Allied World Assurance 10-Q 22 Oct 14 2014 Q3 Quarterly report Financial data

Document_And_Entity_Informatio

Document And Entity Information	9 Months Ended
	Sep. 30, 2014	Oct. 13, 2014
Document And Entity Information [Abstract]	'	'
Entity Registrant Name	'Allied World Assurance Co Holdings, AG	'
Entity Central Index Key	'0001163348	'
Current Fiscal Year End Date	'--12-31	'
Entity Filer Category	'Large Accelerated Filer	'
Document Type	'10-Q	'
Document Period End Date	30-Sep-14	'
Document Fiscal Year Focus	'2014	'
Document Fiscal Period Focus	'Q3	'
Amendment Flag	'false	'
Entity Common Stock, Shares Outstanding	'	96,409,738

Unaudited_Condensed_Consolidat

Unaudited Condensed Consolidated Balance Sheets (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
ASSETS:	'	'
Fixed maturity investments trading, at fair value (amortized cost: 2014: $6,074,752; 2013: $6,065,350)	$6,128,237	$6,100,798
Equity securities trading, at fair value (cost: 2014: $901,300; 2013: $647,301)	945,076	699,846
Other invested assets	929,201	911,392
Total investments	8,002,514	7,712,036
Cash and cash equivalents	831,270	531,936
Restricted cash	178,958	149,393
Insurance balances receivable	926,183	664,731
Funds held	405,703	632,430
Prepaid reinsurance	376,651	340,992
Reinsurance recoverable	1,349,009	1,234,504
Accrued investment income	30,554	32,236
Net deferred acquisition costs	171,827	126,661
Goodwill	278,085	268,376
Intangible assets	46,931	48,831
Balances receivable on sale of investments	60,122	76,544
Net deferred tax assets	41,312	37,469
Other assets	110,449	89,691
Total assets	12,809,568	11,945,830
LIABILITIES:	'	'
Reserve for losses and loss expenses	6,052,263	5,766,529
Unearned premiums	1,716,927	1,396,256
Reinsurance balances payable	203,428	173,023
Balances due on purchases of investments	166,026	104,740
Senior notes	798,725	798,499
Dividends payable	21,686	16,732
Accounts payable and accrued liabilities	176,914	170,225
Total liabilities	9,135,969	8,426,004
Commitments and contingencies	'	'
SHAREHOLDERS’ EQUITY:	'	'
Common shares: 2014: par value CHF 4.10 per share and 2013: par value CHF 4.10 per share (2014: 100,775,256; 2013: 103,477,452 shares issued and 2014: 96,382,238; 2013: 100,253,646 shares outstanding)	407,990	418,988
Treasury shares, at cost (2014: 4,393,018; 2013: 3,223,806)	-134,633	-79,992
Retained earnings	3,400,242	3,180,830
Total shareholders’ equity	3,673,599	3,519,826
Total liabilities and shareholders’ equity	$12,809,568	$11,945,830

Unaudited_Condensed_Consolidat1

Unaudited Condensed Consolidated Balance Sheets (Parenthetical)(USD ($))	Sep. 30, 2014	Dec. 31, 2013
In Thousands, except Share data, unless otherwise specified
Fixed maturity investments trading, amortized cost	$6,074,752	$6,065,350
Equity securities trading - cost	$901,300	$647,301
Common stock, shares issued	100,775,256	103,477,452
Common stock, shares outstanding	96,382,238	100,253,646
Treasury stock (shares)	4,393,018	3,223,806

Unaudited_Condensed_Consolidat2

Unaudited Condensed Consolidated Statements Of Operations And Comprehensive Income (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Share data, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
REVENUES:	'	'	'	'
Gross premiums written	$707,884	$580,893	$2,369,682	$2,183,174
Premiums ceded	-139,142	-127,816	-475,402	-453,823
Net premiums written	568,742	453,077	1,894,280	1,729,351
Change in unearned premiums	-27,005	57,696	-285,011	-248,079
Net premiums earned	541,737	510,773	1,609,269	1,481,272
Net investment income	43,412	39,271	127,824	110,294
Net realized investment (losses) gains	-35,136	27,487	104,286	-8,074
Other income	1,032	0	1,032	0
Total revenues	551,045	577,531	1,842,411	1,583,492
EXPENSES:	'	'	'	'
Net losses and loss expenses	336,090	276,970	926,231	807,276
Acquisition costs	72,403	65,114	214,404	186,416
General and administrative expenses	88,294	88,553	264,822	251,818
Other expense	6,575	0	6,575	0
Amortization of intangible assets	633	633	1,900	1,900
Interest expense	14,325	14,094	43,451	42,416
Foreign exchange loss	278	4,353	978	7,361
Total expenses	518,598	449,717	1,458,361	1,297,187
Income before income taxes	32,447	127,814	384,050	286,305
Income tax expense	1,532	4,971	24,300	6,332
NET INCOME	30,915	122,843	359,750	279,973
Other comprehensive income	0	0	0	0
COMPREHENSIVE INCOME	$30,915	$122,843	$359,750	$279,973
PER SHARE DATA	'	'	'	'
Basic earnings per share	$0.32	$1.20	$3.67	$2.72
Diluted earnings per share	$0.31	$1.18	$3.60	$2.66
Weighted average common shares outstanding	96,458,231	101,974,077	97,926,378	103,020,681
Weighted average common shares and common share equivalents outstanding	98,444,238	104,184,579	99,965,296	105,393,276
Dividends paid per share	$0.23	$0.17	$0.56	$0.29

Unaudited_Condensed_Consolidat3

Unaudited Condensed Consolidated Statements Of Shareholders' Equity (USD $)	Total	Common shares	Treasury shares	Retained earnings
In Thousands
Balance, at beginning of period at Dec. 31, 2012	$3,326,335	$454,980	($113,818)	$2,985,173
Net income	279,973	'	'	279,973
Dividends — par value reduction	-12,981	-12,981	'	'
Dividends	-34,069	'	'	-34,069
Stock compensation	7,815	'	26,093	-18,278
Share repurchases	-123,145	'	-123,145	'
Shares cancelled	0	-17,162	125,025	-107,863
Balance, at end of period at Sep. 30, 2013	3,443,928	424,837	-85,845	3,104,936
Balance, at beginning of period at Dec. 31, 2013	3,519,826	418,988	-79,992	3,180,830
Net income	359,750	'	'	359,750
Dividends	-60,017	'	'	-60,017
Stock compensation	18,568	'	17,235	1,333
Share repurchases	-164,528	'	-164,528	'
Shares cancelled	0	-10,998	92,652	-81,654
Balance, at end of period at Sep. 30, 2014	$3,673,599	$407,990	($134,633)	$3,400,242

Unaudited_Condensed_Consolidat4

Unaudited Condensed Consolidated Statements Of Cash Flows (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013
CASH FLOWS PROVIDED BY OPERATING ACTIVITIES:	'	'
Net income	$359,750	$279,973
Adjustments to reconcile net income to cash provided by operating activities:	'	'
Net realized gains on sales of investments	-118,640	-76,104
Mark to market adjustments	-5,634	80,136
Stock compensation expense	10,822	9,282
Undistributed loss (income) of equity method investments	10,452	-4,313
Changes in:	'	'
Reserve for losses and loss expenses, net of reinsurance recoverables	171,229	50,308
Unearned premiums, net of prepaid reinsurance	285,012	248,079
Insurance balances receivable	-260,627	-229,580
Funds held	226,727	-38,763
Reinsurance balances payable	30,405	57,379
Net deferred acquisition costs	-45,166	-37,941
Net deferred tax assets	-3,511	-16,252
Accounts payable and accrued liabilities	4,473	-18,540
Other items, net	4,441	34,508
Net cash provided by operating activities	669,733	338,172
CASH FLOWS (USED IN) PROVIDED BY INVESTING ACTIVITIES:	'	'
Purchases of trading securities	-5,608,594	-4,955,817
Purchases of other invested assets	-242,227	-211,501
Sales of trading securities	5,500,176	5,137,280
Sales of other invested assets	243,123	189,155
Purchases of fixed assets	-14,490	-4,171
Change in restricted cash	-29,565	-74,032
Net cash paid for acquisitions	-2,565	0
Net cash (used in) provided by investing activities	-154,142	80,914
CASH FLOWS USED IN FINANCING ACTIVITIES:	'	'
Dividends paid - partial par value reduction	0	-12,981
Dividends paid	-55,064	-17,117
Proceeds from the exercise of stock options	7,640	8,465
Share repurchases	-166,207	-120,163
Net cash used in financing activities	-213,631	-141,796
Effect of exchange rate changes on foreign currency cash	-2,626	-6,122
NET INCREASE IN CASH AND CASH EQUIVALENTS	299,334	271,168
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD	531,936	681,879
CASH AND CASH EQUIVALENTS, END OF PERIOD	831,270	953,047
Supplemental disclosure of cash flow information:	'	'
Cash paid for income taxes	18,052	17,249
Cash paid for interest expense	$45,750	$45,750

General

General	9 Months Ended
	Sep. 30, 2014
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.
	The Company has reached definitive agreements to acquire the Hong Kong and Singapore operations of Royal & Sun Alliance Insurance plc for approximately $211,000, at current exchange rates, subject to adjustments at closing. In addition to the purchase price, the Company expects to contribute an additional $90,000 to capitalize the business on an ongoing basis. Subject to regulatory approvals in both Hong Kong and Singapore, as well as court approval in Singapore, the acquisition is expected to be completed in the first half of 2015.

Basis_of_Preparation_and_Conso

Basis of Preparation and Consolidation	9 Months Ended
	Sep. 30, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]	'
Basis of Preparation and Consolidation	'
	BASIS OF PREPARATION AND CONSOLIDATION
	These unaudited condensed consolidated financial statements include the accounts of the Company and have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) for interim financial information and with Article 10 of Regulation S-X as promulgated by the U.S. Securities and Exchange Commission (“SEC”). Accordingly, they do not include all of the information and footnotes required by U.S. GAAP for complete financial statements. In the opinion of management, these unaudited condensed consolidated financial statements reflect all adjustments that are normal and recurring in nature and necessary for a fair presentation of financial position and results of operations as of the end of and for the periods presented. The results of operations for any interim period are not necessarily indicative of the results for a full year.
	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 unaudited condensed consolidated financial statements.
	On May 1, 2014, the shareholders approved a 3-for-1 stock split of the Company's common shares. All historical share and per share amounts reflect the effect of the stock split.
	These unaudited condensed consolidated financial statements, including these notes, should be read in conjunction with the Company’s audited consolidated financial statements, and related notes thereto, included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2013.

