment performance. These derivatives are not designated as hedges and accordingly are carried at fair value on the consolidated balance sheets with realized and unrealized gains and losses included in the consolidated income statements. Refer to Note 5 for the Company’s related disclosure. n) Earnings Per Share Basic earnings per share is defined as net income available to common shareholders divided by the weighted average number of common shares outstanding for the period, giving no effect to dilutive securities. Diluted earnings per share is defined as net income available to common shareholders divided by the weighted average number of common and common share equivalents outstanding calculated using the treasury stock method for all potentially dilutive securities, including employee stock options, employee share repurchase plan awards, RSUs and performance-based awards. When the effect of dilutive securities would be anti-dilutive, these securities are excluded from the calculation of diluted earnings per share. o) Treasury Shares Common shares repurchased by the Company and not subsequently canceled are classified as “treasury shares” on the consolidated balance sheets and are recorded at cost. When shares are reissued from treasury the historical cost, based on the first-in, first-out method, is used to determine the cost of the reissued shares. The difference between the cost of the treasury shares and the par value of the common stock shall be first reflected as additional paid-in capital, but to the extent additional paid-in capital is exhausted the remainder shall reduce retained earnings. The issuance of shares out of treasury have been related to vesting equity-based compensation of the Company's employees and directors. p) New Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update 2014-09, “Revenue from Contracts with Customers" (“ASU 2014-09”). ASU 2014-09 provides a framework, through a five-step process, for recognizing revenue from customers, improves comparability and consistency of recognizing revenue across entities, industries, jurisdictions and capital markets, and requires enhanced disclosures. Certain contracts with customers are specifically excluded from the scope of ASU 2014-09, including, among others, insurance contracts accounted for under Accounting Standard Codification 944, Financial Services - Insurance . With the issuance of ASU 2015-14, this standard will be effective on January 1, 2018 with retrospective adoption required for the comparative periods. The Company is currently assessing the impact the adoption of ASU 2014-09 will have on future financial statements and related disclosures. In February 2015, the FASB issued Accounting Standards Update 2015-02, “Amendments to the Consolidation Analysis” (“ASU 2015-02”). ASU 2015-02 amends certain aspects of the consolidation guidance in U.S. GAAP. In particular, it will modify the evaluation of whether limited partnerships and similar legal entities are VIEs or voting interest entities and also eliminates the presumption that a general partner should consolidate a limited partnership, if certain conditions are met. The new guidance will also affect the consolidation analysis of the Company's interests in VIEs, particularly those that have fee arrangements and related party relationships. ASU 2015-02 is effective on January 1, 2016 and adoption is required retrospectively either through a modified retrospective approach by recording a cumulative-effect adjustment to shareholders' equity as of the beginning of the year of adoption or retrospectively for all comparative periods. The Company has determined that the adoption of ASU 2015-02 will result in several of its limited partnership interests meeting the criteria of being considered VIEs. None of the limited partnership interests that will be considered VIE's will be consolidated as the Company is not considered the primary beneficiary. As a result, the Company does not expect any financial statement impact due to the adoption of ASU 2015-02 other than additional disclosures related to the Company's interests in VIEs. In April 2015, the FASB issued Accounting Standards Update 2015-03, “Interest - Imputation of Interest (Subtopic 835-30): Simplifying the Presentation of Debt Issuance Costs” (“ASU 2015-03”). ASU 2015-03 amends existing guidance on the presentation of debt issuance costs in the balance sheets to be recorded as a direct deduction from the carrying amount of the debt liability, consistent with debt discounts. Under existing U.S. GAAP, capitalized debt issuance costs were capitalized as an asset. ASU 2015-03 is effective January 1, 2016, with early application permitted. The Company adopted ASU 2015-03 as of December 31, 2015 and reclassified debt issuance costs from “other assets” to “unamortized discount and debt issuance costs” in the consolidated balance sheets. As a result of the adoption of ASU 2015-03, the amount of debt issuance costs reclassified to “unamortized discount and debt issuance costs” as of December 31, 2014 was $2.7 million . In May 2015, the FASB issued Accounting Standards Update 2015-07, “Fair Value Measurements (Topic 820): Disclosures for Investments in Certain Entities That Calculate Net Asset Value per Share (or Its Equivalent)” (“ASU 2015-07”). ASU 2015-07 removes the requirement to categorize within the fair value hierarchy investments for which fair value is measured using the net asset value per share practical expedient. The Company has applied the net asset value per share practical expedient to all of its private equity and hedge funds in determining fair value. The Company early adopted ASU 2015-07 during the second quarter of 2015, and as a result removed the fair value category for its investments that are measured using the net asset value per share practical expedient that is disclosed in Note 6. In May 2015, the FASB issued Accounting Standards Update 2015-09, “Financial Services - Insurance (Topic 944): Disclosures about Short-Duration Contracts” (“ASU 2015-09”). ASU 2015-09 provides enhanced disclosures, on an annual basis, related to the reserve for losses and loss expenses. The enhanced disclosures required by ASU 2015-09 include (1) net incurred and paid claims development information by accident year, (2) a reconciliation of incurred and paid claims development information to the aggregate carrying amount of the reserve for losses and loss expenses, (3) for each accident year presented of incurred claims development information, the total of reserves for incurred but not reported (IBNR), including expected development on reported claims, included in the reserve for losses and loss expenses and a description of the reserving methodologies and changes to the reserving methodologies, and (4) for each accident year presented of incurred claims development information, quantitative information about claims frequency, as well as a description of methodologies used for determining claim frequency information. ASU 2015-09 is effective fo

Acquisitions

Acquisitions	12 Months Ended
	Dec. 31, 2015
Business Combinations [Abstract]
Acquisitions	ACQUISITIONS a) Hong Kong and Singapore Branches of Royal & Sun Alliance Insurance plc On April 1, 2015, the Company completed its acquisitions of certain assets and assumed certain liabilities of the Hong Kong and Singapore operations of RSA to further expand its international insurance operations. The assets acquired and liabilities assumed constituted a business, and as such the Company accounted for the acquisitions of the RSA branches under the acquisition method in accordance with U.S. GAAP. The consideration for the branches was $176.5 million in cash, after receipt of cash for post-closing adjustments. The post-closing adjustments were based on the net asset value of the acquired branches at the date of acquisitions that resulted in the Company receiving $17.4 million in cash. The Company has incurred a cumulative total of $9.2 million in acquisition related expenses, mostly related to advisory, legal and valuation services rendered, which were recorded in “other expense” in the consolidated income statements in 2014 and 2015. The following table summarizes the consideration paid for the Hong Kong and Singapore branches of RSA and the preliminary amounts of the assets acquired and liabilities assumed at the acquisition date. Consideration: Fair Value Cash consideration $ 176.5 Recognized amounts of identifiable assets acquired and liabilities assumed: Fixed maturity investments 246.1 Cash and cash equivalents 47.1 Insurance balances receivable 114.4 Prepaid reinsurance 17.5 Reinsurance recoverable 58.9 Value of business acquired 28.9 Intangible assets 79.9 Other assets 9.9 Reserve for losses and loss expenses (314.1 ) Unearned premiums (150.5 ) Reinsurance balances payable (35.8 ) Net deferred tax liabilities (11.9 ) Accounts payable and accrued liabilities (20.1 ) Total identifiable net assets acquired 70.3 Goodwill 106.2 Total net assets acquired $ 176.5 Of the $106.2 million of goodwill acquired, $54.7 million and $51.5 million related to the Hong Kong and Singapore branches, respectively. None of the goodwill recorded was deductible for tax purposes. The Company recognized identifiable finite lived intangible assets, including an intangible asset for the value of businesses acquired (“VOBA”), which will be amortized over a weighted average period of 12 years . The Company also recorded an insurance-related intangible liability related to the reserve for loss and loss expenses of $8.3 million that will be amortized over a weighted average period of 8 years , and included in “net losses and loss expenses” in the consolidated income statements. The insurance-related intangible liability related to the reserve for loss and loss expenses was calculated as the additional risk margin less the impact related to discounting the net reserves for losses and loss expenses. Since the fair value adjustment increased the net reserve for losses and loss expenses, it has been recorded as an insurance-related intangible liability. The following is a breakdown of the intangible assets acquired. Singapore Branch Estimated Useful Life Hong Kong Branch Estimated Useful Life Total VOBA $ 17.8 2 years $ 11.1 1.5 years $ 28.9 Customer renewals 8.6 4 years 4.4 5 years 13.0 Distribution channels 47.7 18 years 19.2 18 years 66.9 $ 74.1 $ 34.7 $ 108.8 The following is an explanation of identifiable finite lived intangible assets acquired: • VOBA: Represents the difference between the expected future losses and expenses and the associated unearned premium reserve. This intangible asset will be amortized consistent with how the associated unearned premiums will be earned and will be recorded in “acquisition costs” in the consolidated income statements. • Customer renewals: The value of inforce policies renewing taking into consideration the net cash flows generated from these renewals. The amortization expense for this intangible asset will be recorded in “amortization and impairment of intangible assets” in the consolidated income statements. • Distribution channels: The value of access to contractual and non-contractual relationships (e.g., brokers and affinity relationships) taking into consideration the net cash flows generated from these relationships. The amortization expense for this intangible asset will be recorded in “amortization and impairment of intangible assets” in the consolidated income statements. The following summarizes the results of the Hong Kong and Singapore branches that have been included in the Company’s consolidated income statement since the acquisitions closed on April 1, 2015. From April 1, 2015 to December 31, 2015 Total revenue $ 155.3 Net loss $ (28.9 ) The following unaudited pro forma information presents the combined results of the Company and the acquired Hong Kong and Singapore RSA branches for the years ended December 31, 2015 and 2014, with pro forma adjustments related to the acquisition method of accounting as if the acquisitions had been consummated as of January 1, 2014. This unaudited pro forma information is not necessarily indicative of what would have occurred had the acquisitions and related transactions been made on the dates indicated, or of future results of the Company. Year Ended December 31, 2015 Year Ended December 31, 2014 Total revenue $ 2,594.2 $ 2,681.7 Net income $ 74.2 $ 505.9 b) Acquisition of Labuan branch of RSA On April 30, 2015, the Company also acquired the assets and assumed the liabilities of the Labuan operations of RSA for consideration of one British pound sterling. The Company recorded goodwill of $1.4 million related to this acquisition. c) Acquisition of Latin American Underwriters Holdings, Ltd. In January 2015, the Company acquired Latin American Underwriters Holdings Ltd. (“LAU”) for cash consideration of $5.1 million . LAU had previously underwritten trade credit insurance and political risk coverages solely for the Company since 2010. As part of the acquisition, the Company recorded goodwill of $2.5 million and customer renewal intangibles of $3.6 million , which have a three -year useful life. The Company also recorded $1.0 million of contingent consideration related to certain earn-out payments. During the third quarter of 2015, it was determined that LAU will not achieve any of the earn-out payments. As a result, the Company reduced the fair value of the contingent consideration to zero with the corresponding gain recorded as a reduction in “general and administrative expenses” in the consolidated income statements. See note 10 for additional information regarding an impairment recorded related to the customer renewal intangible asset.

Investments

Investments	12 Months Ended
	Dec. 31, 2015
Investments [Abstract]
Investments	INVESTMENTS a) Trading Securities Securities accounted for at fair value with changes in fair value recognized in the consolidated income statements by category are as follows: December 31, 2015 December 31, 2014 Fair Value Amortized Cost Fair Value Amortized Cost U.S. government and government agencies $ 1,434.0 $ 1,437.9 $ 1,610.5 $ 1,610.9 Non-U.S. government and government agencies 556.8 579.2 188.2 196.3 States, municipalities and political subdivisions 413.5 396.0 170.6 165.6 Corporate debt: Financial institutions 1,275.4 1,277.3 1,024.7 1,018.8 Industrials 1,308.1 1,345.6 1,029.7 1,037.8 Utilities 118.9 125.4 111.0 111.6 Mortgage-backed: Agency mortgage-backed 751.8 745.4 624.4 611.8 Non-agency residential mortgage-backed 34.0 32.4 93.4 68.8 Commercial mortgage-backed 582.8 600.1 545.7 539.1 Asset-backed 726.2 751.1 670.8 674.5 Total fixed maturity investments, trading $ 7,201.5 $ 7,290.6 $ 6,069.0 $ 6,035.2 December 31, 2015 December 31, 2014 Fair Value Cost Fair Value Cost Equity securities $ 403.0 $ 395.3 $ 844.2 $ 791.2 Other invested assets 840.2 770.9 812.5 725.1 $ 1,243.2 $ 1,166.2 $ 1,656.7 $ 1,516.3 Other invested assets, included in the table above, include investments in private equity funds, hedge funds and a high yield loan fund that are accounted for at fair value, but excludes other private securities described below in Note 4(b) that are accounted for using the equity method of accounting. b) Other Invested Assets Details regarding the carrying value, redemption characteristics and unfunded investment commitments of the other invested assets portfolio as of December 31, 2015 and 2014 were as follows: Fund Type Carrying Value as of December 31, 2015 Investments with Redemption Restrictions Estimated Remaining Restriction Period Investments without Redemption Restrictions Redemption Frequency(1) Redemption Notice Period(1) Unfunded Commitments Private equity (primary and secondary) $ 236.4 $ 236.4 1 - 7 Years $ — $ 231.0 Mezzanine debt 205.9 205.9 4 - 8 Years — 179.0 Distressed 5.1 5.1 2 Years — 3.8 Real estate — — 7 - 9 Years — 200.0 Total private equity 447.4 447.4 — 613.8 Distressed 215.6 54.6 2 Years 161.0 Monthly 90 Days — Equity long/short 58.0 — 58.0 Quarterly 45 Days — Relative value credit 105.4 — 105.4 Quarterly 60 Days — Total hedge funds 379.0 54.6 324.4 — High yield loan fund 13.8 — 13.8 Monthly 30 days — Total other invested assets at fair value 840.2 502.0 338.2 613.8 Other private securities 126.5 — 126.5 — Total other invested assets $ 966.7 $ 502.0 $ 464.7 $ 613.8 Fund Type Carrying Value as of December 31, 2014 Investments Estimated Investments Redemption Redemption Unfunded Private equity (primary and secondary) $ 184.5 $ 184.5 2 - 8 Years $ — $ 223.8 Mezzanine debt 166.9 166.9 5 - 9 Years — 204.2 Distressed 5.9 5.9 3 Years — 5.2 Real estate — — 9 Years — 50.0 Total private equity 357.3 357.3 — 483.2 Distressed 170.2 170.2 — Based on net asset value 60 Days — Equity long/short 84.2 — 84.2 Quarterly 30 - 60 Days — Multi-strategy 51.5 — 51.5 Quarterly 45 - 90 Days — Relative value credit 119.1 — 119.1 Quarterly 60 Days — Total hedge funds 425.0 170.2 254.8 — High yield loan fund 30.2 — 30.2 Monthly 30 days — Total other invested assets at fair value 812.5 527.5 285.0 483.2 Other private securities 143.0 — 143.0 — Total other invested assets $ 955.5 $ 527.5 $ 428.0 $ 483.2 (1) The redemption frequency and notice periods only apply to the investments without redemption restrictions. In general, the Company has invested in hedge funds that require at least 30 days' notice of redemption, and may be redeemed on a monthly, quarterly, semi-annual, annual or longer basis, depending on the fund. Certain hedge funds have lock-up periods ranging from one to three years from initial investment. A lock-up period refers to the initial amount of time an investor is contractually required to invest before having the ability to redeem. Funds that provide for periodic redemptions may, depending on the funds’ governing documents, have the ability to deny or delay a redemption request, called a “gate.” The fund may implement this restriction because the aggregate amount of redemption requests as of a particular date exceeds a specified level, generally ranging from 15% to 25% of the fund’s net assets. The gate is a method for executing an orderly redemption process to reduce the possibility of adversely affecting investors in the fund. Typically, the imposition of a gate delays a portion of the requested redemption, with the remaining portion settled in cash sometime after the redemption date. Certain funds may impose a redemption fee on early redemptions. Interests in private equity funds cannot be redeemed because the investments include restrictions that do not allow for redemption until termination of the fund. The following is a summary of each investment type: • Private equity funds: Primary equity funds may invest in companies and general partnership interests. Secondary equity funds buy limited partnership interests from existing limited partners of primary private equity funds. As owners of private equity funds seek liquidity, they can sell their existing investments, plus any remaining commitment, to secondary market participants. These funds cannot be redeemed because the investments include restrictions that do not allow for redemption until termination of the fund. • Mezzanine debt funds: Mezzanine debt funds primarily focus on providing capital to upper middle market and middle market companies and private equity sponsors, in connection with leveraged buyouts, mergers and acquisitions, recapitalizations, growth financings and other corporate transactions. The most common position in the capital structure will be between the senior secured debt holder and the equity; however, the funds will utilize a flexible approach when structuring investments, which may include secured debt, subordinated debt, preferred stock and/or private equity. These funds cannot be redeemed because the investments include restrictions that do not allow for redemption until termination of the fund. • Distressed funds: In distressed debt investing, managers take positions in the debt of companies experiencing significant financial difficulties, including bankruptcy, or in certain positions of the capital structure of structured securities. The manager relies on the fundamental analysis of these securities, including the claims on the assets and the likely return to bondholders. Certain funds cannot be redeemed because the investments include restrictions that do not allow for redemption until termination of the fund. • Real estate funds: Private real estate funds invest directly in commercial real estate (multifamily units, industrial buildings, office spaces, and retail stores) and some residential property. Real estate managers have diversified portfolios that generally follow core, core-plus, value-added, or opportunistic strategies. These funds cannot be redeemed because the investments include restrictions that do not allow for redemption until termination of the fund. • Equity long/short funds: In equity long/short funds, managers take long positions in companies they deem to be undervalued and short positions in companies they deem to be overvalued. Long/short managers may invest in countries, regions or sectors and vary by their use of leverage and by their targeted net long position. • Multi-strategy funds: These funds may utilize many strategies employed by specialized funds including distressed investing, equity long/short, merger arbitrage, convertible arbitrage, fixed income arbitrage and macro trading. • Relative value credit funds: These funds seek to take exposure to credit-sensitive securities, long and/or short, based upon credit analysis of issuers and securities and credit market views. • Other private securities: These securities include strategic non-controlling minority investments in private asset management companies, claims handling companies and other service companies related to the insurance industry. c) Net Investment Income Year Ended December 31, 2015 2014 2013 Fixed maturity investments 164.2 149.5 130.4 Equity securities 13.3 17.6 19.1 Other invested assets: hedge funds and private equity 19.6 12.6 8.2 Other invested assets: other private securities 2.8 13.3 14.7 Cash and cash equivalents 1.7 2.1 2.0 Expenses (19.5 ) (18.2 ) (16.8 ) Net investment income 182.1 176.9 157.6 Net investment income from other invested assets: other private securities included the distributed and undistributed net income from investments accounted for using the equity method of accounting. The income reported for other invested assets: other private securities for the year ended December 31, 2015 included an other-than-temporary impairment of $6.3 million recorded in the second quarter of 2015 related to one of the Company's equity method investments. The Company recorded the other-than-temporary impairment as the fair value of this investment was below its carrying value. The income reported for other invested assets: other private securities for the year ended December 31, 2014 included a loss of $9.3 million recorded for an equity method investment due to impairment charges that it recorded. At the time, the Company determined the fair value of this investment and concluded that the fair value exceeded the Company's carrying value and as such no other-than-temporary impairment was recorded. d) Components of Realized Gains and Losses Year Ended December 31, 2015 2014 2013 Gross realized gains on sale of invested assets $ 180.3 $ 195.4 $ 213.6 Gross realized losses on sale of invested assets (106.4 ) (48.2 ) (106.3 ) Net realized and unrealized (losses) gains on derivatives (15.4 ) (39.0 ) 9.5 Mark-to-market (losses) gains: Debt securities, trading (126.3 ) (1.7 ) (117.6 ) Equity securities, trading (41.7 ) 0.4 4.3 Other invested assets, trading (18.1 ) (17.9 ) 56.0 Net realized investment (losses) gains $ (127.6 ) $ 89.0 $ 59.5 e) Pledged Assets As of December 31, 2015 and 2014 , $2,748.9 million and $3,585.8 million , respectively, of cash and cash equivalents and investments were deposited, pledged or held in trust accounts in favor of ceding companies and other counterparties or government authorities to comply with reinsurance contract provisions and insurance laws. In addition, as of December 31, 2015 and 2014 , a further $579.3 million and $571.8 million , respectively, of cash and cash equivalents and investments were pledged as collateral for the Company’s letter of credit facilities. See Note 11(g) for details on the Company’s credit facilities.

Derivative Instruments

Derivative Instruments	12 Months Ended
	Dec. 31, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative instruments	DERIVATIVE INSTRUMENTS As of December 31, 2015 and 2014 , none of the Company’s derivatives were designated as hedges for accounting purposes. The following table summarizes information on the location and amounts of derivative fair values on the consolidated balance sheets: December 31, 2015 December 31, 2014 Asset Derivative Notional Amount Asset Derivative Fair Value Liability Derivative Notional Amount Liability Derivative Fair Value Asset Derivative Notional Amount Asset Derivative Fair Value Liability Derivative Notional Amount Liability Derivative Fair Value Foreign exchange contracts $ 41.1 $ 0.1 $ 244.8 $ 3.0 $ 33.9 $ 1.3 $ 167.4 $ 1.0 Interest rate swaps — — 328.2 0.5 — — 571.5 0.7 Total derivatives $ 41.1 $ 0.1 $ 573.0 $ 3.5 $ 33.9 $ 1.3 $ 738.9 $ 1.7 Derivative assets and derivative liabilities are classified within “other assets” or “accounts payable and accrued liabilities” on the consolidated balance sheets. The following table provides the net realized and unrealized (losses) gains on derivatives not designated as hedges recorded on the consolidated income statements: Year Ended December 31, 2015 2014 2013 Foreign exchange contracts $ (7.3 ) $ 0.9 $ 1.3 Total included in foreign exchange loss (7.3 ) 0.9 1.3 Put options — 0.5 (3.8 ) Foreign exchange contracts 0.2 3.5 3.0 Interest rate swaps (13.4 ) (45.4 ) 5.6 Interest rate futures (2.2 ) 2.4 4.7 Total included in net realized investment (losses) gains (15.4 ) (39.0 ) 9.5 Total realized and unrealized (losses) gains on derivatives $ (22.7 ) $ (38.1 ) $ 10.8 The losses related to interest rate swap contracts for the years ended December 31, 2015 and 2014 were the result of selling interest rate swap contracts to reduce the duration of the investment portfolio. Given the decrease in interest rates during the year, the Company recorded a loss related to these interest rate swap contracts. Derivative Instruments Not Designated as Hedging Instruments The Company is exposed to foreign currency risk in its investment portfolio. Accordingly, the fair values of the Company’s investment portfolio are partially influenced by the change in foreign exchange rates. These foreign currency hedging activities have not been designated as specific hedges for financial reporting purposes. The Company’s insurance and reinsurance subsidiaries and branches operate in various foreign countries and consequently the Company’s underwriting portfolio is exposed to foreign currency risk. The Company manages foreign currency risk by seeking to match liabilities under the insurance policies and reinsurance contracts that it writes and that are payable in foreign currencies with cash and investments that are denominated in such currencies. When necessary, the Company may also use derivatives to economically hedge unmatched foreign currency exposures, specifically forward contracts and currency options. For example, during 2014 the Company purchased a forward contract to economically hedge a portion of its foreign currency exposure related to the consideration to be paid for the Hong Kong and Singapore operations of RSA. The Company also purchases and sells interest rate future and interest rate swap contracts to actively manage the duration and yield curve positioning of its fixed income portfolio. Interest rate futures and interest rate swaps can efficiently increase or decrease the overall duration of the portfolio. Additionally, interest rate future and interest rate swap contracts can be utilized to obtain the desired position along the yield curve in order to protect against certain future yield curve shapes. The Company also purchases options to actively manage the Company’s equity portfolio.

Fair Value Of Financial Instrum

Fair Value Of Financial Instruments	12 Months Ended
	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Fair value of financial instruments	FAIR VALUE OF FINANCIAL INSTRUMENTS In accordance with U.S. GAAP, fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. There is a three-level valuation hierarchy for disclosure of fair value measurements. The valuation hierarchy is based upon whether the inputs to the valuation of an asset or liability are observable or unobservable in the market at the measurement date, with quoted market prices being the highest level (Level 1) and unobservable inputs being the lowest level (Level 3). A fair value measurement will fall within the level of the hierarchy based on the input that is significant to determining such measurement. The three levels are defined as follows: • Level 1 : Observable inputs to the valuation methodology that are quoted prices (unadjusted) for identical assets or liabilities in active markets. • Level 2 : Observable inputs to the valuation methodology other than quoted market prices (unadjusted) for identical assets or liabilities in active markets. Level 2 inputs include quoted prices for similar assets and liabilities in active markets, quoted prices for identical assets in markets that are not active and inputs other than quoted prices that are observable for the asset or liability, either directly or indirectly, for substantially the full term of the asset or liability. • Level 3 : Inputs to the valuation methodology that are unobservable for the asset or liability. The following table shows the fair value of the Company’s financial instruments and where in the fair value hierarchy the fair value measurements are included as of the dates indicated below: December 31, 2015 Carrying amount Total fair value Level 1 Level 2 Level 3 ASSETS: Fixed maturity investments: U.S. government and government agencies $ 1,434.0 $ 1,434.0 $ 1,396.4 $ 37.6 $ — Non-U.S. government and government agencies 556.8 556.8 — 556.8 — States, municipalities and political subdivisions 413.5 413.5 — 413.5 — Corporate debt: Financial institutions 1,275.4 1,275.4 — 1,275.4 — Industrials 1,308.1 1,308.1 — 1,308.1 — Utilities 118.9 118.9 — 118.9 — Mortgage-backed: Agency mortgage-backed 751.8 751.8 — 650.8 101.1 Non-agency residential mortgage-backed 34.0 34.0 — 29.0 5.0 Commercial mortgage-backed 582.8 582.8 — 582.8 — Asset-backed 726.2 726.2 — 663.2 63.0 Total fixed maturity investments 7,201.5 7,201.5 1,396.4 5,636.1 169.1 Equity securities 403.0 403.0 403.0 — — Other invested assets (1) 840.2 840.2 — — — Total investments $ 8,444.7 $ 8,444.7 $ 1,799.4 $ 5,636.1 $ 169.1 Derivative assets: Foreign exchange contracts $ 0.1 $ 0.1 $ — $ 0.1 $ — LIABILITIES: Derivative liabilities: Foreign exchange contracts $ 3.0 $ 3.0 $ — $ 3.0 $ — Interest rate swaps 0.5 0.5 — 0.5 — Senior notes $ 1,292.9 $ 1,337.9 $ — $ 1,337.9 $ — Other long-term debt $ 23.0 $ 27.7 $ — $ 27.7 $ — December 31, 2014 Carrying amount Total fair value Level 1 Level 2 Level 3 ASSETS: Fixed maturity investments: U.S. government and government agencies $ 1,610.5 $ 1,610.5 $ 1,499.3 $ 111.2 $ — Non-U.S. government and government agencies 188.2 188.2 — 188.2 — States, municipalities and political subdivisions 170.6 170.6 — 170.6 — Corporate debt Financial institutions 1,024.7 1,024.7 — 1,024.7 — Industrials 1,029.7 1,029.7 — 1,029.7 — Utilities 111.0 111.0 — 111.0 — Mortgage-backed Agency mortgage-backed 624.4 624.4 — 444.3 180.1 Non-agency residential mortgage-backed 93.4 93.4 — 93.4 — Commercial mortgage-backed 545.7 545.7 — 544.0 1.7 Asset-backed 670.8 670.8 — 615.4 55.4 Total fixed maturity investments 6,069.0 6,069.0 1,499.3 4,332.5 237.2 Equity securities 844.2 844.2 800.9 — 43.3 Other invested assets (1) 812.5 812.5 — — — Total investments $ 7,725.7 $ 7,725.7 $ 2,300.2 $ 4,332.5 $ 280.5 Derivative assets: Foreign exchange contracts $ 1.3 $ 1.3 $ — $ 1.3 $ — LIABILITIES: Derivative liabilities: Foreign exchange contracts $ 1.0 $ 1.0 $ — $ 1.0 $ — Interest rate swaps 0.7 0.7 $ — 0.7 $ — Senior notes $ 796.1 $ 879.3 $ — $ 879.3 $ — Other long-term debt $ 19.2 $ 22.6 $ — $ 22.6 $ — (1) In accordance with U.S. GAAP, other invested assets, excluding other private securities, are measured at fair value using the net asset value per share (or its equivalent) practical expedient and have not been classified in the fair value hierarchy. The following describes the valuation techniques used by the Company to determine the fair value of financial instruments held as of the balance sheet date. Fair Value of Financial Instruments U.S. government and government agencies: Comprised primarily of bonds issued by the U.S. Treasury, the Federal Home Loan Bank, the Federal Home Loan Mortgage Corporation and the Federal National Mortgage Association. The fair values of the Company’s U.S. government securities are based on quoted market prices in active markets and are included in the Level 1 fair value hierarchy. The Company believes the market for U.S. Treasury securities is an actively traded market given the high level of daily trading volume. The fair values of U.S. government agency securities are priced using the spread above the risk-free yield curve. As the yields for the risk-free yield curve and the spreads for these securities are observable market inputs, the fair values of U.S. government agency securities are included in the Level 2 fair value hierarchy. Non-U.S. government and government agencies: Comprised of fixed income obligations of non-U.S. governmental entities. The fair values of these securities are based on prices obtained from international indices and are included in the Level 2 fair value hierarchy. States, municipalities and political subdivisions: Comprised of fixed income obligations of U.S. domiciled state and municipality entities. The fair values of these securities are based on prices obtained from the new issue market, and are included in the Level 2 fair value hierarchy. Corporate debt: Comprised of bonds issued by or loan obligations of corporations that are diversified across a wide range of issuers and industries. The fair values of corporate debt that are short-term are priced using spread above the LIBOR yield curve, and the fair value of corporate debt that are long-term are priced using the spread above the risk-free yield curve. The spreads are sourced from broker-dealers, trade prices and the new issue market. As the significant inputs used to price corporate debt are observable market inputs, the fair values of corporate debt are included in the Level 2 fair value hierarchy. Mortgage-backed: Primarily comprised of residential and commercial mortgages originated by both U.S. government agencies (such as the Federal National Mortgage Association) and non-U.S. government agencies. The fair values of mortgage-backed securities originated by U.S. government agencies and non-U.S. government agencies are based on a pricing model that incorporates prepayment speeds and spreads to determine appropriate average life of mortgage-backed securities. The spreads are sourced from broker-dealers, trade prices and the new issue market. As the significant inputs used to price the mortgage-backed securities are observable market inputs, the fair values of these securities are included in the Level 2 fair value hierarchy, unless the significant inputs used to price the mortgage-backed securities are broker-dealer quotes and the Company is not able to determine if those quotes are based on observable market inputs, in which case the fair value is included in the Level 3 hierarchy. Asset-backed: Principally comprised of bonds backed by pools of automobile loan receivables, home equity loans, credit card receivables and collateralized loan obligations originated by a variety of financial institutions. The fair values of asset-backed securities are priced using prepayment speed and spread inputs that are sourced from the new issue market or broker-dealer quotes. As the significant inputs used to price the asset-backed securities are observable market inputs, the fair values of these securities are included in the Level 2 fair value hierarchy, unless the significant inputs used to price the asset-backed securities are broker-dealer quotes and the Company is not able to determine if those quotes are based on observable market inputs, in which case the fair value is included in the Level 3 hierarchy. Equity securities: Comprised of U.S. and foreign common and preferred stocks and mutual funds. Equities are generally included in the Level 1 fair value hierarchy as prices are obtained from market exchanges in active markets. Non-U.S. mutual funds where the net asset value (“NAV”) is not provided on a daily basis are included in the Level 3 fair value hierarchy. Other invested assets: Comprised of funds invested in a range of diversified strategies. In accordance with U.S. GAAP, the fair values of the funds are based on the NAV of the funds as reported by the fund manager. Derivative instruments: The fair value of foreign exchange contracts and interest rate futures and swaps are priced from quoted market prices for similar exchange-traded derivatives and pricing valuation models that utilize independent market data inputs. The fair value of derivatives are included in the Level 2 fair value hierarchy. Senior notes: The fair value of the senior notes is based on reported trades. The fair value of the senior notes is included in the Level 2 fair value hierarchy. Other long-term debt: Comprised of the mortgage and credit facility associated with the purchase of office space in Switzerland. The fair value of the other long-term debt is based on the value of the debt using current interest rates. The fair value of the long-term debt is included in the Level 2 fair value hierarchy. Non-recurring Fair Value of Financial Instruments The Company measures the fair value of certain assets on a non-recurring basis, generally quarterly, annually, or when events or changes in circumstances indicate that the carrying amount of the assets may not be recoverable. These assets include investments accounted for using the equity method, goodwill and intangible assets. The Company uses a variety of techniques to measure the fair value of these assets when appropriate, as described below: Investments accounted for using the equity method: When the Company determines that the carrying value of these assets may not be recoverable, the Company records the assets at fair value with the loss recognized in income. In such cases, the Company measures the fair value of these assets using the techniques discussed above. Goodwill and intangible assets: The Company tests goodwill and intangible assets for impairment whenever events or changes in circumstances indicate that the carrying amount may not be recoverable, but at least annually for goodwill and indefinite-lived intangibles. When the Company determines that goodwill and indefinite-lived intangible assets may be impaired, the Company uses techniques, including discounted expected future cash flows and market multiple models, to measure fair value. Rollforward of Level 3 Financial Instruments The following is a rollforward of the beginning and ending balance of financial instruments using significant unobservable inputs (Level 3): Fair value measurement using significant unobservable inputs (Level 3): Agency MBS Non-agency RMBS CMBS Total mortgage- Asset-backed Equities Balance at December 31, 2013 $ 136.5 $ 9.3 $ 1.6 $ 147.4 $ 93.4 $ 73.9 Realized and unrealized gains (losses) included in net income 5.1 0.4 — 5.5 (2.1 ) (1.3 ) Purchases 98.4 0.1 1.5 100.0 4.7 — Sales (61.4 ) (9.8 ) — (71.2 ) (24.5 ) (29.3 ) Transfers into Level 3 from Level 2 1.5 — — 1.5 28.8 — Transfers out of Level 3 into Level 2 (1) — — (1.4 ) (1.4 ) (44.9 ) — Balance at December 31, 2014 $ 180.1 $ — $ 1.7 $ 181.8 $ 55.4 $ 43.3 Realized and unrealized gains (losses) included in net income (1.0 ) (0.1 ) 0.1 (1.0 ) (6.1 ) 3.5 Purchases 17.7 5.2 1.8 24.7 18.4 — Sales (95.7 ) (0.1 ) (3.6 ) (99.4 ) (23.1 ) (46.8 ) Transfers into Level 3 from Level 2 — — — — 37.3 — Transfers out of Level 3 into Level 2 (1) — — — — (18.9 ) — Balance at December 31, 2015 $ 101.1 $ 5.0 $ — $ 106.1 $ 63.0 $ — Realized and unrealized losses (gains) included in net income for investments still held as of December 31, 2015 $ (1.5 ) $ (0.1 ) $ — $ (1.6 ) $ (0.3 ) $ — Realized and unrealized gains (losses) included in net income for investments still held as of December 31, 2014 $ 4.3 $ — $ — $ 4.3 $ (0.1 ) $ (1.3 ) (1) Transfers out of Level 3 are primarily attributable to the availability of market observable information. The Company attempts to verify the significant inputs used by broker-dealers in determining the fair value of the securities priced by them. If the Company could not obtain sufficient information to determine if the broker-dealers were using significant observable inputs, such securities have been transferred to the Level 3 fair value hierarchy. The Company believes the prices obtained from the broker-dealers are the best estimate of fair value of the securities being priced as the broker-dealers are typically involved in the initial pricing of the security, and the Company has compared the price per the broker-dealer to other pricing sources and noted no material differences. The Company recognizes transfers between levels at the end of the reporting period. There were no transfers between Level 1 and Level 2 during the period. The Company’s external investment accounting service provider receives prices from internationally recognized independent pricing services to measure the fair values of its fixed maturity investments. Pricing sources are evaluated and selected in a manner to ensure that the most reliable sources are used. The independent pricing sources obtain market quotations and actual transaction prices for securities that have quoted prices in active markets. Each pricing service has its own proprietary method for determining the fair value of securities that are not actively traded. In general, these methods involve the use of “matrix pricing” in which the independent pricing service uses observable market inputs, including, but not limited to, reported trades, benchmark yields, broker-dealer quotes, interest rates, prepayment speeds, default rates and such other inputs as are available from market sources to determine a reasonable fair value. All of the Company’s securities classified as Level 3 are valued based on unadjusted broker-dealer quotes. This includes less liquid securities such as lower quality asset-backed securities, commercial mortgage-backed securities and residential mortgage-backed securities. The primary valuation inputs include monthly payment information, the probability of default, loss severity rates and estimated prepayment rates. Significant changes in these inputs in isolation would result in a significantly lower or higher fair value measurement. In general, a change in the assumption of the probability of default is accompanied by a directionally similar change in the assumption used for the loss severity in an event of default and prepayment rates. The Company records the unadjusted price provided and validates this price through a process that includes, but is not limited to monthly and/or quarterly: (i) comparison of prices between two independent sources, with significant differences requiring additional price sources; (ii) quantitative analysis (e.g., comparing the quarterly return for each managed portfolio to their target benchmark, with significant differences identified and investigated); (iii) evaluation of methodologies used by external parties to calculate fair value, including a review of the inputs used for pricing; (iv) comparing the price to the Company’s knowledge of the current investment market; and (v) back-testing, which includes randomly selecting purchased or sold securities and comparing the executed prices to the fair value estimates from the pricing service. In addition to internal controls, management relies on the effectiveness of the valuation controls in place at the Company’s external investment accounting service provider (supported by a Statement on Standards for Attestation Engagements No. 16 report) in conjunction with regular discussion and analysis of the investment portfolio’s structure and performance.