New_Accounting_Pronouncements

New Accounting Pronouncements	9 Months Ended
	Sep. 30, 2014
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]	'
New Accounting Pronouncements	'
	NEW ACCOUNTING PRONOUNCEMENTS
	In April 2014, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update 2014-08, "Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity" ("ASU 2014-08"). ASU 2014-08 changes the requirements for reporting discontinued operations, such that a disposal of a component of the Company's operations is required to be reported as discontinued operations if the disposal represents a strategic shift that has, or will have, a major effect on the Company's operations and financial results. Examples of strategic shifts that could have a major effect on the Company's operations could include a disposal of a major geographical area, a major line of business, a major equity method investment, or other major parts of the Company. ASU 2014-08 is effective for all disposals that occur after January 1, 2015. The Company does not believe the adoption of ASU 2014-08 will have a material impact on future financial statements and related disclosures.
	In May 2014, the 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; amongst others, insurance contracts accounted for under Accounting Standard Codification 944, Financial Services - Insurance. ASU 2014-09 is effective on January 1, 2017 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 August 2014, the FASB issued Accounting Standards Update 2014-15, "Disclosure of Uncertainties about an Entity's Ability to Continue as a Going Concern" ("ASU 2014-15"). Currently, there is no guidance under U.S. GAAP regarding management's responsibility to assess whether there is substantial doubt about an entity's ability to continue as a going concern. Under ASU 2014-15, the Company will be required to assess its ability to continue as a going concern each interim and annual reporting period and provide certain disclosures if there is substantial doubt about the entity's ability to continue as a going concern, including management's plan to alleviate the substantial doubt. ASU 2014-15 is effective on January 1, 2017 and early adoption is permitted. The Company is currently assessing the impact the adoption of ASU 2014-15 will have on future financial statements and related disclosures.

Investments

Investments	9 Months Ended
	Sep. 30, 2014
Investments [Abstract]	'
Investments	'
	INVESTMENTS
	a) Trading Securities
	Securities accounted for at fair value with changes in fair value recognized in the unaudited condensed consolidated statements of operations and comprehensive income (“consolidated income statements”) by category are as follows:
		September 30, 2014						December 31, 2013
		Fair Value			Amortized Cost			Fair Value				Amortized Cost
	U.S. Government and Government agencies	$	1,184,115		$	1,186,185		$	1,676,788			$	1,684,832
	Non-U.S. Government and Government agencies	219,287			229,792			191,776				197,082
	States, municipalities and political subdivisions	260,690			251,628			231,555				234,406
	Corporate debt:
	Financial institutions	1,194,949			1,185,637			958,794				943,518
	Industrials	1,202,906			1,201,341			1,174,047				1,165,448
	Utilities	125,513			125,202			69,426				69,658
	Mortgage-backed	1,240,362			1,196,683			1,292,502				1,267,863
	Asset-backed	700,415			698,284			505,910				502,543
	Total fixed maturity investments	$	6,128,237		$	6,074,752		$	6,100,798			$	6,065,350
		September 30, 2014						December 31, 2013
		Fair Value			Original Cost			Fair Value				Original Cost
	Equity securities	$	945,076		$	901,300		$	699,846			$	647,301
	Other invested assets	806,124			701,794			764,081				658,683
		$	1,751,200		$	1,603,094		$	1,463,927			$	1,305,984
	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 September 30, 2014 and December 31, 2013 were as follows:
	Investment Type	Carrying Value as of September 30, 2014			Investments			Estimated		Investments				Redemption	Redemption	Unfunded
					with			Remaining		without				Frequency(1)	Notice	Commitments
					Redemption			Restriction		Redemption					Period(1)
					Restrictions			Period		Restrictions
	Private equity	$	179,196		$	179,196		2 - 9 Years		$	—					$	223,030
	Mezzanine debt	114,399			114,399			5 - 9 Years		—						251,486
	Distressed	9,516			9,516			4 Years		—						5,119
	Total private equity	303,111			303,111					—						479,635
	Distressed	173,111			173,111			1 Year		—						—
	Equity long/short	111,627			86,721			1 Year		24,906				Quarterly	30 -60 Days	—
	Multi-strategy	81,576			—					81,576				Quarterly	45 -90 Days	—
	Relative value credit	105,155			—					105,155				Quarterly	60 Days	—
	Total hedge funds	471,469			259,832					211,637						—
	High yield loan fund	31,544			—					31,544				Monthly	30 days	—
	Total other invested assets at fair value	806,124			562,943					243,181						479,635
	Other private securities	123,077			—					123,077						—
	Total other invested assets	$	929,201		$	562,943				$	366,258					$	479,635
	Investment Type	Carrying Value as of December 31, 2013			Investments			Estimated		Investments				Redemption	Redemption	Unfunded
					with			Remaining		without				Frequency(1)	Notice	Commitments
					Redemption			Restriction		Redemption					Period(1)
					Restrictions			Period		Restrictions
	Private equity	$	144,422		$	144,422		2 - 9 Years		$	—					$	263,519
	Mezzanine debt	64,627			64,627			8 - 9 Years		—						198,756
	Distressed	7,776			7,776			4 Years		—						5,249
	Total private equity	216,825			216,825					—						467,524
	Distressed	151,227			151,227			1 - 2 Years		—						—
	Equity long/short	99,365			—					99,365				Quarterly	30 -60 Days	—
	Multi-strategy	136,958			—					136,958				Quarterly	45 -90 Days	—
	Event driven	14,018			—					14,018				Annual	60 Days	—
	Relative value credit	113,730			—					113,730				Quarterly	60 Days	—
	Total hedge funds	515,298			151,227					364,071						—
	High yield loan fund	31,958			—					31,958				Monthly	30 days	—
	Total other invested assets at fair value	764,081			368,052					396,029						467,524
	Other private securities	147,311			—					147,311						—
	Total other invested assets	$	911,392		$	368,052				$	543,340					$	467,524
	_______________________
	-1	The redemption frequency and notice periods only apply to the investments without redemption restrictions. Some or all of these investments may be subject to a gate as described below.
	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 describes each investment type:
	•	Private equity funds: Primary funds may invest in companies and general partnership interests. Secondary 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.
•	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.
•	Event driven funds: Event driven strategies seek to deploy capital into specific securities whose returns are affected by a specific event that affects the value of one or more securities of a company. Returns for such securities are linked primarily to the specific outcome of the events and not by the overall direction of the bond or stock markets. Examples could include mergers and acquisitions (arbitrage), corporate restructurings and spin-offs, and capital structure arbitrage.
•	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.
•	High yield loan fund: A long-only private mutual fund that invests in high yield fixed income securities.
•	Other private securities: These securities include strategic non-controlling minority investments in private asset management companies and other insurance related investments that are accounted for using the equity method of accounting.
c) Net Investment Income
	Three Months Ended						Nine Months Ended
	September 30,						September 30,
	2014			2013			2014				2013
Fixed maturity investments	$	38,762		$	31,179		$	110,998			$	96,366
Equity securities	3,711			6,110			12,876				13,718
Other invested assets: hedge funds and private equity	2,249			3,812			8,767				6,001
Other invested assets: other private securities	3,292			1,997			7,291				5,115
Cash and cash equivalents	552			302			1,562				1,319
Expenses	(5,154		)	(4,129		)	(13,670		)		(12,225		)
Net investment income	$	43,412		$	39,271		$	127,824			$	110,294
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 nine months ended September 30, 2014 included a loss of $9,348 recorded for an equity method investment due to impairment charges that it recorded.
d) Components of Realized Gains and Losses
	Three Months Ended						Nine Months Ended
	September 30,						September 30,
	2014			2013			2014				2013
Gross realized gains on sale of invested assets	$	28,773		$	51,915		$	146,780			$	154,387
Gross realized losses on sale of invested assets	(9,955		)	(40,770		)	(26,228		)		(82,812		)
Net realized and unrealized gains (losses) on derivatives	2,171			(4,169		)	(24,469		)		3,392
Mark-to-market (losses) gains:
Fixed maturity investments, trading	(40,843		)	30,383			18,039				(101,205		)
Equity securities, trading	(8,479		)	(17,198		)	(8,768		)		(18,555		)
Other invested assets, trading	(6,803		)	7,326			(1,068		)		36,719
Net realized investment (losses) gains	$	(35,136	)	$	27,487		$	104,286			$	(8,074	)
e) Pledged Assets
As of September 30, 2014 and December 31, 2013, $3,082,601 and $2,894,401, 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, insurance laws and other contract provisions.
In addition, as of September 30, 2014 and December 31, 2013, a further $543,828 and $1,053,632, respectively, of cash and cash equivalents and investments were pledged as collateral for the Company’s letter of credit facilities. See Note 10(d) to the Consolidated Financial Statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2013 for details on the Company’s credit facilities.

Derivative_Instruments

Derivative Instruments	9 Months Ended
	Sep. 30, 2014
Derivative Instruments and Hedging Activities Disclosure [Abstract]	'
Derivative Instruments	'
	DERIVATIVE INSTRUMENTS
	As of September 30, 2014 and December 31, 2013, 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 unaudited condensed consolidated balance sheets (“consolidated balance sheets”):
		September 30, 2014											December 31, 2013
		Asset		Asset			Liability			Liability			Asset		Asset		Liability		Liability
		Derivative		Derivative			Derivative			Derivative			Derivative		Derivative		Derivative		Derivative
		Notional		Fair Value			Notional			Fair Value			Notional		Fair Value		Notional		Fair Value
		Amount					Amount						Amount				Amount
	Foreign exchange contracts	$	38,940	$	814		$	2,355		$	22		$	294,788	$	6,254	$	122,439	$	1,176
	Interest rate swaps	565,600		414			—			—			491,400		6,829		40,000		4,214
	Total derivatives	$	604,540	$	1,228		$	2,355		$	22		$	786,188	$	13,083	$	162,439	$	5,390
	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 gains (losses) on derivatives not designated as hedges recorded on the consolidated income statements:
		Three Months Ended					Nine Months Ended
		September 30,					September 30,
		2014		2013			2014			2013
	Foreign exchange contracts	$	1,886	$	(2,336	)	$	(580	)	$	(1,091	)
	Total included in foreign exchange loss	1,886		(2,336		)	(580		)	(1,091		)
	Put options	—		—			—			(3,822		)
	Foreign exchange contracts	1,701		(4,164		)	857			1,925
	Interest rate futures and swaps	470		(5		)	(25,325		)	5,289
	Total included in net realized investment gains (losses)	2,171		(4,169		)	(24,468		)	3,392
	Total realized and unrealized gains (losses) on derivatives	$	4,057	$	(6,505	)	$	(25,048	)	$	2,301
	The loss related to interest rate future and swap contracts for the nine months ended September 30, 2014 was the result of selling interest rate future and 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 future and 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 un-matched foreign currency exposures, specifically forward contracts and currency options.
	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 its equity portfolio.