Reserve For Losses And Loss Exp

Reserve For Losses And Loss Expenses	12 Months Ended
	Dec. 31, 2015
Insurance Loss Reserves [Abstract]
Reserve for losses and loss expenses	RESERVE FOR LOSSES AND LOSS EXPENSES The reserve for losses and loss expenses consists of the following: December 31, 2015 2014 Outstanding loss reserves $ 1,678.5 $ 1,514.1 Reserves for losses incurred but not reported 4,777.7 4,367.1 Reserve for losses and loss expenses $ 6,456.2 $ 5,881.2 The table below is a reconciliation of the beginning and ending liability for unpaid losses and loss expenses. Losses incurred and paid are reflected net of reinsurance recoverables. Year Ended December 31, 2015 2014 2013 Gross liability at beginning of year 5,881.2 5,766.5 5,645.5 Reinsurance recoverable at beginning of year (1,340.3 ) (1,234.5 ) (1,141.1 ) Net liability at beginning of year 4,540.9 4,532.0 4,504.4 Acquisition of net reserves for losses and loss expenses 259.3 — — Net losses incurred related to: Current year 1,667.9 1,411.8 1,303.5 Prior years (81.6 ) (212.6 ) (180.3 ) Total incurred 1,586.3 1,199.2 1,123.2 Net paid losses related to: Current year 186.0 171.8 115.7 Prior years 1,201.6 1,001.5 974.0 Total paid 1,387.6 1,173.3 1,089.7 Foreign exchange revaluation and other (22.7 ) (17.0 ) (6.0 ) Net liability at end of year 4,976.2 4,540.9 4,532.0 Reinsurance recoverable at end of year 1,480.0 1,340.3 1,234.5 Gross liability at end of year 6,456.2 5,881.2 5,766.5 The net reserve for losses and loss expenses acquired of $259.3 million represents the net reserves acquired from the Hong Kong and Singapore branches of RSA of $255.2 million and the net reserves from the Labuan branch of RSA of $4.1 million . For the year ended December 31, 2015, the Company recognized net favorable prior year reserve development primarily due to lower than expected loss emergence in the Global Markets Insurance and Reinsurance segments and net unfavorable prior year reserve development in the North American Insurance segment . The net favorable reserve development in the Global Markets Insurance segment was primarily due to net favorable loss reserve development in the property, professional liability and casualty lines of business, partially offset by unfavorable prior year reserve development in the specialty and other line of business from the 2013 loss year. T he net favorable reserve development in the Reinsurance segment was primarily related to the property and casualty reinsurance lines of business. The net unfavorable prior year reserve development for the North American Insurance segment primarily related to net unfavorable prior year development in the healthcare and casualty lines of business mainly from the 2012 through 2014 loss years partially offset by favorable prior year reserve development in the professional liability, programs and property lines of business. For the year ended December 31, 2014, the Company recognized net favorable reserve development in each of its operating segments due to actual loss emergence being lower than initially expected. The net favorable prior year reserve development in the North American Insurance segment primarily related to the 2006, 2007, 2009 and 2010 loss years partially offset by unfavorable reserve development from the 2011 to 2013 loss years. The net favorable prior year reserve development in the Global Markets Insurance segment was primarily due to favorable reserve development for the 2008 to 2010 loss years. The net favorable reserve development in the Reinsurance segment was primarily due to benign global property catastrophe activity for the 2013 loss year. For the year ended December 31, 2013, the Company recognized net favorable reserve development in each of its operating segments due to actual loss emergence being lower than initially expected. The net favorable prior year reserve development in the North American Insurance segment primarily related to the 2006 through 2008 loss years partially offset by unfavorable reserve development from the 2010 and 2011 loss years. The net favorable prior year reserve development in the Global Markets Insurance segment was primarily due to favorable reserve development for the 2006 to 2008 loss years. The net favorable prior year reserve development in the Reinsurance segment was primarily due to favorable reserve development for the 2005 to 2008 loss years. While the Company has experienced favorable development in its insurance and reinsurance lines, there is no assurance that conditions and trends that have affected the development of liabilities in the past will continue. It is not appropriate to extrapolate future redundancies based on prior years’ development. The methodology of estimating loss reserves is periodically reviewed to ensure that the key assumptions used in the actuarial models continue to be appropriate.

Ceded Reinsurance

Ceded Reinsurance	12 Months Ended
	Dec. 31, 2015
Reinsurance Disclosures [Abstract]
Ceded reinsurance	CEDED REINSURANCE The Company purchases reinsurance from third-party reinsurance companies to reduce its net exposure to losses. Reinsurance provides for recovery of a portion of gross losses and loss expenses from these reinsurers. The Company remains liable to the extent that its reinsurers do not meet their obligations under the related reinsurance contracts. The Company therefore regularly evaluates the financial condition of its reinsurers and monitors concentration of credit risk. The Company believes that as of December 31, 2015 , its reinsurers are able to meet, and will meet, all of their obligations under the agreements. The Company recorded a provision for unrecoverable reinsurance as of December 31, 2015 and 2014 of $1.2 million and nil , respectively. The amount of reinsurance recoverable is as follows: 2015 2014 OSLR recoverable $ 254.6 $ 232.6 IBNR recoverable 1,225.4 1,107.7 Reinsurance recoverable $ 1,480.0 $ 1,340.3 Reinsurance recoverable on paid losses $ 96.4 $ 86.1 Direct, assumed and ceded premiums written and earned and losses and loss expenses incurred are as follows: Premiums Written Premiums Earned Losses and Loss Expenses Year Ended December 31, 2015 Direct $ 2,291.6 $ 2,255.3 $ 1,471.6 Assumed 801.4 863.6 442.8 Ceded (645.0 ) (630.5 ) (328.1 ) $ 2,448.0 $ 2,488.4 $ 1,586.3 Year Ended December 31, 2014 Direct $ 1,996.8 $ 1,835.1 $ 1,031.3 Assumed 938.6 941.2 464.7 Ceded (613.4 ) (593.6 ) (296.8 ) $ 2,322.0 $ 2,182.7 $ 1,199.2 Year Ended December 31, 2013 Direct $ 1,804.9 $ 1,664.4 $ 936.1 Assumed 933.8 896.1 430.6 Ceded (618.2 ) (554.6 ) (243.5 ) $ 2,120.5 $ 2,005.9 $ 1,123.2 Of the premiums ceded during the years ended December 31, 2015 , 2014 and 2013 , approximately 41.1% , 42.3% and 45.3% were ceded to four reinsurers, respectively. The Company actively manages its reinsurance exposures by generally selecting reinsurers having a credit rating of “A-” or higher and monitoring the overall credit quality of its reinsurers to ensure the recoverables will be collected. December 31, 2015 A.M. Best Reinsurance Recoverable Percentage of Total Prepaid Reinsurance (1) Percentage of Total Munich Re A+ $ 307.9 20.8 % $ 61.7 15.7 % Axis Capital A+ 150.8 10.2 % 32.2 8.2 % Arch Re A+ 115.3 7.8 % 16.0 4.1 % Swiss Re A+ 103.9 7.0 % 57.3 14.6 % RenaissanceRe A+ 94.0 6.4 % 8.0 2.0 % Top five reinsurers 771.9 52.2 % 175.2 44.6 % Other reinsurers’ balances 708.1 47.8 % 217.1 55.4 % Total reinsurance recoverable $ 1,480.0 100.0 % $ 392.3 100.0 % December 31, 2014 A.M. Best Rating Reinsurance Recoverable Percentage of Total Prepaid Reinsurance (1) Percentage of Total Munich Re A+ $ 285.9 21.3 % $ 69.4 19.2 % Axis Capital A+ 148.4 11.1 % 35.5 9.9 % Arch Re A+ 128.4 9.6 % 17.0 4.7 % RenaissanceRe A+ 103.4 7.7 % 12.3 3.4 % Swiss Re A+ 66.9 5.0 % 41.8 11.6 % Top five reinsurers 733.0 54.7 % 176.0 48.8 % Other reinsurers’ balances 607.3 45.3 % 184.7 51.2 % Total reinsurance recoverable $ 1,340.3 100.0 % $ 360.7 100.0 % (1) Prepaid reinsurance represents unearned premiums ceded to reinsurance companies. Approximately 99% of ceded reserves were recoverable from reinsurers who had an A.M. Best rating of “A” or higher as of December 31, 2015 and 2014 .

Funds Held

Funds Held	12 Months Ended
	Dec. 31, 2015
Other Insurance Industry Disclosures [Abstract]
Funds held	FUNDS HELD The Company has a minority interest in Aeolus Capital Management Ltd. (“ACM”), an affiliate of Aeolus Re, Ltd., a Bermuda-based property catastrophe reinsurer (“Aeolus Re”), which it accounts for under the equity method. ACM manages capital on behalf of investors seeking to invest in the property catastrophe reinsurance market. The Company has also entered into a collateralized property catastrophe quota share reinsurance contract with Aeolus Re, whereby the Company assumes property catastrophe business underwritten by Aeolus Re. As part of the agreement to purchase the minority interest in ACM, the Company provided a multi-year capital commitment to support the business being underwritten by Aeolus Re. To the extent that capital is not utilized to support the business being underwritten by Aeolus Re, as all obligations have been settled, the capital is returned to the Company. To the extent the losses are in excess of the premiums written, the capital is utilized to pay the claims. The capital commitment is recorded in "funds held" on the consolidated balance sheets. The funds held balance as of December 31, 2015 and 2014 was $622.4 million and $708.0 million , respectively. For the years ended December 31, 2015 , 2014 and 2013 , the premiums written assumed by the Company through the collateralized property catastrophe quota share reinsurance contract with Aeolus Re were $76.3 million , $87.3 million and $83.3 million , respectively.

Goodwill and Intangible Assets

Goodwill and Intangible Assets	12 Months Ended
	Dec. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and intangible assets	GOODWILL AND INTANGIBLE ASSETS The following table shows the Company’s goodwill and intangible assets at December 31, 2015 and 2014 : Goodwill Indefinite-Lived Intangible Assets Finite-Lived Intangible Assets Net Carrying Value Net Carrying Value Gross Carrying Value Accumulated Amortization Net Carrying Value Balance at December 31, 2013 $ 268.4 $ 23.9 $ 41.3 $ (16.4 ) $ 24.9 Additions 9.9 — — — — Amortization of intangible assets — — — (2.5 ) (2.5 ) Balance at December 31, 2014 278.3 23.9 41.3 (18.9 ) 22.4 Additions 110.1 — 83.5 — 83.5 Impairments — — (1.4 ) — (1.4 ) Amortization of intangible assets — — — (8.3 ) (8.3 ) Foreign currency translation adjustment (0.3 ) — (3.5 ) — (3.5 ) Balance at December 31, 2015 $ 388.1 $ 23.9 $ 119.9 $ (27.2 ) $ 92.7 The additions to goodwill, during the year ended December 31, 2014, related to the Company acquisition of the remaining interest in a claims administration services company it did not own. The goodwill related to this acquisition has been allocated to the U.S. direct insurance operations of the North American Insurance segment. The additions to goodwill and finite-lived intangible assets, during the year ended December 31, 2015, related to the acquisitions of the Hong Kong, Singapore and Labuan branches of RSA and the acquisition of LAU. The goodwill and finite-lived intangible assets related to these acquisitions have been allocated to the Global Markets Insurance segment. The impairment to the finite-lived intangible assets, during the year ended December 31, 2015, related to the customer renewal intangibles from the acquisition of LAU. The trade credit business that is underwritten by LAU underperformed during the current year due to increased frequency of reported losses and as a result the Company took actions to non-renew certain accounts and as a result the customer renewal intangible asset was impaired by $1.4 million and was recorded in “amortization and impairment of intangible assets” in the consolidated income statements. As of December 31, 2015 , goodwill of $274.3 million , $109.9 million and $3.9 million was allocated to the North American Insurance segment, Global Markets Insurance segment and Reinsurance segment, respectively. The impairment reviews for goodwill and indefinite-lived intangibles did not result in the recognition of impairment losses for the years ended December 31, 2015 , 2014 and 2013 . The net carrying value of the goodwill is net of accumulated impairment charges of $0.2 million that occurred prior to December 31, 2013 . As of December 31, 2015 , the net carrying value of the finite-lived intangible assets is net of accumulated impairment charges of $8.2 million . As of December 31, 2015 , the net carrying value of the finite-lived intangible assets is comprised of distribution network intangible assets of $81.0 million and customer renewal intangible assets of $11.7 million . As of December 31, 2014 , the net carrying value of the finite-lived intangible assets of $22.4 million was all related to distribution network intangibles. The remaining finite-lived intangible assets as of December 31, 2015 will be amortized over an expected remaining useful life of 13.6 years . The distribution network intangible asset will be amortized over an expected remaining useful life of 15.0 years , and the customer renewal intangible asset will be amortized over an expected remaining useful life of 3.4 years . The estimated amortization expense for each of the five succeeding fiscal years and thereafter related to the Company’s finite-lived intangible assets is as follows: Amount 2016 $ 9.5 2017 9.5 2018 8.9 2019 7.3 2020 6.2 2021 and thereafter 51.3 Total $ 92.7

Debt and Financing Arrangements

Debt and Financing Arrangements	12 Months Ended
	Dec. 31, 2015
Debt Disclosure [Abstract]
Debt and financing arrangements	DEBT AND FINANCING ARRANGEMENTS a) Financing Structure The following table shows the Company’s financing structure: Outstanding(1) Unamortized discount and debt issuance costs Balance(2) December 31, 2015 2006 Senior notes due 2016 (discount is based on imputed interest rate of 3.77%) $ 500.0 $ 0.5 $ 499.5 2010 Senior notes due 2020 (discount is based on imputed interest rate of 2.78%) 300.0 2.3 297.7 2015 Senior notes due 2025 (discount is based on imputed interest rate of 2.18%) 500.0 4.3 495.7 Swiss office building mortgage 17.9 — 17.9 Swiss office building credit facility 5.1 — 5.1 $1,000 million Secured letter of credit facility — uncommitted 507.5 — — $150 million Secured letter of credit facility — committed — — — $ 1,830.5 $ 7.1 $ 1,315.9 December 31, 2014 2006 Senior notes due 2016 (discount is based on imputed interest rate of 3.77%) $ 500.0 $ 1.2 $ 498.8 2010 Senior notes due 2020 (discount is based on imputed interest rate of 2.78%) 300.0 2.7 297.3 Swiss office building mortgage 14.2 — 14.2 Swiss office building credit facility 5.1 — 5.1 $1,000 million Secured letter of credit facility — uncommitted 497.3 — — $150 million Secured letter of credit facility — committed — — — $ 1,316.6 $ 3.9 $ 815.4 (1) Indicates utilization of commitment amount, not drawn borrowings. (2) Represents the principal amount borrowed, net of unamortized discount and debt issuance costs. b) 2006 Senior Notes Due 2016 In 2006, Allied World Assurance Company Holdings, Ltd, a Bermuda company (“Allied World Bermuda”) issued $500.0 million aggregate principal amount of 7.50% Senior Notes due August 1, 2016 (the “2006 Senior Notes”), with interest payable semi-annually . The 2006 Senior Notes are Allied World Bermuda’s unsecured and unsubordinated obligations and rank equally in right of payment with all existing and future unsecured and unsubordinated indebtedness. The 2006 Senior Notes can be redeemed by Allied World Bermuda prior to maturity subject to payment of a “make-whole” premium. Allied World Bermuda has no current expectations of redeeming the notes prior to maturity. The 2006 Senior Notes include covenants and events of default that are usual and customary, but do not contain any financial covenants. c) 2010 Senior Notes Due 2020 In November 2010, Allied World Bermuda issued $300.0 million aggregate principal amount of 5.50% Senior Notes due November 15, 2020 (the “2010 Senior Notes”), with interest on the notes payable semi-annually . The 2010 Senior Notes are Allied World Bermuda’s unsecured and unsubordinated obligations and rank equally in right of payment with all existing and future unsecured and unsubordinated indebtedness. Allied World Bermuda may redeem the 2010 Senior Notes at any time or from time to time in whole or in part at a redemption price equal to the greater of the principal amount of the 2010 Senior Notes to be redeemed or a make-whole price, plus accrued and unpaid interest. Allied World Bermuda has no current expectations of redeeming the notes prior to maturity. The 2010 Senior Notes include covenants and events of default that are usual and customary, but do not contain any financial covenants. d) 2015 Senior Notes Due 2025 In October 2015, Allied World Bermuda issued $500.0 million aggregate principal amount of 4.35% Senior Notes due October 29, 2025 (the “2025 Senior Notes”), with interest on the notes payable semi-annually commencing on April 29, 2016. The Company intends that the proceeds from these senior notes will be used to refinance the 2006 Senior Notes due to mature in August 2016. The 2025 Senior Notes are Allied World Bermuda’s unsecured and unsubordinated obligations and rank equally in right of payment with all existing and future unsecured and unsubordinated indebtedness. Allied World Bermuda may redeem the 2025 Senior Notes at any time or from time to time in whole or in part at a redemption price equal to the greater of the principal amount of the 2025 Senior Notes to be redeemed or a make-whole price, in each case, plus accrued and unpaid interest. Allied World Bermuda has no current expectations of redeeming the notes prior to maturity. The 2025 Senior Notes include covenants and events of default that are usual and customary, but do not contain any financial covenants. e) Swiss Office Building Mortgage In 2014, the Company entered into a 20 -year mortgage commitment with a Swiss bank for the construction of a company-used office building in Zug, Switzerland. The total proceeds received in 2014 under the mortgage were $14.2 million (CHF 14.0 million ) with a fixed annual interest rate of 3.2% payable quarterly. An additional $4.0 million (CHF 4.0 million ) of proceeds from the mortgage was drawn during the first quarter of 2015. The mortgage payments are $0.3 million (CHF 0.3 million ) per year, plus accrued interest, for the first 19 years with the remaining balance payable at the end of the mortgage. The outstanding balance of the mortgage is included in "other long-term debt" on the consolidated balance sheets. f) Swiss Office Building Credit Facility In conjunction with the above mortgage commitment, the Company entered into a three year credit facility with a Swiss bank that provides up to $5.1 million (CHF 5.0 million ) for general corporate purposes, however the Company will use the proceeds from the credit facility to fund the purchase of the office building in Zug, Switzerland. The Company utilized the full commitment of the credit facility to finance the purchase of the Swiss office space. The interest rate for the credit facility is 2.5% . The outstanding balance of the credit facility is included in "other long-term debt" on the consolidated balance sheets. g) Credit Facilities In the normal course of its operations, the Company enters into agreements with financial institutions to obtain secured and unsecured credit facilities. Allied World Bermuda has a collateralized amended letter of credit facility with Citibank Europe plc. that has been and will continue to be used to issue standby letters of credit. The maximum aggregate amount available under this credit facility as of December 31, 2015 and 2014 is $1,000.0 million on an uncommitted basis. On November 27, 2007 , Allied World Bermuda entered into an $800.0 million five -year senior credit facility (the “Credit Facility”) with a syndication of lenders. The Credit Facility consisted of a $400.0 million secured letter of credit facility for the issuance of standby letters of credit (the “Secured Facility”) and a $400.0 million unsecured facility for the making of revolving loans and for the issuance of standby letters of credit. On June 7, 2012 , Allied World Bermuda amended the Secured Facility. The amended $450.0 million four -year secured credit facility (the “Amended Secured Credit Facility”) is primarily used for the issuance of standby letters of credit to support obligations in connection with the insurance and reinsurance business of Allied World Bermuda and its subsidiaries. A portion of the facility may also be used for revolving loans for general corporate and working capital purposes, up to a maximum of $150.0 million . Allied World Bermuda may request that existing lenders under the Amended Secured Credit Facility make additional commitments from time to time, up to $150.0 million , subject to approval by the lenders. The Amended Secured Credit Facility contains representations, warranties and covenants customary for similar bank loan facilities, including certain covenants that, among other things, require the Company to maintain a certain leverage ratio and financial strength rating. On November 12, 2014, Allied World Bermuda gave irrevocable notice to the administrative agent under the Amended Secured Credit Facility to reduce the aggregate commitment from $450.0 million to $150.0 million . All other material items of the Amended Secured Credit Facility remain unchanged. h) Debt Maturities The following table reflects the Company’s debt maturities, which includes its senior notes and other long-term debt: Amount 2016 $ 500.3 2017 5.4 2018 0.3 2019 0.3 2020 300.3 2021 and thereafter 516.5 Total $ 1,323.1

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Income taxes	INCOME TAXES Under Swiss law, a resident company is subject to income tax at the federal, cantonal and communal levels that is levied on net income. Income attributable to permanent establishments or real estate located abroad is excluded from the Swiss tax base. Allied World Switzerland is a holding company and, therefore, is exempt from cantonal and communal income tax. As a result, Allied World Switzerland is subject to Swiss income tax only at the federal level. Allied World Switzerland is resident of the Canton of Zug and, as such, is subject to an annual cantonal and communal capital tax on the taxable equity of Allied World Switzerland in Switzerland. Allied World Switzerland has a Swiss operating company resident in the Canton of Zug. The operating company is subject to federal, cantonal and communal income tax and to annual cantonal and communal capital tax. Under current Bermuda law, Allied World Bermuda and its Bermuda subsidiaries are not required to pay taxes in Bermuda on either income or capital gains. Allied World Bermuda and Allied World Assurance Company, Ltd have received an assurance from the Bermuda Minister of Finance under the Exempted Undertakings Tax Protection Act 1966 of Bermuda, that in the event of any such taxes being imposed, Allied World Bermuda and Allied World Assurance Company, Ltd will be exempted until March 2035. Certain subsidiaries of Allied World Switzerland file U.S. federal income tax returns and various U.S. state income tax returns, as well as income tax returns in Canada, Hong Kong, Ireland, Singapore, Switzerland and the United Kingdom. The Company has open tax years that are potentially subject to examinations by local tax authorities, in the following major tax jurisdictions: the U.S., 2012 to 2015 ; the United Kingdom, 2014 and 2015 ; Ireland, 2011 to 2015 ; Switzerland, 2013 to 2015 ; Hong Kong, 2009 to 2015 ; and Singapore, 2011 to 2015 . In December 2014, the Company received notice that the U.S. Internal Revenue Service will conduct an audit of the 2012 tax return of the Company's U.S. subsidiaries. The Company does not believe there will be any material findings from the 2012 tax return audit. To the best of the Company’s knowledge, there are no other examinations pending by any other tax authority. Management has deemed all material tax positions to have a greater than 50% likelihood of being sustained based on technical merits if challenged. The Company does not expect any material unrecognized tax benefits within 12 months of December 31, 2015 . The components of income tax expense are as follows: Year Ended December 31, 2015 2014 2013 Current income tax expense $ 9.8 $ 26.8 $ 21.7 Deferred income tax (benefit) expense (4.0 ) 3.7 (11.9 ) Income tax expense $ 5.8 $ 30.5 $ 9.8 Our income is primarily sourced from our Bermuda, U.S., European and Asia Pacific operations. The income before income taxes for these operations are as follows: Year Ended December 31, 2015 2014 2013 Non-U.S. $ 76.9 $ 447.9 $ 401.9 United States 12.8 72.9 25.9 Income before income taxes $ 89.7 $ 520.8 $ 427.8 Deferred income taxes reflect the tax impact of temporary differences between the carrying amounts of assets and liabilities for financial reporting and income tax purposes. The significant components of the net deferred tax assets are as follows: December 31, 2015 2014 Deferred tax assets: Reserve for losses and loss expenses $ 22.2 $ 21.6 Equity compensation 14.2 15.3 Unearned premium 18.1 16.9 Deferred acquisition costs 10.5 11.2 Net loss carryforward 27.3 13.8 Total deferred tax assets 92.3 78.8 Deferred tax liabilities: Intangible assets (23.3 ) (13.9 ) Realized gains (3.0 ) (12.8 ) Depreciation (6.4 ) (2.5 ) Market discount on bonds (1.2 ) (0.7 ) Other (5.2 ) (3.1 ) Total deferred tax liabilities (39.1 ) (33.0 ) Net deferred taxes before valuation allowance 53.2 45.8 Valuation allowance (28.8 ) (12.2 ) Net deferred tax assets $ 24.4 $ 33.6 The valuation allowance reported in the current period relates to net operating loss carryforwards for the European and Asia Pacific operations as it is unlikely those operations will have sufficient income to utilize the net loss carryforwards in the near term. The change in valuation allowance of $16.6 million was included in income tax expense for the year ended December 31, 2015 . The capital loss carryforwards from the United Kingdom and Asia Pacific operations do not expire as along as minimum capital requirements are maintained. Current tax receivable and payable has been included in “other assets” and “accounts payable and accrued liabilities” on the consolidated balance sheets, respectively. Current taxes receivable or payable was as follows: December 31, 2015 2014 Current tax receivable $ 5.5 $ 8.6 Current tax payable $ 2.5 $ 0.8 The expected tax provision has been calculated using the pre-tax accounting income in each jurisdiction multiplied by that jurisdiction’s applicable statutory tax rate. The reconciliation between the Company’s effective tax rate on pre-tax accounting income and the expected tax rate is as follows: Year Ended December 31, 2015 2014 2013 Expected tax rate 7.8 % 7.8 % 7.8 % Income not subject to income tax (14.2 )% (7.1 )% (8.2 )% Valuation allowance 14.5 % 2.3 % — % Foreign taxes at local expected tax rates (1.7 )% 4.4 % 1.4 % Disallowed expenses and capital allowances 3.2 % 0.2 % 1.0 % Prior year refunds and adjustments — % 1.2 % 0.8 % Other (3.2 )% (2.9 )% (0.5 )% Effective tax rate 6.4 % 5.9 % 2.3 %

Shareholders' Equity

Shareholders' Equity	12 Months Ended
	Dec. 31, 2015
Stockholders' Equity Note [Abstract]
Shareholders' equity	SHAREHOLDERS’ EQUITY a) Authorized shares The issued share capital consists of the following: December 31, 2015 2014 Common shares issued and fully paid, 2015 and 2014: CHF 4.10 per share 95,523,230 100,775,256 Share capital at end of year $ 386.7 $ 408.0 2015 2014 Shares issued at beginning of year 100,775,256 103,477,452 Shares canceled (5,252,026 ) (2,702,196 ) Total shares issued at end of year 95,523,230 100,775,256 Treasury shares issued at beginning of year 4,579,774 3,223,806 Shares repurchased 6,047,437 4,906,785 Shares issued out of treasury (811,590 ) (848,621 ) Shares canceled (5,252,026 ) (2,702,196 ) Total treasury shares at end of year 4,563,595 4,579,774 Total shares outstanding at end of year 90,959,635 96,195,482 During the years ended December 31, 2015 , and 2014 , 5,252,026 and 2,702,196 voting shares repurchased and designated for cancellation, respectively, were constructively retired and canceled. As required under Swiss law, the Company cannot hold more than 10% of its registered capital in treasury shares, unless it receives shareholder approval to do so. b) Dividends As a holding company, Allied World Switzerland’s principal source of income is dividends or other sources of permitted payments from its subsidiaries. These funds provide the cash flow required for dividend payments to the Company’s shareholders. The ability of our insurance and reinsurance subsidiaries to make dividend payments is limited by the applicable laws and regulations of the various states and countries in which they operate. The Company’s primary restrictions on net assets of subsidiaries consist of regulatory requirements placed upon the regulated insurance and reinsurance subsidiaries to hold minimum amounts of total statutory capital and surplus and there were no other material restrictions on net assets in place as of December 31, 2015 . Under Swiss law, distributions to shareholders may be paid only if the Company has sufficient distributable profits from previous fiscal years, or if the Company has freely distributable reserves, each as presented on the audited stand-alone statutory balance sheet. Distributions to shareholders out of the share and participation capital may be made by way of a capital reduction in the form of a reduction to par value to achieve a similar result as the payment of a dividend. Under Swiss law, if the Company’s general capital reserves amount to less than 20% of the share and participation capital recorded in the Swiss Commercial Register, then at least 5% of the Company’s annual profit must be retained as general reserves. On May 2, 2013, the shareholders approved the Company’s proposal to pay cash dividends in the form of a distribution out of general legal reserve from capital contributions. The distribution amounts were paid to shareholders in quarterly dividends of $0.167 per share in July 2013, October 2013, January 2014 and April 2014. On May 1, 2014, the shareholders approved the Company’s proposal to pay cash dividends in the form of a distribution out of general legal reserve from capital contributions. The distribution amounts were paid to shareholders in quarterly dividends of $0.225 per share in July 2014, October 2014, January 2015 and April 2015. On April 30, 2015, the shareholders approved the Company's proposal to pay cash dividends in the form of a distribution out of general legal reserve from capital contributions. The distribution amount will be paid to shareholders in quarterly installments of $0.26 per share. The first three installments of the dividend was distributed in July 2015, October 2015 and December 2015. The Company expects to distribute the remaining installment of the dividend in April 2016. The Company paid the following dividends during the years ended December 31, 2015 , 2014 and 2013 : Dividend Paid Partial Per Share Dividend Share Total Paid December 31, 2015 N/A $ 0.260 $ 23.7 October 1, 2015 N/A $ 0.260 $ 23.6 July 2, 2015 N/A $ 0.260 $ 23.6 April 2, 2015 N/A $ 0.225 $ 21.5 January 2, 2015 N/A $ 0.225 $ 21.7 October 2, 2014 N/A $ 0.225 $ 21.7 July 2, 2014 N/A $ 0.225 $ 21.9 April 3, 2014 N/A $ 0.167 $ 16.5 January 2, 2014 N/A $ 0.167 $ 16.7 October 3, 2013 N/A $ 0.167 $ 17.0 July 3, 2013 N/A $ 0.167 $ 17.1 March 12, 2013 CHF 0.11 $ 0.125 $ 13.0 c) Share Repurchases On May 1, 2014, the shareholders approved a share repurchase program in order for the Company to repurchase up to $500.0 million of Allied World Switzerland's common shares. This share repurchase program supersedes the 2012 share repurchase program and no further repurchases will be made under the 2012 share repurchase program. Repurchases may be effected from time to time through open market purchases, privately negotiated transactions, tender offers or otherwise. The timing, form and amount of the share repurchases under the program will depend on a variety of factors, including market conditions, the Company’s capital position, legal requirements and other factors. Under the terms of this share repurchase program, the first three million of common shares repurchased will remain in treasury and will be used by Allied World Switzerland to satisfy share delivery obligations under its equity-based compensation plans. Any additional common shares repurchased will be designated for cancellation at acquisition and will be canceled upon shareholder approval. Shares repurchased and designated for cancellation are constructively retired and recorded as a share cancellation. Shares repurchased by the Company and not designated for cancellation are classified as “Treasury shares, at cost” on the consolidated balance sheets. The Company will issue shares out of treasury principally related to the Company’s employee benefit plans. Shares repurchased and designated for cancellation are constructively retired and recorded as a share cancellation. The Company’s share repurchases were as follows: Year Ended December 31, 2015 2014 2013 Common shares repurchased 6,047,437 4,906,785 5,544,432 Total cost of shares repurchased $ 245.3 $ 175.4 $ 174.7 Average price per share $ 40.56 $ 35.74 $ 31.51 On May 6, 2015, the Company repurchased 4,053,537 shares from Exor S.A. at a repurchase price of $40.546 per share, for an aggregate purchase price of $164.4 million . The repurchase was executed under the 2014 share repurchase program.

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Employee benefit plans	EMPLOYEE BENEFIT PLANS The Company implemented the Allied World Assurance Company Holdings, AG 2012 Omnibus Incentive Compensation Plan (the “2012 Omnibus Plan”). Under the 2012 Omnibus Plan, up to 4,500,000 common shares may be issued, subject to adjustment. The 2012 Omnibus Plan provides for the grant of options intended to qualify as incentive stock options under the Internal Revenue Code, non-qualified stock options, stock appreciation rights, restricted shares, RSUs, deferred share units, cash incentive awards, performance-based compensation awards and other equity-based and equity-related awards. These awards generally vest pro rata over four years from the date of grant, except for the performance-based awards that will generally vest over a three -year period based on the achievement of certain performance conditions. The Allied World Assurance Company Holdings, AG Third Amended and Restated 2001 Employee Stock Option Plan (the “Plan”), the Allied World Assurance Company Holdings, AG Third Amended and Restated 2004 Stock Incentive Plan and the and the Allied World Assurance Company Holdings, AG Third Amended and Restated Long-Term Incentive Plan (the “LTIP”) were automatically terminated, replaced and superseded by the 2012 Omnibus Plan on May 3, 2012, except that any outstanding awards granted under such plans remain in effect pursuant to their terms. a) Employee option plan Options under the Plan are exercisable in certain limited conditions, expire after 10 years , and generally vest pro-rata over four years from the date of grant. The exercise price of options issued were approved by the Compensation Committee but were not less than the fair market value of the common shares of Allied World Switzerland on the date the option award is granted. The Company has not granted stock options since 2011. The following table summarizes the activity related to options granted and exercised: Year Ended December 31, 2015 2014 2013 Options granted — — — Weighted average grant date fair value $ — $ — $ — Options exercised (454,602 ) (479,831 ) (674,187 ) Total intrinsic value of options exercised $ 12.0 $ 10.3 $ 12.2 Proceeds from option exercises $ 10.1 $ 10.0 $ 12.1 The activity related to the Company’s stock options is as follows: Year Ended December 31, 2015 Options Weighted Average Exercise Price Weighted Average Contractual Term Aggregate Intrinsic Value Outstanding at beginning of year 2,426,674 $ 16.40 Granted — — Exercised (454,602 ) (14.38 ) Forfeited (3,465 ) (20.50 ) Expired — — Outstanding at end of year 1,968,607 16.86 4.0 years $ 40.0 Exercisable at end of year 1,968,607 $ 16.86 4.0 years $ 40.0 As of December 31, 2015 , there was no remaining unrecognized compensation expense related to stock options granted under the Plan. b) Restricted stock units and performance-based equity awards The RSUs vest pro-rata over four years from the date of grant. The compensation expense for the RSUs is based on the fair market value of Allied World Switzerland’s common shares at the date of grant. The Company estimates the expected forfeitures of RSUs at the date of grant and recognizes compensation expense only for those awards that the Company expects to vest. The forfeiture assumption is ultimately adjusted to the actual forfeiture rate. Each award for the performance-based RSUs represents the right to receive a number of shares in the future, based upon the achievement of established performance criteria during the applicable performance period. The compensation expense for the performance-based RSUs is based on the fair market value of Allied World Switzerland's common shares at the time of grant. For the performance-based RSUs granted in 2015 , 2014 and 2013 , the Company anticipates that the performance goals are likely to be achieved. Based on the performance goals, the performance-based RSUs granted in 2015 , 2014 and 2013 are expensed at 100% , 100% and 111% , respectively, of the fair market value of Allied World Switzerland’s common shares on the date of grant. The expense is recognized over the performance period. The activity related to the Company’s RSUs awards is as follows: Year Ended December 31, 2015 Number of Awards Weighted Average Grant Date Fair Value Aggregate Intrinsic Value Outstanding at beginning of year 502,506 $ 32.10 RSUs granted 506,505 40.23 RSUs forfeited (26,646 ) (36.08 ) RSUs fully vested (163,056 ) (30.42 ) Outstanding at end of year 819,309 $ 37.33 $ 30.5 As of December 31, 2015 , there was remaining $23.0 million of total unrecognized compensation expense related to 819,309 unvested RSUs awarded. This expense is expected to be recognized over a weighted-average period of 1.8 years . The activity related to the Company’s performance-based equity awards is as follows: Year Ended December 31, 2015 Number of Awards Weighted Average Grant Date Fair Value Aggregate Intrinsic Value Outstanding at beginning of year 616,641 $ 27.52 Performance-based equity awards granted 234,361 40.24 Additional awards granted due to achievement of performance criteria 91,737 22.29 Performance-based equity awards forfeited (4,541 ) (32.25 ) Performance-based equity awards fully vested (346,515 ) (22.29 ) Outstanding at end of year 591,683 $ 34.78 $ 22.0 As of December 31, 2015 , there was remaining $8.1 million of total unrecognized compensation expense related to 591,683 unvested performance-based equity awarded. This expense is expected to be recognized over a weighted-average period of 1.8 years . The RSUs and performance-based equity awards vested in 2015 , 2014 and 2013 had aggregate intrinsic values of $16.9 million , $14.4 million and $28.8 million at the time of vesting, respectively. c) Cash-equivalent stock awards As part of the Company’s annual year-end compensation awards, the Company granted both stock-based awards and cash-equivalent stock awards. The cash-equivalent awards were granted to employees who received RSU and performance-based awards and were granted in lieu of granting the full award as a stock-based award. The cash-equivalent RSU awards vest pro-rata over four years from the date of grant. The cash-equivalent performance-based awards vest after a three -year performance period. As the cash-equivalent awards are settled in cash, the Company establishes a liability equal to the product of the fair market value of Allied World Switzerland’s common shares as of the end of the reporting period and the total awards outstanding. At December 31, 2015 , the liability was $39.0 million , and payments for awards vesting in the period are typically settled within the first three months of the year. The liability is included in “accounts payable and accrued expenses” in the consolidated balance sheets and changes in the liability are recorded in “general and administrative expenses” in the consolidated income statements. The activity related to the Company's cash-equivalent RSUs and performance-based equity awards is as follows: RSU's Performance-based Awards Year Ended December 31, 2015 Number of Awards Weighted Average Grant Date Fair Value Number of Awards Weighted Average Grant Date Fair Value Outstanding at beginning of year 1,654,064 $ 27.99 924,906 27.52 Granted 325,805 40.24 156,238 40.24 Additional awards granted due to achievement of performance criteria — — 137,585 22.29 Forfeited (54,964 ) (30.42 ) (5,527 ) (30.39 ) Fully vested (647,822 ) (26.16 ) (519,725 ) (22.29 ) Outstanding at end of year 1,277,083 $ 31.94 693,477 $ 33.25 d) Total Stock-Related Compensation Expense The following table shows the total stock-related compensation expense relating to the stock options, RSUs, LTIP and cash equivalent awards. Year Ended December 31, 2015 2014 2013 Stock options $ 0.3 $ 1.9 $ 3.3 RSUs and performance-based equity awards 15.0 12.3 10.7 Cash-equivalent stock awards 34.4 37.8 50.9 Total $ 49.7 $ 52.0 $ 64.9 e) Pension Plans The Company provides defined contribution retirement plans for its employees and officers. Contributions are made by the Company, and in some locations, these contributions are supplemented by the local plan participants. Contributions are based on a percentage of the participant’s base salary depending upon competitive local market practice and vesting provisions meeting legal compliance standards. The amount that an individual employee or officer can contribute may also be subject to regulatory requirements relating to the country of which the individual is a citizen. The Company incurred expenses for these defined contribution arrangements of $13.5 million , $10.6 million and $9.3 million for the years ended December 31, 2015 , 2014 and 2013 , respectively. f) Employee Share Purchase Plan Under the Allied World Assurance Company Holdings, AG Amended and Restated 2008 Employee Share Purchase Plan (“ESPP”), eligible employees of the Company may purchase common shares of the Company at a 15% discount from the fair market value of one common share on the last trading day of each offering period. Employees purchase a variable number of common shares through payroll deductions elected as of the beginning of the offering period. The Company may sell up to 3,000,000 common shares to eligible employees under the ESPP.