Fair_Value_Of_Financial_Instru

Fair Value Of Financial Instruments	9 Months Ended
	Sep. 30, 2014
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:
	September 30, 2014		Carrying			Total			Level 1			Level 2		Level 3
			Amount			Fair Value
	Fixed maturity investments:
	U.S. Government and Government agencies		$	1,184,115		$	1,184,115		$	998,487		$	185,628	$	—
	Non-U.S. Government and Government agencies		219,287			219,287			—			219,287		—
	States, municipalities and political subdivisions		260,690			260,690			—			260,690		—
	Corporate debt		2,523,368			2,523,368			—			2,523,368		—
	Mortgage-backed		1,240,362			1,240,362			—			1,120,454		119,908
	Asset-backed		700,415			700,415			—			609,045		91,370
	Total fixed maturity investments		6,128,237			6,128,237			998,487			4,918,472		211,278
	Equity securities		945,076			945,076			907,041			—		38,035
	Other invested assets		806,124			806,124			—			—		806,124
	Total investments		$	7,879,437		$	7,879,437		$	1,905,528		$	4,918,472	$	1,055,437
	Derivative assets:
	Foreign exchange contracts		$	814		$	814		$	—		$	814	$	—
	Interest rate swaps		414			414			—			414		—
	Derivative liabilities:
	Foreign exchange contracts		$	22		$	22		$	—		$	22	$	—
	Interest rate swaps		—			—			—			—		—
	Senior notes		$	798,725		$	888,370		$	—		$	888,370	$	—
	December 31, 2013		Carrying			Total			Level 1			Level 2		Level 3
			Amount			Fair Value
	Fixed maturity investments:
	U.S. Government and Government agencies		$	1,676,788		$	1,676,788		$	1,370,088		$	306,700	$	—
	Non-U.S. Government and Government agencies		191,776			191,776			—			191,776		—
	States, municipalities and political subdivisions		231,555			231,555			—			231,555		—
	Corporate debt		2,202,267			2,202,267			—			2,202,267		—
	Mortgage-backed		1,292,502			1,292,502			—			1,145,164		147,338
	Asset-backed		505,910			505,910			—			412,497		93,413
	Total fixed maturity investments		6,100,798			6,100,798			1,370,088			4,489,959		240,751
	Equity securities		699,846			699,846			625,942			—		73,904
	Other invested assets		764,081			764,081			—			—		764,081
	Total investments		$	7,564,725		$	7,564,725		$	1,996,030		$	4,489,959	$	1,078,736
	Derivative assets:
	Foreign exchange contracts		$	6,254		$	6,254		$	—		$	6,254	$	—
	Interest rate swaps		6,829			6,829			—			6,829		—
	Derivative liabilities:
	Foreign exchange contracts		$	1,176		$	1,176		$	—		$	1,176	$	—
	Interest rate swaps		$	4,214		$	4,214		$	—		$	4,214	$	—
	Senior notes		$	798,499		$	897,601		$	—		$	897,601	$	—
	“Other invested assets” excluded other private securities that the Company did not measure at fair value, but are accounted for using the equity method of accounting. Derivative assets and derivative liabilities relating to foreign exchange contracts and interest rate swaps are classified within “other assets” or “accounts payable and accrued liabilities” on the consolidated balance sheets.
	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.
	Recurring 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 values 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 bonds 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 the 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 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 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 net asset value ("NAV") of the funds as reported by the fund manager. The fair value of these investments are included in the Level 3 fair value hierarchy as the Company believes NAV is an unobservable input and these securities are not redeemable in the near term.
	Derivative instruments: The fair value of foreign exchange contracts, interest rate futures and interest rate 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.
	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 discounted cash flow models and market multiple models.
	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. If the Company determines that goodwill and 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 reconciliation of the beginning and ending balance of financial instruments using significant unobservable inputs (Level 3):
Three Months Ended September 30, 2014	Other invested			Mortgage-backed			Asset-backed			Equities
	assets
Opening balance	$	804,505		$	146,801		$	71,232		$	34,863
Realized and unrealized gains (losses) included in net income	6,797			(882		)	(253		)	3,172
Purchases	78,629			16,311			18,021			—
Sales	(83,807		)	(28,761		)	(9,970		)	—
Transfers into Level 3 from Level 2	—			1,628			17,863			—
Transfers out of Level 3 into Level 2 (1)	—			(15,189		)	(5,523		)	—
Ending balance	$	806,124		$	119,908		$	91,370		$	38,035
Three Months Ended September 30, 2013
Opening balance	$	714,391		$	198,003		$	61,285		$	53,499
Realized and unrealized gains (losses) included in net income	9,403			464			(313		)	3,972
Purchases	67,554			69,775			16,969			10,000
Sales	(24,277		)	(79,001		)	(1,302		)	—
Transfers into Level 3 from Level 2	—			13			3,394			—
Transfers out of Level 3 into Level 2 (1)	—			—			—			—
Ending balance	$	767,071		$	189,254		$	80,033		$	67,471
Nine Months Ended September 30, 2014	Other invested			Mortgage-backed			Asset-backed			Equities
	assets
Opening balance	$	764,081		$	147,338		$	93,413		$	73,904
Realized and unrealized gains (losses) included in net income	51,921			3,654			(659		)	(6,572		)
Purchases	267,549			34,187			35,526			—
Sales	(277,427		)	(65,038		)	(19,871		)	(29,297		)
Transfers into Level 3 from Level 2	—			1,253			13,923			—
Transfers out of Level 3 into Level 2 (1)	—			(1,486		)	(30,962		)	—
Ending balance	$	806,124		$	119,908		$	91,370		$	38,035
Nine Months Ended September 30, 2013
Opening balance	$	655,888		$	167,825		$	62,246		$	54,680
Realized and unrealized gains (losses) included in net income	53,365			(5,910		)	(791		)	2,791
Purchases	237,506			102,369			42,956			10,000
Sales	(179,688		)	(69,968		)	(26,728		)	—
Transfers into Level 3 from Level 2	—			5,073			2,350			—
Transfers out of Level 3 into Level 2 (1)	—			(10,135		)	—			—
Ending balance	$	767,071		$	189,254		$	80,033		$	67,471
_______________________
-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, then 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 Company uses a pricing service ranking to consistently select the most appropriate pricing service in instances where it receives multiple quotes on the same security. The Company obtains multiple quotes for the majority of its securities. 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, other than investments in other invested assets, 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_Ex

Reserve For Losses And Loss Expenses	9 Months Ended
	Sep. 30, 2014
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:
		September 30,			December 31,
		2014			2013
	Outstanding loss reserves	$	1,585,900		$	1,520,867
	Reserves for losses incurred but not reported	4,466,363			4,245,662
	Reserve for losses and loss expenses	$	6,052,263		$	5,766,529
	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.
		Three Months Ended						Nine Months Ended
		September 30,						September 30,
		2014			2013			2014			2013
	Gross liability at beginning of period	$	5,935,678		$	5,696,865		$	5,766,529		$	5,645,549
	Reinsurance recoverable at beginning of period	(1,301,742		)	(1,179,525		)	(1,234,504		)	(1,141,110		)
	Net liability at beginning of period	4,633,936			4,517,340			4,532,025			4,504,439
	Net losses incurred related to:
	Current year	382,970			338,420			1,067,111			961,224
	Prior years	(46,880		)	(61,450		)	(140,880		)	(153,948		)
	Total incurred	336,090			276,970			926,231			807,276
	Net paid losses related to:
	Current year	53,596			30,399			80,401			54,983
	Prior years	202,626			213,252			666,555			696,137
	Total paid	256,222			243,651			746,956			751,120
	Foreign exchange revaluation	(10,550		)	4,088			(8,046		)	(5,848		)
	Net liability at end of period	4,703,254			4,554,747			4,703,254			4,554,747
	Reinsurance recoverable at end of period	1,349,009			1,226,034			1,349,009			1,226,034
	Gross liability at end of period	$	6,052,263		$	5,780,781		$	6,052,263		$	5,780,781
	For the three months ended September 30, 2014, the Company recognized unfavorable prior year reserve development in its U.S. insurance segment and net favorable reserve development in its international insurance and reinsurance segments. The net unfavorable prior year reserve development for the U.S. insurance segment primarily related to the 2011 through 2013 loss years was due to a higher level of reported claims in the healthcare line of business and net unfavorable prior year reserve development for the 2005 loss year primarily related to the professional liability line of business. The net favorable reserve development in the international insurance segment was primarily due to lower than expected loss emergence across most lines of business and loss years partially offset by unfavorable prior reserve development for the 2012 loss year related to adverse development on two reported claims in our professional liability line of business. The net favorable reserve development in the reinsurance segment was primarily due to lower than expected loss activity in the property reinsurance line of business for the 2013 loss year.
	For the nine months ended September 30, 2014, the Company recognized unfavorable prior year reserve development in its U.S. insurance segment and net favorable reserve development in its international insurance and reinsurance segments. The net unfavorable prior year reserve development in the U.S. insurance segment primarily related to the 2011 through 2013 loss years in our healthcare lines of business and was due to higher than expected loss frequency and severity. The net favorable prior year reserve development in the international insurance segment was primarily due to favorable reserve development for the 2007 loss year in the professional liability line of business, net favorable development for the 2009 and 2010 loss years due to actual loss emergence being lower than anticipated across several lines of business, net unfavorable development for the 2012 loss year in the professional liability line of business and the unfavorable reserve development for the 2013 loss year in the healthcare line of business. The net favorable reserve development in the reinsurance segment was primarily due to lower than expected loss activity in the property reinsurance line of business for the 2013 loss year.
	For the three months ended September 30, 2013, the Company had net favorable reserve development in its international insurance and reinsurance segments due to actual loss emergence being lower than initially expected. The majority of the net favorable reserve development was recognized in the 2007 through 2011 loss years across most lines of business. In addition, the reinsurance segment recognized net favorable reserve development for the 2012 loss year due to the low level of reported property losses. This was partially offset by unfavorable development in the U.S. insurance segment in the 2011 and 2012 loss years primarily due to a higher level of reported claims for certain healthcare, errors and omissions and private/not for profit directors’ and officers’ lines of business.
	For the nine months ended September 30, 2013, the Company had net favorable reserve development in its international insurance and reinsurance segments due to actual loss emergence being lower than initially expected for most loss years. The reinsurance segment recognized net favorable reserve development for the 2012 loss year due to the low level of reported property losses. This was partially offset by adverse development in the U.S. insurance segment in the 2011 and 2012 loss years for certain healthcare, errors and omissions and not-for-profit directors’ and officers’ classes of business.
	While the Company at times has experienced favorable reserve 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.

Income_Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2014
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 a resident of the Canton of Zug and, as such, is subject to an annual cantonal and communal capital tax on its taxable equity. One of Allied World Switzerland's subsidiaries is a Swiss operating company, which is a 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 Assurance Company Holdings, Ltd (“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, Labuan, the United Kingdom, Singapore and Switzerland. To the best of the Company’s knowledge, there are no income tax examinations pending by any 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 September 30, 2014.

Shareholders_Equity

Shareholders' Equity	9 Months Ended
	Sep. 30, 2014
Stockholders' Equity Note [Abstract]	'
Shareholders' Equity	'
	SHAREHOLDERS’ EQUITY
	a) Authorized shares
	The issued share capital consists of the following:
		September 30,			December 31,
		2014			2013
	Common shares issued and fully paid, 2014: CHF 4.10 per share; 2013: CHF 4.10 per share	100,775,256			103,477,452
	Share capital at end of period	$	407,990		$	418,988
		Nine Months Ended September 30, 2014
	Shares issued at beginning of period	103,477,452
	Shares cancelled	(2,702,196	)
	Total shares issued at end of period	100,775,256
	Treasury shares issued at beginning of period	3,223,806
	Shares repurchased	4,616,543
	Shares issued out of treasury	(745,135	)
	Shares cancelled	(2,702,196	)
	Total treasury shares at end of period	4,393,018
	Total shares outstanding at end of period	96,382,238
	During the nine months ended September 30, 2014, 2,702,196 shares repurchased and designated for cancellation were constructively retired and cancelled.
	b) Dividends
	The Company paid the following dividends during the nine months ended September 30, 2014:
	Dividend Paid		Dividend			Total
			Per			Amount
			Share			Paid
	2-Jan-14		$	0.167		$	16,732
	3-Apr-14		$	0.167		$	16,495
	2-Jul-14		$	0.225		$	21,870
	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 amount will be paid to shareholders in quarterly dividends of $0.225 per share. The first dividend was on July 2, 2014 and the second dividend was on October 2, 2014. The Company expects to distribute the remaining dividends in January 2015 and April 2015.
	c) Share Repurchases
	On May 1, 2014, the shareholders approved a new share repurchase program in order for the Company to repurchase up to $500,000 of its common shares. This new 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 the Company 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.
	The Company’s share repurchases were as follows:
		Three Months Ended						Nine Months Ended
		September 30,						September 30,
		2014			2013			2014		2013
	Common shares repurchased	654,851			1,282,164			4,616,543		4,103,499
	Total cost of shares repurchased	$	24,996		$	40,574		$	164,528	$	123,145
	Average price per share	$	38.17		$	31.64		$	35.64	$	30.01

Employee_Benefit_Plans

Employee Benefit Plans	9 Months Ended
	Sep. 30, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]	'
Employee Benefit Plans	'
	EMPLOYEE BENEFIT PLANS
	a) Restricted stock units and performance-based equity awards
	Restricted stock units ("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.
	Performance-based equity awards represent the right to receive a number of common shares in the future, based upon the achievement of established performance criteria during an applicable performance period. For the performance-based equity awards granted in 2014, 2013 and 2012, the Company anticipates that the performance goals are likely to be achieved. Based on the performance goals, the performance-based equity awards granted in 2014, 2013 and 2012 are expensed at 100%, 100% and 135%, respectively, of the fair 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:
		Nine Months Ended September 30, 2014
		Number of Awards		Weighted
				Average
				Grant Date
				Fair Value
	Outstanding at beginning of period	143,697		$	21.69
	RSUs granted	454,176		33.56
	RSUs forfeited	(8,061	)	(31.71		)
	RSUs fully vested	(77,700	)	(21.68		)
	Outstanding at end of period	512,112		$	32.06
	The activity related to the Company’s performance-based equity awards is as follows:
		Nine Months Ended September 30, 2014
		Number of Awards		Weighted
				Average
				Grant Date
				Fair Value
	Outstanding at beginning of period	804,519		$	23.21
	Performance-based equity awards granted	166,302		33.56
	Additional awards granted due to achievement of performance criteria	104,895		20.5
	Performance-based equity awards forfeited	(1,848	)	(25.28		)
	Performance-based equity awards fully vested	(454,440	)	(20.50		)
	Outstanding at end of period	619,428		$	27.51
	b) Cash-equivalent stock awards
	As part of the Company’s annual year-end compensation awards, the Company granted both awards classified as equity and cash-equivalent stock awards. The cash-equivalent awards were granted to employees who received RSUs and performance-based equity awards in tandem with stock-based awards. The cash-equivalent RSU awards vest pro-rata over four years from the date of grant. The cash-equivalent performance-based equity 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 ratably over the service period. The liability is included in “accounts payable and accrued liabilities” 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 awards is as follows:
		RSU's					Performance-based Awards
	Nine Months Ended September 30, 2014	Number of Awards		Weighted Average Grant Date Fair Value			Number of Awards			Weighted Average Grant Date Fair Value
	Outstanding at beginning of period	2,049,084		$	24.69		1,031,961			23.67
	Granted	438,162		33.56			249,438			33.56
	Additional awards granted due to achievement of performance criteria	—		—			104,895			20.5
	Forfeited	(50,106	)	(26.75		)	(2,769	)		(25.28		)
	Fully vested	(752,668	)	(22.51		)	(454,440	)		(20.50		)
	Outstanding at end of period	1,684,472		$	27.98		929,085			$	27.51
	c) Total Stock Related Compensation Expense
	The following table shows the total stock-related compensation expense relating to the stock options, RSUs and cash equivalent awards.
		Three Months Ended						Nine Months Ended
		September 30,						September 30,
		2014			2013			2014				2013
	Stock options	$	424		$	647		$	1,564			$	2,662
	RSUs and performance-based equity awards	2,767			2,070			9,258				6,621
	Cash-equivalent stock awards	8,433			13,699			25,930				34,666
	Total	$	11,624		$	16,416		$	36,752			$	43,949

Earnings_Per_Share

Earnings Per Share	9 Months Ended
	Sep. 30, 2014
Earnings Per Share [Abstract]	'
Earnings Per Share	'
	EARNINGS PER SHARE
	The following table sets forth the comparison of basic and diluted earnings per share:
		Three Months Ended				Nine Months Ended
		September 30,				September 30,
		2014		2013		2014		2013
	Basic earnings per share:
	Net income	$	30,915	$	122,843	$	359,750	$	279,973
	Weighted average common shares outstanding	96,458,231		101,974,077		97,926,378		103,020,681
	Basic earnings per share	$	0.32	$	1.2	$	3.67	$	2.72
		Three Months Ended				Nine Months Ended
		September 30,				September 30,
		2014		2013		2014		2013
	Diluted earnings per share:
	Net income	$	30,915	$	122,843	$	359,750	$	279,973
	Weighted average common shares outstanding	96,458,231		101,974,077		97,926,378		103,020,681
	Share equivalents:
	Stock options	1,430,243		1,500,342		1,449,641		1,492,374
	RSUs and performance-based equity awards	541,711		708,399		575,675		877,107
	Employee share purchase plan	14,053		1,761		13,602		3,114
	Weighted average common shares and common share equivalents outstanding - diluted	98,444,238		104,184,579		99,965,296		105,393,276
	Diluted earnings per share	$	0.31	$	1.18	$	3.6	$	2.66
	For the three months ended September 30, 2014, and 2013, there were no common shares considered anti-dilutive and therefore excluded from the calculation of the diluted earnings per share.
	For the nine months ended September 30, 2014 and 2013, there were no common shares considered anti-dilutive and therefore excluded from the calculation of the diluted earnings per share.