Earnings Per Share

Earnings Per Share	12 Months Ended
	Dec. 31, 2015
Earnings Per Share [Abstract]
Earnings per share	EARNINGS PER SHARE The following table sets forth the comparison of basic and diluted earnings per share: Year Ended December 31, 2015 2014 2013 Basic earnings per share: Net income $ 83.9 $ 490.3 $ 418.0 Weighted average common shares outstanding 92,530,208 97,538,319 102,464,715 Basic earnings per share $ 0.91 $ 5.03 $ 4.08 Year Ended December 31, 2015 2014 2013 Diluted earnings per share: Net income $ 83.9 $ 490.3 $ 418.0 Weighted average common shares outstanding 92,530,208 97,538,319 102,464,715 Share equivalents: Stock options 1,031,666 1,432,960 1,536,939 RSU and LTIP awards 591,773 605,808 864,180 Employee share purchase plan 20,813 14,686 — Weighted average common shares and common share equivalents outstanding — diluted 94,174,460 99,591,773 104,865,834 Diluted earnings per share $ 0.89 $ 4.92 $ 3.98 For the years ended December 31, 2015 , 2014 and 2013 , a weighted average of 308,405 , nil and nil RSUs were considered anti-dilutive and were therefore excluded from the calculation of the diluted earnings per share, respectively.

Commitments And Contingencies

Commitments And Contingencies	12 Months Ended
	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Commitments and contingencies	COMMITMENTS AND CONTINGENCIES a) Concentrations of Credit Risk Credit risk arises out of the failure of a counterparty to perform according to the terms of the contract. The Company’s investment portfolio is managed pursuant to guidelines that follow prudent standards of diversification. The guidelines limit the allowable holdings of a single issue and issuers. The Company believes that there are no significant concentrations of credit risk associated with its investment portfolio. As of December 31, 2015 and 2014 , substantially all of the Company’s cash and investments were held with one custodian. Insurance balances receivable primarily consist of net premiums due from insureds and reinsureds. The Company believes that the counterparties to these receivables are able to meet, and will meet, all of their obligations. The Company’s credit risk is further reduced by the contractual right to offset loss obligations or unearned premiums against premiums receivable. Consequently, the Company has not included any material allowance for doubtful accounts against the receivable balance. b) Operating Leases The Company leases office space under operating leases expiring in various years through 2031. The following are future minimum rental payments as of December 31, 2015 : Amount 2016 $ 19.3 2017 25.7 2018 24.8 2019 19.3 2020 14.5 2021 and thereafter 115.3 $ 218.9 Total rent expense for the years ended December 31, 2015 , 2014 and 2013 was $25.9 million , $19.0 million and $11.4 million , respectively. The rent expense for the years ended December 31, 2015 , 2014 and 2013 are net of sublease income of $0.7 million , $0.1 million and nil , respectively. c) Producers The three largest individual producers as a percentage of gross premiums written are as follows: Year Ended December 31, 2015 2014 2013 Marsh & McLennan Companies, Inc. 24 % 25 % 26 % Aon Corporation 16 % 17 % 18 % Willis Group Holdings 11 % 10 % 12 % d) Legal Proceedings The Company, in common with the insurance industry in general, is subject to litigation and arbitration in the normal course of its business. These legal proceedings generally relate to claims asserted by or against the Company in the ordinary course of insurance or reinsurance operations. Estimated amounts payable under these proceedings are included in the reserve for losses and loss expenses in the Company’s consolidated balance sheets. As of December 31, 2015 , the Company was not a party to any material legal proceedings arising outside the ordinary course of business that management believes will have a material adverse effect on the Company’s results of operations, financial position or cash flow.

Statutory Capital and Surplus

Statutory Capital and Surplus	12 Months Ended
	Dec. 31, 2015
Disclosure Dividend Restrictions And Statutory Requirements [Abstract]
Statutory capital and surplus	STATUTORY CAPITAL AND SURPLUS Allied World Switzerland’s ability to pay dividends is subject to certain regulatory restrictions on the payment of dividends by its subsidiaries. The payment of such dividends is limited by applicable laws and statutory requirements of the jurisdictions in which Allied World Switzerland and its subsidiaries operate. The total amount of restricted net assets for the Company’s consolidated subsidiaries as of December 31, 2015 was $2,682.7 million . The minimum required statutory capital and surplus is the amount of statutory capital and surplus necessary to satisfy regulatory requirements based on the Company’s current operations. The statutory capital and surplus and minimum required statutory capital and surplus for the Company’s most significant regulatory jurisdictions at December 31, 2015 and 2014 were as follows: December 31, 2015 December 31, 2014 Statutory Capital and Surplus Minimum Required Statutory Capital and Surplus Statutory Capital and Surplus Minimum Required Statutory Capital and Surplus Bermuda $ 3,270.9 $ 853.2 $ 3,273.7 $ 876.2 United States 1,215.5 241.0 1,220.3 226.9 Ireland 414.0 26.9 410.8 29.2 Switzerland 183.6 17.7 172.3 19.9 United Kingdom 245.9 231.8 231.7 203.7 There were no state-prescribed or permitted regulatory accounting practices for any of our insurance entities that resulted in reported statutory surplus that differed from that which would have been reported under the prescribed practices of the respective regulatory authorities, including the National Association of Insurance Commissioners. Statutory accounting under the prescribed practices of the respective regulatory authorities differs from U.S. GAAP accounting in the treatment of various items, including reporting of investments, acquisition costs and deferred income taxes. The statutory net income (loss) for the Company’s most significant regulatory jurisdictions for the years ended December 31, 2015 , 2014 and 2013 was as follows: Year Ended December 31, 2015 2014 2013 Bermuda $ 221.5 $ 487.1 $ 467.3 United States 40.5 45.4 36.7 Ireland 3.2 3.2 (4.9 ) Switzerland 10.7 7.4 (6.4 ) United Kingdom (39.4 ) (7.8 ) 9.4 At December 31, 2015 , the maximum amount of ordinary dividends or distributions that can be paid, without prior regulatory approval, for the Company’s most significant regulatory jurisdictions, were as follows: December 31, 2015 Bermuda $ 817.7 United States 90.0 Ireland 54.0 Switzerland 32.2 United Kingdom 2.4 a) Bermuda The Company’s Bermuda subsidiary, Allied World Assurance Company, Ltd, is registered under the Bermuda Insurance Act 1978 and Related Regulations as amended. As a Class 4 insurer, Allied World Assurance Company, Ltd is required to maintain minimum solvency standards and to hold available statutory capital and surplus equal to or exceeding the enhanced capital requirements as determined by the Bermuda Monetary Authority under the Bermuda Solvency Capital Requirement model (“BSCR model”). The BSCR model is a risk-based capital model that provides a method for determining an insurer’s minimum required capital taking into account the risk characteristics of different aspects of the company’s business. In addition, this subsidiary is required to maintain a minimum liquidity ratio. As of December 31, 2015 and 2014 , this subsidiary met the requirements. b) United States The Company’s U.S. insurance subsidiaries are subject to the insurance laws and regulations of the states in which they are domiciled, and also states in which they are licensed or authorized to transact business. These laws also restrict the amount of ordinary shareholder dividends the subsidiaries can pay. The restrictions are generally based on statutory surplus and/or statutory net income as determined in accordance with the relevant statutory accounting requirements of the individual domiciliary states. The U.S. subsidiaries are required to file annual statements with insurance regulatory authorities prepared on an accounting basis prescribed or permitted by such authorities. The U.S. subsidiaries are also required to maintain minimum levels of solvency and liquidity as determined by law, and comply with capital requirements and licensing rules. As of December 31, 2015 and 2014 , the actual levels of solvency, liquidity and capital of each U.S. subsidiary were in excess of the minimum levels required. c) Ireland The Company’s Irish insurance subsidiary is regulated by the Central Bank of Ireland pursuant to the Insurance Acts 1909 to 2000, the Central Bank Acts 1942 to 2015 and all statutory instruments relating to insurance made or adopted under the European Communities Acts 1972 to 2014, including the European Union (Insurance and Reinsurance) Regulations, 2015. This subsidiary is required to maintain a minimum level of capital. As of December 31, 2015 and 2014 , these requirements were met. The amount of dividends that this subsidiary is permitted to distribute is restricted to accumulated realized profits that have not been capitalized or distributed, less accumulated realized losses that have not been written off. The solvency and capital requirements must still be met following any distribution. d) Switzerland The Company’s Swiss insurance subsidiary, Allied World Assurance Company, AG, is regulated by the Swiss Financial Market Supervisory Authority (“FINMA”) pursuant to the Insurance Supervisory Law 2004 to 2014. This subsidiary’s accounts are prepared in accordance with the Swiss Code of Obligations and the Insurance Supervisory Law. This subsidiary is obligated to maintain a minimum level of capital based on the Swiss Code of Obligation, a minimum of tied assets based on the Insurance Supervisory Law and a minimum solvency margin based on the Solvency I and Swiss Solvency Test (effective as of July 1, 2015) regulations as stipulated by the Insurance Supervisory Law. As of December 31, 2015 and 2014 , this subsidiary met the requirements. The amount of dividends that this subsidiary is permitted to distribute is restricted to freely distributable reserves which consist of retained earnings, the current year profit and legal reserves to a certain extent. Any dividend requires approval of the shareholders and in case of the dividend exceeding the current year profit, approval is also required from FINMA. The solvency and capital requirements must still be met following any distribution. e) United Kingdom Allied World Capital (Europe) Limited is the sole corporate member of Syndicate 2232. Syndicate 2232 is managed by Allied World Managing Agency Limited, which is authorized and regulated by the Prudential Regulatory Authority ("PRA") and the Financial Conduct Authority. As a member of Lloyd’s, Allied World Capital (Europe) Limited is obliged to comply with Lloyd’s byelaws and regulations (made pursuant to the Lloyd’s Acts 1871 to 1982) and applicable provisions of the Financial and Services and Markets Act 2000. The Council of Lloyd’s has wide discretionary powers to regulate members’ underwriting at Lloyd’s and its exercise of these powers might affect the return on an investment of the corporate member in a given underwriting year. The capital required to support a Syndicate’s underwriting capacity, referred to as “funds at Lloyd’s”, is assessed annually and is determined by Lloyd’s in accordance with the capital adequacy rules established by the PRA. If a member of Lloyd’s is unable to pay its debts to policyholders, such debts may be payable from the Lloyd’s Central Fund, which in many respects acts as an equivalent to a state guaranty fund in the United States. The Company has provided capital to support the underwriting of Syndicate 2232 in the form of pledged assets provided by Allied World Assurance Company, Ltd. The amount which the Company provides as funds at Lloyd’s is not available for distribution to the Company for the payment of dividends. Lloyd’s is supervised by the PRA and required to implement certain rules prescribed by the PRA under the Lloyd’s Act of 1982 regarding the operation of the Lloyd’s market. With respect to managing agents and corporate members, Lloyd’s prescribes certain minimum standards relating to management and control, solvency and other requirements and monitors managing agents’ compliance with such standards. f) Branch Offices The Company’s insurance subsidiaries maintain branch offices in Australia, Bermuda, England, Switzerland, Hong Kong, Canada, Singapore and Labuan. As branch offices are not considered separate legal entities, the required and actual statutory capital and surplus amounts for each jurisdiction in the table above include amounts related to the branch offices. These branch offices are subject to additional minimum capital or asset requirements in their countries of domicile. At December 31, 2015 and 2014 , the actual capital and surplus for each of these branches exceeded the relevant local regulatory requirements.

Segment Information

Segment Information	12 Months Ended
	Dec. 31, 2015
Segment Reporting [Abstract]
Segment information	SEGMENT INFORMATION The determination of reportable segments is based on how the Company's chief operating decision maker, the Chief Executive Officer, monitors the Company’s underwriting operations. Management monitors the performance of its direct underwriting operations based on the geographic location of the Company’s offices, the markets and customers served and the type of accounts written. The Company is currently organized into three operating segments: North American Insurance, Global Markets Insurance and Reinsurance. All product lines fall within these classifications. The North American Insurance segment includes the Company’s direct specialty insurance operations in the United States, Bermuda and Canada, as well as the Company's claim administration services operation. This segment provides both direct property and specialty casualty insurance to North American domiciled accounts. The Global Markets Insurance segment includes the Company’s direct insurance operations in Europe and Asia Pacific, which includes offices in Australia, Hong Kong and Singapore. This segment provides both direct property and casualty insurance primarily to non-North American domiciled accounts. The Reinsurance segment includes the Company’s reinsurance operations in the United States, Bermuda, Europe and Singapore. This segment provides reinsurance of property, general casualty, professional liability, specialty lines and property catastrophe coverages written by insurance companies. The Company presently writes reinsurance on both a treaty and a facultative basis, targeting several niche reinsurance markets. Responsibility and accountability for the results of underwriting operations are assigned by major line of business within each segment. Because the Company does not manage its assets by segment, investment income, interest expense and total assets are not allocated to individual reportable segments. General and administrative expenses are allocated to segments based on various factors, including staff count and each segment’s proportional share of gross premiums written. The Company measures its segment profit or loss as underwriting income or loss plus other insurance-related income and expenses, which may include the net earnings from our claims administration services operations and other income or expense that is not directly related to our underwriting operations. Management measures results of each segment's underwriting income or loss on the basis of the “loss and loss expense ratio,” “acquisition cost ratio,” “general and administrative expense ratio”, “expense ratio” and the “combined ratio.” The “loss and loss expense ratio” is derived by dividing net losses and loss expenses by net premiums earned. The “acquisition cost ratio” is derived by dividing acquisition costs by net premiums earned. The “general and administrative expense ratio” is derived by dividing general and administrative expenses by net premiums earned. The expense ratio is the sum of the “acquisition cost ratio” and the “general and administrative expense ratio”. The “combined ratio” is the sum of the “loss and loss expense ratio,” the “acquisition cost ratio” and the “general and administrative expense ratio.” The following tables provide a summary of the segment results: Year Ended December 31, 2015 North American Insurance Global Markets Insurance Reinsurance Total Gross premiums written $ 1,815.3 $ 476.3 $ 801.4 $ 3,093.0 Net premiums written 1,358.1 324.1 765.8 2,448.0 Net premiums earned 1,301.4 366.8 820.2 2,488.4 Net losses and loss expenses (910.2 ) (240.3 ) (435.8 ) (1,586.3 ) Acquisition costs (139.6 ) (70.9 ) (164.9 ) (375.4 ) General and administrative expenses (224.6 ) (108.4 ) (73.3 ) (406.3 ) Underwriting income (loss) 27.0 (52.8 ) 146.2 120.4 Other insurance-related revenue 3.5 — — 3.5 Other insurance-related expenses (2.7 ) (2.5 ) (1.0 ) (6.2 ) Segment income (loss) 27.8 (55.3 ) 145.2 117.7 Net investment income 182.1 Net realized investment losses (127.6 ) Amortization and impairment of intangible assets (9.8 ) Interest expense (61.4 ) Foreign exchange loss (11.3 ) Income before income taxes $ 89.7 Loss and loss expense ratio 69.9 % 65.5 % 53.1 % 63.7 % Acquisition cost ratio 10.7 % 19.3 % 20.1 % 15.1 % General and administrative expense ratio 17.3 % 29.5 % 8.9 % 16.3 % Expense ratio 28.0 % 48.8 % 29.0 % 31.4 % Combined ratio 97.9 % 114.3 % 82.1 % 95.1 % Year Ended December 31, 2014 North American Insurance Global Markets Reinsurance Total Gross premiums written $ 1,716.3 $ 280.5 $ 938.6 $ 2,935.4 Net premiums written 1,230.8 188.0 903.2 2,322.0 Net premiums earned 1,111.1 162.6 909.0 2,182.7 Net losses and loss expenses (683.8 ) (61.1 ) (454.3 ) (1,199.2 ) Acquisition costs (105.9 ) (18.2 ) (171.0 ) (295.1 ) General and administrative expenses (219.6 ) (68.1 ) (78.0 ) (365.7 ) Underwriting income 101.8 15.2 205.7 322.7 Other insurance-related revenue 2.1 — — 2.1 Other insurance-related expenses (1.9 ) (6.7 ) — (8.6 ) Segment income 102.0 8.5 205.7 316.2 Net investment income 176.9 Net realized investment gains 89.0 Amortization of intangible assets (2.5 ) Interest expense (57.8 ) Foreign exchange loss (1.0 ) Income before income taxes $ 520.8 Loss and loss expense ratio 61.5 % 37.6 % 50.0 % 54.9 % Acquisition cost ratio 9.5 % 11.2 % 18.8 % 13.5 % General and administrative expense ratio 19.8 % 41.9 % 8.6 % 16.8 % Expense ratio 29.3 % 53.1 % 27.4 % 30.3 % Combined ratio 90.8 % 90.7 % 77.4 % 85.2 % Year Ended December 31, 2013 North American Insurance Global Markets Reinsurance Total Gross premiums written $ 1,572.3 $ 232.6 $ 933.8 $ 2,738.7 Net premiums written 1,082.5 145.0 893.0 2,120.5 Net premiums earned 1,023.0 126.0 856.9 2,005.9 Net losses and loss expenses (651.2 ) (50.4 ) (421.6 ) (1,123.2 ) Acquisition costs (94.8 ) (10.1 ) (147.8 ) (252.7 ) General and administrative expenses (209.0 ) (63.2 ) (80.1 ) (352.3 ) Underwriting income 68.0 2.3 207.4 277.7 Other insurance-related revenue — — — — Other insurance-related expenses — — — — Segment income 68.0 2.3 207.4 277.7 Net investment income 157.6 Net realized investment gains 59.5 Amortization of intangible assets (2.5 ) Interest expense (56.5 ) Foreign exchange loss (8.0 ) Income before income taxes $ 427.8 Loss and loss expense ratio 63.7 % 40.0 % 49.2 % 56.0 % Acquisition cost ratio 9.3 % 8.0 % 17.2 % 12.6 % General and administrative expense ratio 20.4 % 50.1 % 9.3 % 17.6 % Expense ratio 29.7 % 58.1 % 26.5 % 30.2 % Combined ratio 93.4 % 98.1 % 75.7 % 86.2 % The following table shows an analysis of the Company’s gross premiums written by geographic location of the Company’s subsidiaries. All intercompany premiums have been eliminated. Year Ended December 31, 2015 2014 2013 United States $ 1,893.4 $ 1,795.6 $ 1,636.0 Bermuda 543.6 640.9 676.2 Europe 326.9 318.6 264.9 Asia Pacific 313.1 167.3 161.6 Canada 16.0 13.0 — Total gross premiums written $ 3,093.0 $ 2,935.4 $ 2,738.7 Gross premiums written attributable to Switzerland were $58.2 million , $67.6 million and $61.0 million for the years ended December 31, 2015 , 2014 and 2013 , respectively. The following table shows the Company’s net premiums earned by line of business for each segment for the years ended December 31, 2015 , 2014 and 2013 . Year Ended December 31, 2015 2014 2013 North American Insurance: Casualty $ 424.0 $ 334.6 $ 269.1 Professional liability 343.6 276.1 259.2 Property 162.8 170.3 168.0 Healthcare 144.7 168.5 194.3 Programs 150.7 119.8 107.9 Specialty and other 75.6 41.9 24.5 Total 1,301.4 1,111.1 1,023.0 Global Markets Insurance: Property 106.7 34.0 31.4 Professional liability 102.5 69.1 57.1 Specialty and other 99.8 44.2 23.6 Casualty 57.8 15.3 13.9 Total 366.8 162.6 126.0 Reinsurance: Property 403.5 412.0 336.0 Casualty 224.4 175.5 171.8 Specialty 192.3 321.5 349.1 Total 820.2 909.0 856.9 Total net premiums earned $ 2,488.4 $ 2,182.7 $ 2,005.9

Condensed Consolidated Guaranto

Condensed Consolidated Guarantor Financial Statements	12 Months Ended
	Dec. 31, 2015
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Condensed consolidated guarantor financial statements	CONDENSED CONSOLIDATED PARENT COMPANY AND GUARANTOR FINANCIAL STATEMENTS The following tables present condensed consolidating financial information as of December 31, 2015 and 2014 and for the years ended December 31, 2015 , 2014 and 2013 for Allied World Switzerland (the “Parent Guarantor”) and Allied World Bermuda (the “Subsidiary Issuer”). The Subsidiary Issuer is a direct 100% -owned subsidiary of the Parent Guarantor. Investments in subsidiaries are accounted for by the Parent Guarantor under the equity method for purposes of the supplemental consolidating presentation. Earnings of subsidiaries are reflected in the Parent Guarantor’s investment accounts and earnings. The Parent Guarantor fully and unconditionally guarantees the senior notes issued by the Subsidiary Issuer. Condensed Consolidating Balance Sheet: As of December 31, 2015 Allied World Switzerland (Parent Guarantor) Allied World Bermuda (Subsidiary Issuer) Other Allied World Subsidiaries Consolidating Adjustments Allied World Switzerland Consolidated ASSETS: Investments $ — $ — $ 8,571.2 $ — $ 8,571.2 Cash and cash equivalents 21.8 1.0 585.2 — 608.0 Insurance balances receivable — — 745.9 — 745.9 Funds held — — 640.8 — 640.8 Reinsurance recoverable — — 1,480.0 — 1,480.0 Reinsurance recoverable on paid losses — — 96.4 96.4 Net deferred acquisition costs — — 165.2 — 165.2 Goodwill and intangible assets — — 504.7 — 504.7 Balances receivable on sale of investments — — 36.9 — 36.9 Investments in subsidiaries 3,347.0 4,396.3 — (7,743.3 ) — Due from subsidiaries 173.1 36.4 16.8 (226.3 ) — Other assets 1.8 0.1 660.9 — 662.8 Total assets $ 3,543.7 $ 4,433.8 $ 13,504.0 $ (7,969.6 ) $ 13,511.9 LIABILITIES: Reserve for losses and loss expenses $ — $ — $ 6,456.2 $ — $ 6,456.2 Unearned premiums — — 1,683.3 — 1,683.3 Reinsurance balances payable — — 214.4 — 214.4 Balances due on purchases of investments — — 125.1 — 125.1 Senior notes — 1,292.9 — — 1,292.9 Other long-term debt — — 23.0 — 23.0 Due to subsidiaries 8.5 8.3 209.5 (226.3 ) — Other liabilities 2.7 22.2 159.7 — 184.5 Total liabilities 11.2 1,323.4 8,871.2 (226.3 ) 9,979.4 Total shareholders’ equity 3,532.5 3,110.4 4,632.8 (7,743.3 ) 3,532.5 Total liabilities and shareholders’ equity $ 3,543.7 $ 4,433.8 $ 13,504.0 $ (7,969.6 ) $ 13,511.9 As of December 31, 2014 Allied World Switzerland (Parent Guarantor) Allied World Bermuda (Subsidiary Issuer) Other Allied World Subsidiaries Consolidating Adjustments Allied World Switzerland Consolidated ASSETS: Investments $ — $ — $ 7,868.7 $ — $ 7,868.7 Cash and cash equivalents 32.6 1.7 555.0 — 589.3 Insurance balances receivable — — 664.8 — 664.8 Funds held — — 724.0 — 724.0 Reinsurance recoverable — — 1,340.3 — 1,340.3 Reinsurance recoverable on paid losses — — 86.1 86.1 Net deferred acquisition costs — — 151.5 — 151.5 Goodwill and intangible assets — — 324.6 — 324.6 Balances receivable on sale of investments — — 47.1 — 47.1 Investments in subsidiaries 3,629.3 4,218.0 — (7,847.3 ) — Due from subsidiaries 147.1 19.2 14.4 (180.7 ) — Other assets 1.4 0.5 620.5 — 622.4 Total assets $ 3,810.4 $ 4,239.4 $ 12,397.0 $ (8,028.0 ) $ 12,418.8 LIABILITIES: Reserve for losses and loss expenses $ — $ — $ 5,881.2 $ — $ 5,881.2 Unearned premiums — — 1,555.3 — 1,555.3 Reinsurance balances payable — — 180.1 — 180.1 Balances due on purchases of investments — — 5.4 — 5.4 Senior notes — 796.1 — — 796.1 Other long-term debt — — 19.2 — 19.2 Due to subsidiaries 7.6 6.8 166.3 (180.7 ) — Other liabilities 24.6 19.6 159.1 — 203.3 Total liabilities 32.2 822.5 7,966.6 (180.7 ) 8,640.6 Total shareholders’ equity 3,778.2 3,416.9 4,430.4 (7,847.3 ) 3,778.2 Total liabilities and shareholders’ equity $ 3,810.4 $ 4,239.4 $ 12,397.0 $ (8,028.0 ) $ 12,418.8 Condensed Consolidating Income Statement: Year Ended December 31, 2015 Allied World Switzerland (Parent Guarantor) Allied World Bermuda (Subsidiary Issuer) Other Allied World Subsidiaries Consolidating Adjustments Allied World Switzerland Consolidated Net premiums earned $ — $ — $ 2,488.4 $ — $ 2,488.4 Net investment income — 0.1 182.0 — 182.1 Net realized investment losses — — (127.6 ) — (127.6 ) Other income — — 3.5 — 3.5 Net losses and loss expenses — — (1,586.3 ) — (1,586.3 ) Acquisition costs — — (375.4 ) — (375.4 ) General and administrative expenses (36.7 ) (0.5 ) (369.1 ) — (406.3 ) Other expense — — (6.2 ) — (6.2 ) Amortization of intangible assets — — (9.8 ) — (9.8 ) Interest expense — (59.2 ) (2.2 ) — (61.4 ) Foreign exchange gain (loss) — — (11.3 ) — (11.3 ) Income tax (expense) benefit (0.1 ) — (5.7 ) — (5.8 ) Equity in earnings of consolidated subsidiaries 120.7 157.3 — (278.0 ) — NET INCOME (LOSS) $ 83.9 $ 97.7 $ 180.3 $ (278.0 ) $ 83.9 Other comprehensive income (loss) (9.3 ) — (9.3 ) 9.3 (9.3 ) COMPREHENSIVE INCOME (LOSS) $ 74.6 $ 97.7 $ 171.0 $ (268.7 ) $ 74.6 Year Ended December 31, 2014 Allied World Switzerland (Parent Guarantor) Allied World Bermuda (Subsidiary Issuer) Other Allied World Subsidiaries Consolidating Adjustments Allied World Switzerland Consolidated Net premiums earned $ — $ — $ 2,182.7 $ — $ 2,182.7 Net investment income 0.1 — 176.8 — 176.9 Net realized investment gains — — 89.0 — 89.0 Other income — — 2.1 — 2.1 Net losses and loss expenses — — (1,199.2 ) — (1,199.2 ) Acquisition costs — — (295.1 ) — (295.1 ) General and administrative expenses (35.6 ) (3.1 ) (327.1 ) — (365.7 ) Other expense — — (8.6 ) — (8.6 ) Amortization of intangible assets — — (2.5 ) — (2.5 ) Interest expense — (55.4 ) (2.3 ) — (57.8 ) Foreign exchange gain (loss) — 0.1 (1.1 ) — (1.0 ) Income tax (expense) benefit (0.1 ) — (30.4 ) — (30.5 ) Equity in earnings of consolidated subsidiaries 525.9 564.6 — (1,090.5 ) — NET INCOME (LOSS) $ 490.3 $ 506.2 $ 584.3 $ (1,090.5 ) $ 490.3 Other comprehensive income (loss) — — — — — COMPREHENSIVE INCOME (LOSS) $ 490.3 $ 506.2 $ 584.3 $ (1,090.5 ) $ 490.3 Year Ended December 31, 2013 Allied World Switzerland (Parent Guarantor) Allied World Bermuda (Subsidiary Issuer) Other Allied World Subsidiaries Consolidating Adjustments Allied World Switzerland Consolidated Net premiums earned $ — $ — $ 2,005.9 $ — $ 2,005.9 Net investment income 0.1 — 157.5 — 157.6 Net realized investment gains — — 59.5 — 59.5 Other income — — — — — Net losses and loss expenses — — (1,123.2 ) — (1,123.2 ) Acquisition costs — — (252.7 ) — (252.7 ) General and administrative expenses (42.1 ) (1.3 ) (308.8 ) — (352.3 ) Other expense — — — — — Amortization of intangible assets — — (2.5 ) — (2.5 ) Interest expense — (55.3 ) (1.2 ) — (56.5 ) Foreign exchange gain (loss) 0.3 (1.0 ) (7.2 ) — (8.0 ) Income tax (expense) benefit 0.1 — (9.9 ) — (9.8 ) Equity in earnings of consolidated subsidiaries 459.6 515.2 — (974.8 ) — NET INCOME (LOSS) $ 418.0 $ 457.6 $ 517.4 $ (974.8 ) $ 418.0 Other comprehensive income (loss) — — — — — COMPREHENSIVE INCOME (LOSS) $ 418.0 $ 457.6 $ 517.4 $ (974.8 ) $ 418.0 Condensed Consolidating Statement of Cash Flows: Year Ended December 31, 2015 Allied World Switzerland (Parent Guarantor) Allied World Bermuda (Subsidiary Issuer) Other Allied World Subsidiaries Consolidating Adjustments Allied World Switzerland Consolidated CASH FLOWS PROVIDED BY (USED IN) OPERATING ACTIVITIES $ 339.6 $ 377.7 $ 598.1 $ (811.1 ) $ 504.3 CASH FLOWS PROVIDED BY (USED IN) INVESTING ACTIVITIES: Purchases trading securities — — (5,863.2 ) — (5,863.2 ) Purchases of other invested assets — — (126.7 ) — (126.7 ) Sales of trading securities — — 5,328.8 — 5,328.8 Sales of other invested assets — — 161.3 — 161.3 Net cash paid for acquisitions — — (124.4 ) — (124.4 ) Capital contributions — (496.7 ) 496.7 — — Other — — (11.5 ) — (11.5 ) Net cash provided by (used in) investing activities — (496.7 ) (139.0 ) — (635.7 ) CASH FLOWS PROVIDED BY (USED IN) FINANCING ACTIVITIES: Dividends paid (114.1 ) — — — (114.1 ) Intercompany dividends paid — (378.4 ) (432.7 ) 811.1 — Proceeds from the exercise of stock options 10.1 — — — 10.1 Share repurchases (246.4 ) — — — (246.4 ) Proceeds from senior notes — 496.7 — — 496.7 Proceeds from other long-term debt — — 4.0 — 4.0 Repayment of other long-term debt — — (0.2 ) — (0.2 ) Net cash provided by (used in) financing activities (350.4 ) 118.3 (428.9 ) 811.1 150.1 NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS (10.8 ) (0.7 ) 30.2 — 18.7 CASH AND CASH EQUIVALENTS, BEGINNING OF YEAR 32.6 1.7 555.0 — 589.3 CASH AND CASH EQUIVALENTS, END OF YEAR $ 21.8 $ 1.0 $ 585.2 $ — $ 608.0 Year Ended December 31, 2014 Allied World Switzerland (Parent Guarantor) Allied World Bermuda (Subsidiary Issuer) Other Allied World Subsidiaries Consolidating Adjustments Allied World Switzerland Consolidated CASH FLOWS PROVIDED BY (USED IN) OPERATING ACTIVITIES $ 264.4 $ 292.9 $ 493.8 $ (643.3 ) $ 407.8 CASH FLOWS PROVIDED BY (USED IN) INVESTING ACTIVITIES: Purchases of trading securities — — (7,630.0 ) — (7,630.0 ) Purchases of other invested assets — — (307.9 ) — (307.9 ) Sales of trading securities — — 7,536.9 — 7,536.9 Sales of other invested assets — — 267.9 — 267.9 Net cash paid for acquisitions — — (2.6 ) — (2.6 ) Other — — 8.7 — 8.7 Net cash provided by (used in) investing activities — — (127.0 ) — (127.0 ) CASH FLOWS PROVIDED BY (USED IN) FINANCING ACTIVITIES: Dividends paid (76.7 ) — — — (76.7 ) Intercompany dividends paid — (294.0 ) (349.3 ) 643.3 — Proceeds from the exercise of stock options 10.0 — — — 10.0 Share repurchases (175.9 ) — — — (175.9 ) Proceeds from other long-term debt — — 19.2 — 19.2 Net cash provided by (used in) financing activities (242.6 ) (294.0 ) (330.1 ) 643.3 (223.4 ) NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS 21.8 (1.1 ) 36.7 — 57.4 CASH AND CASH EQUIVALENTS, BEGINNING OF YEAR 10.8 2.8 518.3 — 531.9 CASH AND CASH EQUIVALENTS, END OF YEAR $ 32.6 $ 1.7 $ 555.0 $ — $ 589.3 Year Ended December 31, 2013 Allied World Switzerland (Parent Guarantor) Allied World Bermuda (Subsidiary Issuer) Other Allied World Subsidiaries Consolidating Adjustments Allied World Switzerland Consolidated CASH FLOWS PROVIDED BY (USED IN) OPERATING ACTIVITIES: $ 198.7 $ 265.9 $ 237.9 $ (596.5 ) $ 106.0 CASH FLOWS PROVIDED BY (USED IN) INVESTING ACTIVITIES: Purchases of trading securities — — (7,527.7 ) — (7,527.7 ) Purchases of other invested assets — — (276.9 ) — (276.9 ) Sales of trading securities — — 7,540.2 — 7,540.2 Sales of other invested assets — — 187.5 — 187.5 Other — — 28.8 — 28.8 Net cash provided by (used in) investing activities — — (48.1 ) — (48.1 ) CASH FLOWS PROVIDED BY (USED IN) FINANCING ACTIVITIES: Partial par value reduction (13.0 ) — — — (13.0 ) Dividends paid (34.0 ) — — — (34.0 ) Intercompany dividends paid — (274.5 ) (322.0 ) 596.5 — Proceeds from the exercise of stock options 12.1 — — — 12.1 Share repurchases (173.0 ) — — — (173.0 ) Net cash provided by (used in) financing activities (207.9 ) (274.5 ) (322.0 ) 596.5 (207.9 ) NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS (9.2 ) (8.6 ) (132.2 ) — (150.0 ) CASH AND CASH EQUIVALENTS, BEGINNING OF YEAR 20.0 11.4 650.5 — 681.9 CASH AND CASH EQUIVALENTS, END OF YEAR $ 10.8 $ 2.8 $ 518.3 $ — $ 531.9 Notes to Parent Company Condensed Financial Information a) Dividends Allied World Switzerland received cash dividends from its subsidiaries of $378.4 million , $294.0 million and $274.5 million for the years ended December 31, 2015 , 2014 and 2013 , respectively. Such dividends are included in “cash flows provided by (used in) operating activities” in the condensed consolidating statement of cash flows.