Segment_Information

Segment Information	9 Months Ended
	Sep. 30, 2014
Segment Reporting [Abstract]	'
Segment Information	'
	SEGMENT INFORMATION
	The determination of reportable segments is based on how senior management 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: U.S. insurance, international insurance and reinsurance. All lines of business fall within these classifications.
	The U.S. insurance segment includes the Company’s direct specialty insurance operations in the United States and Canada, as well as the Company's claim administration services operations. The Company acquired the remaining interest in a claims administration services company it did not own in May 2014 and recorded goodwill of $9,709 related to the transaction. The U.S. insurance segment provides both direct property and specialty casualty insurance primarily to non-Fortune 1000 North American domiciled accounts, as well as third-party claims administration services.
	The international insurance segment includes the Company’s direct insurance operations in Bermuda, Europe, and Asia Pacific, which includes offices in Australia, Hong Kong and Singapore. This segment primarily provides both direct property and casualty insurance to Fortune 1000 North American domiciled accounts from the Bermuda office and direct property and specialty casualty insurance to non-North American domiciled accounts from the European and Asia Pacific offices.
	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 for 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:
	Three Months Ended September 30, 2014		U.S. Insurance				International				Reinsurance				Total
							Insurance
	Gross premiums written		$	386,681			$	144,236			$	176,967			$	707,884
	Net premiums written		321,713				87,820				159,209				568,742
	Net premiums earned		224,764				94,013				222,960				541,737
	Net losses and loss expenses		(153,010		)		(55,814		)		(127,266		)		(336,090		)
	Acquisition costs		(31,131		)		(1,209		)		(40,063		)		(72,403		)
	General and administrative expenses		(41,730		)		(27,993		)		(18,571		)		(88,294		)
	Underwriting (loss) income		(1,107		)		8,997				37,060				44,950
	Other insurance-related income		1,032				—				—				1,032
	Other insurance-related expenses		(1,270		)		(5,305		)		—				(6,575		)
	Segment (loss) income		$	(1,345	)		$	3,692			$	37,060			$	39,407
	Net investment income														43,412
	Net realized investment losses														(35,136		)
	Amortization of intangible assets														(633		)
	Interest expense														(14,325		)
	Foreign exchange loss														(278		)
	Income before income taxes														$	32,447
	Loss and loss expense ratio		68.1		%		59.4		%		57.1		%		62		%
	Acquisition cost ratio		13.9		%		1.3		%		18		%		13.4		%
	General and administrative expense ratio		18.6		%		29.8		%		8.3		%		16.3		%
	Expense ratio		32.5		%		31.1		%		26.3		%		29.7		%
	Combined ratio		100.6		%		90.5		%		83.4		%		91.7		%
	Three Months Ended September 30, 2013		U.S. Insurance				International				Reinsurance				Total
							Insurance
	Gross premiums written		$	308,709			$	132,881			$	139,303			$	580,893
	Net premiums written		238,792				75,632				138,653				453,077
	Net premiums earned		207,602				87,554				215,617				510,773
	Net losses and loss expenses		(141,222		)		(31,094		)		(104,654		)		(276,970		)
	Acquisition costs		(28,426		)		282				(36,970		)		(65,114		)
	General and administrative expenses		(41,616		)		(26,450		)		(20,487		)		(88,553		)
	Underwriting (loss) income		(3,662		)		30,292				53,506				80,136
	Other insurance-related income		—				—				—				—
	Other insurance-related expenses		—				—				—				—
	Segment (loss) income		$	(3,662	)		$	30,292			$	53,506			$	80,136
	Net investment income														39,271
	Net realized investment gains														27,487
	Amortization of intangible assets														(633		)
	Interest expense														(14,094		)
	Foreign exchange loss														(4,353		)
	Income before income taxes														$	127,814
	Loss and loss expense ratio		68		%		35.5		%		48.5		%		54.2		%
	Acquisition cost ratio		13.7		%		(0.3		)%		17.1		%		12.7		%
	General and administrative expense ratio		20		%		30.2		%		9.5		%		17.3		%
	Expense ratio		33.7		%		29.9		%		26.6		%		30		%
	Combined ratio		101.7		%		65.4		%		75.1		%		84.2		%
	Nine Months Ended September 30, 2014		U.S. Insurance				International				Reinsurance				Total
							Insurance
	Gross premiums written		$	998,051			$	483,079			$	888,552			$	2,369,682
	Net premiums written		746,403				285,450				862,427				1,894,280
	Net premiums earned		651,480				271,557				686,232				1,609,269
	Net losses and loss expenses		(440,491		)		(115,299		)		(370,441		)		(926,231		)
	Acquisition costs		(88,311		)		(835		)		(125,258		)		(214,404		)
	General and administrative expenses		(125,760		)		(82,164		)		(56,898		)		(264,822		)
	Underwriting (loss) income		(3,082		)		73,259				133,635				203,812
Other insurance-related income		1,032				—				—				1,032
Other insurance-related expenses		(1,270		)		(5,305		)		—				(6,575		)
Segment (loss) income		$	(3,320	)		$	67,954			$	133,635			$	198,269
Net investment income														127,824
Net realized investment gains														104,286
Amortization of intangible assets														(1,900		)
Interest expense														(43,451		)
Foreign exchange loss														(978		)
Income before income taxes														$	384,050
Loss and loss expense ratio		67.6		%		42.5		%		54		%		57.6		%
Acquisition cost ratio		13.6		%		0.3		%		18.3		%		13.3		%
General and administrative expense ratio		19.3		%		30.3		%		8.3		%		16.5		%
Expense ratio		32.9		%		30.6		%		26.6		%		29.8		%
Combined ratio		100.5		%		73.1		%		80.6		%		87.4		%
Nine Months Ended September 30, 2013		U.S. Insurance				International				Reinsurance				Total
						Insurance
Gross premiums written		$	872,024			$	453,990			$	857,160			$	2,183,174
Net premiums written		652,464				259,771				817,116				1,729,351
Net premiums earned		593,477				258,809				628,986				1,481,272
Net losses and loss expenses		(398,910		)		(90,997		)		(317,369		)		(807,276		)
Acquisition costs		(78,824		)		1,489				(109,081		)		(186,416		)
General and administrative expenses		(119,514		)		(75,374		)		(56,930		)		(251,818		)
Underwriting (loss) income		(3,771		)		93,927				145,606				235,762
Other insurance-related income		—				—				—				—
Other insurance-related expenses		—				—				—				—
Segment (loss) income		$	(3,771	)		$	93,927			$	145,606			$	235,762
Net investment income														110,294
Net realized investment losses														(8,074		)
Amortization of intangible assets														(1,900		)
Interest expense														(42,416		)
Foreign exchange loss														(7,361		)
Income before income taxes														$	286,305
Loss and loss expense ratio		67.2		%		35.2		%		50.5		%		54.5		%
Acquisition cost ratio		13.3		%		(0.6		)%		17.3		%		12.6		%
General and administrative expense ratio		20.1		%		29.1		%		9.1		%		17		%
Expense ratio		33.4		%		28.5		%		26.4		%		29.6		%
Combined ratio		100.6		%		63.7		%		76.9		%		84.1		%
The following table shows an analysis of the Company’s gross premiums written by geographic location of the Company’s subsidiaries and branches. All intercompany premiums have been eliminated.
	Three Months Ended								Nine Months Ended
	September 30,								September 30,
	2014				2013				2014				2013
United States	$	483,992			$	377,618			$	1,447,652			$	1,296,212
Bermuda	109,503				111,103				525,005				550,815
Europe	64,947				52,004				245,931				198,747
Asia Pacific	45,070				40,168				142,798				137,400
Canada	4,372				—				8,296				—
Total gross premiums written	$	707,884			$	580,893			$	2,369,682			$	2,183,174
Europe includes gross premiums written attributable to Switzerland of $11,130 and $10,509 for the three months ended September 30, 2014 and 2013, respectively and $65,684 and $57,183 for the nine months ended September 30, 2014 and 2013.

Commitments_And_Contingencies

Commitments And Contingencies	9 Months Ended
	Sep. 30, 2014
Commitments and Contingencies Disclosure [Abstract]	'
Commitments And Contingencies	'
	COMMITMENTS AND CONTINGENCIES
	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 September 30, 2014, 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.