Unaudited Quarterly Financial D

Unaudited Quarterly Financial Data	12 Months Ended
	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Unaudited quarterly financial data	UNAUDITED QUARTERLY FINANCIAL DATA The following are the unaudited consolidated statements of income by quarter for the years ended December 31, 2015 and 2014 : Quarter Ended December 31, September 30, June 30, March 31, REVENUES: Gross premiums written $ 632.3 $ 754.1 $ 826.0 $ 880.6 Premiums ceded (167.5 ) (147.1 ) (222.3 ) (108.1 ) Net premiums written 464.8 607.0 603.7 772.5 Change in unearned premiums 158.0 43.7 42.7 (204.0 ) Net premiums earned 622.8 650.7 646.4 568.5 Net investment income 49.1 45.7 42.8 44.5 Net realized investment (losses) gains (38.8 ) (113.6 ) (20.2 ) 45.0 Other income 1.0 0.7 0.9 0.9 634.1 583.5 669.9 658.9 EXPENSES: Net losses and loss expenses 412.7 416.9 431.5 325.2 Acquisition costs 96.0 100.1 100.6 78.7 General and administrative expenses 95.0 105.8 108.4 97.1 Other expense 1.9 1.3 1.2 1.8 Amortization of intangible assets 3.7 2.7 2.8 0.6 Interest expense 18.1 14.5 14.5 14.3 Foreign exchange loss (gain) 0.9 (0.8 ) 1.3 9.9 628.3 640.5 660.3 527.6 Income (loss) before income taxes 5.8 (57.0 ) 9.6 131.3 Income tax expense (benefit) 4.0 (5.3 ) 0.1 7.0 NET INCOME (LOSS) $ 1.8 $ (51.7 ) $ 9.5 $ 124.3 PER SHARE DATA Basic earnings (loss) per share $ 0.02 $ (0.57 ) $ 0.10 $ 1.30 Diluted earnings (loss) per share $ 0.02 $ (0.57 ) $ 0.10 $ 1.27 Weighted average common shares outstanding 90,934,107 90,882,511 92,441,730 95,935,551 Weighted average common shares and common share equivalents outstanding 92,422,422 90,882,511 93,984,226 97,577,029 Quarter Ended December 31, September 30, June 30, March 31, REVENUES: Gross premiums written $ 565.7 $ 707.9 $ 760.4 $ 901.4 Premiums ceded (137.9 ) (139.2 ) (206.5 ) (129.8 ) Net premiums written 427.8 568.7 553.9 771.6 Change in unearned premiums 145.7 (27.0 ) (16.7 ) (241.3 ) Net premiums earned 573.5 541.7 537.2 530.3 Net investment income 49.1 43.4 36.8 47.6 Net realized investment (losses) gains (15.4 ) (35.1 ) 85.3 54.2 Other income 1.1 1.0 — — 608.3 551.0 659.3 632.1 EXPENSES: Net losses and loss expenses 273.0 336.1 314.9 275.3 Acquisition costs 80.7 72.4 74.3 67.7 General and administrative expenses 100.9 88.3 96.2 80.3 Other expense 2.0 6.6 — — Amortization of intangible assets 0.6 0.6 0.7 0.6 Interest expense 14.3 14.3 14.6 14.5 Foreign exchange (gain) loss — 0.3 0.7 — 471.5 518.6 501.4 438.4 Income before income taxes 136.8 32.4 157.9 193.7 Income tax expense 6.2 1.5 6.2 16.6 NET INCOME $ 130.6 $ 30.9 $ 151.7 $ 177.1 PER SHARE DATA Basic earnings per share 1.35 0.32 1.55 1.78 Diluted earnings per share 1.33 0.31 1.52 1.74 Weighted average common shares outstanding 96,386,796 96,458,231 97,809,639 99,545,187 Weighted average common shares and common share equivalents outstanding 98,394,432 98,444,238 99,724,802 101,584,662

Schedule III - Supplementary In

Schedule III - Supplementary Insurance Information	12 Months Ended
	Dec. 31, 2015
Supplementary Insurance Information [Abstract]
Schedule III - Supplementary insurance information	Schedule III ALLIED WORLD ASSURANCE COMPANY HOLDINGS, AG SUPPLEMENTARY INSURANCE INFORMATION (Expressed in thousands of United States dollars Year Ended December 31, 2015 Net Deferred Acquisition Costs Reserve for Losses and Loss Expenses Unearned Premiums Net Premiums Earned Net Investment Income Losses and Loss Expenses Amortization of Deferred Acquisition Costs Other Operating Costs Net Premiums Written North American Insurance $ 70.1 $ 3,998.2 $ 1,061.5 $ 1,301.4 $ — $ 910.2 $ 139.6 $ 224.6 $ 1,358.1 Global Markets Insurance 26.2 972.4 327.8 366.8 — 240.3 70.9 108.4 324.1 Reinsurance 68.9 1,485.6 294.0 820.2 — 435.8 164.9 73.3 765.8 Corporate — — — — 182.1 — — — — Total $ 165.2 $ 6,456.2 $ 1,683.3 $ 2,488.4 $ 182.1 $ 1,586.3 $ 375.4 $ 406.3 $ 2,448.0 Year Ended December 31, 2014 Net Deferred Acquisition Costs Reserve for Losses and Loss Expenses Unearned Premiums Net Premiums Earned Net Investment Income Losses and Loss Expenses Amortization of Deferred Acquisition Costs Other Operating Costs Net Premiums Written North American Insurance $ 55.7 $ 3,806.6 $ 1,003.1 $ 1,111.1 $ — $ 683.8 $ 105.9 $ 219.7 $ 1,230.8 Global Markets Insurance 23.3 568.2 223.4 162.6 — 61.1 18.2 68.1 188.0 Reinsurance 72.5 1,506.4 328.8 909.0 — 454.3 171.0 78.0 903.2 Corporate — — — — 176.9 — — — — Total $ 151.5 $ 5,881.2 $ 1,555.3 $ 2,182.7 $ 176.9 $ 1,199.2 $ 295.1 $ 365.7 $ 2,322.0 Year Ended December 31, 2013 Net Deferred Acquisition Costs Reserve for Losses and Loss Expenses Unearned Premiums Net Premiums Earned Net Investment Income Losses and Loss Expenses Amortization of Deferred Acquisition Costs Other Operating Costs Net Premiums Written North American Insurance $ 45.4 $ 3,701.7 $ 872.6 $ 1,023.0 $ — $ 651.2 $ 94.8 $ 209.0 $ 1,082.5 Global Markets Insurance 9.8 568.7 164.8 126.0 — 50.4 10.1 63.2 145.0 Reinsurance 71.4 1,496.1 358.8 856.9 — 421.6 147.8 80.1 893.0 Corporate — — — — 157.6 — — — — Total $ 126.6 $ 5,766.5 $ 1,396.2 $ 2,005.9 $ 157.6 $ 1,123.2 $ 252.7 $ 352.3 $ 2,120.5

Schedule IV - Supplementary Rei

Schedule IV - Supplementary Reinsurance Information	12 Months Ended
	Dec. 31, 2015
Supplemental Schedule of Reinsurance Premiums for Insurance Companies [Abstract]
Schedule IV - Supplementary reinsurance information	Schedule IV ALLIED WORLD ASSURANCE COMPANY HOLDINGS, AG SUPPLEMENTARY REINSURANCE INFORMATION (Expressed in thousands of United States dollars) Property and Casualty: (a) Gross (b) Ceded to Other Companies (c) Assumed from Other Companies (d) Net Amount (a) - (b) + (c) Percentage of Amount Assumed to Net (c) / (d) Year Ended December 31, 2015 $ 2,291.6 $ 645.0 $ 801.4 $ 2,448.0 33% Year Ended December 31, 2014 $ 1,996.8 $ 613.4 $ 938.6 $ 2,322.0 40% Year Ended December 31, 2013 $ 1,804.9 $ 618.2 $ 933.8 $ 2,120.5 44%

Significant Accounting Polici29

Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Basis of accounting	Intercompany accounts and transactions have been eliminated on consolidation and all entities meeting consolidation requirements have been included in the consolidated financial statements. To facilitate comparison of information across periods, certain reclassifications have been made to prior year amounts to conform to the current year's presentation. These consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States (“U.S. GAAP”).
Use of estimates	The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. The significant estimates reflected in the Company’s financial statements include, but are not limited to: • The premium estimates for certain reinsurance agreements, • Recoverability of deferred acquisition costs, • The reserve for outstanding losses and loss expenses, • Valuation of ceded reinsurance recoverables, • Determination of impairment of goodwill and other intangible assets, and • Valuation of financial instruments.
Premiums	Premiums are recorded as written on the inception date of the policy. For certain types of business written by the Company, notably assumed reinsurance, the exact premium income may not be known at the policy inception date. In the case of quota share reinsurance treaties assumed by the Company, the underwriter makes an estimate of premium income at inception. The underwriter’s estimate is based on statistical data provided by reinsureds and the underwriter’s judgment and experience. Such estimations are refined over the reporting period of each treaty as actual written premium information is reported by ceding companies and intermediaries. Premiums resulting from changes in the estimate of the premium income are recorded in the period the estimate is changed. Certain insurance and reinsurance contracts may require that the premium be adjusted at the expiry of the contract to reflect the change in exposure or loss experience of the insured or reinsured. Premiums are recognized as earned over the period of policy coverage in proportion to the risks to which they relate. Reinsurance premiums under a losses-occurring reinsurance contract are earned over the coverage period. Reinsurance premiums under a risks-attaching reinsurance contract are earned over the same period as the underlying policies, or risks, covered by the contract. As a result, the earning pattern of a risks-attaching reinsurance contract may extend up to 24 months, reflecting the inception dates of the underlying policies. Premiums relating to the unexpired periods of coverage are recorded on the consolidated balance sheets as “unearned premiums”.
Acquisition costs	Acquisition costs, comprised of commissions, brokerage fees and insurance taxes, are costs that are directly related to the successful acquisition of new and renewal business and are deferred. While permitted under U.S. GAAP to defer certain internal costs that are directly related to the successful acquisition of new and renewal business, the Company does not defer such costs. Acquisition costs that are deferred, and carried on the balance sheets as an asset, are expensed as the premiums to which they relate are earned. Expected losses and loss expenses, other costs and anticipated investment income related to these unearned premiums are considered in determining the recoverability or deficiency of deferred acquisition costs. If it is determined that deferred acquisition costs are not recoverable, they are expensed. Further analysis is performed to determine if a liability is required to provide for losses which may exceed the related unearned premiums. Acquisition costs recorded in the consolidated statements of operations and comprehensive income (“consolidated income statements”) includes other acquisition-related costs such as profit commissions that are expensed as incurred and the amortization of insurance-related intangible assets.
Reserve for losses and loss expenses	The reserve for losses and loss expenses is comprised of two main elements: outstanding loss reserves (“OSLR,” also known as case reserves) and reserves for losses incurred but not reported (“IBNR”). OSLR relate to known claims and represent management’s best estimate of the likely loss payment. Reserves for IBNR relates to reserves established by the Company for claims that have occurred but have not yet been reported to us as well as for changes in the values of claims that have been reported to us but are not yet settled. The reserve for IBNR is estimated by management for each line of business based on various factors including underwriters’ expectations about loss experience, actuarial analysis, comparisons with the results of industry benchmarks and loss experience to date. The Company’s actuaries employ generally accepted actuarial methodologies to determine estimated ultimate loss reserves. The adequacy of the reserves is re-evaluated quarterly by the Company’s actuaries. At the completion of each quarterly review of the reserves, a reserve analysis is prepared and reviewed with the Company’s loss reserve committee. This committee determines management’s best estimate for loss and loss expense reserves based upon the reserve analysis. While management believes that OSLR and the reserves for IBNR are sufficient to cover losses assumed by the Company, there can be no assurance that losses will not deviate from the Company’s reserves, possibly by material amounts. The methodology of estimating loss reserves is periodically reviewed to ensure that the assumptions made continue to be appropriate. The Company recognizes any changes in its loss reserve estimates, including prior year loss reserve development, and the related reinsurance recoverables are recorded in “net losses and loss expenses” in the consolidated income statements in the periods in which they are determined.
Ceded reinsurance	In the ordinary course of business, the Company uses both treaty and facultative reinsurance to minimize its net loss exposure to any one catastrophic loss event or to an accumulation of losses from a number of smaller events. Reinsurance premiums ceded are expensed and any commissions recorded thereon are earned over the period the reinsurance coverage is provided in proportion to the risks to which they relate. For reinsurance treaties that have contractual minimum premium provisions, premiums ceded are recorded at the inception of the treaty based on the minimum premiums. Prepaid reinsurance represents unearned premiums ceded to reinsurance companies. Any unearned ceding commission is included in “net deferred acquisitions costs” on the consolidated balance sheets and is recorded as a reduction to the overall net deferred acquisition cost balance. Reinsurance recoverable includes the balances due from those reinsurance companies under the terms of the Company’s reinsurance agreements for unpaid losses and loss reserves, including IBNR, and is presented net of a provision for uncollectible reinsurance. Amounts recoverable from reinsurers are estimated in a manner consistent with the estimated claim liability associated with the reinsured policy. The Company determines the portion of the IBNR liability that will be recoverable under its reinsurance contracts by reference to the terms of the reinsurance protection purchased. This determination is necessarily based on the estimate of IBNR and accordingly, is subject to the same uncertainties as the estimate of IBNR. The Company remains liable to the extent that its reinsurers do not meet their obligations under the reinsurance contracts; therefore, the Company regularly evaluates the financial condition of its reinsurers and monitors concentration of credit risk.
Investments	Investment securities are recorded on a trade date basis. Investment income is recognized when earned and includes the accrual of discount or amortization of premium on fixed maturity investments using the effective yield method and is net of related expenses. Interest income for fixed maturity investments is accrued and recognized based on the contractual terms of the fixed maturity investments and is included in “net investment income” in the consolidated income statements. The Company’s share of distributed and undistributed net income from equity method investments is included in net investment income. The return on investments is managed on a total financial statement portfolio return basis, which includes the distributed and undistributed net income from equity method investments, and as such have classified these amounts in net investment income. Realized gains and losses on the disposition of investments, which are based upon the first-in first-out method of identification, are included in “net realized investment (losses) gains” in the consolidated income statements. For mortgage-backed and asset-backed securities and any other holdings for which there is a prepayment risk, prepayment assumptions are evaluated and revised on a regular basis. Revised prepayment assumptions are applied to securities on a retrospective basis to the date of acquisition. The cumulative adjustments to amortized cost required due to these changes in effective yields and maturities are recognized in net investment income in the same period as the revision of the assumptions. All fixed maturity investments and equity securities are classified as trading securities as the Company has elected the fair value option permitted under U.S. GAAP for these investments. Trading securities are carried at fair value with any change in unrealized gains or losses recognized in the consolidated income statements and included in “net realized investment (losses) gains”. As a result of this investment classification, the Company does not record any change in unrealized gains or losses on investments as a separate component of accumulated other comprehensive income on the consolidated balance sheets. Other invested assets consist primarily of investments in hedge funds and private equity funds, which have been accounted for as trading securities as the Company has elected the fair value option as permitted under U.S. GAAP. In addition, included in the Company’s other invested assets are various investments which are accounted for using the equity method of accounting. Generally, the Company uses the equity method where it does not have a controlling interest and is not the primary beneficiary. Equity method investments are recorded at cost and adjusted for the Company’s proportionate share of earnings or losses on a quarterly lag basis. An other-than-temporary impairment charge related to the equity method investments is assessed when facts and circumstances exists that indicate an impairment may exist. An other-than-temporary impairment charge is recorded when it is determined that the carrying value of the equity method investment is below its fair value and the Company does not have the intent and ability to hold to recovery. See note 4(c) for additional information regarding an other-than-temporary impairment charge recorded related to one of the Company's equity method investments. No equity method investment, individually or in the aggregate, was deemed significant to disclose summarized financial data. Other investments are recorded based on valuation techniques depending on the nature of the individual assets.
Fair value measurements	At each measurement date, the Company estimates the fair value of the financial instruments using various valuation techniques. The Company utilizes, to the extent available, quoted market prices in active markets or observable market inputs in estimating the fair value of financial instruments. When quoted market prices or observable market inputs are not available, the Company may utilize valuation techniques that rely on unobservable inputs to estimate the fair value of financial instruments. The Company bases its determination of whether a market is active or inactive on the spread between what a seller is asking for a security and what a buyer is bidding for that security. Spreads that are significantly above historical spreads are considered inactive markets. The Company also considers the volume of trading activity in the determination of whether a market is active or inactive. See note 6 for additional information regarding the fair value of financial instruments. The Company utilizes independent pricing sources to obtain market quotations for securities that have quoted prices in active markets. In general, the independent pricing sources use observable market inputs including, but not limited to, investment yields, credit risks and spreads, benchmarking of like securities, reported trades and sector groupings to determine the fair value. For a majority of the portfolio, the Company obtained two or more prices per security as of December 31, 2015 . When multiple prices are obtained, a price source hierarchy is utilized to determine which price source is the best estimate of the fair value of the security. The price source hierarchy emphasizes more weighting to significant observable inputs such as index pricing and less weighting towards non-binding broker-dealer quotes. In addition, to validate all prices obtained from these pricing sources including non-binding broker-dealer quotes, the Company also obtains prices from its investment portfolio managers and other sources ( e.g. , another pricing vendor), and compares the prices obtained from the independent pricing sources to those obtained from the Company’s investment portfolio managers and other sources. The Company investigates any material differences between the multiple sources and determines which price best reflects the fair value of the individual security. There were no material differences between the prices obtained from the independent pricing sources and the prices obtained from the Company’s investment portfolio managers and other sources as of December 31, 2015 and 2014 .
Variable interest entities	The Company is involved in the normal course of business with variable interest entities (“VIEs”) as a passive investor in certain asset-backed securities issued by third-party VIEs and affiliated VIEs. The Company performs a qualitative assessment at the date when it becomes initially involved in the VIE, followed by ongoing reassessments related to its involvement in VIEs. The Company’s maximum exposure to loss with respect to these investments is limited to the investment carrying amounts reported in the Company’s consolidated balance sheets and any unfunded commitments.
Translation of foreign currencies	Transactions in currencies other than a foreign operation's functional currency are translated into the functional currency of the foreign operation. Foreign currency transaction gains and losses, including those arising from forward exchange contracts, are included in “foreign exchange loss” in the consolidated income statements. Functional currency assets and liabilities are translated into the reporting currency, U.S. dollars, using period-end exchange rates, and functional currency income statements are translated using average exchange rates with the related foreign currency translation adjustment recorded as a separate component of accumulated other comprehensive income or loss.
Cash and cash equivalents	Cash and cash equivalents include amounts held in banks, time deposits, commercial paper, discount notes and U.S. Treasury Bills with maturities of less than three months from the date of purchase.
Income taxes	Allied World Switzerland and certain of its subsidiaries operate in jurisdictions where they are subject to income taxation. Current and deferred income taxes are charged or credited to operations, or to shareholders' equity in certain cases, based upon enacted tax laws and rates applicable in the relevant jurisdiction in the period in which the tax becomes payable. Deferred income taxes are provided for all temporary differences between the bases of assets and liabilities used in the financial statements and those used in the various jurisdictional tax returns. It is the Company’s policy to recognize interest accrued related to unrecognized tax benefits in “interest expense” and penalties in “general and administrative expenses” in the consolidated income statements. The Company has not recorded any interest or penalties during the years ended December 31, 2015 , 2014 and 2013 and the Company has not accrued any payment of interest and penalties as of December 31, 2015 and 2014 .
Employee stock options, restricted stock units and performance-based equity awards	The Company has granted performance-based equity awards to key employees in order to promote the long-term growth and profitability of the Company. Each award represents the right to receive a number of common shares in the future, based upon the achievement of established performance criteria during the applicable performance period. These performance-based equity awards vest after a three-year performance period. The compensation expense for these awards is based on the market value of Allied World Switzerland’s common shares on the grant date, and is recognized on a straight-line basis over the applicable performance and vesting period. The Company will also adjust the compensation expense, as a cumulative adjustment, to the extent the Company's performance is above or below the targeted performance criteria. The Company has also granted cash-equivalent, performance-based awards to certain employees that vest based upon the achievement of established performance criteria during the applicable performance period. These cash-equivalent, performance-based awards vest after a three-year performance period. The amount payable per unit awarded will be equal to the price per share of Allied World Switzerland’s common shares, and as such the Company measures the value of the award each reporting period based on the period-ending share price. The effects of changes in the share price at each period end during the service period are recognized as changes in compensation expense over the service period. The Company will also adjust the compensation expense, as a cumulative adjustment, to the extent the Company's performance is above or below the targeted performance criteria. The Company has an employee stock option plan, which is in run-off, in which the amount of Allied World Switzerland's common shares received as compensation through the issuance of stock options is determined by reference to the value of the shares. Compensation expense for stock options granted to employees is recorded on a straight-line basis over the option vesting period and is based on the fair value of the stock options on the grant date. The fair value of each stock option on the grant date is determined by using the Black-Scholes option-pricing model. The Company has granted restricted stock units (“RSUs”) to certain employees. The compensation expense for the RSUs is based on the market value of Allied World Switzerland’s common shares on the grant date, and is recognized on a straight-line basis over the applicable vesting period. The Company has also granted cash-equivalent RSUs to certain employees that vest on a straight-line basis over the applicable vesting period. The amount payable per unit awarded will be equal to the price per share of Allied World Switzerland’s common shares and as such the Company measures the value of the award each reporting period based on the period ending share price. The effects of changes in the share price at each period end during the service period are recognized as increases or decreases in compensation expense over the service period.
Goodwill and intangible assets	The Company classifies its intangible assets into three categories: (1) intangible assets with finite lives subject to amortization, (2) intangible assets with indefinite lives not subject to amortization, and (3) goodwill. Intangible assets, other than goodwill, generally consist of customer renewal rights, distribution channels, internally generated software, non-compete covenants, trademarks, and insurance licenses. For intangible assets with finite lives, the value of the assets is amortized over their expected useful lives and the expense is included in “amortization and impairment of intangible assets” in the consolidated income statements. The Company tests assets for impairment if conditions exist that indicate the carrying value may not be recoverable. If, as a result of the evaluation, the Company determines that the value of the intangible assets is impaired, then the value of the assets will be written-down in the period in which the determination of the impairment is made. See note 10 for additional information regarding an impairment recorded for one of the Company's intangible assets with finite lives. For indefinite lived intangible assets the Company does not amortize the intangible asset but evaluates and compares the fair value of the assets to their carrying values on an annual basis or more frequently if circumstances warrant. If, as a result of the evaluation, the Company determines that the value of the intangible assets is impaired, then the value of the assets will be written-down in the period in which the determination of the impairment is made. Goodwill represents the excess of the cost of acquisitions over the fair value of net assets acquired and is not amortized. Goodwill is assigned at acquisition to the applicable reporting unit(s) based on the expected benefit to be received by the reporting units from the business combination. The Company determines the expected benefit based on several factors including the purpose of the business combination, the strategy of the Company subsequent to the business combination and structure of the acquired company subsequent to the business combination. A reporting unit is a component of the Company’s business that has discrete financial information that is reviewed by management. In determining the reporting unit, the Company analyzes the inputs, processes, outputs and overall operating performance of the reporting unit. The Company has several reporting units to which the goodwill is allocated to. For goodwill, the Company performs an annual impairment test, or more frequently if circumstances are warranted. The Company may first assess qualitative factors to determine whether it is more likely than not that the fair value of a reporting unit is less than its carrying amount. The results of the qualitative assessment will determine if an entity needs to proceed with the two-step goodwill impairment test. For the year ended December 31, 2015 , the Company elected to bypass the qualitative assessment and performed the first step of the goodwill impairment test. During the fourth quarter of 2015, the Company changed its annual impairment test date from September 30th to October 1st. The Company believes the change in impairment test date is preferable as it aligns to the quarter in which the Company performs the impairment test, which is during the fourth quarter of each year. This change does not result in any delay, acceleration or avoidance of impairment. The first step of the goodwill impairment test is to compare the fair value of the reporting unit with its carrying value, including goodwill. If the carrying amount of the reporting unit exceeds its fair value then the second step of the goodwill impairment test is performed. The second step of the goodwill impairment test compares the implied fair value of the reporting unit’s goodwill with the carrying amount of that goodwill in order to determine the amount of impairment to be recognized. The implied fair value of goodwill is determined by deducting the fair value of a reporting unit’s identifiable assets and liabilities from the fair value of the reporting unit as a whole. The excess of the carrying value of goodwill above the implied goodwill, if any, would be recognized as an impairment charge in the consolidated income statements. We recorded no goodwill impairments during the years ended December 31, 2015 , 2014 and 2013 .
Derivative instruments	The Company utilizes derivative financial instruments as part of its overall risk management strategy. The Company recognizes all derivative financial instruments at fair value as either assets or liabilities on the consolidated balance sheets. The accounting for gains and losses associated with changes in the fair value of a derivative and the effect on the consolidated financial statements depends on its hedge designation and whether the hedge is highly effective in achieving offsetting changes in the fair value of the asset or liability hedged. The Company uses currency forward contracts and foreign currency swaps to manage currency exposure. The Company also utilizes various derivative instruments such as interest rate futures, interest rate swaps and index options, for the purpose of managing market exposures, interest rate volatility, portfolio duration, hedging certain investments, or enhancing investment performance. These derivatives are not designated as hedges and accordingly are carried at fair value on the consolidated balance sheets with realized and unrealized gains and losses included in the consolidated income statements. Refer to Note 5 for the Company’s related disclosure.
Earnings per share	Basic earnings per share is defined as net income available to common shareholders divided by the weighted average number of common shares outstanding for the period, giving no effect to dilutive securities. Diluted earnings per share is defined as net income available to common shareholders divided by the weighted average number of common and common share equivalents outstanding calculated using the treasury stock method for all potentially dilutive securities, including employee stock options, employee share repurchase plan awards, RSUs and performance-based awards. When the effect of dilutive securities would be anti-dilutive, these securities are excluded from the calculation of diluted earnings per share.
Treasury shares	Common shares repurchased by the Company and not subsequently canceled are classified as “treasury shares” on the consolidated balance sheets and are recorded at cost. When shares are reissued from treasury the historical cost, based on the first-in, first-out method, is used to determine the cost of the reissued shares. The difference between the cost of the treasury shares and the par value of the common stock shall be first reflected as additional paid-in capital, but to the extent additional paid-in capital is exhausted the remainder shall reduce retained earnings. The issuance of shares out of treasury have been related to vesting equity-based compensation of the Company's employees and directors.
New accounting pronouncements	In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update 2014-09, “Revenue from Contracts with Customers" (“ASU 2014-09”). ASU 2014-09 provides a framework, through a five-step process, for recognizing revenue from customers, improves comparability and consistency of recognizing revenue across entities, industries, jurisdictions and capital markets, and requires enhanced disclosures. Certain contracts with customers are specifically excluded from the scope of ASU 2014-09, including, among others, insurance contracts accounted for under Accounting Standard Codification 944, Financial Services - Insurance . With the issuance of ASU 2015-14, this standard will be effective on January 1, 2018 with retrospective adoption required for the comparative periods. The Company is currently assessing the impact the adoption of ASU 2014-09 will have on future financial statements and related disclosures. In February 2015, the FASB issued Accounting Standards Update 2015-02, “Amendments to the Consolidation Analysis” (“ASU 2015-02”). ASU 2015-02 amends certain aspects of the consolidation guidance in U.S. GAAP. In particular, it will modify the evaluation of whether limited partnerships and similar legal entities are VIEs or voting interest entities and also eliminates the presumption that a general partner should consolidate a limited partnership, if certain conditions are met. The new guidance will also affect the consolidation analysis of the Company's interests in VIEs, particularly those that have fee arrangements and related party relationships. ASU 2015-02 is effective on January 1, 2016 and adoption is required retrospectively either through a modified retrospective approach by recording a cumulative-effect adjustment to shareholders' equity as of the beginning of the year of adoption or retrospectively for all comparative periods. The Company has determined that the adoption of ASU 2015-02 will result in several of its limited partnership interests meeting the criteria of being considered VIEs. None of the limited partnership interests that will be considered VIE's will be consolidated as the Company is not considered the primary beneficiary. As a result, the Company does not expect any financial statement impact due to the adoption of ASU 2015-02 other than additional disclosures related to the Company's interests in VIEs. In April 2015, the FASB issued Accounting Standards Update 2015-03, “Interest - Imputation of Interest (Subtopic 835-30): Simplifying the Presentation of Debt Issuance Costs” (“ASU 2015-03”). ASU 2015-03 amends existing guidance on the presentation of debt issuance costs in the balance sheets to be recorded as a direct deduction from the carrying amount of the debt liability, consistent with debt discounts. Under existing U.S. GAAP, capitalized debt issuance costs were capitalized as an asset. ASU 2015-03 is effective January 1, 2016, with early application permitted. The Company adopted ASU 2015-03 as of December 31, 2015 and reclassified debt issuance costs from “other assets” to “unamortized discount and debt issuance costs” in the consolidated balance sheets. As a result of the adoption of ASU 2015-03, the amount of debt issuance costs reclassified to “unamortized discount and debt issuance costs” as of December 31, 2014 was $2.7 million . In May 2015, the FASB issued Accounting Standards Update 2015-07, “Fair Value Measurements (Topic 820): Disclosures for Investments in Certain Entities That Calculate Net Asset Value per Share (or Its Equivalent)” (“ASU 2015-07”). ASU 2015-07 removes the requirement to categorize within the fair value hierarchy investments for which fair value is measured using the net asset value per share practical expedient. The Company has applied the net asset value per share practical expedient to all of its private equity and hedge funds in determining fair value. The Company early adopted ASU 2015-07 during the second quarter of 2015, and as a result removed the fair value category for its investments that are measured using the net asset value per share practical expedient that is disclosed in Note 6. In May 2015, the FASB issued Accounting Standards Update 2015-09, “Financial Services - Insurance (Topic 944): Disclosures about Short-Duration Contracts” (“ASU 2015-09”). ASU 2015-09 provides enhanced disclosures, on an annual basis, related to the reserve for losses and loss expenses. The enhanced disclosures required by ASU 2015-09 include (1) net incurred and paid claims development information by accident year, (2) a reconciliation of incurred and paid claims development information to the aggregate carrying amount of the reserve for losses and loss expenses, (3) for each accident year presented of incurred claims development information, the total of reserves for incurred but not reported (IBNR), including expected development on reported claims, included in the reserve for losses and loss expenses and a description of the reserving methodologies and changes to the reserving methodologies, and (4) for each accident year presented of incurred claims development information, quantitative information about claims frequency, as well as a description of methodologies used for determining claim frequency information. ASU 2015-09 is effective for annual periods beginning after December 15, 2015, and as such the disclosures will first be presented in the Company's Annual Report on Form 10-K for the year ended December 31, 2016. The Company is currently assessing the impact the adoption of ASU 2015-09 will have on future disclosures. In September 2015, the FASB issued Accounting Standards Update 2015-16, “Business Combinations (Topic 805): Simplifying the Accounting for Measurement-Period Adjustments” (“ASU 2015-16”). ASU 2015-16 requires an acquirer in a business combination to recognize adjustments to the provisional amounts identified during the measurement period in the reporting period in which the adjustment amounts are determined. The acquirer is also required to either present separately on the face of the income statement or disclose in the notes to the financial statements the portion of the amounts recorded in the current-period earnings by line item that would have been recorded in previous periods if the adjustment to the provisional amounts had been recognized as of the acquisition date. Under existing U.S. GAAP, the acquirer is required to retrospectively adjust provisional amounts recognized at the acquisition date with a corresponding adjustment to goodwill. ASU 2015-16 is effective for annual periods beginning after December 31, 2015, with early application permitted, and shall apply to adjustments to provisional amounts that occur after the effective date. The Company early adopted ASU 2015-16 during the fourth quarter of 2015. As a result of the adoption of ASU 2015-16, the final measurement-period adjustments recorded for the acquisitions of the Hong Kong and Singapore operations of Royal & Sun Alliance Insurance plc (“RSA”) were recorded during the fourth quarter of 2015, which was the period in which the Company finalized its purchase price accounting. In January 2016, the FASB issued Accounting Standards Update 2016-01, “Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities” (“ASU 2016-01”). ASU 2016-01 changes current U.S. GAAP for public entities by requiring the following, among others: (1) equity securities, except those accounted for under the equity method of accounting, to be measured at fair value with changes in fair value recognized in net income; (2) the use of the exit price when measuring fair value of financial instruments for disclosure purposes; (3) an entity to present separately in other comprehensive income the portion of the total change in the 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; and (4) separate presentation of financial assets and financial liabilities by measurement category and form of financial asset on the balance sheet or notes to the financial statements. ASU 2016-01 is effective for annual periods beginning after January 1, 2018, including interim periods. Early application is permitted. The Company is currently assessing the impact the adoption of ASU 2016-01 will have on future financial statements and disclosures.

Acquisitions (Tables)

Acquisitions (Tables)	12 Months Ended
	Dec. 31, 2015
Business Combinations [Abstract]
Summary of consideration paid and amounts of assets acquired and liabilities assumed	The following table summarizes the consideration paid for the Hong Kong and Singapore branches of RSA and the preliminary amounts of the assets acquired and liabilities assumed at the acquisition date. Consideration: Fair Value Cash consideration $ 176.5 Recognized amounts of identifiable assets acquired and liabilities assumed: Fixed maturity investments 246.1 Cash and cash equivalents 47.1 Insurance balances receivable 114.4 Prepaid reinsurance 17.5 Reinsurance recoverable 58.9 Value of business acquired 28.9 Intangible assets 79.9 Other assets 9.9 Reserve for losses and loss expenses (314.1 ) Unearned premiums (150.5 ) Reinsurance balances payable (35.8 ) Net deferred tax liabilities (11.9 ) Accounts payable and accrued liabilities (20.1 ) Total identifiable net assets acquired 70.3 Goodwill 106.2 Total net assets acquired $ 176.5
Summary of intangible assets acquired	The following is a breakdown of the intangible assets acquired. Singapore Branch Estimated Useful Life Hong Kong Branch Estimated Useful Life Total VOBA $ 17.8 2 years $ 11.1 1.5 years $ 28.9 Customer renewals 8.6 4 years 4.4 5 years 13.0 Distribution channels 47.7 18 years 19.2 18 years 66.9 $ 74.1 $ 34.7 $ 108.8
Summary of results since acquisition	The following summarizes the results of the Hong Kong and Singapore branches that have been included in the Company’s consolidated income statement since the acquisitions closed on April 1, 2015. From April 1, 2015 to December 31, 2015 Total revenue $ 155.3 Net loss $ (28.9 )
Pro forma information	The following unaudited pro forma information presents the combined results of the Company and the acquired Hong Kong and Singapore RSA branches for the years ended December 31, 2015 and 2014, with pro forma adjustments related to the acquisition method of accounting as if the acquisitions had been consummated as of January 1, 2014. This unaudited pro forma information is not necessarily indicative of what would have occurred had the acquisitions and related transactions been made on the dates indicated, or of future results of the Company. Year Ended December 31, 2015 Year Ended December 31, 2014 Total revenue $ 2,594.2 $ 2,681.7 Net income $ 74.2 $ 505.9

Investments (Tables)

Investments (Tables)	12 Months Ended
	Dec. 31, 2015
Investments [Abstract]
Schedule of trading securities	Securities accounted for at fair value with changes in fair value recognized in the consolidated income statements by category are as follows: December 31, 2015 December 31, 2014 Fair Value Amortized Cost Fair Value Amortized Cost U.S. government and government agencies $ 1,434.0 $ 1,437.9 $ 1,610.5 $ 1,610.9 Non-U.S. government and government agencies 556.8 579.2 188.2 196.3 States, municipalities and political subdivisions 413.5 396.0 170.6 165.6 Corporate debt: Financial institutions 1,275.4 1,277.3 1,024.7 1,018.8 Industrials 1,308.1 1,345.6 1,029.7 1,037.8 Utilities 118.9 125.4 111.0 111.6 Mortgage-backed: Agency mortgage-backed 751.8 745.4 624.4 611.8 Non-agency residential mortgage-backed 34.0 32.4 93.4 68.8 Commercial mortgage-backed 582.8 600.1 545.7 539.1 Asset-backed 726.2 751.1 670.8 674.5 Total fixed maturity investments, trading $ 7,201.5 $ 7,290.6 $ 6,069.0 $ 6,035.2 December 31, 2015 December 31, 2014 Fair Value Cost Fair Value Cost Equity securities $ 403.0 $ 395.3 $ 844.2 $ 791.2 Other invested assets 840.2 770.9 812.5 725.1 $ 1,243.2 $ 1,166.2 $ 1,656.7 $ 1,516.3
Schedule of other invested assets	Details regarding the carrying value, redemption characteristics and unfunded investment commitments of the other invested assets portfolio as of December 31, 2015 and 2014 were as follows: Fund Type Carrying Value as of December 31, 2015 Investments with Redemption Restrictions Estimated Remaining Restriction Period Investments without Redemption Restrictions Redemption Frequency(1) Redemption Notice Period(1) Unfunded Commitments Private equity (primary and secondary) $ 236.4 $ 236.4 1 - 7 Years $ — $ 231.0 Mezzanine debt 205.9 205.9 4 - 8 Years — 179.0 Distressed 5.1 5.1 2 Years — 3.8 Real estate — — 7 - 9 Years — 200.0 Total private equity 447.4 447.4 — 613.8 Distressed 215.6 54.6 2 Years 161.0 Monthly 90 Days — Equity long/short 58.0 — 58.0 Quarterly 45 Days — Relative value credit 105.4 — 105.4 Quarterly 60 Days — Total hedge funds 379.0 54.6 324.4 — High yield loan fund 13.8 — 13.8 Monthly 30 days — Total other invested assets at fair value 840.2 502.0 338.2 613.8 Other private securities 126.5 — 126.5 — Total other invested assets $ 966.7 $ 502.0 $ 464.7 $ 613.8 Fund Type Carrying Value as of December 31, 2014 Investments Estimated Investments Redemption Redemption Unfunded Private equity (primary and secondary) $ 184.5 $ 184.5 2 - 8 Years $ — $ 223.8 Mezzanine debt 166.9 166.9 5 - 9 Years — 204.2 Distressed 5.9 5.9 3 Years — 5.2 Real estate — — 9 Years — 50.0 Total private equity 357.3 357.3 — 483.2 Distressed 170.2 170.2 — Based on net asset value 60 Days — Equity long/short 84.2 — 84.2 Quarterly 30 - 60 Days — Multi-strategy 51.5 — 51.5 Quarterly 45 - 90 Days — Relative value credit 119.1 — 119.1 Quarterly 60 Days — Total hedge funds 425.0 170.2 254.8 — High yield loan fund 30.2 — 30.2 Monthly 30 days — Total other invested assets at fair value 812.5 527.5 285.0 483.2 Other private securities 143.0 — 143.0 — Total other invested assets $ 955.5 $ 527.5 $ 428.0 $ 483.2 (1) The redemption frequency and notice periods only apply to the investments without redemption restrictions.
Schedule of net investment income	Year Ended December 31, 2015 2014 2013 Fixed maturity investments 164.2 149.5 130.4 Equity securities 13.3 17.6 19.1 Other invested assets: hedge funds and private equity 19.6 12.6 8.2 Other invested assets: other private securities 2.8 13.3 14.7 Cash and cash equivalents 1.7 2.1 2.0 Expenses (19.5 ) (18.2 ) (16.8 ) Net investment income 182.1 176.9 157.6
Components of realized gains and losses	Year Ended December 31, 2015 2014 2013 Gross realized gains on sale of invested assets $ 180.3 $ 195.4 $ 213.6 Gross realized losses on sale of invested assets (106.4 ) (48.2 ) (106.3 ) Net realized and unrealized (losses) gains on derivatives (15.4 ) (39.0 ) 9.5 Mark-to-market (losses) gains: Debt securities, trading (126.3 ) (1.7 ) (117.6 ) Equity securities, trading (41.7 ) 0.4 4.3 Other invested assets, trading (18.1 ) (17.9 ) 56.0 Net realized investment (losses) gains $ (127.6 ) $ 89.0 $ 59.5