Condensed_Consolidated_Guarant

Condensed Consolidated Guarantor Financial Statements	9 Months Ended
	Sep. 30, 2014
Condensed Financial Information of Parent Company Only Disclosure [Abstract]	'
Condensed Consolidated Guarantor Financial Statements	'
	CONDENSED CONSOLIDATED GUARANTOR FINANCIAL STATEMENTS
	The following tables present unaudited condensed consolidating financial information as of September 30, 2014 and December 31, 2013 and for the three and nine months ended September 30, 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.
	Unaudited Condensed Consolidating Balance Sheet:
	As of September 30, 2014	Allied World			Allied World			Other Allied			Consolidating			Allied World
		Switzerland			Bermuda			World			Adjustments			Switzerland
		(Parent			(Subsidiary			Subsidiaries						Consolidated
		Guarantor)			Issuer)
	ASSETS:
	Investments	$	—		$	—		$	8,002,514		$	—		$	8,002,514
	Cash and cash equivalents	38,196			2,329			790,745			—			831,270
	Insurance balances receivable	—			—			926,183			—			926,183
	Funds held	—			—			405,703			—			405,703
	Reinsurance recoverable	—			—			1,349,009			—			1,349,009
	Net deferred acquisition costs	—			—			171,827			—			171,827
	Goodwill and intangible assets	—			—			325,016			—			325,016
	Balances receivable on sale of investments	—			—			60,122			—			60,122
	Investments in subsidiaries	3,644,932			4,255,136			—			(7,900,068		)	—
	Due from subsidiaries	18,497			407			15,508			(34,412		)	—
	Other assets	2,009			3,576			732,339			—			737,924
	Total assets	$	3,703,634		$	4,261,448		$	12,778,966		$	(7,934,480	)	$	12,809,568
	LIABILITIES:
	Reserve for losses and loss expenses	$	—		$	—		$	6,052,263		$	—		$	6,052,263
	Unearned premiums	—			—			1,716,927			—			1,716,927
	Reinsurance balances payable	—			—			203,428			—			203,428
	Balances due on purchases of investments	—			—			166,026			—			166,026
	Senior notes	—			798,725			—			—			798,725
	Due to subsidiaries	6,826			8,682			18,904			(34,412		)	—
	Other liabilities	23,209			12,513			162,878			—			198,600
	Total liabilities	30,035			819,920			8,320,426			(34,412		)	9,135,969
	Total shareholders’ equity	3,673,599			3,441,528			4,458,540			(7,900,068		)	3,673,599
	Total liabilities and shareholders’ equity	$	3,703,634		$	4,261,448		$	12,778,966		$	(7,934,480	)	$	12,809,568
	As of December 31, 2013	Allied World			Allied World			Other Allied			Consolidating			Allied World
		Switzerland			Bermuda			World			Adjustments			Switzerland
		(Parent			(Subsidiary			Subsidiaries						Consolidated
		Guarantor)			Issuer)
	ASSETS:
	Investments	$	—		$	—		$	7,712,036		$	—		$	7,712,036
	Cash and cash equivalents	10,790			2,775			518,371			—			531,936
	Insurance balances receivable	—			—			664,731			—			664,731
	Funds held	—			—			632,430			—			632,430
	Reinsurance recoverable	—			—			1,234,504			—			1,234,504
	Net deferred acquisition costs	—			—			126,661			—			126,661
	Goodwill and intangible assets	—			—			317,207			—			317,207
	Balances receivable on sale of investments	—			—			76,544			—			76,544
	Investments in subsidiaries	3,413,001			4,018,619			—			(7,431,620		)	—
	Due from subsidiaries	111,172			122,846			123,479			(357,497		)	—
	Other assets	1,757			4,671			643,353			—			649,781
	Total assets	$	3,536,720		$	4,148,911		$	12,049,316		$	(7,789,117	)	$	11,945,830
	LIABILITIES:
	Reserve for losses and loss expenses	$	—		$	—		$	5,766,529		$	—		$	5,766,529
	Unearned premiums	—			—			1,396,256			—			1,396,256
	Reinsurance balances payable	—			—			173,023			—			173,023
	Balances due on purchases of investments	—			—			104,740			—			104,740
	Senior notes	—			798,499			—			—			798,499
	Due to subsidiaries	12,945			110,534			234,018			(357,497		)	—
	Other liabilities	3,949			17,797			165,211			—			186,957
	Total liabilities	16,894			926,830			7,839,777			(357,497		)	8,426,004
	Total shareholders’ equity	3,519,826			3,222,081			4,209,539			(7,431,620		)	3,519,826
	Total liabilities and shareholders’ equity	$	3,536,720		$	4,148,911		$	12,049,316		$	(7,789,117	)	$	11,945,830
	The investment in subsidiaries and total shareholders' equity balances reported above in the Unaudited Condensed Consolidating Balance Sheet for Allied World Bermuda (Subsidiary Issuer) as of December 31, 2013 were reduced by $776,000 from the previously reported amounts to properly record intercompany dividends as a reduction in the investment in subsidiaries balance due to a miscalculation. Since the intercompany dividends were eliminated in consolidation there was no impact to consolidated total shareholders' equity.
	Unaudited Condensed Consolidating Statement of Operations and Comprehensive Income:
	Three Months Ended September 30, 2014	Allied World			Allied World			Other Allied			Consolidating			Allied World
		Switzerland			Bermuda			World			Adjustments			Switzerland
(Parent			(Subsidiary			Subsidiaries						Consolidated
Guarantor)			Issuer)
Net premiums earned	$	—		$	—		$	541,737		$	—		$	541,737
Net investment income	2			—			43,410			—			43,412
Net realized investment gains (losses)	—			—			(35,136		)	—			(35,136		)
Other income	—			—			1,032			—			1,032
Net losses and loss expenses	—			—			(336,090		)	—			(336,090		)
Acquisition costs	—			—			(72,403		)	—			(72,403		)
General and administrative expenses	(8,285		)	(182		)	(79,827		)	—			(88,294		)
Other expense	—			—			(6,575		)	—			(6,575		)
Amortization of intangible assets	—			—			(633		)	—			(633		)
Interest expense	—			(13,855		)	(470		)	—			(14,325		)
Foreign exchange gain (loss)	16			47			(341		)	—			(278		)
Income tax (expense) benefit	—			—			(1,532		)	—			(1,532		)
Equity in earnings of consolidated subsidiaries	39,182			49,491			—			(88,673		)	—
NET INCOME (LOSS)	$	30,915		$	35,501		$	53,172		$	(88,673	)	$	30,915
Other comprehensive income	—			—			—			—			—
COMPREHENSIVE INCOME (LOSS)	$	30,915		$	35,501		$	53,172		$	(88,673	)	$	30,915
Three Months Ended September 30, 2013	Allied World			Allied World			Other Allied			Consolidating			Allied World
	Switzerland			Bermuda			World			Adjustments			Switzerland
	(Parent			(Subsidiary			Subsidiaries						Consolidated
	Guarantor)			Issuer)
Net premiums earned	$	—		$	—		$	510,773		$	—		$	510,773
Net investment income	3			—			39,268			—			39,271
Net realized investment gains (losses)	—			—			27,487			—			27,487
Other income	—			—			—			—			—
Net losses and loss expenses	—			—			(276,970		)	—			(276,970		)
Acquisition costs	—			—			(65,114		)	—			(65,114		)
General and administrative expenses	(7,323		)	(4,961		)	(76,269		)	—			(88,553		)
Other expense	—			—			—			—			—
Amortization of intangible assets	—			—			(633		)	—			(633		)
Interest expense	—			(13,838		)	(256		)	—			(14,094		)
Foreign exchange gain (loss)	(13		)	(212		)	(4,128		)	—			(4,353		)
Income tax (expense) benefit	—			—			(4,971		)	—			(4,971		)
Equity in earnings of consolidated subsidiaries	130,176			150,653			—			(280,829		)	—
NET INCOME (LOSS)	$	122,843		$	131,642		$	149,187		$	(280,829	)	$	122,843
Other comprehensive income	—			—			—			—			—
COMPREHENSIVE INCOME (LOSS)	$	122,843		$	131,642		$	149,187		$	(280,829	)	$	122,843
Nine Months Ended September 30, 2014	Allied World			Allied World			Other Allied			Consolidating			Allied World
	Switzerland			Bermuda			World			Adjustments			Switzerland
	(Parent			(Subsidiary			Subsidiaries						Consolidated
	Guarantor)			Issuer)
Net premiums earned	$	—		$	—		$	1,609,269		$	—		$	1,609,269
Net investment income	6			—			127,818			—			127,824
Net realized investment gains (losses)	—			—			104,286			—			104,286
Other income	—			—			1,032			—			1,032
Net losses and loss expenses	—			—			(926,231		)	—			(926,231		)
Acquisition costs	—			—			(214,404		)	—			(214,404		)
General and administrative expenses	(28,012		)	(919		)	(235,891		)	—			(264,822		)
Other expense	—			—			(6,575		)	—			(6,575		)
Amortization of intangible assets	—			—			(1,900		)	—			(1,900		)
Interest expense	—			(41,556		)	(1,895		)	—			(43,451		)
Foreign exchange gain (loss)	12			68			(1,058		)	—			(978		)
Income tax (expense) benefit	(86		)	—			(24,214		)	—			(24,300		)
Equity in earnings of consolidated subsidiaries	387,830			419,294			—			(807,124		)	—
NET INCOME (LOSS)	$	359,750		$	376,887		$	430,237		$	(807,124	)	$	359,750
Other comprehensive income	—			—			—			—			—
COMPREHENSIVE INCOME (LOSS)	$	359,750		$	376,887		$	430,237		$	(807,124	)	$	359,750
Nine Months Ended September 30, 2013	Allied World			Allied World			Other Allied			Consolidating			Allied World
	Switzerland			Bermuda			World			Adjustments			Switzerland
	(Parent			(Subsidiary			Subsidiaries						Consolidated
	Guarantor)			Issuer)
Net premiums earned	$	—		$	—		$	1,481,272		$	—		$	1,481,272
Net investment income	11			4			110,279			—			110,294
Net realized investment gains (losses)	—			—			(8,074		)	—			(8,074		)
Other income	—			—			—			—			—
Net losses and loss expenses	—			—			(807,276		)	—			(807,276		)
Acquisition costs	—			—			(186,416		)	—			(186,416		)
General and administrative expenses	(26,875		)	(5,873		)	(219,070		)	—			(251,818		)
Other expense	—			—			—			—			—
Amortization of intangible assets	—			—			(1,900		)	—			(1,900		)
Interest expense	—			(41,503		)	(913		)	—			(42,416		)
Foreign exchange gain (loss)	261			(935		)	(6,687		)	—			(7,361		)
Income tax (expense) benefit	—			—			(6,332		)	—			(6,332		)
Equity in earnings of consolidated subsidiaries	306,576			353,280			—			(659,856		)	—
NET INCOME (LOSS)	$	279,973		$	304,973		$	354,883		$	(659,856	)	$	279,973
Other comprehensive income	—			—			—			—			—
COMPREHENSIVE INCOME (LOSS)	$	279,973		$	304,973		$	354,883		$	(659,856	)	$	279,973
Unaudited Condensed Consolidating Statement of Cash Flows:
Nine Months Ended September 30, 2014	Allied World			Allied World			Other Allied			Consolidating			Allied World
	Switzerland			Bermuda			World			Adjustments			Switzerland
	(Parent			(Subsidiary			Subsidiaries						Consolidated
	Guarantor)			Issuer)
CASH FLOWS PROVIDED BY (USED IN) OPERATING ACTIVITIES	$	241,037		$	263,554		$	737,516		$	(575,000	)	$	667,107
CASH FLOWS PROVIDED BY (USED IN) INVESTING ACTIVITIES:
Purchases trading securities	—			—			(5,608,594		)	—			(5,608,594		)
Purchases of other invested assets	—			—			(242,227		)	—			(242,227		)
Sales of trading securities	—			—			5,500,176			—			5,500,176
Sales of other invested assets	—			—			243,123			—			243,123
Other	—			—			(46,620		)	—			(46,620		)
Net cash provided by (used in) investing activities	—			—			(154,142		)	—			(154,142		)
CASH FLOWS PROVIDED BY (USED IN) FINANCING ACTIVITIES:
Dividends paid	(55,064		)	—			—			—			(55,064		)
Intercompany dividends paid	—			(264,000		)	(311,000		)	575,000			—
Proceeds from the exercise of stock options	7,640			—			—			—			7,640
Share repurchases	(166,207		)	—			—			—			(166,207		)
Net cash provided by (used in) financing activities	(213,631		)	(264,000		)	(311,000		)	575,000			(213,631		)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	27,406			(446		)	272,374			—			299,334
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD	10,790			2,775			518,371			—			531,936
CASH AND CASH EQUIVALENTS, END OF PERIOD	$	38,196		$	2,329		$	790,745		$	—		$	831,270
Nine Months Ended September 30, 2013	Allied World			Allied World			Other Allied			Consolidating			Allied World
	Switzerland			Bermuda			World			Adjustments			Switzerland
	(Parent			(Subsidiary			Subsidiaries						Consolidated
	Guarantor)			Issuer)
CASH FLOWS PROVIDED BY (USED IN) OPERATING ACTIVITIES:	$	177,859		$	226,564		$	431,127		$	(503,500	)	$	332,050
CASH FLOWS PROVIDED BY (USED IN) INVESTING ACTIVITIES:
Purchases of trading securities	—			—			(4,955,817		)	—			(4,955,817		)
Purchases of other invested assets	—			—			(211,501		)	—			(211,501		)
Sales of trading securities	—			—			5,137,280			—			5,137,280
Sales of other invested assets	—			—			189,155			—			189,155
Other	—			—			(78,203		)	—			(78,203		)
Net cash provided by (used in) investing activities	—			—			80,914			—			80,914
CASH FLOWS PROVIDED BY (USED IN) FINANCING ACTIVITIES:
Dividends paid - partial par value reduction	(12,981		)	—			—			—			(12,981		)
Dividends paid	(17,117		)	—			—			—			(17,117		)
Intercompany dividends paid	—			(229,500		)	(274,000		)	503,500			—
Proceeds from the exercise of stock options	8,465			—			—			—			8,465
Share repurchases	(120,163		)	—			—			—			(120,163		)
Net cash provided by (used in) financing activities	(141,796		)	(229,500		)	(274,000		)	503,500			(141,796		)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	36,063			(2,936		)	238,041			—			271,168
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD	19,997			11,324			650,558			—			681,879
CASH AND CASH EQUIVALENTS, END OF PERIOD	$	56,060		$	8,388		$	888,599		$	—		$	953,047
Notes to Parent Company Condensed Financial Information
a) Dividends
Allied World Switzerland received cash dividends from its subsidiaries of $264,000 and $229,500 for the nine months ended September 30, 2014 and 2013, respectively. Such dividends are included in “cash flows provided by (used in) operating activities” in the unaudited condensed consolidating cash flows.