Derivative Instruments (Tables)

Derivative Instruments (Tables)	12 Months Ended
	Dec. 31, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Location and amounts of derivative fair values on the unaudited condensed consolidated balance sheets	The following table summarizes information on the location and amounts of derivative fair values on the consolidated balance sheets: December 31, 2015 December 31, 2014 Asset Derivative Notional Amount Asset Derivative Fair Value Liability Derivative Notional Amount Liability Derivative Fair Value Asset Derivative Notional Amount Asset Derivative Fair Value Liability Derivative Notional Amount Liability Derivative Fair Value Foreign exchange contracts $ 41.1 $ 0.1 $ 244.8 $ 3.0 $ 33.9 $ 1.3 $ 167.4 $ 1.0 Interest rate swaps — — 328.2 0.5 — — 571.5 0.7 Total derivatives $ 41.1 $ 0.1 $ 573.0 $ 3.5 $ 33.9 $ 1.3 $ 738.9 $ 1.7
Unrealized and realized gains (losses) on derivatives recorded in the unaudited condensed consolidated income statements	The following table provides the net realized and unrealized (losses) gains on derivatives not designated as hedges recorded on the consolidated income statements: Year Ended December 31, 2015 2014 2013 Foreign exchange contracts $ (7.3 ) $ 0.9 $ 1.3 Total included in foreign exchange loss (7.3 ) 0.9 1.3 Put options — 0.5 (3.8 ) Foreign exchange contracts 0.2 3.5 3.0 Interest rate swaps (13.4 ) (45.4 ) 5.6 Interest rate futures (2.2 ) 2.4 4.7 Total included in net realized investment (losses) gains (15.4 ) (39.0 ) 9.5 Total realized and unrealized (losses) gains on derivatives $ (22.7 ) $ (38.1 ) $ 10.8

Fair Value Of Financial Instr33

Fair Value Of Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Fair value hierarchy and related disclosures	The following table shows the fair value of the Company’s financial instruments and where in the fair value hierarchy the fair value measurements are included as of the dates indicated below: December 31, 2015 Carrying amount Total fair value Level 1 Level 2 Level 3 ASSETS: Fixed maturity investments: U.S. government and government agencies $ 1,434.0 $ 1,434.0 $ 1,396.4 $ 37.6 $ — Non-U.S. government and government agencies 556.8 556.8 — 556.8 — States, municipalities and political subdivisions 413.5 413.5 — 413.5 — Corporate debt: Financial institutions 1,275.4 1,275.4 — 1,275.4 — Industrials 1,308.1 1,308.1 — 1,308.1 — Utilities 118.9 118.9 — 118.9 — Mortgage-backed: Agency mortgage-backed 751.8 751.8 — 650.8 101.1 Non-agency residential mortgage-backed 34.0 34.0 — 29.0 5.0 Commercial mortgage-backed 582.8 582.8 — 582.8 — Asset-backed 726.2 726.2 — 663.2 63.0 Total fixed maturity investments 7,201.5 7,201.5 1,396.4 5,636.1 169.1 Equity securities 403.0 403.0 403.0 — — Other invested assets (1) 840.2 840.2 — — — Total investments $ 8,444.7 $ 8,444.7 $ 1,799.4 $ 5,636.1 $ 169.1 Derivative assets: Foreign exchange contracts $ 0.1 $ 0.1 $ — $ 0.1 $ — LIABILITIES: Derivative liabilities: Foreign exchange contracts $ 3.0 $ 3.0 $ — $ 3.0 $ — Interest rate swaps 0.5 0.5 — 0.5 — Senior notes $ 1,292.9 $ 1,337.9 $ — $ 1,337.9 $ — Other long-term debt $ 23.0 $ 27.7 $ — $ 27.7 $ — December 31, 2014 Carrying amount Total fair value Level 1 Level 2 Level 3 ASSETS: Fixed maturity investments: U.S. government and government agencies $ 1,610.5 $ 1,610.5 $ 1,499.3 $ 111.2 $ — Non-U.S. government and government agencies 188.2 188.2 — 188.2 — States, municipalities and political subdivisions 170.6 170.6 — 170.6 — Corporate debt Financial institutions 1,024.7 1,024.7 — 1,024.7 — Industrials 1,029.7 1,029.7 — 1,029.7 — Utilities 111.0 111.0 — 111.0 — Mortgage-backed Agency mortgage-backed 624.4 624.4 — 444.3 180.1 Non-agency residential mortgage-backed 93.4 93.4 — 93.4 — Commercial mortgage-backed 545.7 545.7 — 544.0 1.7 Asset-backed 670.8 670.8 — 615.4 55.4 Total fixed maturity investments 6,069.0 6,069.0 1,499.3 4,332.5 237.2 Equity securities 844.2 844.2 800.9 — 43.3 Other invested assets (1) 812.5 812.5 — — — Total investments $ 7,725.7 $ 7,725.7 $ 2,300.2 $ 4,332.5 $ 280.5 Derivative assets: Foreign exchange contracts $ 1.3 $ 1.3 $ — $ 1.3 $ — LIABILITIES: Derivative liabilities: Foreign exchange contracts $ 1.0 $ 1.0 $ — $ 1.0 $ — Interest rate swaps 0.7 0.7 $ — 0.7 $ — Senior notes $ 796.1 $ 879.3 $ — $ 879.3 $ — Other long-term debt $ 19.2 $ 22.6 $ — $ 22.6 $ —
Fair value measurements using significant unobservable inputs (Level 3)	The following is a rollforward of the beginning and ending balance of financial instruments using significant unobservable inputs (Level 3): Fair value measurement using significant unobservable inputs (Level 3): Agency MBS Non-agency RMBS CMBS Total mortgage- Asset-backed Equities Balance at December 31, 2013 $ 136.5 $ 9.3 $ 1.6 $ 147.4 $ 93.4 $ 73.9 Realized and unrealized gains (losses) included in net income 5.1 0.4 — 5.5 (2.1 ) (1.3 ) Purchases 98.4 0.1 1.5 100.0 4.7 — Sales (61.4 ) (9.8 ) — (71.2 ) (24.5 ) (29.3 ) Transfers into Level 3 from Level 2 1.5 — — 1.5 28.8 — Transfers out of Level 3 into Level 2 (1) — — (1.4 ) (1.4 ) (44.9 ) — Balance at December 31, 2014 $ 180.1 $ — $ 1.7 $ 181.8 $ 55.4 $ 43.3 Realized and unrealized gains (losses) included in net income (1.0 ) (0.1 ) 0.1 (1.0 ) (6.1 ) 3.5 Purchases 17.7 5.2 1.8 24.7 18.4 — Sales (95.7 ) (0.1 ) (3.6 ) (99.4 ) (23.1 ) (46.8 ) Transfers into Level 3 from Level 2 — — — — 37.3 — Transfers out of Level 3 into Level 2 (1) — — — — (18.9 ) — Balance at December 31, 2015 $ 101.1 $ 5.0 $ — $ 106.1 $ 63.0 $ — Realized and unrealized losses (gains) included in net income for investments still held as of December 31, 2015 $ (1.5 ) $ (0.1 ) $ — $ (1.6 ) $ (0.3 ) $ — Realized and unrealized gains (losses) included in net income for investments still held as of December 31, 2014 $ 4.3 $ — $ — $ 4.3 $ (0.1 ) $ (1.3 ) (1) Transfers out of Level 3 are primarily attributable to the availability of market observable information.

Reserve For Losses And Loss E34

Reserve For Losses And Loss Expenses (Tables)	12 Months Ended
	Dec. 31, 2015
Insurance Loss Reserves [Abstract]
Components of liabilty for unpaid losses and loss expenses	The reserve for losses and loss expenses consists of the following: December 31, 2015 2014 Outstanding loss reserves $ 1,678.5 $ 1,514.1 Reserves for losses incurred but not reported 4,777.7 4,367.1 Reserve for losses and loss expenses $ 6,456.2 $ 5,881.2
Reconciliation of beginning and ending liability for unpaid losses and loss expenses	The table below is a reconciliation of the beginning and ending liability for unpaid losses and loss expenses. Losses incurred and paid are reflected net of reinsurance recoverables. Year Ended December 31, 2015 2014 2013 Gross liability at beginning of year 5,881.2 5,766.5 5,645.5 Reinsurance recoverable at beginning of year (1,340.3 ) (1,234.5 ) (1,141.1 ) Net liability at beginning of year 4,540.9 4,532.0 4,504.4 Acquisition of net reserves for losses and loss expenses 259.3 — — Net losses incurred related to: Current year 1,667.9 1,411.8 1,303.5 Prior years (81.6 ) (212.6 ) (180.3 ) Total incurred 1,586.3 1,199.2 1,123.2 Net paid losses related to: Current year 186.0 171.8 115.7 Prior years 1,201.6 1,001.5 974.0 Total paid 1,387.6 1,173.3 1,089.7 Foreign exchange revaluation and other (22.7 ) (17.0 ) (6.0 ) Net liability at end of year 4,976.2 4,540.9 4,532.0 Reinsurance recoverable at end of year 1,480.0 1,340.3 1,234.5 Gross liability at end of year 6,456.2 5,881.2 5,766.5

Ceded Reinsurance (Tables)

Ceded Reinsurance (Tables)	12 Months Ended
	Dec. 31, 2015
Reinsurance Disclosures [Abstract]
Components of reinsurance recoverable	The amount of reinsurance recoverable is as follows: 2015 2014 OSLR recoverable $ 254.6 $ 232.6 IBNR recoverable 1,225.4 1,107.7 Reinsurance recoverable $ 1,480.0 $ 1,340.3 Reinsurance recoverable on paid losses $ 96.4 $ 86.1
Effects of reinsurance	Direct, assumed and ceded premiums written and earned and losses and loss expenses incurred are as follows: Premiums Written Premiums Earned Losses and Loss Expenses Year Ended December 31, 2015 Direct $ 2,291.6 $ 2,255.3 $ 1,471.6 Assumed 801.4 863.6 442.8 Ceded (645.0 ) (630.5 ) (328.1 ) $ 2,448.0 $ 2,488.4 $ 1,586.3 Year Ended December 31, 2014 Direct $ 1,996.8 $ 1,835.1 $ 1,031.3 Assumed 938.6 941.2 464.7 Ceded (613.4 ) (593.6 ) (296.8 ) $ 2,322.0 $ 2,182.7 $ 1,199.2 Year Ended December 31, 2013 Direct $ 1,804.9 $ 1,664.4 $ 936.1 Assumed 933.8 896.1 430.6 Ceded (618.2 ) (554.6 ) (243.5 ) $ 2,120.5 $ 2,005.9 $ 1,123.2
Schedule of ceded credit risk by reinsurer	December 31, 2015 A.M. Best Reinsurance Recoverable Percentage of Total Prepaid Reinsurance (1) Percentage of Total Munich Re A+ $ 307.9 20.8 % $ 61.7 15.7 % Axis Capital A+ 150.8 10.2 % 32.2 8.2 % Arch Re A+ 115.3 7.8 % 16.0 4.1 % Swiss Re A+ 103.9 7.0 % 57.3 14.6 % RenaissanceRe A+ 94.0 6.4 % 8.0 2.0 % Top five reinsurers 771.9 52.2 % 175.2 44.6 % Other reinsurers’ balances 708.1 47.8 % 217.1 55.4 % Total reinsurance recoverable $ 1,480.0 100.0 % $ 392.3 100.0 % December 31, 2014 A.M. Best Rating Reinsurance Recoverable Percentage of Total Prepaid Reinsurance (1) Percentage of Total Munich Re A+ $ 285.9 21.3 % $ 69.4 19.2 % Axis Capital A+ 148.4 11.1 % 35.5 9.9 % Arch Re A+ 128.4 9.6 % 17.0 4.7 % RenaissanceRe A+ 103.4 7.7 % 12.3 3.4 % Swiss Re A+ 66.9 5.0 % 41.8 11.6 % Top five reinsurers 733.0 54.7 % 176.0 48.8 % Other reinsurers’ balances 607.3 45.3 % 184.7 51.2 % Total reinsurance recoverable $ 1,340.3 100.0 % $ 360.7 100.0 % (1) Prepaid reinsurance represents unearned premiums ceded to reinsurance companies.

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of goodwill and intangible assets	The following table shows the Company’s goodwill and intangible assets at December 31, 2015 and 2014 : Goodwill Indefinite-Lived Intangible Assets Finite-Lived Intangible Assets Net Carrying Value Net Carrying Value Gross Carrying Value Accumulated Amortization Net Carrying Value Balance at December 31, 2013 $ 268.4 $ 23.9 $ 41.3 $ (16.4 ) $ 24.9 Additions 9.9 — — — — Amortization of intangible assets — — — (2.5 ) (2.5 ) Balance at December 31, 2014 278.3 23.9 41.3 (18.9 ) 22.4 Additions 110.1 — 83.5 — 83.5 Impairments — — (1.4 ) — (1.4 ) Amortization of intangible assets — — — (8.3 ) (8.3 ) Foreign currency translation adjustment (0.3 ) — (3.5 ) — (3.5 ) Balance at December 31, 2015 $ 388.1 $ 23.9 $ 119.9 $ (27.2 ) $ 92.7
Schedule of estimated amortization expense	The estimated amortization expense for each of the five succeeding fiscal years and thereafter related to the Company’s finite-lived intangible assets is as follows: Amount 2016 $ 9.5 2017 9.5 2018 8.9 2019 7.3 2020 6.2 2021 and thereafter 51.3 Total $ 92.7

Debt and Financing Arrangemen37

Debt and Financing Arrangements (Tables)	12 Months Ended
	Dec. 31, 2015
Debt Disclosure [Abstract]
Schedule of financing structure	The following table shows the Company’s financing structure: Outstanding(1) Unamortized discount and debt issuance costs Balance(2) December 31, 2015 2006 Senior notes due 2016 (discount is based on imputed interest rate of 3.77%) $ 500.0 $ 0.5 $ 499.5 2010 Senior notes due 2020 (discount is based on imputed interest rate of 2.78%) 300.0 2.3 297.7 2015 Senior notes due 2025 (discount is based on imputed interest rate of 2.18%) 500.0 4.3 495.7 Swiss office building mortgage 17.9 — 17.9 Swiss office building credit facility 5.1 — 5.1 $1,000 million Secured letter of credit facility — uncommitted 507.5 — — $150 million Secured letter of credit facility — committed — — — $ 1,830.5 $ 7.1 $ 1,315.9 December 31, 2014 2006 Senior notes due 2016 (discount is based on imputed interest rate of 3.77%) $ 500.0 $ 1.2 $ 498.8 2010 Senior notes due 2020 (discount is based on imputed interest rate of 2.78%) 300.0 2.7 297.3 Swiss office building mortgage 14.2 — 14.2 Swiss office building credit facility 5.1 — 5.1 $1,000 million Secured letter of credit facility — uncommitted 497.3 — — $150 million Secured letter of credit facility — committed — — — $ 1,316.6 $ 3.9 $ 815.4 (1) Indicates utilization of commitment amount, not drawn borrowings. (2) Represents the principal amount borrowed, net of unamortized discount and debt issuance costs.
Schedule of debt maturities	The following table reflects the Company’s debt maturities, which includes its senior notes and other long-term debt: Amount 2016 $ 500.3 2017 5.4 2018 0.3 2019 0.3 2020 300.3 2021 and thereafter 516.5 Total $ 1,323.1

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Schedule of components of income tax expense	The components of income tax expense are as follows: Year Ended December 31, 2015 2014 2013 Current income tax expense $ 9.8 $ 26.8 $ 21.7 Deferred income tax (benefit) expense (4.0 ) 3.7 (11.9 ) Income tax expense $ 5.8 $ 30.5 $ 9.8
Schedule of sources of income before income tax	Our income is primarily sourced from our Bermuda, U.S., European and Asia Pacific operations. The income before income taxes for these operations are as follows: Year Ended December 31, 2015 2014 2013 Non-U.S. $ 76.9 $ 447.9 $ 401.9 United States 12.8 72.9 25.9 Income before income taxes $ 89.7 $ 520.8 $ 427.8
Schedule of significant components of net deferred tax assets	The significant components of the net deferred tax assets are as follows: December 31, 2015 2014 Deferred tax assets: Reserve for losses and loss expenses $ 22.2 $ 21.6 Equity compensation 14.2 15.3 Unearned premium 18.1 16.9 Deferred acquisition costs 10.5 11.2 Net loss carryforward 27.3 13.8 Total deferred tax assets 92.3 78.8 Deferred tax liabilities: Intangible assets (23.3 ) (13.9 ) Realized gains (3.0 ) (12.8 ) Depreciation (6.4 ) (2.5 ) Market discount on bonds (1.2 ) (0.7 ) Other (5.2 ) (3.1 ) Total deferred tax liabilities (39.1 ) (33.0 ) Net deferred taxes before valuation allowance 53.2 45.8 Valuation allowance (28.8 ) (12.2 ) Net deferred tax assets $ 24.4 $ 33.6
Schedule of current taxes receivable or payable	Current taxes receivable or payable was as follows: December 31, 2015 2014 Current tax receivable $ 5.5 $ 8.6 Current tax payable $ 2.5 $ 0.8
Schedule of reconciliation between effective and expected tax rate	The reconciliation between the Company’s effective tax rate on pre-tax accounting income and the expected tax rate is as follows: Year Ended December 31, 2015 2014 2013 Expected tax rate 7.8 % 7.8 % 7.8 % Income not subject to income tax (14.2 )% (7.1 )% (8.2 )% Valuation allowance 14.5 % 2.3 % — % Foreign taxes at local expected tax rates (1.7 )% 4.4 % 1.4 % Disallowed expenses and capital allowances 3.2 % 0.2 % 1.0 % Prior year refunds and adjustments — % 1.2 % 0.8 % Other (3.2 )% (2.9 )% (0.5 )% Effective tax rate 6.4 % 5.9 % 2.3 %

Shareholders' Equity (Tables)

Shareholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2015
Stockholders' Equity Note [Abstract]
Issued share capital	The issued share capital consists of the following: December 31, 2015 2014 Common shares issued and fully paid, 2015 and 2014: CHF 4.10 per share 95,523,230 100,775,256 Share capital at end of year $ 386.7 $ 408.0
Schedule of common stock outstanding roll forward	2015 2014 Shares issued at beginning of year 100,775,256 103,477,452 Shares canceled (5,252,026 ) (2,702,196 ) Total shares issued at end of year 95,523,230 100,775,256 Treasury shares issued at beginning of year 4,579,774 3,223,806 Shares repurchased 6,047,437 4,906,785 Shares issued out of treasury (811,590 ) (848,621 ) Shares canceled (5,252,026 ) (2,702,196 ) Total treasury shares at end of year 4,563,595 4,579,774 Total shares outstanding at end of year 90,959,635 96,195,482
Dividends paid	The Company paid the following dividends during the years ended December 31, 2015 , 2014 and 2013 : Dividend Paid Partial Per Share Dividend Share Total Paid December 31, 2015 N/A $ 0.260 $ 23.7 October 1, 2015 N/A $ 0.260 $ 23.6 July 2, 2015 N/A $ 0.260 $ 23.6 April 2, 2015 N/A $ 0.225 $ 21.5 January 2, 2015 N/A $ 0.225 $ 21.7 October 2, 2014 N/A $ 0.225 $ 21.7 July 2, 2014 N/A $ 0.225 $ 21.9 April 3, 2014 N/A $ 0.167 $ 16.5 January 2, 2014 N/A $ 0.167 $ 16.7 October 3, 2013 N/A $ 0.167 $ 17.0 July 3, 2013 N/A $ 0.167 $ 17.1 March 12, 2013 CHF 0.11 $ 0.125 $ 13.0
Share repurchases	The Company’s share repurchases were as follows: Year Ended December 31, 2015 2014 2013 Common shares repurchased 6,047,437 4,906,785 5,544,432 Total cost of shares repurchased $ 245.3 $ 175.4 $ 174.7 Average price per share $ 40.56 $ 35.74 $ 31.51

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Summary of activity related to options	The following table summarizes the activity related to options granted and exercised: Year Ended December 31, 2015 2014 2013 Options granted — — — Weighted average grant date fair value $ — $ — $ — Options exercised (454,602 ) (479,831 ) (674,187 ) Total intrinsic value of options exercised $ 12.0 $ 10.3 $ 12.2 Proceeds from option exercises $ 10.1 $ 10.0 $ 12.1 The activity related to the Company’s stock options is as follows: Year Ended December 31, 2015 Options Weighted Average Exercise Price Weighted Average Contractual Term Aggregate Intrinsic Value Outstanding at beginning of year 2,426,674 $ 16.40 Granted — — Exercised (454,602 ) (14.38 ) Forfeited (3,465 ) (20.50 ) Expired — — Outstanding at end of year 1,968,607 16.86 4.0 years $ 40.0 Exercisable at end of year 1,968,607 $ 16.86 4.0 years $ 40.0
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Summary of compensation expense by type of award	The following table shows the total stock-related compensation expense relating to the stock options, RSUs, LTIP and cash equivalent awards. Year Ended December 31, 2015 2014 2013 Stock options $ 0.3 $ 1.9 $ 3.3 RSUs and performance-based equity awards 15.0 12.3 10.7 Cash-equivalent stock awards 34.4 37.8 50.9 Total $ 49.7 $ 52.0 $ 64.9
Rsus Other Than Performance Based Rsus
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Summary of activity related to equity based awards granted and exercised	The activity related to the Company’s RSUs awards is as follows: Year Ended December 31, 2015 Number of Awards Weighted Average Grant Date Fair Value Aggregate Intrinsic Value Outstanding at beginning of year 502,506 $ 32.10 RSUs granted 506,505 40.23 RSUs forfeited (26,646 ) (36.08 ) RSUs fully vested (163,056 ) (30.42 ) Outstanding at end of year 819,309 $ 37.33 $ 30.5
Performance Based Rsus
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Summary of activity related to equity based awards granted and exercised	The activity related to the Company’s performance-based equity awards is as follows: Year Ended December 31, 2015 Number of Awards Weighted Average Grant Date Fair Value Aggregate Intrinsic Value Outstanding at beginning of year 616,641 $ 27.52 Performance-based equity awards granted 234,361 40.24 Additional awards granted due to achievement of performance criteria 91,737 22.29 Performance-based equity awards forfeited (4,541 ) (32.25 ) Performance-based equity awards fully vested (346,515 ) (22.29 ) Outstanding at end of year 591,683 $ 34.78 $ 22.0
Cash-equivalent stock awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Summary of activity related to cash-equivalent equity awards	The activity related to the Company's cash-equivalent RSUs and performance-based equity awards is as follows: RSU's Performance-based Awards Year Ended December 31, 2015 Number of Awards Weighted Average Grant Date Fair Value Number of Awards Weighted Average Grant Date Fair Value Outstanding at beginning of year 1,654,064 $ 27.99 924,906 27.52 Granted 325,805 40.24 156,238 40.24 Additional awards granted due to achievement of performance criteria — — 137,585 22.29 Forfeited (54,964 ) (30.42 ) (5,527 ) (30.39 ) Fully vested (647,822 ) (26.16 ) (519,725 ) (22.29 ) Outstanding at end of year 1,277,083 $ 31.94 693,477 $ 33.25

Earnings Per Share (Tables)

Earnings Per Share (Tables)	12 Months Ended
	Dec. 31, 2015
Earnings Per Share [Abstract]
Comparison of basic and diluted earnings per share	The following table sets forth the comparison of basic and diluted earnings per share: Year Ended December 31, 2015 2014 2013 Basic earnings per share: Net income $ 83.9 $ 490.3 $ 418.0 Weighted average common shares outstanding 92,530,208 97,538,319 102,464,715 Basic earnings per share $ 0.91 $ 5.03 $ 4.08 Year Ended December 31, 2015 2014 2013 Diluted earnings per share: Net income $ 83.9 $ 490.3 $ 418.0 Weighted average common shares outstanding 92,530,208 97,538,319 102,464,715 Share equivalents: Stock options 1,031,666 1,432,960 1,536,939 RSU and LTIP awards 591,773 605,808 864,180 Employee share purchase plan 20,813 14,686 — Weighted average common shares and common share equivalents outstanding — diluted 94,174,460 99,591,773 104,865,834 Diluted earnings per share $ 0.89 $ 4.92 $ 3.98

Commitments And Contingencies (

Commitments And Contingencies (Tables)	12 Months Ended
	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Summary of future minimum rental payments on operating leases	The Company leases office space under operating leases expiring in various years through 2031. The following are future minimum rental payments as of December 31, 2015 : Amount 2016 $ 19.3 2017 25.7 2018 24.8 2019 19.3 2020 14.5 2021 and thereafter 115.3 $ 218.9
Summary of three largest individual producers	The three largest individual producers as a percentage of gross premiums written are as follows: Year Ended December 31, 2015 2014 2013 Marsh & McLennan Companies, Inc. 24 % 25 % 26 % Aon Corporation 16 % 17 % 18 % Willis Group Holdings 11 % 10 % 12 %

Statutory Capital and Surplus (

Statutory Capital and Surplus (Tables)	12 Months Ended
	Dec. 31, 2015
Disclosure Dividend Restrictions And Statutory Requirements [Abstract]
Schedule of statutory capital	The statutory capital and surplus and minimum required statutory capital and surplus for the Company’s most significant regulatory jurisdictions at December 31, 2015 and 2014 were as follows: December 31, 2015 December 31, 2014 Statutory Capital and Surplus Minimum Required Statutory Capital and Surplus Statutory Capital and Surplus Minimum Required Statutory Capital and Surplus Bermuda $ 3,270.9 $ 853.2 $ 3,273.7 $ 876.2 United States 1,215.5 241.0 1,220.3 226.9 Ireland 414.0 26.9 410.8 29.2 Switzerland 183.6 17.7 172.3 19.9 United Kingdom 245.9 231.8 231.7 203.7
Schedule of statutory net income loss	The statutory net income (loss) for the Company’s most significant regulatory jurisdictions for the years ended December 31, 2015 , 2014 and 2013 was as follows: Year Ended December 31, 2015 2014 2013 Bermuda $ 221.5 $ 487.1 $ 467.3 United States 40.5 45.4 36.7 Ireland 3.2 3.2 (4.9 ) Switzerland 10.7 7.4 (6.4 ) United Kingdom (39.4 ) (7.8 ) 9.4
Schedule of allowable dividends by jurisdiction	At December 31, 2015 , the maximum amount of ordinary dividends or distributions that can be paid, without prior regulatory approval, for the Company’s most significant regulatory jurisdictions, were as follows: December 31, 2015 Bermuda $ 817.7 United States 90.0 Ireland 54.0 Switzerland 32.2 United Kingdom 2.4

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2015
Segment Reporting [Abstract]
Summary of segment results	The following tables provide a summary of the segment results: Year Ended December 31, 2015 North American Insurance Global Markets Insurance Reinsurance Total Gross premiums written $ 1,815.3 $ 476.3 $ 801.4 $ 3,093.0 Net premiums written 1,358.1 324.1 765.8 2,448.0 Net premiums earned 1,301.4 366.8 820.2 2,488.4 Net losses and loss expenses (910.2 ) (240.3 ) (435.8 ) (1,586.3 ) Acquisition costs (139.6 ) (70.9 ) (164.9 ) (375.4 ) General and administrative expenses (224.6 ) (108.4 ) (73.3 ) (406.3 ) Underwriting income (loss) 27.0 (52.8 ) 146.2 120.4 Other insurance-related revenue 3.5 — — 3.5 Other insurance-related expenses (2.7 ) (2.5 ) (1.0 ) (6.2 ) Segment income (loss) 27.8 (55.3 ) 145.2 117.7 Net investment income 182.1 Net realized investment losses (127.6 ) Amortization and impairment of intangible assets (9.8 ) Interest expense (61.4 ) Foreign exchange loss (11.3 ) Income before income taxes $ 89.7 Loss and loss expense ratio 69.9 % 65.5 % 53.1 % 63.7 % Acquisition cost ratio 10.7 % 19.3 % 20.1 % 15.1 % General and administrative expense ratio 17.3 % 29.5 % 8.9 % 16.3 % Expense ratio 28.0 % 48.8 % 29.0 % 31.4 % Combined ratio 97.9 % 114.3 % 82.1 % 95.1 % Year Ended December 31, 2014 North American Insurance Global Markets Reinsurance Total Gross premiums written $ 1,716.3 $ 280.5 $ 938.6 $ 2,935.4 Net premiums written 1,230.8 188.0 903.2 2,322.0 Net premiums earned 1,111.1 162.6 909.0 2,182.7 Net losses and loss expenses (683.8 ) (61.1 ) (454.3 ) (1,199.2 ) Acquisition costs (105.9 ) (18.2 ) (171.0 ) (295.1 ) General and administrative expenses (219.6 ) (68.1 ) (78.0 ) (365.7 ) Underwriting income 101.8 15.2 205.7 322.7 Other insurance-related revenue 2.1 — — 2.1 Other insurance-related expenses (1.9 ) (6.7 ) — (8.6 ) Segment income 102.0 8.5 205.7 316.2 Net investment income 176.9 Net realized investment gains 89.0 Amortization of intangible assets (2.5 ) Interest expense (57.8 ) Foreign exchange loss (1.0 ) Income before income taxes $ 520.8 Loss and loss expense ratio 61.5 % 37.6 % 50.0 % 54.9 % Acquisition cost ratio 9.5 % 11.2 % 18.8 % 13.5 % General and administrative expense ratio 19.8 % 41.9 % 8.6 % 16.8 % Expense ratio 29.3 % 53.1 % 27.4 % 30.3 % Combined ratio 90.8 % 90.7 % 77.4 % 85.2 % Year Ended December 31, 2013 North American Insurance Global Markets Reinsurance Total Gross premiums written $ 1,572.3 $ 232.6 $ 933.8 $ 2,738.7 Net premiums written 1,082.5 145.0 893.0 2,120.5 Net premiums earned 1,023.0 126.0 856.9 2,005.9 Net losses and loss expenses (651.2 ) (50.4 ) (421.6 ) (1,123.2 ) Acquisition costs (94.8 ) (10.1 ) (147.8 ) (252.7 ) General and administrative expenses (209.0 ) (63.2 ) (80.1 ) (352.3 ) Underwriting income 68.0 2.3 207.4 277.7 Other insurance-related revenue — — — — Other insurance-related expenses — — — — Segment income 68.0 2.3 207.4 277.7 Net investment income 157.6 Net realized investment gains 59.5 Amortization of intangible assets (2.5 ) Interest expense (56.5 ) Foreign exchange loss (8.0 ) Income before income taxes $ 427.8 Loss and loss expense ratio 63.7 % 40.0 % 49.2 % 56.0 % Acquisition cost ratio 9.3 % 8.0 % 17.2 % 12.6 % General and administrative expense ratio 20.4 % 50.1 % 9.3 % 17.6 % Expense ratio 29.7 % 58.1 % 26.5 % 30.2 % Combined ratio 93.4 % 98.1 % 75.7 % 86.2 %
Analysis of gross premiums written by geographic location	The following table shows an analysis of the Company’s gross premiums written by geographic location of the Company’s subsidiaries. All intercompany premiums have been eliminated. Year Ended December 31, 2015 2014 2013 United States $ 1,893.4 $ 1,795.6 $ 1,636.0 Bermuda 543.6 640.9 676.2 Europe 326.9 318.6 264.9 Asia Pacific 313.1 167.3 161.6 Canada 16.0 13.0 — Total gross premiums written $ 3,093.0 $ 2,935.4 $ 2,738.7
Premiums earned by segment and line of business	The following table shows the Company’s net premiums earned by line of business for each segment for the years ended December 31, 2015 , 2014 and 2013 . Year Ended December 31, 2015 2014 2013 North American Insurance: Casualty $ 424.0 $ 334.6 $ 269.1 Professional liability 343.6 276.1 259.2 Property 162.8 170.3 168.0 Healthcare 144.7 168.5 194.3 Programs 150.7 119.8 107.9 Specialty and other 75.6 41.9 24.5 Total 1,301.4 1,111.1 1,023.0 Global Markets Insurance: Property 106.7 34.0 31.4 Professional liability 102.5 69.1 57.1 Specialty and other 99.8 44.2 23.6 Casualty 57.8 15.3 13.9 Total 366.8 162.6 126.0 Reinsurance: Property 403.5 412.0 336.0 Casualty 224.4 175.5 171.8 Specialty 192.3 321.5 349.1 Total 820.2 909.0 856.9 Total net premiums earned $ 2,488.4 $ 2,182.7 $ 2,005.9

Condensed Consolidated Guaran45

Condensed Consolidated Guarantor Financial Statements (Tables)	12 Months Ended
	Dec. 31, 2015
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Schedule of condensed consolidating balance sheet	Condensed Consolidating Balance Sheet: As of December 31, 2015 Allied World Switzerland (Parent Guarantor) Allied World Bermuda (Subsidiary Issuer) Other Allied World Subsidiaries Consolidating Adjustments Allied World Switzerland Consolidated ASSETS: Investments $ — $ — $ 8,571.2 $ — $ 8,571.2 Cash and cash equivalents 21.8 1.0 585.2 — 608.0 Insurance balances receivable — — 745.9 — 745.9 Funds held — — 640.8 — 640.8 Reinsurance recoverable — — 1,480.0 — 1,480.0 Reinsurance recoverable on paid losses — — 96.4 96.4 Net deferred acquisition costs — — 165.2 — 165.2 Goodwill and intangible assets — — 504.7 — 504.7 Balances receivable on sale of investments — — 36.9 — 36.9 Investments in subsidiaries 3,347.0 4,396.3 — (7,743.3 ) — Due from subsidiaries 173.1 36.4 16.8 (226.3 ) — Other assets 1.8 0.1 660.9 — 662.8 Total assets $ 3,543.7 $ 4,433.8 $ 13,504.0 $ (7,969.6 ) $ 13,511.9 LIABILITIES: Reserve for losses and loss expenses $ — $ — $ 6,456.2 $ — $ 6,456.2 Unearned premiums — — 1,683.3 — 1,683.3 Reinsurance balances payable — — 214.4 — 214.4 Balances due on purchases of investments — — 125.1 — 125.1 Senior notes — 1,292.9 — — 1,292.9 Other long-term debt — — 23.0 — 23.0 Due to subsidiaries 8.5 8.3 209.5 (226.3 ) — Other liabilities 2.7 22.2 159.7 — 184.5 Total liabilities 11.2 1,323.4 8,871.2 (226.3 ) 9,979.4 Total shareholders’ equity 3,532.5 3,110.4 4,632.8 (7,743.3 ) 3,532.5 Total liabilities and shareholders’ equity $ 3,543.7 $ 4,433.8 $ 13,504.0 $ (7,969.6 ) $ 13,511.9 As of December 31, 2014 Allied World Switzerland (Parent Guarantor) Allied World Bermuda (Subsidiary Issuer) Other Allied World Subsidiaries Consolidating Adjustments Allied World Switzerland Consolidated ASSETS: Investments $ — $ — $ 7,868.7 $ — $ 7,868.7 Cash and cash equivalents 32.6 1.7 555.0 — 589.3 Insurance balances receivable — — 664.8 — 664.8 Funds held — — 724.0 — 724.0 Reinsurance recoverable — — 1,340.3 — 1,340.3 Reinsurance recoverable on paid losses — — 86.1 86.1 Net deferred acquisition costs — — 151.5 — 151.5 Goodwill and intangible assets — — 324.6 — 324.6 Balances receivable on sale of investments — — 47.1 — 47.1 Investments in subsidiaries 3,629.3 4,218.0 — (7,847.3 ) — Due from subsidiaries 147.1 19.2 14.4 (180.7 ) — Other assets 1.4 0.5 620.5 — 622.4 Total assets $ 3,810.4 $ 4,239.4 $ 12,397.0 $ (8,028.0 ) $ 12,418.8 LIABILITIES: Reserve for losses and loss expenses $ — $ — $ 5,881.2 $ — $ 5,881.2 Unearned premiums — — 1,555.3 — 1,555.3 Reinsurance balances payable — — 180.1 — 180.1 Balances due on purchases of investments — — 5.4 — 5.4 Senior notes — 796.1 — — 796.1 Other long-term debt — — 19.2 — 19.2 Due to subsidiaries 7.6 6.8 166.3 (180.7 ) — Other liabilities 24.6 19.6 159.1 — 203.3 Total liabilities 32.2 822.5 7,966.6 (180.7 ) 8,640.6 Total shareholders’ equity 3,778.2 3,416.9 4,430.4 (7,847.3 ) 3,778.2 Total liabilities and shareholders’ equity $ 3,810.4 $ 4,239.4 $ 12,397.0 $ (8,028.0 ) $ 12,418.8
Schedule of condensed consolidating income statement	Condensed Consolidating Income Statement: Year Ended December 31, 2015 Allied World Switzerland (Parent Guarantor) Allied World Bermuda (Subsidiary Issuer) Other Allied World Subsidiaries Consolidating Adjustments Allied World Switzerland Consolidated Net premiums earned $ — $ — $ 2,488.4 $ — $ 2,488.4 Net investment income — 0.1 182.0 — 182.1 Net realized investment losses — — (127.6 ) — (127.6 ) Other income — — 3.5 — 3.5 Net losses and loss expenses — — (1,586.3 ) — (1,586.3 ) Acquisition costs — — (375.4 ) — (375.4 ) General and administrative expenses (36.7 ) (0.5 ) (369.1 ) — (406.3 ) Other expense — — (6.2 ) — (6.2 ) Amortization of intangible assets — — (9.8 ) — (9.8 ) Interest expense — (59.2 ) (2.2 ) — (61.4 ) Foreign exchange gain (loss) — — (11.3 ) — (11.3 ) Income tax (expense) benefit (0.1 ) — (5.7 ) — (5.8 ) Equity in earnings of consolidated subsidiaries 120.7 157.3 — (278.0 ) — NET INCOME (LOSS) $ 83.9 $ 97.7 $ 180.3 $ (278.0 ) $ 83.9 Other comprehensive income (loss) (9.3 ) — (9.3 ) 9.3 (9.3 ) COMPREHENSIVE INCOME (LOSS) $ 74.6 $ 97.7 $ 171.0 $ (268.7 ) $ 74.6 Year Ended December 31, 2014 Allied World Switzerland (Parent Guarantor) Allied World Bermuda (Subsidiary Issuer) Other Allied World Subsidiaries Consolidating Adjustments Allied World Switzerland Consolidated Net premiums earned $ — $ — $ 2,182.7 $ — $ 2,182.7 Net investment income 0.1 — 176.8 — 176.9 Net realized investment gains — — 89.0 — 89.0 Other income — — 2.1 — 2.1 Net losses and loss expenses — — (1,199.2 ) — (1,199.2 ) Acquisition costs — — (295.1 ) — (295.1 ) General and administrative expenses (35.6 ) (3.1 ) (327.1 ) — (365.7 ) Other expense — — (8.6 ) — (8.6 ) Amortization of intangible assets — — (2.5 ) — (2.5 ) Interest expense — (55.4 ) (2.3 ) — (57.8 ) Foreign exchange gain (loss) — 0.1 (1.1 ) — (1.0 ) Income tax (expense) benefit (0.1 ) — (30.4 ) — (30.5 ) Equity in earnings of consolidated subsidiaries 525.9 564.6 — (1,090.5 ) — NET INCOME (LOSS) $ 490.3 $ 506.2 $ 584.3 $ (1,090.5 ) $ 490.3 Other comprehensive income (loss) — — — — — COMPREHENSIVE INCOME (LOSS) $ 490.3 $ 506.2 $ 584.3 $ (1,090.5 ) $ 490.3 Year Ended December 31, 2013 Allied World Switzerland (Parent Guarantor) Allied World Bermuda (Subsidiary Issuer) Other Allied World Subsidiaries Consolidating Adjustments Allied World Switzerland Consolidated Net premiums earned $ — $ — $ 2,005.9 $ — $ 2,005.9 Net investment income 0.1 — 157.5 — 157.6 Net realized investment gains — — 59.5 — 59.5 Other income — — — — — Net losses and loss expenses — — (1,123.2 ) — (1,123.2 ) Acquisition costs — — (252.7 ) — (252.7 ) General and administrative expenses (42.1 ) (1.3 ) (308.8 ) — (352.3 ) Other expense — — — — — Amortization of intangible assets — — (2.5 ) — (2.5 ) Interest expense — (55.3 ) (1.2 ) — (56.5 ) Foreign exchange gain (loss) 0.3 (1.0 ) (7.2 ) — (8.0 ) Income tax (expense) benefit 0.1 — (9.9 ) — (9.8 ) Equity in earnings of consolidated subsidiaries 459.6 515.2 — (974.8 ) — NET INCOME (LOSS) $ 418.0 $ 457.6 $ 517.4 $ (974.8 ) $ 418.0 Other comprehensive income (loss) — — — — — COMPREHENSIVE INCOME (LOSS) $ 418.0 $ 457.6 $ 517.4 $ (974.8 ) $ 418.0
Schedule of condensed consolidating statement of cash flows	Condensed Consolidating Statement of Cash Flows: Year Ended December 31, 2015 Allied World Switzerland (Parent Guarantor) Allied World Bermuda (Subsidiary Issuer) Other Allied World Subsidiaries Consolidating Adjustments Allied World Switzerland Consolidated CASH FLOWS PROVIDED BY (USED IN) OPERATING ACTIVITIES $ 339.6 $ 377.7 $ 598.1 $ (811.1 ) $ 504.3 CASH FLOWS PROVIDED BY (USED IN) INVESTING ACTIVITIES: Purchases trading securities — — (5,863.2 ) — (5,863.2 ) Purchases of other invested assets — — (126.7 ) — (126.7 ) Sales of trading securities — — 5,328.8 — 5,328.8 Sales of other invested assets — — 161.3 — 161.3 Net cash paid for acquisitions — — (124.4 ) — (124.4 ) Capital contributions — (496.7 ) 496.7 — — Other — — (11.5 ) — (11.5 ) Net cash provided by (used in) investing activities — (496.7 ) (139.0 ) — (635.7 ) CASH FLOWS PROVIDED BY (USED IN) FINANCING ACTIVITIES: Dividends paid (114.1 ) — — — (114.1 ) Intercompany dividends paid — (378.4 ) (432.7 ) 811.1 — Proceeds from the exercise of stock options 10.1 — — — 10.1 Share repurchases (246.4 ) — — — (246.4 ) Proceeds from senior notes — 496.7 — — 496.7 Proceeds from other long-term debt — — 4.0 — 4.0 Repayment of other long-term debt — — (0.2 ) — (0.2 ) Net cash provided by (used in) financing activities (350.4 ) 118.3 (428.9 ) 811.1 150.1 NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS (10.8 ) (0.7 ) 30.2 — 18.7 CASH AND CASH EQUIVALENTS, BEGINNING OF YEAR 32.6 1.7 555.0 — 589.3 CASH AND CASH EQUIVALENTS, END OF YEAR $ 21.8 $ 1.0 $ 585.2 $ — $ 608.0 Year Ended December 31, 2014 Allied World Switzerland (Parent Guarantor) Allied World Bermuda (Subsidiary Issuer) Other Allied World Subsidiaries Consolidating Adjustments Allied World Switzerland Consolidated CASH FLOWS PROVIDED BY (USED IN) OPERATING ACTIVITIES $ 264.4 $ 292.9 $ 493.8 $ (643.3 ) $ 407.8 CASH FLOWS PROVIDED BY (USED IN) INVESTING ACTIVITIES: Purchases of trading securities — — (7,630.0 ) — (7,630.0 ) Purchases of other invested assets — — (307.9 ) — (307.9 ) Sales of trading securities — — 7,536.9 — 7,536.9 Sales of other invested assets — — 267.9 — 267.9 Net cash paid for acquisitions — — (2.6 ) — (2.6 ) Other — — 8.7 — 8.7 Net cash provided by (used in) investing activities — — (127.0 ) — (127.0 ) CASH FLOWS PROVIDED BY (USED IN) FINANCING ACTIVITIES: Dividends paid (76.7 ) — — — (76.7 ) Intercompany dividends paid — (294.0 ) (349.3 ) 643.3 — Proceeds from the exercise of stock options 10.0 — — — 10.0 Share repurchases (175.9 ) — — — (175.9 ) Proceeds from other long-term debt — — 19.2 — 19.2 Net cash provided by (used in) financing activities (242.6 ) (294.0 ) (330.1 ) 643.3 (223.4 ) NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS 21.8 (1.1 ) 36.7 — 57.4 CASH AND CASH EQUIVALENTS, BEGINNING OF YEAR 10.8 2.8 518.3 — 531.9 CASH AND CASH EQUIVALENTS, END OF YEAR $ 32.6 $ 1.7 $ 555.0 $ — $ 589.3 Year Ended December 31, 2013 Allied World Switzerland (Parent Guarantor) Allied World Bermuda (Subsidiary Issuer) Other Allied World Subsidiaries Consolidating Adjustments Allied World Switzerland Consolidated CASH FLOWS PROVIDED BY (USED IN) OPERATING ACTIVITIES: $ 198.7 $ 265.9 $ 237.9 $ (596.5 ) $ 106.0 CASH FLOWS PROVIDED BY (USED IN) INVESTING ACTIVITIES: Purchases of trading securities — — (7,527.7 ) — (7,527.7 ) Purchases of other invested assets — — (276.9 ) — (276.9 ) Sales of trading securities — — 7,540.2 — 7,540.2 Sales of other invested assets — — 187.5 — 187.5 Other — — 28.8 — 28.8 Net cash provided by (used in) investing activities — — (48.1 ) — (48.1 ) CASH FLOWS PROVIDED BY (USED IN) FINANCING ACTIVITIES: Partial par value reduction (13.0 ) — — — (13.0 ) Dividends paid (34.0 ) — — — (34.0 ) Intercompany dividends paid — (274.5 ) (322.0 ) 596.5 — Proceeds from the exercise of stock options 12.1 — — — 12.1 Share repurchases (173.0 ) — — — (173.0 ) Net cash provided by (used in) financing activities (207.9 ) (274.5 ) (322.0 ) 596.5 (207.9 ) NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS (9.2 ) (8.6 ) (132.2 ) — (150.0 ) CASH AND CASH EQUIVALENTS, BEGINNING OF YEAR 20.0 11.4 650.5 — 681.9 CASH AND CASH EQUIVALENTS, END OF YEAR $ 10.8 $ 2.8 $ 518.3 $ — $ 531.9

Unaudited Quarterly Financial46

Unaudited Quarterly Financial Data (Tables)	12 Months Ended
	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Summary of unaudited consolidated statements of income by quarter	The following are the unaudited consolidated statements of income by quarter for the years ended December 31, 2015 and 2014 : Quarter Ended December 31, September 30, June 30, March 31, REVENUES: Gross premiums written $ 632.3 $ 754.1 $ 826.0 $ 880.6 Premiums ceded (167.5 ) (147.1 ) (222.3 ) (108.1 ) Net premiums written 464.8 607.0 603.7 772.5 Change in unearned premiums 158.0 43.7 42.7 (204.0 ) Net premiums earned 622.8 650.7 646.4 568.5 Net investment income 49.1 45.7 42.8 44.5 Net realized investment (losses) gains (38.8 ) (113.6 ) (20.2 ) 45.0 Other income 1.0 0.7 0.9 0.9 634.1 583.5 669.9 658.9 EXPENSES: Net losses and loss expenses 412.7 416.9 431.5 325.2 Acquisition costs 96.0 100.1 100.6 78.7 General and administrative expenses 95.0 105.8 108.4 97.1 Other expense 1.9 1.3 1.2 1.8 Amortization of intangible assets 3.7 2.7 2.8 0.6 Interest expense 18.1 14.5 14.5 14.3 Foreign exchange loss (gain) 0.9 (0.8 ) 1.3 9.9 628.3 640.5 660.3 527.6 Income (loss) before income taxes 5.8 (57.0 ) 9.6 131.3 Income tax expense (benefit) 4.0 (5.3 ) 0.1 7.0 NET INCOME (LOSS) $ 1.8 $ (51.7 ) $ 9.5 $ 124.3 PER SHARE DATA Basic earnings (loss) per share $ 0.02 $ (0.57 ) $ 0.10 $ 1.30 Diluted earnings (loss) per share $ 0.02 $ (0.57 ) $ 0.10 $ 1.27 Weighted average common shares outstanding 90,934,107 90,882,511 92,441,730 95,935,551 Weighted average common shares and common share equivalents outstanding 92,422,422 90,882,511 93,984,226 97,577,029 Quarter Ended December 31, September 30, June 30, March 31, REVENUES: Gross premiums written $ 565.7 $ 707.9 $ 760.4 $ 901.4 Premiums ceded (137.9 ) (139.2 ) (206.5 ) (129.8 ) Net premiums written 427.8 568.7 553.9 771.6 Change in unearned premiums 145.7 (27.0 ) (16.7 ) (241.3 ) Net premiums earned 573.5 541.7 537.2 530.3 Net investment income 49.1 43.4 36.8 47.6 Net realized investment (losses) gains (15.4 ) (35.1 ) 85.3 54.2 Other income 1.1 1.0 — — 608.3 551.0 659.3 632.1 EXPENSES: Net losses and loss expenses 273.0 336.1 314.9 275.3 Acquisition costs 80.7 72.4 74.3 67.7 General and administrative expenses 100.9 88.3 96.2 80.3 Other expense 2.0 6.6 — — Amortization of intangible assets 0.6 0.6 0.7 0.6 Interest expense 14.3 14.3 14.6 14.5 Foreign exchange (gain) loss — 0.3 0.7 — 471.5 518.6 501.4 438.4 Income before income taxes 136.8 32.4 157.9 193.7 Income tax expense 6.2 1.5 6.2 16.6 NET INCOME $ 130.6 $ 30.9 $ 151.7 $ 177.1 PER SHARE DATA Basic earnings per share 1.35 0.32 1.55 1.78 Diluted earnings per share 1.33 0.31 1.52 1.74 Weighted average common shares outstanding 96,386,796 96,458,231 97,809,639 99,545,187 Weighted average common shares and common share equivalents outstanding 98,394,432 98,444,238 99,724,802 101,584,662

Significant Accounting Polici47

Significant Accounting Policies (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
New Accounting Pronouncement, Early Adoption [Line Items]
Unamortized discount and debt issuance costs	$ 7.1	$ 3.9
New Accounting Pronouncement, Early Adoption, Effect [Member]
New Accounting Pronouncement, Early Adoption [Line Items]
Unamortized discount and debt issuance costs		$ 2.7

Acquisitions (Consideration Tra

Acquisitions (Consideration Transferred and Recognized Amounts of Identifiable Assets and Liabilities) (Details) - USD ($) $ in Millions	Apr. 02, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Recognized amounts of identifiable assets acquired and liabilities assumed:
Goodwill		$ 388.1	$ 278.3	$ 268.4
Hong Kong And Singapore Operations Of Royal Sun Alliance Insurance Plc
Consideration:
Cash consideration	$ 176.5
Recognized amounts of identifiable assets acquired and liabilities assumed:
Fixed maturity investments	246.1
Cash and cash equivalents	47.1
Insurance balances receivable	114.4
Prepaid reinsurance	17.5
Reinsurance recoverable	58.9
Value of business acquired	28.9
Intangible assets	79.9
Other assets	9.9
Reserve for losses and loss expenses	(314.1)
Unearned premiums	(150.5)
Reinsurance balances payable	(35.8)
Net deferred tax liabilities	(11.9)
Accounts payable and accrued liabilities	(20.1)
Total identifiable net assets acquired	70.3
Goodwill	106.2
Total net assets acquired	$ 176.5

Acquisitions (Summary of Intang

Acquisitions (Summary of Intangible Assets Acquired) (Details) - Hong Kong And Singapore Operations Of Royal Sun Alliance Insurance Plc $ in Millions	Apr. 02, 2015USD ($)
Business Acquisition [Line Items]
Intangible assets acquired	$ 108.8
VOBA
Business Acquisition [Line Items]
Intangible assets acquired	28.9
Customer renewals
Business Acquisition [Line Items]
Intangible assets acquired	13
Distribution channels
Business Acquisition [Line Items]
Intangible assets acquired	66.9
SINGAPORE
Business Acquisition [Line Items]
Intangible assets acquired	74.1
SINGAPORE | VOBA
Business Acquisition [Line Items]
Intangible assets acquired	$ 17.8
Estimated useful life	2 years
SINGAPORE | Customer renewals
Business Acquisition [Line Items]
Intangible assets acquired	$ 8.6
Estimated useful life	4 years
SINGAPORE | Distribution channels
Business Acquisition [Line Items]
Intangible assets acquired	$ 47.7
Estimated useful life	18 years
HONG KONG
Business Acquisition [Line Items]
Intangible assets acquired	$ 34.7
HONG KONG | VOBA
Business Acquisition [Line Items]
Intangible assets acquired	$ 11.1
Estimated useful life	1 year 6 months
HONG KONG | Customer renewals
Business Acquisition [Line Items]
Intangible assets acquired	$ 4.4
Estimated useful life	5 years
HONG KONG | Distribution channels
Business Acquisition [Line Items]
Intangible assets acquired	$ 19.2
Estimated useful life	18 years

Acquisitions (Results Since Acq

Acquisitions (Results Since Acquisition and Pro Forma Information) (Details) - Hong Kong And Singapore Operations Of Royal Sun Alliance Insurance Plc - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2014
Business Acquisition [Line Items]
Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual	$ 155.3
Business Combination, Pro Forma Information, Earnings or Loss of Acquiree since Acquisition Date, Actual	$ (28.9)
Business Acquisition, Pro Forma Revenue		$ 2,594.2	$ 2,681.7
Business Acquisition, Pro Forma Net Income (Loss)		$ 74.2	$ 505.9

Acquisitions (Other Details) (D

Acquisitions (Other Details) (Details) - USD ($)	Apr. 02, 2015	Jan. 31, 2015	Dec. 31, 2015	Dec. 31, 2015	Sep. 30, 2015	Apr. 30, 2015	Dec. 31, 2014	Dec. 31, 2013
Business Acquisition [Line Items]
Goodwill			$ 388,100,000	$ 388,100,000			$ 278,300,000	$ 268,400,000
Finite-lived Intangible Assets Acquired				$ 83,500,000
Hong Kong And Singapore Operations Of Royal Sun Alliance Insurance Plc
Business Acquisition [Line Items]
Cash consideration	$ 176,500,000
Cash Acquired from Acquisition			17,400,000
Business Combination, Acquisition Related Costs			9,200,000
Goodwill	106,200,000
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life				12 years
Insurance Related Intangible Liability			$ 8,300,000	$ 8,300,000
Insurance Related Intangible Liability Amortization Period				8 years
Latin American Underwriters Holdings Ltd [Member]
Business Acquisition [Line Items]
Cash consideration		$ 5,100,000
Goodwill		2,500,000
Finite-lived Intangible Assets Acquired		$ 3,600,000
Estimated useful life		3 years
Business Combination, Contingent Consideration, Liability		$ 1,000,000			$ 0
HONG KONG | Hong Kong And Singapore Operations Of Royal Sun Alliance Insurance Plc
Business Acquisition [Line Items]
Goodwill	54,700,000
SINGAPORE | Hong Kong And Singapore Operations Of Royal Sun Alliance Insurance Plc
Business Acquisition [Line Items]
Goodwill	$ 51,500,000
LABUAN | Hong Kong And Singapore Operations Of Royal Sun Alliance Insurance Plc
Business Acquisition [Line Items]
Goodwill						$ 1,400,000

Investments (Narrative) (Detail

Investments (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Jun. 30, 2015	Dec. 31, 2015	Dec. 31, 2014
Other invested assets
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Income (loss) from equity method investments	$ 6.3		$ 9.3
Minimum | Investments with redemption restrictions
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Redemption restriction, lock-up period		1 year
Minimum | Investments without redemption restrictions | Hedge funds
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Redemption notice period		30 days
Gate trigger, percentage		15.00%
Maximum | Investments with redemption restrictions
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Redemption restriction, lock-up period		3 years
Maximum | Investments without redemption restrictions | Hedge funds
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Gate trigger, percentage		25.00%

Investments (Schedule Of Tradin

Investments (Schedule Of Trading Securities) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Equity securities and other invested assets [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities, Fair Value	$ 1,243.2	$ 1,656.7
Trading securities, Amortized Cost	1,166.2	1,516.3
Equity securities
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities, Fair Value	403	844.2
Trading securities, Amortized Cost	395.3	791.2
Other invested assets
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities, Fair Value	840.2	812.5
Trading securities, Amortized Cost	770.9	725.1
Fixed Maturities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities, Fair Value	7,201.5	6,069
Trading securities, Amortized Cost	7,290.6	6,035.2
U.S. Government and Government Agencies
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities, Fair Value	1,434	1,610.5
Trading securities, Amortized Cost	1,437.9	1,610.9
Non-U.S. Government and Government Agencies
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities, Fair Value	556.8	188.2
Trading securities, Amortized Cost	579.2	196.3
States, municipalities and political subdivisions
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities, Fair Value	413.5	170.6
Trading securities, Amortized Cost	396	165.6
Corporate debt: financial institutions
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities, Fair Value	1,275.4	1,024.7
Trading securities, Amortized Cost	1,277.3	1,018.8
Corporate debt: Industrials
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities, Fair Value	1,308.1	1,029.7
Trading securities, Amortized Cost	1,345.6	1,037.8
Corporate debt: utilities
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities, Fair Value	118.9	111
Trading securities, Amortized Cost	125.4	111.6
Agency mortgage-backed
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities, Fair Value	751.8	624.4
Trading securities, Amortized Cost	745.4	611.8
Non-agency residential mortgage-backed
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities, Fair Value	34	93.4
Trading securities, Amortized Cost	32.4	68.8
Commercial mortgage-backed
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities, Fair Value	582.8	545.7
Trading securities, Amortized Cost	600.1	539.1
Asset-backed
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities, Fair Value	726.2	670.8
Trading securities, Amortized Cost	$ 751.1	$ 674.5

Investments (Schedule Of Other

Investments (Schedule Of Other Investments) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets		$ 966.7	$ 955.5
Unfunded commitments		613.8	483.2
Investments with redemption restrictions
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets		502	527.5
Investments without redemption restrictions
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets		$ 464.7	$ 428
Private equity (primary and secondary) | Investments with redemption restrictions | Minimum
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Estimated remaining restriction period		1 year	2 years
Private equity (primary and secondary) | Investments with redemption restrictions | Maximum
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Estimated remaining restriction period		7 years	8 years
Mezzanine debt | Investments with redemption restrictions | Minimum
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Estimated remaining restriction period		4 years	5 years
Mezzanine debt | Investments with redemption restrictions | Maximum
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Estimated remaining restriction period		8 years	9 years
Distressed | Investments with redemption restrictions
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Estimated remaining restriction period		2 years	3 years
Real estate | Investments with redemption restrictions
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Estimated remaining restriction period			9 years
Real estate | Investments with redemption restrictions | Minimum
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Estimated remaining restriction period		7 years
Real estate | Investments with redemption restrictions | Maximum
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Estimated remaining restriction period		9 years
Hedge funds | Investments without redemption restrictions | Minimum
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Redemption notice period		30 days
Distressed funds | Investments with redemption restrictions
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Estimated remaining restriction period			2 years
Distressed funds | Investments without redemption restrictions
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Redemption notice period	[1]	90 days	60 days
Equity long/short | Investments without redemption restrictions
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Redemption notice period	[1]	45 days
Equity long/short | Investments without redemption restrictions | Minimum
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Redemption notice period	[1]		30 days
Equity long/short | Investments without redemption restrictions | Maximum
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Redemption notice period	[1]		60 days
Multi-strategy | Investments without redemption restrictions | Minimum
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Redemption notice period	[1]		45 days
Multi-strategy | Investments without redemption restrictions | Maximum
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Redemption notice period	[1]		90 days
Relative value credit | Investments without redemption restrictions
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Redemption notice period		60 days	60 days	[1]
High yield loan fund | Investments without redemption restrictions
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Redemption notice period	[1]	30 days	30 days
Total Fair Value
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets		$ 840.2	$ 812.5
Unfunded commitments		613.8	483.2
Total Fair Value | Investments with redemption restrictions
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets		502	527.5
Total Fair Value | Investments without redemption restrictions
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets		338.2	285
Total Fair Value | Private equity funds
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets		447.4	357.3
Unfunded commitments		613.8	483.2
Total Fair Value | Private equity funds | Investments with redemption restrictions
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets		447.4	357.3
Total Fair Value | Private equity funds | Investments without redemption restrictions
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets		0	0
Total Fair Value | Private equity (primary and secondary)
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets		236.4	184.5
Unfunded commitments		231	223.8
Total Fair Value | Private equity (primary and secondary) | Investments with redemption restrictions
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets		236.4	184.5
Total Fair Value | Private equity (primary and secondary) | Investments without redemption restrictions
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets		0	0
Total Fair Value | Mezzanine debt
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets		205.9	166.9
Unfunded commitments		179	204.2
Total Fair Value | Mezzanine debt | Investments with redemption restrictions
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets		205.9	166.9
Total Fair Value | Mezzanine debt | Investments without redemption restrictions
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets		0	0
Total Fair Value | Distressed
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets		5.1	5.9
Unfunded commitments		3.8	5.2
Total Fair Value | Distressed | Investments with redemption restrictions
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets		5.1	5.9
Total Fair Value | Distressed | Investments without redemption restrictions
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets		0	0
Total Fair Value | Real estate
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets		0	0
Unfunded commitments		200	50
Total Fair Value | Real estate | Investments with redemption restrictions
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets		0	0
Total Fair Value | Real estate | Investments without redemption restrictions
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets		0	0
Total Fair Value | Hedge funds
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets		379	425
Unfunded commitments		0	0
Total Fair Value | Hedge funds | Investments with redemption restrictions
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets		54.6	170.2
Total Fair Value | Hedge funds | Investments without redemption restrictions
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets		324.4	254.8
Total Fair Value | Distressed funds
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets		215.6	170.2
Unfunded commitments		0	0
Total Fair Value | Distressed funds | Investments with redemption restrictions
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets		54.6	170.2
Total Fair Value | Distressed funds | Investments without redemption restrictions
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets		$ 161	0
Redemption frequency	[1]	Monthly
Total Fair Value | Equity long/short
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets		$ 58	84.2
Unfunded commitments		0	0
Total Fair Value | Equity long/short | Investments with redemption restrictions
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets		0	0
Total Fair Value | Equity long/short | Investments without redemption restrictions
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets		$ 58	$ 84.2
Redemption frequency	[1]	Quarterly	Quarterly
Total Fair Value | Multi-strategy
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets			$ 51.5
Unfunded commitments			0
Total Fair Value | Multi-strategy | Investments with redemption restrictions
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets			0
Total Fair Value | Multi-strategy | Investments without redemption restrictions
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets			$ 51.5
Redemption frequency	[1]		Quarterly
Total Fair Value | Relative value credit
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets		$ 105.4	$ 119.1
Unfunded commitments		0	0
Total Fair Value | Relative value credit | Investments with redemption restrictions
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets		0	0
Total Fair Value | Relative value credit | Investments without redemption restrictions
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets		$ 105.4	$ 119.1
Redemption frequency	[1]	Quarterly	Quarterly
Total Fair Value | High yield loan fund
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets		$ 13.8	$ 30.2
Unfunded commitments		0	0
Total Fair Value | High yield loan fund | Investments with redemption restrictions
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets		0	0
Total Fair Value | High yield loan fund | Investments without redemption restrictions
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets		$ 13.8	$ 30.2
Redemption frequency	[1]	Monthly	Monthly
Carrying Value [Member] | Other private securities
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets		$ 126.5	$ 143
Unfunded commitments		0	0
Carrying Value [Member] | Other private securities | Investments with redemption restrictions
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets		0	0
Carrying Value [Member] | Other private securities | Investments without redemption restrictions
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Other invested assets		$ 126.5	$ 143
[1]	The redemption frequency and notice periods only apply to the investments without redemption restrictions.

Investments (Schedule Of Net In

Investments (Schedule Of Net Investment Income) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Net investment income	$ 49.1	$ 45.7	$ 42.8	$ 44.5	$ 49.1	$ 43.4	$ 36.8	$ 47.6	$ 182.1	$ 176.9	$ 157.6
Fixed maturity investments
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Net investment income									164.2	149.5	130.4
Equity securities
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Net investment income									13.3	17.6	19.1
Other invested assets: hedge funds and private equity
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Income (loss) from equity method investments			$ 6.3							9.3
Net investment income									19.6	12.6	8.2
Other invested assets: other private securities
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Net investment income									2.8	13.3	14.7
Cash and cash equivalents
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Net investment income									1.7	2.1	2
Expenses
Schedule of Investment Income, Reported Amounts, by Category [Line Items]
Net investment income									$ (19.5)	$ (18.2)	$ (16.8)

Investments (Components Of Real

Investments (Components Of Realized Gains And Losses) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Gain (Loss) on Investments [Line Items]
Gross realized gains on sale of invested assets									$ 180.3	$ 195.4	$ 213.6
Gross realized losses on sale of invested assets									(106.4)	(48.2)	(106.3)
Net realized and unrealized losses on derivatives									(15.4)	(39)	9.5
Net realized investment (losses) gains	$ (38.8)	$ (113.6)	$ (20.2)	$ 45	$ (15.4)	$ (35.1)	$ 85.3	$ 54.2	(127.6)	89	59.5
Debt securities
Gain (Loss) on Investments [Line Items]
Mark-to-market changes									(126.3)	(1.7)	(117.6)
Equity securities
Gain (Loss) on Investments [Line Items]
Mark-to-market changes									(41.7)	0.4	4.3
Other invested assets
Gain (Loss) on Investments [Line Items]
Mark-to-market changes									$ (18.1)	$ (17.9)	$ 56

Investments (Pledged Assets) (D

Investments (Pledged Assets) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
In favor of ceding companies, other counterparties, or government authorities
Schedule of Trading Securities and Other Trading Assets [Line Items]
Restricted cash, cash equivalents and investments	$ 2,748.9	$ 3,585.8
Pledged as collateral for letter of credity facility
Schedule of Trading Securities and Other Trading Assets [Line Items]
Restricted cash, cash equivalents and investments	$ 579.3	$ 571.8

Derivative Instruments (Locatio

Derivative Instruments (Location and Amounts of Derivative Fair Values On The Condensed Consolidated Balance Sheets) (Details) - Not designated as hedging instruments - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Other assets
Derivatives, Fair Value [Line Items]
Asset Derivative Notional Amount	$ 41.1	$ 33.9
Asset Derivative Fair Value	0.1	1.3
Accounts payable and accrued liabilities
Derivatives, Fair Value [Line Items]
Liability Derivative Notional Amount	573	738.9
Liability Derivative Fair Value	3.5	1.7
Foreign exchange contracts | Other assets
Derivatives, Fair Value [Line Items]
Asset Derivative Notional Amount	41.1	33.9
Asset Derivative Fair Value	0.1	1.3
Foreign exchange contracts | Accounts payable and accrued liabilities
Derivatives, Fair Value [Line Items]
Liability Derivative Notional Amount	244.8	167.4
Liability Derivative Fair Value	3	1
Interest rate swaps | Other assets
Derivatives, Fair Value [Line Items]
Asset Derivative Notional Amount	0	0
Asset Derivative Fair Value	0	0
Interest rate swaps | Accounts payable and accrued liabilities
Derivatives, Fair Value [Line Items]
Liability Derivative Notional Amount	328.2	571.5
Liability Derivative Fair Value	$ 0.5	$ 0.7

Derivative Instruments (Locat59

Derivative Instruments (Location and Amounts of Unrealized And Realized Gains (Losses) On Derivatives Recorded In The Condensed Consolidated Income Statements) (Details) - Not designated as hedging instruments - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Derivative Instruments, Gain (Loss) [Line Items]
Total realized and unrealized losses (gains) on derivatives	$ (22.7)	$ (38.1)	$ 10.8
Foreign exchange gain (loss)
Derivative Instruments, Gain (Loss) [Line Items]
Total realized and unrealized losses (gains) on derivatives	(7.3)	0.9	1.3
Foreign exchange gain (loss) | Foreign exchange contracts
Derivative Instruments, Gain (Loss) [Line Items]
Total realized and unrealized losses (gains) on derivatives	(7.3)	0.9	1.3
Net realized investment gains (losses)
Derivative Instruments, Gain (Loss) [Line Items]
Total realized and unrealized losses (gains) on derivatives	(15.4)	(39)	9.5
Net realized investment gains (losses) | Put options
Derivative Instruments, Gain (Loss) [Line Items]
Total realized and unrealized losses (gains) on derivatives	0	0.5	(3.8)
Net realized investment gains (losses) | Foreign exchange contracts
Derivative Instruments, Gain (Loss) [Line Items]
Total realized and unrealized losses (gains) on derivatives	0.2	3.5	3
Net realized investment gains (losses) | Interest rate swaps
Derivative Instruments, Gain (Loss) [Line Items]
Total realized and unrealized losses (gains) on derivatives	(13.4)	(45.4)	5.6
Net realized investment gains (losses) | Interest rate futures
Derivative Instruments, Gain (Loss) [Line Items]
Total realized and unrealized losses (gains) on derivatives	$ (2.2)	$ 2.4	$ 4.7

Fair Value Of Financial Instr60

Fair Value Of Financial Instruments (Schedule Of Fair Value Of Financial Instruments) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	$ 7,201.5	$ 6,069
Equity securities	403	844.2
Other invested assets	966.7	955.5
Total investments	8,571.2	7,868.7
Senior notes, net of unamortized discount and debt issuance costs	1,292.9	796.1
Other long-term debt	23	19.2
Total Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	840.2	812.5
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	7,201.5	6,069
Equity securities	403	844.2
Other invested assets	840.2	812.5
Total investments	8,444.7	7,725.7
Senior notes, net of unamortized discount and debt issuance costs	1,292.9	796.1
Other long-term debt	23	19.2
Fair Value, Measurements, Recurring | Foreign exchange contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0.1	1.3
Derivative liabilities	3	1
Fair Value, Measurements, Recurring | Interest rate swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	0.5	0.7
Fair Value, Measurements, Recurring | U.S. Government and Government Agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	1,434	1,610.5
Fair Value, Measurements, Recurring | Non-U.S. Government and Government Agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	556.8	188.2
Fair Value, Measurements, Recurring | States, municipalities and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	413.5	170.6
Fair Value, Measurements, Recurring | Corporate debt: financial institutions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	1,275.4	1,024.7
Fair Value, Measurements, Recurring | Corporate debt: Industrials
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	1,308.1	1,029.7
Fair Value, Measurements, Recurring | Corporate debt: utilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	118.9	111
Fair Value, Measurements, Recurring | Agency mortgage-backed
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	751.8	624.4
Fair Value, Measurements, Recurring | Non-agency residential mortgage-backed
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	34	93.4
Fair Value, Measurements, Recurring | Commercial mortgage-backed
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	582.8	545.7
Fair Value, Measurements, Recurring | Asset-backed
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	726.2	670.8
Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	1,396.4	1,499.3
Equity securities	403	800.9
Other invested assets	0	0
Total investments	1,799.4	2,300.2
Senior notes, net of unamortized discount and debt issuance costs	0	0
Other long-term debt	0	0
Fair Value, Measurements, Recurring | Level 1 | Foreign exchange contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0	0
Derivative liabilities	0	0
Fair Value, Measurements, Recurring | Level 1 | Interest rate swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	0	0
Fair Value, Measurements, Recurring | Level 1 | U.S. Government and Government Agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	1,396.4	1,499.3
Fair Value, Measurements, Recurring | Level 1 | Non-U.S. Government and Government Agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	0	0
Fair Value, Measurements, Recurring | Level 1 | States, municipalities and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	0	0
Fair Value, Measurements, Recurring | Level 1 | Corporate debt: financial institutions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	0	0
Fair Value, Measurements, Recurring | Level 1 | Corporate debt: Industrials
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	0	0
Fair Value, Measurements, Recurring | Level 1 | Corporate debt: utilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	0	0
Fair Value, Measurements, Recurring | Level 1 | Agency mortgage-backed
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	0	0
Fair Value, Measurements, Recurring | Level 1 | Non-agency residential mortgage-backed
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	0	0
Fair Value, Measurements, Recurring | Level 1 | Commercial mortgage-backed
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	0	0
Fair Value, Measurements, Recurring | Level 1 | Asset-backed
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	0	0
Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	5,636.1	4,332.5
Equity securities	0	0
Other invested assets	0	0
Total investments	5,636.1	4,332.5
Senior notes, net of unamortized discount and debt issuance costs	1,337.9	879.3
Other long-term debt	27.7	22.6
Fair Value, Measurements, Recurring | Level 2 | Foreign exchange contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0.1	1.3
Derivative liabilities	3	1
Fair Value, Measurements, Recurring | Level 2 | Interest rate swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	0.5	0.7
Fair Value, Measurements, Recurring | Level 2 | U.S. Government and Government Agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	37.6	111.2
Fair Value, Measurements, Recurring | Level 2 | Non-U.S. Government and Government Agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	556.8	188.2
Fair Value, Measurements, Recurring | Level 2 | States, municipalities and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	413.5	170.6
Fair Value, Measurements, Recurring | Level 2 | Corporate debt: financial institutions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	1,275.4	1,024.7
Fair Value, Measurements, Recurring | Level 2 | Corporate debt: Industrials
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	1,308.1	1,029.7
Fair Value, Measurements, Recurring | Level 2 | Corporate debt: utilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	118.9	111
Fair Value, Measurements, Recurring | Level 2 | Agency mortgage-backed
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	650.8	444.3
Fair Value, Measurements, Recurring | Level 2 | Non-agency residential mortgage-backed
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	29	93.4
Fair Value, Measurements, Recurring | Level 2 | Commercial mortgage-backed
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	582.8	544
Fair Value, Measurements, Recurring | Level 2 | Asset-backed
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	663.2	615.4
Fair Value, Measurements, Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	169.1	237.2
Equity securities	0	43.3
Other invested assets	0	0
Total investments	169.1	280.5
Senior notes, net of unamortized discount and debt issuance costs	0	0
Other long-term debt	0	0
Fair Value, Measurements, Recurring | Level 3 | Foreign exchange contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0	0
Derivative liabilities	0	0
Fair Value, Measurements, Recurring | Level 3 | Interest rate swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	0	0
Fair Value, Measurements, Recurring | Level 3 | U.S. Government and Government Agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	0	0
Fair Value, Measurements, Recurring | Level 3 | Non-U.S. Government and Government Agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	0	0
Fair Value, Measurements, Recurring | Level 3 | States, municipalities and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	0	0
Fair Value, Measurements, Recurring | Level 3 | Corporate debt: financial institutions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	0	0
Fair Value, Measurements, Recurring | Level 3 | Corporate debt: Industrials
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	0	0
Fair Value, Measurements, Recurring | Level 3 | Corporate debt: utilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	0	0
Fair Value, Measurements, Recurring | Level 3 | Agency mortgage-backed
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	101.1	180.1
Fair Value, Measurements, Recurring | Level 3 | Non-agency residential mortgage-backed
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	5	0
Fair Value, Measurements, Recurring | Level 3 | Commercial mortgage-backed
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	0	1.7
Fair Value, Measurements, Recurring | Level 3 | Asset-backed
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	63	55.4
Fair Value, Measurements, Recurring | Total Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	7,201.5	6,069
Equity securities	403	844.2
Other invested assets	840.2	812.5
Total investments	8,444.7	7,725.7
Senior notes, net of unamortized discount and debt issuance costs	1,337.9	879.3
Other long-term debt	27.7	22.6
Fair Value, Measurements, Recurring | Total Fair Value | Foreign exchange contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0.1	1.3
Derivative liabilities	3	1
Fair Value, Measurements, Recurring | Total Fair Value | Interest rate swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	0.5	0.7
Fair Value, Measurements, Recurring | Total Fair Value | U.S. Government and Government Agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	1,434	1,610.5
Fair Value, Measurements, Recurring | Total Fair Value | Non-U.S. Government and Government Agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	556.8	188.2
Fair Value, Measurements, Recurring | Total Fair Value | States, municipalities and political subdivisions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	413.5	170.6
Fair Value, Measurements, Recurring | Total Fair Value | Corporate debt: financial institutions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	1,275.4	1,024.7
Fair Value, Measurements, Recurring | Total Fair Value | Corporate debt: Industrials
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	1,308.1	1,029.7
Fair Value, Measurements, Recurring | Total Fair Value | Corporate debt: utilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	118.9	111
Fair Value, Measurements, Recurring | Total Fair Value | Agency mortgage-backed
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	751.8	624.4
Fair Value, Measurements, Recurring | Total Fair Value | Non-agency residential mortgage-backed
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	34	93.4
Fair Value, Measurements, Recurring | Total Fair Value | Commercial mortgage-backed
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	582.8	545.7
Fair Value, Measurements, Recurring | Total Fair Value | Asset-backed
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading fixed maturity investments	$ 726.2	$ 670.8

Fair Value Of Financial Instr61

Fair Value Of Financial Instruments (Schedule Of Fair Value Measurement Using Significant Unobservable Inputs Level Three) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014
Mortgage-backed
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Opening balance		$ 181.8	$ 147.4
Realized and unrealized gains (losses) included in net income		(1)	5.5
Purchases		24.7	100
Sales		(99.4)	(71.2)
Transfers into Level 3 from Level 2		0	1.5
Transfers out of Level 3 to Level 2		0	(1.4)
Ending balance		106.1	181.8
Realized and unrealized gains (losses) included in net income for investments still held as of balance sheet date		(1.6)	4.3
Non-agency residential mortgage-backed
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Opening balance		0	9.3
Realized and unrealized gains (losses) included in net income		(0.1)	0.4
Purchases		5.2	0.1
Sales		(0.1)	(9.8)
Transfers into Level 3 from Level 2		0	0
Transfers out of Level 3 to Level 2	[1]	0	0
Ending balance		5	0
Realized and unrealized gains (losses) included in net income for investments still held as of balance sheet date		(0.1)	0
Agency mortgage-backed
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Opening balance		180.1	136.5
Realized and unrealized gains (losses) included in net income		(1)	5.1
Purchases		17.7	98.4
Sales		(95.7)	(61.4)
Transfers into Level 3 from Level 2		0	1.5
Transfers out of Level 3 to Level 2	[1]	0	0
Ending balance		101.1	180.1
Realized and unrealized gains (losses) included in net income for investments still held as of balance sheet date		(1.5)	4.3
Commercial mortgage-backed
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Opening balance		1.7	1.6
Realized and unrealized gains (losses) included in net income		0.1	0
Purchases		1.8	1.5
Sales		(3.6)	0
Transfers into Level 3 from Level 2		0	0
Transfers out of Level 3 to Level 2	[1]	0	(1.4)
Ending balance		0	1.7
Realized and unrealized gains (losses) included in net income for investments still held as of balance sheet date		0	0
Asset-backed
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Opening balance		55.4	93.4
Realized and unrealized gains (losses) included in net income		(6.1)	(2.1)
Purchases		18.4	4.7
Sales		(23.1)	(24.5)
Transfers into Level 3 from Level 2		37.3	28.8
Transfers out of Level 3 to Level 2	[1]	(18.9)	(44.9)
Ending balance		63	55.4
Realized and unrealized gains (losses) included in net income for investments still held as of balance sheet date		(0.3)	(0.1)
Equities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Opening balance		43.3	73.9
Realized and unrealized gains (losses) included in net income		3.5	(1.3)
Purchases		0	0
Sales		(46.8)	(29.3)
Transfers into Level 3 from Level 2		0	0
Transfers out of Level 3 to Level 2	[1]	0	0
Ending balance		0	43.3
Realized and unrealized gains (losses) included in net income for investments still held as of balance sheet date		$ 0	$ (1.3)
[1]	Transfers out of Level 3 are primarily attributable to the availability of market observable information.