Subsequent_Events

Subsequent Events	9 Months Ended
	Sep. 30, 2014
Subsequent Events [Abstract]	'
Subsequent Events	'
	SUBSEQUENT EVENTS
	On October 2, 2014, the Company paid a quarterly dividend of $0.225 per share to shareholders of record on September 23, 2014.
	In October 2014, the Company, through its subsidiary Allied World Financial Services, Inc., acquired a minority interest in Blue Vista Capital Management, LLC ("Blue Vista"). Blue Vista invests across real estate asset classes and capital structures through limited partnerships and separate accounts. As part of the acquisition, the Company has agreed to invest $225,000 to various funds managed by Blue Vista over the next several years.
	Effective December 31, 2014, the Company will reorganize how it manages its business, and as a result it will realign its executive management team and change its reportable segments to correspond to the reorganization. The Company's Bermuda direct insurance operations, which had previously been included in the international insurance segment, will now be combined with the U.S. insurance segment and renamed North American Insurance. The remaining direct insurance operations of the international insurance segment will be renamed Global Markets Insurance. The reinsurance segment will remain unchanged. The newly created segments will be presented in the Company's financial statements beginning with the period ended December 31, 2014 and prior periods will be recast to conform to the new presentation.

Basis_of_Preparation_and_Conso1

Basis of Preparation and Consolidation (Policies)	9 Months Ended
	Sep. 30, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]	'
Basis of accounting	'
	Intercompany accounts and transactions have been eliminated on consolidation and all entities meeting consolidation requirements have been included in the unaudited condensed consolidated financial statements.
	These unaudited condensed consolidated financial statements include the accounts of the Company and have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) for interim financial information and with Article 10 of Regulation S-X as promulgated by the U.S. Securities and Exchange Commission (“SEC”). Accordingly, they do not include all of the information and footnotes required by U.S. GAAP for complete financial statements. In the opinion of management, these unaudited condensed consolidated financial statements reflect all adjustments that are normal and recurring in nature and necessary for a fair presentation of financial position and results of operations as of the end of and for the periods presented. The results of operations for any interim period are not necessarily indicative of the results for a full year.
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.

Investments_Tables

Investments (Tables)	9 Months Ended
	Sep. 30, 2014
Investments [Abstract]	'
Schedule of trading securities	'
	Securities accounted for at fair value with changes in fair value recognized in the unaudited condensed consolidated statements of operations and comprehensive income (“consolidated income statements”) by category are as follows:
		September 30, 2014						December 31, 2013
		Fair Value			Amortized Cost			Fair Value				Amortized Cost
	U.S. Government and Government agencies	$	1,184,115		$	1,186,185		$	1,676,788			$	1,684,832
	Non-U.S. Government and Government agencies	219,287			229,792			191,776				197,082
	States, municipalities and political subdivisions	260,690			251,628			231,555				234,406
	Corporate debt:
	Financial institutions	1,194,949			1,185,637			958,794				943,518
	Industrials	1,202,906			1,201,341			1,174,047				1,165,448
	Utilities	125,513			125,202			69,426				69,658
	Mortgage-backed	1,240,362			1,196,683			1,292,502				1,267,863
	Asset-backed	700,415			698,284			505,910				502,543
	Total fixed maturity investments	$	6,128,237		$	6,074,752		$	6,100,798			$	6,065,350
		September 30, 2014						December 31, 2013
		Fair Value			Original Cost			Fair Value				Original Cost
	Equity securities	$	945,076		$	901,300		$	699,846			$	647,301
	Other invested assets	806,124			701,794			764,081				658,683
		$	1,751,200		$	1,603,094		$	1,463,927			$	1,305,984
Schedule of other invested assets	'
	Details regarding the carrying value, redemption characteristics and unfunded investment commitments of the other invested assets portfolio as of September 30, 2014 and December 31, 2013 were as follows:
	Investment Type	Carrying Value as of September 30, 2014			Investments			Estimated		Investments				Redemption	Redemption	Unfunded
					with			Remaining		without				Frequency(1)	Notice	Commitments
					Redemption			Restriction		Redemption					Period(1)
					Restrictions			Period		Restrictions
	Private equity	$	179,196		$	179,196		2 - 9 Years		$	—					$	223,030
	Mezzanine debt	114,399			114,399			5 - 9 Years		—						251,486
	Distressed	9,516			9,516			4 Years		—						5,119
	Total private equity	303,111			303,111					—						479,635
	Distressed	173,111			173,111			1 Year		—						—
	Equity long/short	111,627			86,721			1 Year		24,906				Quarterly	30 -60 Days	—
	Multi-strategy	81,576			—					81,576				Quarterly	45 -90 Days	—
	Relative value credit	105,155			—					105,155				Quarterly	60 Days	—
	Total hedge funds	471,469			259,832					211,637						—
	High yield loan fund	31,544			—					31,544				Monthly	30 days	—
	Total other invested assets at fair value	806,124			562,943					243,181						479,635
	Other private securities	123,077			—					123,077						—
	Total other invested assets	$	929,201		$	562,943				$	366,258					$	479,635
	Investment Type	Carrying Value as of December 31, 2013			Investments			Estimated		Investments				Redemption	Redemption	Unfunded
					with			Remaining		without				Frequency(1)	Notice	Commitments
					Redemption			Restriction		Redemption					Period(1)
					Restrictions			Period		Restrictions
	Private equity	$	144,422		$	144,422		2 - 9 Years		$	—					$	263,519
	Mezzanine debt	64,627			64,627			8 - 9 Years		—						198,756
	Distressed	7,776			7,776			4 Years		—						5,249
	Total private equity	216,825			216,825					—						467,524
	Distressed	151,227			151,227			1 - 2 Years		—						—
	Equity long/short	99,365			—					99,365				Quarterly	30 -60 Days	—
	Multi-strategy	136,958			—					136,958				Quarterly	45 -90 Days	—
	Event driven	14,018			—					14,018				Annual	60 Days	—
	Relative value credit	113,730			—					113,730				Quarterly	60 Days	—
	Total hedge funds	515,298			151,227					364,071						—
	High yield loan fund	31,958			—					31,958				Monthly	30 days	—
	Total other invested assets at fair value	764,081			368,052					396,029						467,524
	Other private securities	147,311			—					147,311						—
	Total other invested assets	$	911,392		$	368,052				$	543,340					$	467,524
	_______________________
	-1	The redemption frequency and notice periods only apply to the investments without redemption restrictions. Some or all of these investments may be subject to a gate as described below.
Schedule of net investment income	'
		Three Months Ended						Nine Months Ended
		September 30,						September 30,
		2014			2013			2014				2013
	Fixed maturity investments	$	38,762		$	31,179		$	110,998			$	96,366
	Equity securities	3,711			6,110			12,876				13,718
	Other invested assets: hedge funds and private equity	2,249			3,812			8,767				6,001
	Other invested assets: other private securities	3,292			1,997			7,291				5,115
	Cash and cash equivalents	552			302			1,562				1,319
	Expenses	(5,154		)	(4,129		)	(13,670		)		(12,225		)
	Net investment income	$	43,412		$	39,271		$	127,824			$	110,294
Components of realized gains and losses	'
		Three Months Ended						Nine Months Ended
		September 30,						September 30,
		2014			2013			2014				2013
	Gross realized gains on sale of invested assets	$	28,773		$	51,915		$	146,780			$	154,387
	Gross realized losses on sale of invested assets	(9,955		)	(40,770		)	(26,228		)		(82,812		)
	Net realized and unrealized gains (losses) on derivatives	2,171			(4,169		)	(24,469		)		3,392
	Mark-to-market (losses) gains:
	Fixed maturity investments, trading	(40,843		)	30,383			18,039				(101,205		)
	Equity securities, trading	(8,479		)	(17,198		)	(8,768		)		(18,555		)
	Other invested assets, trading	(6,803		)	7,326			(1,068		)		36,719
	Net realized investment (losses) gains	$	(35,136	)	$	27,487		$	104,286			$	(8,074	)

Derivative_Instruments_Tables

Derivative Instruments (Tables)	9 Months Ended
	Sep. 30, 2014
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 unaudited condensed consolidated balance sheets (“consolidated balance sheets”):
		September 30, 2014											December 31, 2013
		Asset		Asset			Liability			Liability			Asset		Asset		Liability		Liability
		Derivative		Derivative			Derivative			Derivative			Derivative		Derivative		Derivative		Derivative
		Notional		Fair Value			Notional			Fair Value			Notional		Fair Value		Notional		Fair Value
		Amount					Amount						Amount				Amount
	Foreign exchange contracts	$	38,940	$	814		$	2,355		$	22		$	294,788	$	6,254	$	122,439	$	1,176
	Interest rate swaps	565,600		414			—			—			491,400		6,829		40,000		4,214
	Total derivatives	$	604,540	$	1,228		$	2,355		$	22		$	786,188	$	13,083	$	162,439	$	5,390
Unrealized and realized gains (losses) on derivatives recorded in the unaudited condensed consolidated income statements	'
	The following table provides the net realized and unrealized gains (losses) on derivatives not designated as hedges recorded on the consolidated income statements:
		Three Months Ended					Nine Months Ended
		September 30,					September 30,
		2014		2013			2014			2013
	Foreign exchange contracts	$	1,886	$	(2,336	)	$	(580	)	$	(1,091	)
	Total included in foreign exchange loss	1,886		(2,336		)	(580		)	(1,091		)
	Put options	—		—			—			(3,822		)
	Foreign exchange contracts	1,701		(4,164		)	857			1,925
	Interest rate futures and swaps	470		(5		)	(25,325		)	5,289
	Total included in net realized investment gains (losses)	2,171		(4,169		)	(24,468		)	3,392
	Total realized and unrealized gains (losses) on derivatives	$	4,057	$	(6,505	)	$	(25,048	)	$	2,301