Reserve For Losses And Loss E62

Reserve For Losses And Loss Expenses (Schedule Of Reserve For Losses And Loss Expenses) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Insurance Loss Reserves [Abstract]
Outstanding loss reserves	$ 1,678.5	$ 1,514.1
Reserves for losses incurred but not reported	4,777.7	4,367.1
Reserve for losses and loss expenses	$ 6,456.2	$ 5,881.2	$ 5,766.5	$ 5,645.5

Reserve For Losses And Loss E63

Reserve For Losses And Loss Expenses (Schedule Of Reconciliation Of Unpaid Losses And Loss Expenses) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Business Acquisition [Line Items]
Gross liability at beginning of year	$ 5,881.2	$ 5,766.5	$ 5,645.5
Reinsurance recoverable at beginning of year	(1,340.3)	(1,234.5)	(1,141.1)
Net liability at beginning of year	4,540.9	4,532	4,504.4
Acquisition of net reserves for losses and loss expenses	259.3	0	0
Net losses incurred related to:
Current year	1,667.9	1,411.8	1,303.5
Prior years	(81.6)	(212.6)	(180.3)
Total incurred	1,586.3	1,199.2	1,123.2
Net paid losses related to:
Current year	186	171.8	115.7
Prior years	1,201.6	1,001.5	974
Total paid	1,387.6	1,173.3	1,089.7
Foreign exchange revaluation	(22.7)	(17)	(6)
Net liability at end of year	4,976.2	4,540.9	4,532
Reinsurance recoverable at end of year	1,480	1,340.3	1,234.5
Gross liability at end of year	6,456.2	$ 5,881.2	$ 5,766.5
Hong Kong And Singapore Operations Of Royal Sun Alliance Insurance Plc
Business Acquisition [Line Items]
Acquisition of net reserves for losses and loss expenses	255.2
Labuan Operations of Royal Sun Alliance
Business Acquisition [Line Items]
Acquisition of net reserves for losses and loss expenses	$ 4.1

Ceded Reinsurance (Narrative) (

Ceded Reinsurance (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2015USD ($)reinsurers	Dec. 31, 2014USD ($)	Dec. 31, 2013
Concentration Risk [Line Items]
Reinsurance Recoverables, Allowance | $	$ 1.2	$ 0
Reinsurance recoverable
Concentration Risk [Line Items]
Concentration risk, percentage	100.00%	100.00%
Credit concentration risk | Premiums ceded
Concentration Risk [Line Items]
Number of ceded reinsurers | reinsurers	4
Concentration risk, percentage	41.10%	42.30%	45.30%
Credit concentration risk | Reinsurance recoverable | A or better rating
Concentration Risk [Line Items]
Concentration risk, percentage	99.00%	99.00%

Ceded Reinsurance (Components o

Ceded Reinsurance (Components of Reinsurance) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Reinsurance Disclosures [Abstract]
OSLR recoverable	$ 254.6	$ 232.6
IBNR recoverable	1,225.4	1,107.7
Reinsurance recoverable	1,480	1,340.3	$ 1,234.5	$ 1,141.1
Reinsurance recoverable on paid losses	$ 96.4	$ 86.1

Ceded Reinsurance (Effects of R

Ceded Reinsurance (Effects of Reinsurance) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reinsurance Disclosures [Abstract]
Direct premiums written									$ 2,291.6	$ 1,996.8	$ 1,804.9
Assumed premiums written									801.4	938.6	933.8
Ceded premiums written	$ (167.5)	$ (147.1)	$ (222.3)	$ (108.1)	$ (137.9)	$ (139.2)	$ (206.5)	$ (129.8)	(645)	(613.4)	(618.2)
Net premiums written	464.8	607	603.7	772.5	427.8	568.7	553.9	771.6	2,448	2,322	2,120.5
Direct premiums earned									2,255.3	1,835.1	1,664.4
Assumed premiums earned									863.6	941.2	896.1
Ceded premiums earned									(630.5)	(593.6)	(554.6)
Net premiums earned	622.8	650.7	646.4	568.5	573.5	541.7	537.2	530.3	2,488.4	2,182.7	2,005.9
Direct losses and loss expenses									1,471.6	1,031.3	936.1
Assumed losses and loss expenses									442.8	464.7	430.6
Ceded losses and loss expenses									(328.1)	(296.8)	(243.5)
Net losses and loss expenses	$ 412.7	$ 416.9	$ 431.5	$ 325.2	$ 273	$ 336.1	$ 314.9	$ 275.3	$ 1,586.3	$ 1,199.2	$ 1,123.2

Ceded Reinsurance (Credit Risk

Ceded Reinsurance (Credit Risk by Reinsurer) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Ceded Credit Risk [Line Items]
Reinsurance recoverable		$ 1,480	$ 1,340.3	$ 1,234.5	$ 1,141.1
Prepaid reinsurance		392.3	360.7
Reinsurance recoverable
Ceded Credit Risk [Line Items]
Reinsurance recoverable		$ 1,480	$ 1,340.3
Percentage of total		100.00%	100.00%
Reinsurance recoverable | Top five reinsurers
Ceded Credit Risk [Line Items]
Reinsurance recoverable		$ 771.9	$ 733
Percentage of total		52.20%	54.70%
Reinsurance recoverable | Top five reinsurers | A plus | Munich Re
Ceded Credit Risk [Line Items]
Reinsurance recoverable		$ 307.9	$ 285.9
Percentage of total		20.80%	21.30%
Reinsurance recoverable | Top five reinsurers | A plus | Axis Capital
Ceded Credit Risk [Line Items]
Reinsurance recoverable		$ 150.8	$ 148.4
Percentage of total		10.20%	11.10%
Reinsurance recoverable | Top five reinsurers | A plus | Arch Re
Ceded Credit Risk [Line Items]
Reinsurance recoverable		$ 115.3	$ 128.4
Percentage of total		7.80%	9.60%
Reinsurance recoverable | Top five reinsurers | A plus | Swiss Re
Ceded Credit Risk [Line Items]
Reinsurance recoverable		$ 103.9	$ 66.9
Percentage of total		7.00%	5.00%
Reinsurance recoverable | Top five reinsurers | A plus | RenaissanceRe
Ceded Credit Risk [Line Items]
Reinsurance recoverable		$ 94	$ 103.4
Percentage of total		6.40%	7.70%
Reinsurance recoverable | Other reinsurers' balances
Ceded Credit Risk [Line Items]
Reinsurance recoverable		$ 708.1	$ 607.3
Percentage of total		47.80%	45.30%
Prepaid Reinsurance [Member]
Ceded Credit Risk [Line Items]
Prepaid reinsurance		$ 392.3	$ 360.7
Percentage of total		100.00%	100.00%
Prepaid Reinsurance [Member] | Top five reinsurers
Ceded Credit Risk [Line Items]
Prepaid reinsurance	[1]	$ 175.2	$ 176
Percentage of total		44.60%	48.80%
Prepaid Reinsurance [Member] | Top five reinsurers | A plus | Munich Re
Ceded Credit Risk [Line Items]
Prepaid reinsurance	[1]	$ 61.7	$ 69.4
Percentage of total		15.70%	19.20%
Prepaid Reinsurance [Member] | Top five reinsurers | A plus | Axis Capital
Ceded Credit Risk [Line Items]
Prepaid reinsurance	[1]	$ 32.2	$ 35.5
Percentage of total		8.20%	9.90%
Prepaid Reinsurance [Member] | Top five reinsurers | A plus | Arch Re
Ceded Credit Risk [Line Items]
Prepaid reinsurance	[1]	$ 16	$ 17
Percentage of total		4.10%	4.70%
Prepaid Reinsurance [Member] | Top five reinsurers | A plus | Swiss Re
Ceded Credit Risk [Line Items]
Prepaid reinsurance	[1]	$ 57.3	$ 41.8
Percentage of total		14.60%	11.60%
Prepaid Reinsurance [Member] | Top five reinsurers | A plus | RenaissanceRe
Ceded Credit Risk [Line Items]
Prepaid reinsurance	[1]	$ 8	$ 12.3
Percentage of total		2.00%	3.40%
Prepaid Reinsurance [Member] | Other reinsurers' balances
Ceded Credit Risk [Line Items]
Prepaid reinsurance	[1]	$ 217.1	$ 184.7
Percentage of total		55.40%	51.20%
[1]	Prepaid reinsurance represents unearned premiums ceded to reinsurance companies.

Funds Held (Details)

Funds Held (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Effects of Reinsurance [Line Items]
Funds held	$ 640.8	$ 724
Assumed premiums written	801.4	938.6	$ 933.8
Aeolus Capital Management [Member]
Effects of Reinsurance [Line Items]
Funds held	622.4	708
Assumed premiums written	$ 76.3	$ 87.3	$ 83.3

Goodwill and Intangible Asset69

Goodwill and Intangible Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Schedule Of Goodwill And Intangible Assets [Line Items]
Goodwill, beginning of year	$ 278.3	$ 268.4
Additions	110.1	9.9
Foreign currency translation adjustment	(0.3)
Goodwill, end of year	388.1	278.3
Indefinite-lived intangible assets, net carrying value, beginning of year	23.9	23.9
Indefinite-lived intangible assets, net carrying value, end of year	23.9	23.9
Finite-Lived Intangible Assets, Net [Abstract]
Gross carrying value	119.9	41.3	$ 41.3
Additions	83.5
Impairments	(1.4)
Accumulated amortization	(27.2)	(18.9)	(16.4)
Foreign currency translation adjustment	(3.5)
Net carrying value	92.7	22.4	24.9
Amortization of intangible assets	(8.3)	(2.5)
Goodwill, accumulated impairment loss			$ 0.2
Intangible assets, accumulated impairment loss	$ 8.2
Expected remaining useful life	13 years 7 months 6 days
North American Insurance
Schedule Of Goodwill And Intangible Assets [Line Items]
Goodwill, end of year	$ 274.3
Global Markets Insurance
Schedule Of Goodwill And Intangible Assets [Line Items]
Goodwill, end of year	109.9
Reinsurance
Schedule Of Goodwill And Intangible Assets [Line Items]
Goodwill, end of year	3.9
Distribution channels
Finite-Lived Intangible Assets, Net [Abstract]
Net carrying value	$ 81	$ 22.4
Expected remaining useful life	15 years
Customer renewals
Finite-Lived Intangible Assets, Net [Abstract]
Net carrying value	$ 11.7
Expected remaining useful life	3 years 4 months 27 days

Goodwill and Intangible Asset70

Goodwill and Intangible Assets (Future amortization expense) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
2,016	$ 9.5
2,017	9.5
2,018	8.9
2,019	7.3
2,020	6.2
2021 and thereafter	51.3
Net carrying value	$ 92.7	$ 22.4	$ 24.9

Debt and Financing Arrangemen71

Debt and Financing Arrangements (Financing Structure) (Details) - USD ($) $ in Millions		Dec. 31, 2015	Dec. 31, 2014
Components of financing structure:
Unamortized discount and debt issuance costs		$ 7.1	$ 3.9
Outstanding, total	[1]	1,830.5	1,316.6
Balance, debt	[2]	1,315.9	815.4
2006 Senior notes due 2016
Components of financing structure:
Outstanding, debt	[1]	500	500
Unamortized discount and debt issuance costs		0.5	1.2
Balance, debt	[2]	$ 499.5	$ 498.8
Imputed interest rate on debt		3.77%	3.77%
2010 Senior notes due 2020
Components of financing structure:
Outstanding, debt	[1]	$ 300	$ 300
Unamortized discount and debt issuance costs		2.3	2.7
Balance, debt	[2]	$ 297.7	$ 297.3
Imputed interest rate on debt		2.78%	2.78%
2015 Senior notes Due 2025
Components of financing structure:
Outstanding, debt	[1]	$ 500
Unamortized discount and debt issuance costs		4.3
Balance, debt	[2]	$ 495.7
Imputed interest rate on debt		2.18%
Swiss office building mortgage
Components of financing structure:
Outstanding, debt	[1]	$ 17.9	$ 14.2
Unamortized discount and debt issuance costs		0	0
Balance, debt	[2]	17.9	14.2
Swiss office building credit facility
Components of financing structure:
Outstanding, credit facility	[1]	5.1	5.1
Unamortized discount and debt issuance costs		0	0
Balance, credit facility	[1]	5.1	5.1
$1,000,000 secured letter of credit facility - uncommitted
Components of financing structure:
Outstanding, credit facility	[1]	507.5	497.3
Unamortized discount and debt issuance costs		0	0
Credit facility, maximum borrowing capacity		1,000	1,000
$150,000 secured letter of credit facility - committed
Components of financing structure:
Outstanding, credit facility	[1]	0	0
Unamortized discount and debt issuance costs		0	0
Credit facility, maximum borrowing capacity		$ 150	$ 450
[1]	Indicates utilization of commitment amount, not drawn borrowings.
[2]	Represents the principal amount borrowed, net of unamortized discount and debt issuance costs.

Debt and Financing Arrangemen72

Debt and Financing Arrangements (Debt Maturities) (Details) $ in Millions	Dec. 31, 2015USD ($)
Maturities of Long-term Debt [Abstract]
2,016	$ 500.3
2,017	5.4
2,018	0.3
2,019	0.3
2,020	300.3
2021 and thereafter	516.5
Total	$ 1,323.1

Debt and Financing Arrangemen73

Debt and Financing Arrangements (Narrative) (Details) SFr in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2015USD ($)	Dec. 31, 2015CHF (SFr)	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)	Dec. 31, 2015CHF (SFr)
Debt Instrument [Line Items]
Principal amount	$ 1,300		$ 800
Proceeds from other long-term debt	4		19.2	$ 0
Allied World Bermuda (Subsidiary Issuer)
Debt Instrument [Line Items]
Proceeds from other long-term debt	0		0
2006 Senior notes due 2016 | Allied World Bermuda (Subsidiary Issuer)
Debt Instrument [Line Items]
Principal amount	$ 500
Debt Instrument, interest rate	7.50%				7.50%
Senior Notes, maturity date	Aug. 1, 2016	Aug. 1, 2016
Senior Notes, frequency of periodic payment	semi-annually	semi-annually
2010 Senior notes due 2020 | Allied World Bermuda (Subsidiary Issuer)
Debt Instrument [Line Items]
Principal amount	$ 300
Debt Instrument, interest rate	5.50%				5.50%
Senior Notes, maturity date	Nov. 15, 2020	Nov. 15, 2020
2015 Senior notes Due 2025 | Allied World Bermuda (Subsidiary Issuer)
Debt Instrument [Line Items]
Principal amount	$ 500
Debt Instrument, interest rate	4.35%				4.35%
Senior Notes, frequency of periodic payment	semi-annually	semi-annually
$1,000,000 secured letter of credit facility - uncommitted
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 1,000		1,000
$1,000,000 secured letter of credit facility - uncommitted | Allied World Bermuda (Subsidiary Issuer)
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 1,000		1,000
$800,000 secured letter of credit facility [Member] | Allied World Bermuda (Subsidiary Issuer)
Debt Instrument [Line Items]
Line of Credit Facility, Initiation Date	Nov. 27, 2007	Nov. 27, 2007
Line of Credit Facility, Maximum Borrowing Capacity	$ 800
Debt instrument term	5 years	5 years
$400,000 secured letter of credit facility (pre-amendment) | Allied World Bermuda (Subsidiary Issuer)
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 400
$400,000 unsecured letter of credit facility | Allied World Bermuda (Subsidiary Issuer)
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	400
$150,000 secured letter of credit facility
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 150		$ 450
$150,000 secured letter of credit facility | Allied World Bermuda (Subsidiary Issuer)
Debt Instrument [Line Items]
Line of Credit Facility, Initiation Date	Jun. 7, 2012	Jun. 7, 2012
Line of Credit Facility, Maximum Borrowing Capacity	$ 450
Debt instrument term	4 years	4 years
Line of Credit Facility, Capacity Available for Specific Purpose Other than for Trade Purchases	$ 150
Additional commitments subject to lender approval	$ 150
Switzerland
Debt Instrument [Line Items]
Number of annual principal payments required	19 years	19 years
Switzerland | Swiss office building mortgage
Debt Instrument [Line Items]
Debt Instrument, interest rate	3.20%				3.20%
Proceeds from other long-term debt	$ 14.2	SFr 14
Additional borrowing capacity	4				SFr 4
Annual principal payment	$ 0.3				SFr 0.3
Debt instrument term	20 years	20 years
Switzerland | Swiss office building credit facility
Debt Instrument [Line Items]
Debt Instrument, interest rate	2.50%				2.50%
Line of Credit Facility, Maximum Borrowing Capacity	$ 5.1				SFr 5
Debt instrument term	3 years	3 years

Income Taxes (Components of Inc

Income Taxes (Components of Income Taxes) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Components of Income Tax Expense (Benefit), Continuing Operations [Abstract]
Current income tax expense									$ 9.8	$ 26.8	$ 21.7
Deferred income tax (benefit) expense									(4)	3.7	(11.9)
Income tax expense	$ 4	$ (5.3)	$ 0.1	$ 7	$ 6.2	$ 1.5	$ 6.2	$ 16.6	$ 5.8	$ 30.5	$ 9.8

Income Taxes (Sources of Income

Income Taxes (Sources of Income) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Before Income Tax Domestic And Foreign [Line Items]
Income before income taxes	$ 5.8	$ (57)	$ 9.6	$ 131.3	$ 136.8	$ 32.4	$ 157.9	$ 193.7	$ 89.7	$ 520.8	$ 427.8
Non-U.S.
Income Before Income Tax Domestic And Foreign [Line Items]
Income before income taxes									76.9	447.9	401.9
United States
Income Before Income Tax Domestic And Foreign [Line Items]
Income before income taxes									$ 12.8	$ 72.9	$ 25.9

Income Taxes (Deferred Tax Comp

Income Taxes (Deferred Tax Components) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Increase in valuation allowance	$ (16.6)
Deferred tax assets:
Reserve for losses and loss expenses	22.2	$ 21.6
Equity compensation	14.2	15.3
Unearned premium	18.1	16.9
Deferred acquisition costs	10.5	11.2
Net loss carryforward	27.3	13.8
Total deferred tax assets	92.3	78.8
Deferred tax liabilities:
Intangible assets	(23.3)	(13.9)
Realized gains	(3)	(12.8)
Depreciation	(6.4)	(2.5)
Market discount on bonds	(1.2)	(0.7)
Other	(5.2)	(3.1)
Total deferred tax liabilities	(39.1)	(33)
Net deferred taxes before valuation allowance	53.2	45.8
Valuation allowance	(28.8)	(12.2)
Net deferred tax assets	$ 24.4	$ 33.6

Income Taxes (Current Taxes) (D

Income Taxes (Current Taxes) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Current tax receivable	$ 5.5	$ 8.6
Current tax payable	$ 2.5	$ 0.8

Income Taxes (Reconciliation of

Income Taxes (Reconciliation of Effective Tax Rate) (Details)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Expected tax rate	7.80%	7.80%	7.80%
Income not subject to income tax	(14.20%)	(7.10%)	(8.20%)
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Percent	14.50%	2.30%	0.00%
Foreign taxes at local expected tax rates	(1.70%)	4.40%	1.40%
Disallowed expenses and capital allowances	3.20%	0.20%	1.00%
Prior year refunds and adjustments	0.00%	1.20%	0.80%
Other	(3.20%)	(2.90%)	(0.50%)
Effective tax rate	6.40%	5.90%	2.30%

Shareholders' Equity (Narrative

Shareholders' Equity (Narrative) (Details) - $ / shares	Apr. 30, 2015	May. 01, 2014	May. 02, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Class of Stock [Line Items]
Stock Repurchased and Retired During Period, Shares				5,252,026	2,702,196
Treasury Stock, Shares, Acquired				6,047,437	4,906,785	5,544,432
Common stock, shares outstanding				90,959,635	96,195,482
Shares cancelled, shares				5,252,026	2,702,196
Maximum percentage of registered capital in treasury shares				10.00%
Allied World Switzerland (Parent Guarantor)
Class of Stock [Line Items]
Threshold for dividend restrictions				20.00%
Minimum Annual Profit Percentage Required				5.00%
Common shares
Class of Stock [Line Items]
Dividends declared per share	$ 0.26	$ 0.225	$ 0.167

Shareholders' Equity (Issued Sh

Shareholders' Equity (Issued Share Capital) (Details) $ in Millions	Dec. 31, 2015USD ($)shares	Dec. 31, 2015SFr / shares	Dec. 31, 2014USD ($)shares	Dec. 31, 2014SFr / shares	Dec. 31, 2013shares
Stockholders' Equity Note [Abstract]
Common shares issued and fully paid, 2015 and 2014: CHF 4.10 per share | shares	95,523,230		100,775,256		103,477,452
Common shares, par value | SFr / shares		SFr 4.1		SFr 4.1
Total share capital | $	$ 386.7		$ 408

Shareholders' Equity (Schedule

Shareholders' Equity (Schedule Of Common Stock Outstanding Roll Forward) (Details) - shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Stockholders' Equity Note [Abstract]
Stock Repurchased and Retired During Period, Shares	(5,252,026)	(2,702,196)
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Shares issued at beginning of year	100,775,256	103,477,452
Shares cancelled, shares	(5,252,026)	(2,702,196)
Shares issued at end of year	95,523,230	100,775,256	103,477,452
Treasury Stock Transactions, Excluding Value of Shares Reissued [Abstract]
Treasury shares issued at beginning of year	4,579,774	3,223,806
Shares repurchased, shares	6,047,437	4,906,785	5,544,432
Shares issued out of treasury	(811,590)	(848,621)
Shares cancelled, shares	(5,252,026)	(2,702,196)
Total treasury shares at end of year	4,563,595	4,579,774	3,223,806
Total shares outstanding at end of year	90,959,635	96,195,482

Shareholders' Equity (Schedul82

Shareholders' Equity (Schedule Of Dividends Paid) (Details) $ / shares in Units, $ in Millions	Dec. 31, 2015USD ($)$ / shares	Oct. 02, 2015USD ($)$ / shares	Jul. 02, 2015USD ($)$ / shares	Apr. 02, 2015USD ($)$ / shares	Jan. 02, 2015USD ($)$ / shares	Oct. 02, 2014USD ($)$ / shares	Jul. 02, 2014USD ($)$ / shares	Apr. 03, 2014USD ($)$ / shares	Jan. 02, 2014USD ($)$ / shares	Oct. 03, 2013USD ($)$ / shares	Jul. 03, 2013USD ($)$ / shares	Mar. 12, 2013USD ($)$ / shares	Mar. 12, 2013SFr / shares	Dec. 31, 2015$ / shares	Dec. 31, 2014$ / shares	Dec. 31, 2013$ / shares
Dividends, Common Stock [Abstract]
Dividends paid per common share | $ / shares														$ 1.23	$ 0.784	$ 0.458
Common shares
Dividends, Common Stock [Abstract]
Dividends paid per common share | $ / shares	$ 0.26	$ 0.26	$ 0.26	$ 0.225	$ 0.225	$ 0.225	$ 0.225	$ 0.1666666667	$ 0.167	$ 0.167	$ 0.167
Payment of quarterly dividends | $	$ 23.7	$ 23.6	$ 23.6	$ 21.5	$ 21.7	$ 21.7	$ 21.9	$ 16.5	$ 16.7	$ 17	$ 17.1
Common shares | Par Value Reduction
Dividends, Common Stock [Abstract]
Dividends paid per common share | (per share)												$ 0.125	SFr 0.11
Payment of quarterly dividends | $												$ 13

Shareholders' Equity (Schedul83

Shareholders' Equity (Schedule Of Share Repurchases) (Details) - USD ($) $ / shares in Units, $ in Millions	May. 06, 2015	May. 01, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Class of Stock [Line Items]
Stock repurchase program, authorized amount		$ 500
Treasury shares reserved for issuance under stock compensation plans		3,000,000
Shares repurchased, shares			6,047,437	4,906,785	5,544,432
Cost of shares repurchased			$ 245.3	$ 175.4	$ 174.7
Shares repurchased, average price per share			$ 40.56	$ 35.74	$ 31.51
Exor SA
Class of Stock [Line Items]
Shares repurchased, shares	4,053,537
Cost of shares repurchased	$ 164.4
Shares repurchased, average price per share	$ 40.546

Employee Benefit Plans (Options

Employee Benefit Plans (Options) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding, beginning of year	2,426,674
Granted	0	0	0
Exercised	(454,602)	(479,831)	(674,187)
Forfeited	(3,465)
Expired	0
Outstanding, end of year	1,968,607	2,426,674
Exercisable, end of year	1,968,607
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Outstanding, beginning of year - weighted average exercise price	$ 16.40
Granted - weighted average exercise price	0
Exercised - weighted average exercise price	(14.38)
Forfeited - weighted average exercise price	(20.50)
Expired - weighted average exercise price	0
Outstanding, end of year - weighted average exercise price	16.86	$ 16.40
Exercisable, end of year - weighted average exercise price	$ 16.86
Additional disclosures:
Outstanding, end of year, weighted average contractual term	4 years
Exercisable, end of year, weighted average contractual term	4 years
Outstanding, end of year, aggregate intrinsic value	$ 40
Exercisable, end of year, aggregate intrinsic value	$ 40
Weighted average grant date fair value	$ 0	$ 0	$ 0
Total intrinsic value of options exercised	$ 12	$ 10.3	$ 12.2
Proceeds from option exercises	$ 10.1	$ 10	$ 12.1
Stock options
Additional disclosures:
Life of award	10 years
Vesting period	4 years

Employee Benefit Plans (Restric

Employee Benefit Plans (Restricted Stock Units) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
RSUs and performance-based equity awards
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]
Aggregate intrinsic value of vested awards	$ 16.9	$ 14.4	$ 28.8
Vesting period	4 years
Rsus Other Than Performance Based Rsus
Activity:
Outstanding, beginning of year	502,506
Granted, shares	506,505
Forfeited, shares	(26,646)
Fully vested, shares	(163,056)
Outstanding, end of year	819,309	502,506
Weighted average grant date fair value:
Outstanding, beginning of year - weighted average grant date fair value	$ 32.10
Granted - weighted average grant date fair value	40.23
Forfeited - weighted average grant date fair value	(36.08)
Vested - weighted average grant date fair value	(30.42)
Outstanding, end of year - weighted average grant date fair value	$ 37.33	$ 32.10
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]
Aggregate intrinsic value	$ 30.5
Total compensation cost not yet recognized	$ 23
Compensation cost not yet recognized, period for recognition	1 year 9 months 29 days
Performance Based Rsus
Activity:
Outstanding, beginning of year	616,641
Granted, shares	234,361
Additional awards granted due to achievement of performance criteria, shares	91,737
Forfeited, shares	(4,541)
Fully vested, shares	(346,515)
Outstanding, end of year	591,683	616,641
Weighted average grant date fair value:
Outstanding, beginning of year - weighted average grant date fair value	$ 27.52
Granted - weighted average grant date fair value	40.24
Additional awards granted due to achievement of performance criteria - weighted average grant date fair value	22.29
Forfeited - weighted average grant date fair value	(32.25)
Vested - weighted average grant date fair value	(22.29)
Outstanding, end of year - weighted average grant date fair value	$ 34.78	$ 27.52
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]
Aggregate intrinsic value	$ 22
Total compensation cost not yet recognized	$ 8.1
Compensation cost not yet recognized, period for recognition	1 year 9 months 7 days
The rate at which performance awards are expensed	100.00%	100.00%	111.00%

Employee Benefit Plans (Cash-Eq

Employee Benefit Plans (Cash-Equivalent Stock Awards) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]
Accounts payable and accrued liabilities	$ 184.5	$ 181.6
Cash-equivalent stock awards
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]
Accounts payable and accrued liabilities	$ 39
Cash Equivalent Stock Awards Rsus [Member]
Activity:
Outstanding, beginning of year	1,654,064
Granted, shares	325,805
Additional awards granted due to achievement of performance criteria, shares	0
Forfeited, shares	(54,964)
Fully vested, shares	(647,822)
Outstanding, end of year	1,277,083
Weighted average grant date fair value:
Outstanding, beginning of year - weighted average grant date fair value	$ 27.99
Granted - weighted average grant date fair value	40.24
Additional awards granted due to achievement of performance criteria - weighted average grant date fair value	0
Forfeited - weighted average grant date fair value	(30.42)
Vested - weighted average grant date fair value	(26.16)
Outstanding, end of year - weighted average grant date fair value	$ 31.94
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]
Vesting period	4 years
Cash Equivalent Stock Awards Performance Based [Member]
Activity:
Outstanding, beginning of year	924,906
Granted, shares	156,238
Additional awards granted due to achievement of performance criteria, shares	137,585
Forfeited, shares	(5,527)
Fully vested, shares	(519,725)
Outstanding, end of year	693,477
Weighted average grant date fair value:
Outstanding, beginning of year - weighted average grant date fair value	$ 27.52
Granted - weighted average grant date fair value	40.24
Additional awards granted due to achievement of performance criteria - weighted average grant date fair value	22.29
Forfeited - weighted average grant date fair value	(30.39)
Vested - weighted average grant date fair value	(22.29)
Outstanding, end of year - weighted average grant date fair value	$ 33.25
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]
Vesting period	3 years

Employee Benefit Plans (Other D

Employee Benefit Plans (Other Details) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 49.7	$ 52	$ 64.9
Expense related to defined contribution arrangements	13.5	10.6	9.3
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 0.3	1.9	3.3
Vesting period	4 years
RSUs and performance-based equity awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 15	12.3	10.7
Vesting period	4 years
Cash-equivalent stock awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 34.4	$ 37.8	$ 50.9
2012 Omnibus Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized	4,500,000
2012 Omnibus Plan | Awards other than performance-based
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	4 years
2012 Omnibus Plan | Performance-based awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	3 years
Employee Share Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share purchase plan, discount from fair market value	15.00%
Number of shares authorized	3,000,000

Earnings Per Share (Narrative)

Earnings Per Share (Narrative) (Details) - shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Employee stock options and RSUs
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of earnings per share	308,405	0	0

Earnings Per Share (Comparison

Earnings Per Share (Comparison Of Basic And Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Basic earnings per share:
Net income	$ 1.8	$ (51.7)	$ 9.5	$ 124.3	$ 130.6	$ 30.9	$ 151.7	$ 177.1	$ 83.9	$ 490.3	$ 418
Weighted average common shares outstanding	90,934,107	90,882,511	92,441,730	95,935,551	96,386,796	96,458,231	97,809,639	99,545,187	92,530,208	97,538,319	102,464,715
Basic earnings per share	$ 0.02	$ (0.57)	$ 0.10	$ 1.30	$ 1.35	$ 0.32	$ 1.55	$ 1.78	$ 0.91	$ 5.03	$ 4.08
Diluted earnings per share:
Net income	$ 1.8	$ (51.7)	$ 9.5	$ 124.3	$ 130.6	$ 30.9	$ 151.7	$ 177.1	$ 83.9	$ 490.3	$ 418
Weighted average common shares outstanding	90,934,107	90,882,511	92,441,730	95,935,551	96,386,796	96,458,231	97,809,639	99,545,187	92,530,208	97,538,319	102,464,715
Share equivalents:
Warrants and options									1,031,666	1,432,960	1,536,939
RSUs and LTIP awards									591,773	605,808	864,180
Employee share purchase plan									20,813	14,686	0
Weighted average common shares and common share equivalents outstanding - diluted	92,422,422	90,882,511	93,984,226	97,577,029	98,394,432	98,444,238	99,724,802	101,584,662	94,174,460	99,591,773	104,865,834
Diluted earnings per share	$ 0.02	$ (0.57)	$ 0.10	$ 1.27	$ 1.33	$ 0.31	$ 1.52	$ 1.74	$ 0.89	$ 4.92	$ 3.98

Commitments And Contingencies90

Commitments And Contingencies (Operating Leases) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2,016	$ 19.3
2,017	25.7
2,018	24.8
2,019	19.3
2,020	14.5
2021 and thereafter	115.3
Total	218.9
Other details:
Total rent expense	25.9	$ 19	$ 11.4
Sublease income	$ 0.7	$ 0.1	$ 0

Commitments And Contingencies91

Commitments And Contingencies (Credit Concentration Disclosure) (Details) - Custodian	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Concentration Risk [Line Items]
Number of custodians	1	1
Gross written premium | Credit concentration risk | Marsh & McLennan Companies, Inc.
Concentration Risk [Line Items]
Concentration risk, percentage	24.00%	25.00%	26.00%
Gross written premium | Credit concentration risk | Aon Corporation
Concentration Risk [Line Items]
Concentration risk, percentage	16.00%	17.00%	18.00%
Gross written premium | Credit concentration risk | Willis Group Holdings
Concentration Risk [Line Items]
Concentration risk, percentage	11.00%	10.00%	12.00%

Statutory Capital and Surplus92

Statutory Capital and Surplus (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statutory Accounting Practices [Line Items]
Amount of restricted net assets for the Company's consolidated subsidiaries	$ 2,682.7
Bermuda
Statutory Accounting Practices [Line Items]
Statutory Capital and Surplus	3,270.9	$ 3,273.7
Minimum Required Statutory Capital and Surplus	853.2	876.2
Statutory Net Income (Loss)	221.5	487.1	$ 467.3
Statutory Amount Available for Dividend Payments	817.7
United States
Statutory Accounting Practices [Line Items]
Statutory Capital and Surplus	1,215.5	1,220.3
Minimum Required Statutory Capital and Surplus	241	226.9
Statutory Net Income (Loss)	40.5	45.4	36.7
Statutory Amount Available for Dividend Payments	90
Ireland
Statutory Accounting Practices [Line Items]
Statutory Capital and Surplus	414	410.8
Minimum Required Statutory Capital and Surplus	26.9	29.2
Statutory Net Income (Loss)	3.2	3.2	(4.9)
Statutory Amount Available for Dividend Payments	54
Switzerland
Statutory Accounting Practices [Line Items]
Statutory Capital and Surplus	183.6	172.3
Minimum Required Statutory Capital and Surplus	17.7	19.9
Statutory Net Income (Loss)	10.7	7.4	(6.4)
Statutory Amount Available for Dividend Payments	32.2
United Kingdom
Statutory Accounting Practices [Line Items]
Statutory Capital and Surplus	245.9	231.7
Minimum Required Statutory Capital and Surplus	231.8	203.7
Statutory Net Income (Loss)	(39.4)	$ (7.8)	$ 9.4
Statutory Amount Available for Dividend Payments	$ 2.4

Segment Information (Summary Of

Segment Information (Summary Of Segment Results) (Details) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015USD ($)	Sep. 30, 2015USD ($)	Jun. 30, 2015USD ($)	Mar. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Sep. 30, 2014USD ($)	Jun. 30, 2014USD ($)	Mar. 31, 2014USD ($)	Dec. 31, 2015USD ($)segments	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)
Segment Reporting Information [Line Items]
Gross premiums written	$ 632.3	$ 754.1	$ 826	$ 880.6	$ 565.7	$ 707.9	$ 760.4	$ 901.4	$ 3,093	$ 2,935.4	$ 2,738.7
Net premiums written	464.8	607	603.7	772.5	427.8	568.7	553.9	771.6	2,448	2,322	2,120.5
Net premiums earned	622.8	650.7	646.4	568.5	573.5	541.7	537.2	530.3	2,488.4	2,182.7	2,005.9
Net losses and loss expenses	(412.7)	(416.9)	(431.5)	(325.2)	(273)	(336.1)	(314.9)	(275.3)	(1,586.3)	(1,199.2)	(1,123.2)
Acquisition costs	(96)	(100.1)	(100.6)	(78.7)	(80.7)	(72.4)	(74.3)	(67.7)	(375.4)	(295.1)	(252.7)
General and administrative expenses	(95)	(105.8)	(108.4)	(97.1)	(100.9)	(88.3)	(96.2)	(80.3)	(406.3)	(365.7)	(352.3)
Underwriting income									120.4	322.7	277.7
Other insurance-related revenue	1	0.7	0.9	0.9	1.1	1	0	0	3.5	2.1	0
Other insurance-related expenses	(1.9)	(1.3)	(1.2)	(1.8)	(2)	(6.6)	0	0	(6.2)	(8.6)	0
Segment income									117.7	316.2	277.7
Net investment income	49.1	45.7	42.8	44.5	49.1	43.4	36.8	47.6	182.1	176.9	157.6
Net realized investment gains (losses)	(38.8)	(113.6)	(20.2)	45	(15.4)	(35.1)	85.3	54.2	(127.6)	89	59.5
Amortization of intangible assets	(3.7)	(2.7)	(2.8)	(0.6)	(0.6)	(0.6)	(0.7)	(0.6)	(9.8)	(2.5)	(2.5)
Interest expense	(18.1)	(14.5)	(14.5)	(14.3)	(14.3)	(14.3)	(14.6)	(14.5)	(61.4)	(57.8)	(56.5)
Foreign exchange (loss) gain	(0.9)	0.8	(1.3)	(9.9)	0	(0.3)	(0.7)	0	(11.3)	(1)	(8)
Income before income taxes	$ 5.8	$ (57)	$ 9.6	$ 131.3	$ 136.8	$ 32.4	$ 157.9	$ 193.7	$ 89.7	$ 520.8	$ 427.8
Loss and loss expense ratio									63.70%	54.90%	56.00%
Acquisition cost ratio									15.10%	13.50%	12.60%
General and administrative expense ratio									16.30%	16.80%	17.60%
Expense ratio									31.40%	30.30%	30.20%
Combined ratio									95.10%	85.20%	86.20%
Number of operating segments | segments									3
Operating segments | North American Insurance
Segment Reporting Information [Line Items]
Gross premiums written									$ 1,815.3	$ 1,716.3	$ 1,572.3
Net premiums written									1,358.1	1,230.8	1,082.5
Net premiums earned									1,301.4	1,111.1	1,023
Net losses and loss expenses									(910.2)	(683.8)	(651.2)
Acquisition costs									(139.6)	(105.9)	(94.8)
General and administrative expenses									(224.6)	(219.6)	(209)
Underwriting income									27	101.8	68
Other insurance-related revenue									3.5	2.1	0
Other insurance-related expenses									(2.7)	(1.9)	0
Segment income									$ 27.8	$ 102	$ 68
Loss and loss expense ratio									69.90%	61.50%	63.70%
Acquisition cost ratio									10.70%	9.50%	9.30%
General and administrative expense ratio									17.30%	19.80%	20.40%
Expense ratio									28.00%	29.30%	29.70%
Combined ratio									97.90%	90.80%	93.40%
Operating segments | Global Markets Insurance
Segment Reporting Information [Line Items]
Gross premiums written									$ 476.3	$ 280.5	$ 232.6
Net premiums written									324.1	188	145
Net premiums earned									366.8	162.6	126
Net losses and loss expenses									(240.3)	(61.1)	(50.4)
Acquisition costs									(70.9)	(18.2)	(10.1)
General and administrative expenses									(108.4)	(68.1)	(63.2)
Underwriting income									(52.8)	15.2	2.3
Other insurance-related revenue									0	0	0
Other insurance-related expenses									(2.5)	(6.7)	0
Segment income									$ (55.3)	$ 8.5	$ 2.3
Loss and loss expense ratio									65.50%	37.60%	40.00%
Acquisition cost ratio									19.30%	11.20%	8.00%
General and administrative expense ratio									29.50%	41.90%	50.10%
Expense ratio									48.80%	53.10%	58.10%
Combined ratio									114.30%	90.70%	98.10%
Operating segments | Reinsurance
Segment Reporting Information [Line Items]
Gross premiums written									$ 801.4	$ 938.6	$ 933.8
Net premiums written									765.8	903.2	893
Net premiums earned									820.2	909	856.9
Net losses and loss expenses									(435.8)	(454.3)	(421.6)
Acquisition costs									(164.9)	(171)	(147.8)
General and administrative expenses									(73.3)	(78)	(80.1)
Underwriting income									146.2	205.7	207.4
Other insurance-related revenue									0	0	0
Other insurance-related expenses									(1)	0	0
Segment income									$ 145.2	$ 205.7	$ 207.4
Loss and loss expense ratio									53.10%	50.00%	49.20%
Acquisition cost ratio									20.10%	18.80%	17.20%
General and administrative expense ratio									8.90%	8.60%	9.30%
Expense ratio									29.00%	27.40%	26.50%
Combined ratio									82.10%	77.40%	75.70%

Segment Information (Gross Prem

Segment Information (Gross Premiums Written By Geographic Location) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues from External Customers and Long-Lived Assets [Line Items]
Gross premiums written	$ 632.3	$ 754.1	$ 826	$ 880.6	$ 565.7	$ 707.9	$ 760.4	$ 901.4	$ 3,093	$ 2,935.4	$ 2,738.7
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Gross premiums written									1,893.4	1,795.6	1,636
Bermuda
Revenues from External Customers and Long-Lived Assets [Line Items]
Gross premiums written									543.6	640.9	676.2
Europe
Revenues from External Customers and Long-Lived Assets [Line Items]
Gross premiums written									326.9	318.6	264.9
Asia Pacific
Revenues from External Customers and Long-Lived Assets [Line Items]
Gross premiums written									313.1	167.3	161.6
Canada
Revenues from External Customers and Long-Lived Assets [Line Items]
Gross premiums written									16	13	0
Switzerland
Revenues from External Customers and Long-Lived Assets [Line Items]
Gross premiums written									$ 58.2	$ 67.6	$ 61

Segment Information (Net Premiu

Segment Information (Net Premiums Earned by Line of Business) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]
Net premiums earned	$ 622.8	$ 650.7	$ 646.4	$ 568.5	$ 573.5	$ 541.7	$ 537.2	$ 530.3	$ 2,488.4	$ 2,182.7	$ 2,005.9
Operating segments | North American Insurance
Segment Reporting Information [Line Items]
Net premiums earned									1,301.4	1,111.1	1,023
Operating segments | North American Insurance | General casualty
Segment Reporting Information [Line Items]
Net premiums earned									424	334.6	269.1
Operating segments | North American Insurance | Professional liability
Segment Reporting Information [Line Items]
Net premiums earned									343.6	276.1	259.2
Operating segments | North American Insurance | General property
Segment Reporting Information [Line Items]
Net premiums earned									162.8	170.3	168
Operating segments | North American Insurance | Healthcare
Segment Reporting Information [Line Items]
Net premiums earned									144.7	168.5	194.3
Operating segments | North American Insurance | Programs
Segment Reporting Information [Line Items]
Net premiums earned									150.7	119.8	107.9
Operating segments | North American Insurance | Specialty and other
Segment Reporting Information [Line Items]
Net premiums earned									75.6	41.9	24.5
Operating segments | Global Markets Insurance
Segment Reporting Information [Line Items]
Net premiums earned									366.8	162.6	126
Operating segments | Global Markets Insurance | General casualty
Segment Reporting Information [Line Items]
Net premiums earned									57.8	15.3	13.9
Operating segments | Global Markets Insurance | Professional liability
Segment Reporting Information [Line Items]
Net premiums earned									102.5	69.1	57.1
Operating segments | Global Markets Insurance | General property
Segment Reporting Information [Line Items]
Net premiums earned									106.7	34	31.4
Operating segments | Global Markets Insurance | Specialty and other
Segment Reporting Information [Line Items]
Net premiums earned									99.8	44.2	23.6
Operating segments | Reinsurance
Segment Reporting Information [Line Items]
Net premiums earned									820.2	909	856.9
Operating segments | Reinsurance | Property
Segment Reporting Information [Line Items]
Net premiums earned									403.5	412	336
Operating segments | Reinsurance | Casualty
Segment Reporting Information [Line Items]
Net premiums earned									224.4	175.5	171.8
Operating segments | Reinsurance | Specialty
Segment Reporting Information [Line Items]
Net premiums earned									$ 192.3	$ 321.5	$ 349.1

Condensed Consolidated Guaran96

Condensed Consolidated Guarantor Financial Statements (Schedule Of Condensed Consolidating Balance Sheet) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
ASSETS:
Investments	$ 8,571.2	$ 7,868.7
Cash and cash equivalents	608	589.3	$ 531.9	$ 681.9
Insurance balances receivable	745.9	664.8
Funds held	640.8	724
Reinsurance recoverable	1,480	1,340.3	1,234.5	1,141.1
Reinsurance recoverable on paid losses	96.4	86.1
Net deferred acquisition costs	165.2	151.5
Goodwill and intangible assets	504.7	324.6
Balances receivable on sale of investments	36.9	47.1
Investments in subsidiaries	0	0
Due from subsidiaries	0	0
Other assets	662.8	622.4
Total assets	13,511.9	12,418.8
LIABILITIES:
Reserve for losses and loss expenses	6,456.2	5,881.2	5,766.5	5,645.5
Unearned premiums	1,683.3	1,555.3
Reinsurance balances payable	214.4	180.1
Balances due on purchases of investments	125.1	5.4
Senior notes, net of unamortized discount and debt issuance costs	1,292.9	796.1
Other long-term debt	23	19.2
Due to subsidiaries	0	0
Other liabilities	184.5	203.3
Total liabilities	9,979.4	8,640.6
Total shareholders' equity	3,532.5	3,778.2	3,519.8	3,326.4
Total liabilities and shareholders' equity	13,511.9	12,418.8
Consolidating Adjustments
ASSETS:
Investments	0	0
Cash and cash equivalents	0	0	0	0
Insurance balances receivable	0	0
Funds held	0	0
Reinsurance recoverable	$ 0	$ 0
Reinsurance recoverable on paid losses
Net deferred acquisition costs	$ 0	$ 0
Goodwill and intangible assets	0	0
Balances receivable on sale of investments	0	0
Investments in subsidiaries	(7,743.3)	(7,847.3)
Due from subsidiaries	(226.3)	(180.7)
Other assets	0	0
Total assets	(7,969.6)	(8,028)
LIABILITIES:
Reserve for losses and loss expenses	0	0
Unearned premiums	0	0
Reinsurance balances payable	0	0
Balances due on purchases of investments	0	0
Senior notes, net of unamortized discount and debt issuance costs	0	0
Other long-term debt	0	0
Due to subsidiaries	(226.3)	(180.7)
Other liabilities	0	0
Total liabilities	(226.3)	(180.7)
Total shareholders' equity	(7,743.3)	(7,847.3)
Total liabilities and shareholders' equity	(7,969.6)	(8,028)
Allied World Switzerland (Parent Guarantor)
ASSETS:
Investments	0	0
Cash and cash equivalents	21.8	32.6	10.8	20
Insurance balances receivable	0	0
Funds held	0	0
Reinsurance recoverable	0	0
Reinsurance recoverable on paid losses	0	0
Net deferred acquisition costs	0	0
Goodwill and intangible assets	0	0
Balances receivable on sale of investments	0	0
Investments in subsidiaries	3,347	3,629.3
Due from subsidiaries	173.1	147.1
Other assets	1.8	1.4
Total assets	3,543.7	3,810.4
LIABILITIES:
Reserve for losses and loss expenses	0	0
Unearned premiums	0	0
Reinsurance balances payable	0	0
Balances due on purchases of investments	0	0
Senior notes, net of unamortized discount and debt issuance costs	0	0
Other long-term debt	0	0
Due to subsidiaries	8.5	7.6
Other liabilities	2.7	24.6
Total liabilities	11.2	32.2
Total shareholders' equity	3,532.5	3,778.2
Total liabilities and shareholders' equity	3,543.7	3,810.4
Allied World Bermuda (Subsidiary Issuer)
ASSETS:
Investments	0	0
Cash and cash equivalents	1	1.7	2.8	11.4
Insurance balances receivable	0	0
Funds held	0	0
Reinsurance recoverable	0	0
Reinsurance recoverable on paid losses	0	0
Net deferred acquisition costs	0	0
Goodwill and intangible assets	0	0
Balances receivable on sale of investments	0	0
Investments in subsidiaries	4,396.3	4,218
Due from subsidiaries	36.4	19.2
Other assets	0.1	0.5
Total assets	4,433.8	4,239.4
LIABILITIES:
Reserve for losses and loss expenses	0	0
Unearned premiums	0	0
Reinsurance balances payable	0	0
Balances due on purchases of investments	0	0
Senior notes, net of unamortized discount and debt issuance costs	1,292.9	796.1
Other long-term debt	0	0
Due to subsidiaries	8.3	6.8
Other liabilities	22.2	19.6
Total liabilities	1,323.4	822.5
Total shareholders' equity	3,110.4	3,416.9
Total liabilities and shareholders' equity	4,433.8	4,239.4
Other Allied World Subsidiaries
ASSETS:
Investments	8,571.2	7,868.7
Cash and cash equivalents	585.2	555	$ 518.3	$ 650.5
Insurance balances receivable	745.9	664.8
Funds held	640.8	724
Reinsurance recoverable	1,480	1,340.3
Reinsurance recoverable on paid losses	96.4	86.1
Net deferred acquisition costs	165.2	151.5
Goodwill and intangible assets	504.7	324.6
Balances receivable on sale of investments	36.9	47.1
Investments in subsidiaries	0	0
Due from subsidiaries	16.8	14.4
Other assets	660.9	620.5
Total assets	13,504	12,397
LIABILITIES:
Reserve for losses and loss expenses	6,456.2	5,881.2
Unearned premiums	1,683.3	1,555.3
Reinsurance balances payable	214.4	180.1
Balances due on purchases of investments	125.1	5.4
Senior notes, net of unamortized discount and debt issuance costs	0	0
Other long-term debt	23	19.2
Due to subsidiaries	209.5	166.3
Other liabilities	159.7	159.1
Total liabilities	8,871.2	7,966.6
Total shareholders' equity	4,632.8	4,430.4
Total liabilities and shareholders' equity	$ 13,504	$ 12,397

Condensed Consolidated Guaran97

Condensed Consolidated Guarantor Financial Statements (Schedule Of Condensed Consolidating Income Statement) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Condensed Income Statements, Captions [Line Items]
Net premiums earned	$ 622.8	$ 650.7	$ 646.4	$ 568.5	$ 573.5	$ 541.7	$ 537.2	$ 530.3	$ 2,488.4	$ 2,182.7	$ 2,005.9
Net investment income	49.1	45.7	42.8	44.5	49.1	43.4	36.8	47.6	182.1	176.9	157.6
Net realized investment gains (losses)	(38.8)	(113.6)	(20.2)	45	(15.4)	(35.1)	85.3	54.2	(127.6)	89	59.5
Other income	1	0.7	0.9	0.9	1.1	1	0	0	3.5	2.1	0
Net losses and loss expenses	(412.7)	(416.9)	(431.5)	(325.2)	(273)	(336.1)	(314.9)	(275.3)	(1,586.3)	(1,199.2)	(1,123.2)
Acquisition costs	(96)	(100.1)	(100.6)	(78.7)	(80.7)	(72.4)	(74.3)	(67.7)	(375.4)	(295.1)	(252.7)
General and administrative expenses	(95)	(105.8)	(108.4)	(97.1)	(100.9)	(88.3)	(96.2)	(80.3)	(406.3)	(365.7)	(352.3)
Other expense	(1.9)	(1.3)	(1.2)	(1.8)	(2)	(6.6)	0	0	(6.2)	(8.6)	0
Amortization of intangible assets	(3.7)	(2.7)	(2.8)	(0.6)	(0.6)	(0.6)	(0.7)	(0.6)	(9.8)	(2.5)	(2.5)
Interest expense	(18.1)	(14.5)	(14.5)	(14.3)	(14.3)	(14.3)	(14.6)	(14.5)	(61.4)	(57.8)	(56.5)
Foreign exchange (loss) gain	(0.9)	0.8	(1.3)	(9.9)	0	(0.3)	(0.7)	0	(11.3)	(1)	(8)
Income tax (expense) benefit	(4)	5.3	(0.1)	(7)	(6.2)	(1.5)	(6.2)	(16.6)	(5.8)	(30.5)	(9.8)
Equity in earnings of consolidated subsidiaries									0	0	0
NET INCOME	$ 1.8	$ (51.7)	$ 9.5	$ 124.3	$ 130.6	$ 30.9	$ 151.7	$ 177.1	83.9	490.3	418
Other comprehensive loss									(9.3)	0	0
COMPREHENSIVE INCOME (LOSS)									74.6	490.3	418
Consolidating Adjustments
Condensed Income Statements, Captions [Line Items]
Net premiums earned									0	0	0
Net investment income									0	0	0
Net realized investment gains (losses)									0	0	0
Other income									0	0	0
Net losses and loss expenses									0	0	0
Acquisition costs									0	0	0
General and administrative expenses									0	0	0
Other expense									0	0	0
Amortization of intangible assets									0	0	0
Interest expense									0	0	0
Foreign exchange (loss) gain									0	0	0
Income tax (expense) benefit									0	0	0
Equity in earnings of consolidated subsidiaries									(278)	(1,090.5)	(974.8)
NET INCOME									(278)	(1,090.5)	(974.8)
Other comprehensive loss									9.3	0	0
COMPREHENSIVE INCOME (LOSS)									(268.7)	(1,090.5)	(974.8)
Allied World Switzerland (Parent Guarantor)
Condensed Income Statements, Captions [Line Items]
Net premiums earned									0	0	0
Net investment income									0	0.1	0.1
Net realized investment gains (losses)									0	0	0
Other income									0	0	0
Net losses and loss expenses									0	0	0
Acquisition costs									0	0	0
General and administrative expenses									(36.7)	(35.6)	(42.1)
Other expense									0	0	0
Amortization of intangible assets									0	0	0
Interest expense									0	0	0
Foreign exchange (loss) gain									0	0	0.3
Income tax (expense) benefit									(0.1)	(0.1)	0.1
Equity in earnings of consolidated subsidiaries									120.7	525.9	459.6
NET INCOME									83.9	490.3	418
Other comprehensive loss									(9.3)	0	0
COMPREHENSIVE INCOME (LOSS)									74.6	490.3	418
Allied World Bermuda (Subsidiary Issuer)
Condensed Income Statements, Captions [Line Items]
Net premiums earned									0	0	0
Net investment income									0.1	0	0
Net realized investment gains (losses)									0	0	0
Other income									0	0	0
Net losses and loss expenses									0	0	0
Acquisition costs									0	0	0
General and administrative expenses									(0.5)	(3.1)	(1.3)
Other expense									0	0	0
Amortization of intangible assets									0	0	0
Interest expense									(59.2)	(55.4)	(55.3)
Foreign exchange (loss) gain									0	0.1	(1)
Income tax (expense) benefit									0	0	0
Equity in earnings of consolidated subsidiaries									157.3	564.6	515.2
NET INCOME									97.7	506.2	457.6
Other comprehensive loss									0	0	0
COMPREHENSIVE INCOME (LOSS)									97.7	506.2	457.6
Other Allied World Subsidiaries
Condensed Income Statements, Captions [Line Items]
Net premiums earned									2,488.4	2,182.7	2,005.9
Net investment income									182	176.8	157.5
Net realized investment gains (losses)									(127.6)	89	59.5
Other income									3.5	2.1	0
Net losses and loss expenses									(1,586.3)	(1,199.2)	(1,123.2)
Acquisition costs									(375.4)	(295.1)	(252.7)
General and administrative expenses									(369.1)	(327.1)	(308.8)
Other expense									(6.2)	(8.6)	0
Amortization of intangible assets									(9.8)	(2.5)	(2.5)
Interest expense									(2.2)	(2.3)	(1.2)
Foreign exchange (loss) gain									(11.3)	(1.1)	(7.2)
Income tax (expense) benefit									(5.7)	(30.4)	(9.9)
Equity in earnings of consolidated subsidiaries									0	0	0
NET INCOME									180.3	584.3	517.4
Other comprehensive loss									(9.3)	0	0
COMPREHENSIVE INCOME (LOSS)									$ 171	$ 584.3	$ 517.4

Condensed Consolidated Guaran98

Condensed Consolidated Guarantor Financial Statements (Schedule Of Condensed Consolidating Cash Flows) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Condensed Cash Flow Statements, Captions [Line Items]
CASH FLOWS PROVIDED BY (USED IN) OPERATING ACTIVITIES:	$ 504.3	$ 407.8	$ 106
CASH FLOWS USED IN INVESTING ACTIVITIES:
Purchases of trading securities	(5,863.2)	(7,630)	(7,527.7)
Purchases of other invested assets	(126.7)	(307.9)	(276.9)
Sales of trading securities	5,328.8	7,536.9	7,540.2
Sales of other invested assets	161.3	267.9	187.5
Net cash paid for acquisitions	(124.4)	(2.6)
Capital contributions	0
Other	(11.5)	8.7	28.8
Net cash used in investing activities	(635.7)	(127)	(48.1)
CASH FLOWS PROVIDED BY (USED IN) FINANCING ACTIVITIES:
Partial par value reduction	0	0	(13)
Dividends paid	(114.1)	(76.7)	(34)
Intercompany dividends paid	0	0	0
Proceeds from the exercise of stock options	10.1	10	12.1
Proceeds from other long-term debt	4	19.2	0
Repayment of other long-term debt	(0.2)	0	0
Share repurchases	(246.4)	(175.9)	(173)
Proceeds from senior notes	496.7	0	0
Net cash provided by (used in) used in financing activities	150.1	(223.4)	(207.9)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	18.7	57.4	(150)
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD	589.3	531.9	681.9
CASH AND CASH EQUIVALENTS, END OF PERIOD	608	589.3	531.9
Consolidating Adjustments
Condensed Cash Flow Statements, Captions [Line Items]
CASH FLOWS PROVIDED BY (USED IN) OPERATING ACTIVITIES:	(811.1)	(643.3)	(596.5)
CASH FLOWS USED IN INVESTING ACTIVITIES:
Purchases of trading securities	0	0	0
Purchases of other invested assets	0	0	0
Sales of trading securities	0	0	0
Sales of other invested assets	0	0	0
Net cash paid for acquisitions	0	0
Capital contributions	0
Other	0	0	0
Net cash used in investing activities	0	0	0
CASH FLOWS PROVIDED BY (USED IN) FINANCING ACTIVITIES:
Partial par value reduction			0
Dividends paid	0	0	0
Intercompany dividends paid	811.1	643.3	596.5
Proceeds from the exercise of stock options	0	0	0
Proceeds from other long-term debt	0	0
Repayment of other long-term debt	0
Share repurchases	0	0	0
Proceeds from senior notes	0
Net cash provided by (used in) used in financing activities	811.1	643.3	596.5
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	0	0	0
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD	0	0	0
CASH AND CASH EQUIVALENTS, END OF PERIOD	0	0	0
Allied World Switzerland (Parent Guarantor)
Condensed Cash Flow Statements, Captions [Line Items]
CASH FLOWS PROVIDED BY (USED IN) OPERATING ACTIVITIES:	339.6	264.4	198.7
CASH FLOWS USED IN INVESTING ACTIVITIES:
Purchases of trading securities	0	0	0
Purchases of other invested assets	0	0	0
Sales of trading securities	0	0	0
Sales of other invested assets	0	0	0
Net cash paid for acquisitions	0	0
Capital contributions	0
Other	0	0	0
Net cash used in investing activities	0	0	0
CASH FLOWS PROVIDED BY (USED IN) FINANCING ACTIVITIES:
Partial par value reduction			(13)
Dividends paid	(114.1)	(76.7)	(34)
Intercompany dividends paid	0	0	0
Proceeds from the exercise of stock options	10.1	10	12.1
Proceeds from other long-term debt	0	0
Repayment of other long-term debt	0
Share repurchases	(246.4)	(175.9)	(173)
Proceeds from senior notes	0
Net cash provided by (used in) used in financing activities	(350.4)	(242.6)	(207.9)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	(10.8)	21.8	(9.2)
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD	32.6	10.8	20
CASH AND CASH EQUIVALENTS, END OF PERIOD	21.8	32.6	10.8
Allied World Bermuda (Subsidiary Issuer)
Condensed Cash Flow Statements, Captions [Line Items]
CASH FLOWS PROVIDED BY (USED IN) OPERATING ACTIVITIES:	377.7	292.9	265.9
CASH FLOWS USED IN INVESTING ACTIVITIES:
Purchases of trading securities	0	0	0
Purchases of other invested assets	0	0	0
Sales of trading securities	0	0	0
Sales of other invested assets	0	0	0
Net cash paid for acquisitions	0	0
Capital contributions	(496.7)
Other	0	0	0
Net cash used in investing activities	(496.7)	0	0
CASH FLOWS PROVIDED BY (USED IN) FINANCING ACTIVITIES:
Partial par value reduction			0
Dividends paid	0	0	0
Intercompany dividends paid	(378.4)	(294)	(274.5)
Proceeds from the exercise of stock options	0	0	0
Proceeds from other long-term debt	0	0
Repayment of other long-term debt	0
Share repurchases	0	0	0
Proceeds from senior notes	496.7
Net cash provided by (used in) used in financing activities	118.3	(294)	(274.5)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	(0.7)	(1.1)	(8.6)
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD	1.7	2.8	11.4
CASH AND CASH EQUIVALENTS, END OF PERIOD	1	1.7	2.8
Other Allied World Subsidiaries
Condensed Cash Flow Statements, Captions [Line Items]
CASH FLOWS PROVIDED BY (USED IN) OPERATING ACTIVITIES:	598.1	493.8	237.9
CASH FLOWS USED IN INVESTING ACTIVITIES:
Purchases of trading securities	(5,863.2)	(7,630)	(7,527.7)
Purchases of other invested assets	(126.7)	(307.9)	(276.9)
Sales of trading securities	5,328.8	7,536.9	7,540.2
Sales of other invested assets	161.3	267.9	187.5
Net cash paid for acquisitions	(124.4)	(2.6)
Capital contributions	496.7
Other	(11.5)	8.7	28.8
Net cash used in investing activities	(139)	(127)	(48.1)
CASH FLOWS PROVIDED BY (USED IN) FINANCING ACTIVITIES:
Partial par value reduction			0
Dividends paid	0	0	0
Intercompany dividends paid	(432.7)	(349.3)	(322)
Proceeds from the exercise of stock options	0	0	0
Proceeds from other long-term debt	4	19.2
Repayment of other long-term debt	(0.2)
Share repurchases	0	0	0
Proceeds from senior notes	0
Net cash provided by (used in) used in financing activities	(428.9)	(330.1)	(322)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	30.2	36.7	(132.2)
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD	555	518.3	650.5
CASH AND CASH EQUIVALENTS, END OF PERIOD	$ 585.2	$ 555	$ 518.3

Condensed Consolidated Guaran99

Condensed Consolidated Guarantor Financial Statements (Notes to Consolidated Guarantor Financial Statements) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Condensed Financial Statements, Captions [Line Items]
Subsidiary Investee Percentage Ownership	100.00%
Allied World Switzerland (Parent Guarantor)
Condensed Financial Statements, Captions [Line Items]
Cash Dividends Paid to Parent Company by Consolidated Subsidiaries	$ 378.4	$ 294	$ 274.5

Unaudited Quarterly Financia100

Unaudited Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
REVENUES:
Gross premiums written	$ 632.3	$ 754.1	$ 826	$ 880.6	$ 565.7	$ 707.9	$ 760.4	$ 901.4	$ 3,093	$ 2,935.4	$ 2,738.7
Premiums ceded	(167.5)	(147.1)	(222.3)	(108.1)	(137.9)	(139.2)	(206.5)	(129.8)	(645)	(613.4)	(618.2)
Net premiums written	464.8	607	603.7	772.5	427.8	568.7	553.9	771.6	2,448	2,322	2,120.5
Change in unearned premiums	158	43.7	42.7	(204)	145.7	(27)	(16.7)	(241.3)	40.4	(139.3)	(114.6)
Net premiums earned	622.8	650.7	646.4	568.5	573.5	541.7	537.2	530.3	2,488.4	2,182.7	2,005.9
Net investment income	49.1	45.7	42.8	44.5	49.1	43.4	36.8	47.6	182.1	176.9	157.6
Net realized investment (losses) gains	(38.8)	(113.6)	(20.2)	45	(15.4)	(35.1)	85.3	54.2	(127.6)	89	59.5
Other income	1	0.7	0.9	0.9	1.1	1	0	0	3.5	2.1	0
Total revenues	634.1	583.5	669.9	658.9	608.3	551	659.3	632.1	2,546.4	2,450.7	2,223
EXPENSES:
Net losses and loss expenses	412.7	416.9	431.5	325.2	273	336.1	314.9	275.3	1,586.3	1,199.2	1,123.2
Acquisition costs	96	100.1	100.6	78.7	80.7	72.4	74.3	67.7	375.4	295.1	252.7
General and administrative expenses	95	105.8	108.4	97.1	100.9	88.3	96.2	80.3	406.3	365.7	352.3
Other expense	1.9	1.3	1.2	1.8	2	6.6	0	0	6.2	8.6	0
Amortization and impairment of intangible assets	3.7	2.7	2.8	0.6	0.6	0.6	0.7	0.6	9.8	2.5	2.5
Interest expense	18.1	14.5	14.5	14.3	14.3	14.3	14.6	14.5	61.4	57.8	56.5
Foreign exchange loss	0.9	(0.8)	1.3	9.9	0	0.3	0.7	0	11.3	1	8
Total expenses	628.3	640.5	660.3	527.6	471.5	518.6	501.4	438.4	2,456.7	1,929.9	1,795.2
Income before income taxes	5.8	(57)	9.6	131.3	136.8	32.4	157.9	193.7	89.7	520.8	427.8
Income tax expense	4	(5.3)	0.1	7	6.2	1.5	6.2	16.6	5.8	30.5	9.8
Net income	$ 1.8	$ (51.7)	$ 9.5	$ 124.3	$ 130.6	$ 30.9	$ 151.7	$ 177.1	$ 83.9	$ 490.3	$ 418
PER SHARE DATA
Basic earnings (loss) per share	$ 0.02	$ (0.57)	$ 0.10	$ 1.30	$ 1.35	$ 0.32	$ 1.55	$ 1.78	$ 0.91	$ 5.03	$ 4.08
Diluted earnings (loss) per share	$ 0.02	$ (0.57)	$ 0.10	$ 1.27	$ 1.33	$ 0.31	$ 1.52	$ 1.74	$ 0.89	$ 4.92	$ 3.98
Weighted average common shares outstanding	90,934,107	90,882,511	92,441,730	95,935,551	96,386,796	96,458,231	97,809,639	99,545,187	92,530,208	97,538,319	102,464,715
Weighted average common shares and common share equivalents outstanding	92,422,422	90,882,511	93,984,226	97,577,029	98,394,432	98,444,238	99,724,802	101,584,662	94,174,460	99,591,773	104,865,834

Schedule III - Supplementary101

Schedule III - Supplementary Insurance Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Supplementary Insurance Information, by Segment [Line Items]
Net deferred acquisition costs	$ 165.2	$ 151.5	$ 126.6
Reserves for losses and loss expenses	6,456.2	5,881.2	5,766.5
Unearned premiums	1,683.3	1,555.3	1,396.2
Net premiums earned	2,488.4	2,182.7	2,005.9
Net investment income	182.1	176.9	157.6
Losses and loss expenses	1,586.3	1,199.2	1,123.2
Amortization of deferred acquisition costs	375.4	295.1	252.7
Other operating costs	406.3	365.7	352.3
Net premiums written	2,448	2,322	2,120.5
North American Insurance
Supplementary Insurance Information, by Segment [Line Items]
Net deferred acquisition costs	70.1	55.7	45.4
Reserves for losses and loss expenses	3,998.2	3,806.6	3,701.7
Unearned premiums	1,061.5	1,003.1	872.6
Net premiums earned	1,301.4	1,111.1	1,023
Net investment income	0	0	0
Losses and loss expenses	910.2	683.8	651.2
Amortization of deferred acquisition costs	139.6	105.9	94.8
Other operating costs	224.6	219.7	209
Net premiums written	1,358.1	1,230.8	1,082.5
Global Markets Insurance
Supplementary Insurance Information, by Segment [Line Items]
Net deferred acquisition costs	26.2	23.3	9.8
Reserves for losses and loss expenses	972.4	568.2	568.7
Unearned premiums	327.8	223.4	164.8
Net premiums earned	366.8	162.6	126
Net investment income	0	0	0
Losses and loss expenses	240.3	61.1	50.4
Amortization of deferred acquisition costs	70.9	18.2	10.1
Other operating costs	108.4	68.1	63.2
Net premiums written	324.1	188	145
Reinsurance
Supplementary Insurance Information, by Segment [Line Items]
Net deferred acquisition costs	68.9	72.5	71.4
Reserves for losses and loss expenses	1,485.6	1,506.4	1,496.1
Unearned premiums	294	328.8	358.8
Net premiums earned	820.2	909	856.9
Net investment income	0	0	0
Losses and loss expenses	435.8	454.3	421.6
Amortization of deferred acquisition costs	164.9	171	147.8
Other operating costs	73.3	78	80.1
Net premiums written	765.8	903.2	893
Corporate
Supplementary Insurance Information, by Segment [Line Items]
Net deferred acquisition costs	0	0	0
Reserves for losses and loss expenses	0	0	0
Unearned premiums	0	0	0
Net premiums earned	0	0	0
Net investment income	182.1	176.9	157.6
Losses and loss expenses	0	0	0
Amortization of deferred acquisition costs	0	0	0
Other operating costs	0	0	0
Net premiums written	$ 0	$ 0	$ 0

Schedule IV - Supplementary 102

Schedule IV - Supplementary Reinsurance Information (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reinsurance Premiums for Insurance Companies, by Product Segment, Net Amount [Abstract]
Gross									$ 2,291.6	$ 1,996.8	$ 1,804.9
Ceded to other companies	$ 167.5	$ 147.1	$ 222.3	$ 108.1	$ 137.9	$ 139.2	$ 206.5	$ 129.8	645	613.4	618.2
Assumed from other companies									801.4	938.6	933.8
Net premiums written	$ 464.8	$ 607	$ 603.7	$ 772.5	$ 427.8	$ 568.7	$ 553.9	$ 771.6	2,448	2,322	2,120.5
Property and casualty
Reinsurance Premiums for Insurance Companies, by Product Segment, Net Amount [Abstract]
Gross									2,291.6	1,996.8	1,804.9
Ceded to other companies									645	613.4	618.2
Assumed from other companies									801.4	938.6	933.8
Net premiums written									$ 2,448	$ 2,322	$ 2,120.5
Percentage of amount assumed to net									33.00%	40.00%	44.00%