Fair_Value_Of_Financial_Instru1

Fair Value Of Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2014
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:
	September 30, 2014		Carrying			Total			Level 1			Level 2		Level 3
			Amount			Fair Value
	Fixed maturity investments:
	U.S. Government and Government agencies		$	1,184,115		$	1,184,115		$	998,487		$	185,628	$	—
	Non-U.S. Government and Government agencies		219,287			219,287			—			219,287		—
	States, municipalities and political subdivisions		260,690			260,690			—			260,690		—
	Corporate debt		2,523,368			2,523,368			—			2,523,368		—
	Mortgage-backed		1,240,362			1,240,362			—			1,120,454		119,908
	Asset-backed		700,415			700,415			—			609,045		91,370
	Total fixed maturity investments		6,128,237			6,128,237			998,487			4,918,472		211,278
	Equity securities		945,076			945,076			907,041			—		38,035
	Other invested assets		806,124			806,124			—			—		806,124
	Total investments		$	7,879,437		$	7,879,437		$	1,905,528		$	4,918,472	$	1,055,437
	Derivative assets:
	Foreign exchange contracts		$	814		$	814		$	—		$	814	$	—
	Interest rate swaps		414			414			—			414		—
	Derivative liabilities:
	Foreign exchange contracts		$	22		$	22		$	—		$	22	$	—
	Interest rate swaps		—			—			—			—		—
	Senior notes		$	798,725		$	888,370		$	—		$	888,370	$	—
	December 31, 2013		Carrying			Total			Level 1			Level 2		Level 3
			Amount			Fair Value
	Fixed maturity investments:
	U.S. Government and Government agencies		$	1,676,788		$	1,676,788		$	1,370,088		$	306,700	$	—
	Non-U.S. Government and Government agencies		191,776			191,776			—			191,776		—
	States, municipalities and political subdivisions		231,555			231,555			—			231,555		—
	Corporate debt		2,202,267			2,202,267			—			2,202,267		—
	Mortgage-backed		1,292,502			1,292,502			—			1,145,164		147,338
	Asset-backed		505,910			505,910			—			412,497		93,413
	Total fixed maturity investments		6,100,798			6,100,798			1,370,088			4,489,959		240,751
	Equity securities		699,846			699,846			625,942			—		73,904
	Other invested assets		764,081			764,081			—			—		764,081
	Total investments		$	7,564,725		$	7,564,725		$	1,996,030		$	4,489,959	$	1,078,736
	Derivative assets:
	Foreign exchange contracts		$	6,254		$	6,254		$	—		$	6,254	$	—
	Interest rate swaps		6,829			6,829			—			6,829		—
	Derivative liabilities:
	Foreign exchange contracts		$	1,176		$	1,176		$	—		$	1,176	$	—
	Interest rate swaps		$	4,214		$	4,214		$	—		$	4,214	$	—
	Senior notes		$	798,499		$	897,601		$	—		$	897,601	$	—
Fair value measurements using significant unobservable inputs (Level 3)	'
	The following is a reconciliation of the beginning and ending balance of financial instruments using significant unobservable inputs (Level 3):
	Three Months Ended September 30, 2014	Other invested			Mortgage-backed			Asset-backed			Equities
		assets
	Opening balance	$	804,505		$	146,801		$	71,232		$	34,863
	Realized and unrealized gains (losses) included in net income	6,797			(882		)	(253		)	3,172
	Purchases	78,629			16,311			18,021			—
	Sales	(83,807		)	(28,761		)	(9,970		)	—
	Transfers into Level 3 from Level 2	—			1,628			17,863			—
	Transfers out of Level 3 into Level 2 (1)	—			(15,189		)	(5,523		)	—
	Ending balance	$	806,124		$	119,908		$	91,370		$	38,035
	Three Months Ended September 30, 2013
	Opening balance	$	714,391		$	198,003		$	61,285		$	53,499
	Realized and unrealized gains (losses) included in net income	9,403			464			(313		)	3,972
	Purchases	67,554			69,775			16,969			10,000
	Sales	(24,277		)	(79,001		)	(1,302		)	—
	Transfers into Level 3 from Level 2	—			13			3,394			—
	Transfers out of Level 3 into Level 2 (1)	—			—			—			—
	Ending balance	$	767,071		$	189,254		$	80,033		$	67,471
	Nine Months Ended September 30, 2014	Other invested			Mortgage-backed			Asset-backed			Equities
		assets
	Opening balance	$	764,081		$	147,338		$	93,413		$	73,904
	Realized and unrealized gains (losses) included in net income	51,921			3,654			(659		)	(6,572		)
	Purchases	267,549			34,187			35,526			—
	Sales	(277,427		)	(65,038		)	(19,871		)	(29,297		)
	Transfers into Level 3 from Level 2	—			1,253			13,923			—
	Transfers out of Level 3 into Level 2 (1)	—			(1,486		)	(30,962		)	—
	Ending balance	$	806,124		$	119,908		$	91,370		$	38,035
	Nine Months Ended September 30, 2013
	Opening balance	$	655,888		$	167,825		$	62,246		$	54,680
	Realized and unrealized gains (losses) included in net income	53,365			(5,910		)	(791		)	2,791
	Purchases	237,506			102,369			42,956			10,000
	Sales	(179,688		)	(69,968		)	(26,728		)	—
	Transfers into Level 3 from Level 2	—			5,073			2,350			—
	Transfers out of Level 3 into Level 2 (1)	—			(10,135		)	—			—
	Ending balance	$	767,071		$	189,254		$	80,033		$	67,471
	_______________________
	-1	Transfers out of Level 3 are primarily attributable to the availability of market observable information.

Reserve_For_Losses_And_Loss_Ex1

Reserve For Losses And Loss Expenses (Tables)	9 Months Ended
	Sep. 30, 2014
Insurance Loss Reserves [Abstract]	'
Components of liabilty for unpaid losses and loss expenses	'
	The reserve for losses and loss expenses consists of the following:
		September 30,			December 31,
		2014			2013
	Outstanding loss reserves	$	1,585,900		$	1,520,867
	Reserves for losses incurred but not reported	4,466,363			4,245,662
	Reserve for losses and loss expenses	$	6,052,263		$	5,766,529
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.
		Three Months Ended						Nine Months Ended
		September 30,						September 30,
		2014			2013			2014			2013
	Gross liability at beginning of period	$	5,935,678		$	5,696,865		$	5,766,529		$	5,645,549
	Reinsurance recoverable at beginning of period	(1,301,742		)	(1,179,525		)	(1,234,504		)	(1,141,110		)
	Net liability at beginning of period	4,633,936			4,517,340			4,532,025			4,504,439
	Net losses incurred related to:
	Current year	382,970			338,420			1,067,111			961,224
	Prior years	(46,880		)	(61,450		)	(140,880		)	(153,948		)
	Total incurred	336,090			276,970			926,231			807,276
	Net paid losses related to:
	Current year	53,596			30,399			80,401			54,983
	Prior years	202,626			213,252			666,555			696,137
	Total paid	256,222			243,651			746,956			751,120
	Foreign exchange revaluation	(10,550		)	4,088			(8,046		)	(5,848		)
	Net liability at end of period	4,703,254			4,554,747			4,703,254			4,554,747
	Reinsurance recoverable at end of period	1,349,009			1,226,034			1,349,009			1,226,034
	Gross liability at end of period	$	6,052,263		$	5,780,781		$	6,052,263		$	5,780,781

Shareholders_Equity_Tables

Shareholders' Equity (Tables)	9 Months Ended
	Sep. 30, 2014
Stockholders' Equity Note [Abstract]	'
Issued share capital	'
	The issued share capital consists of the following:
		September 30,			December 31,
		2014			2013
	Common shares issued and fully paid, 2014: CHF 4.10 per share; 2013: CHF 4.10 per share	100,775,256			103,477,452
	Share capital at end of period	$	407,990		$	418,988
Schedule of common stock outstanding roll forward	'
		Nine Months Ended September 30, 2014
	Shares issued at beginning of period	103,477,452
	Shares cancelled	(2,702,196	)
	Total shares issued at end of period	100,775,256
	Treasury shares issued at beginning of period	3,223,806
	Shares repurchased	4,616,543
	Shares issued out of treasury	(745,135	)
	Shares cancelled	(2,702,196	)
	Total treasury shares at end of period	4,393,018
	Total shares outstanding at end of period	96,382,238
Dividends paid	'
	The Company paid the following dividends during the nine months ended September 30, 2014:
	Dividend Paid		Dividend			Total
			Per			Amount
			Share			Paid
	2-Jan-14		$	0.167		$	16,732
	3-Apr-14		$	0.167		$	16,495
	2-Jul-14		$	0.225		$	21,870
Share repurchases	'
	The Company’s share repurchases were as follows:
		Three Months Ended						Nine Months Ended
		September 30,						September 30,
		2014			2013			2014		2013
	Common shares repurchased	654,851			1,282,164			4,616,543		4,103,499
	Total cost of shares repurchased	$	24,996		$	40,574		$	164,528	$	123,145
	Average price per share	$	38.17		$	31.64		$	35.64	$	30.01

Employee_Benefit_Plans_Tables

Employee Benefit Plans (Tables)	9 Months Ended
	Sep. 30, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Schedule of stock-related compensation expense	'
	The following table shows the total stock-related compensation expense relating to the stock options, RSUs and cash equivalent awards.
		Three Months Ended						Nine Months Ended
		September 30,						September 30,
		2014			2013			2014				2013
	Stock options	$	424		$	647		$	1,564			$	2,662
	RSUs and performance-based equity awards	2,767			2,070			9,258				6,621
	Cash-equivalent stock awards	8,433			13,699			25,930				34,666
	Total	$	11,624		$	16,416		$	36,752			$	43,949
Rsus Other Than Performance Based Rsus [Member]	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Schedule of activity of stock awards	'
	The activity related to the Company’s RSUs awards is as follows:
		Nine Months Ended September 30, 2014
		Number of Awards		Weighted
				Average
				Grant Date
				Fair Value
	Outstanding at beginning of period	143,697		$	21.69
	RSUs granted	454,176		33.56
	RSUs forfeited	(8,061	)	(31.71		)
	RSUs fully vested	(77,700	)	(21.68		)
	Outstanding at end of period	512,112		$	32.06
Performance Based Rsus [Member]	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Schedule of activity of stock awards	'
	The activity related to the Company’s performance-based equity awards is as follows:
		Nine Months Ended September 30, 2014
		Number of Awards		Weighted
				Average
				Grant Date
				Fair Value
	Outstanding at beginning of period	804,519		$	23.21
	Performance-based equity awards granted	166,302		33.56
	Additional awards granted due to achievement of performance criteria	104,895		20.5
	Performance-based equity awards forfeited	(1,848	)	(25.28		)
	Performance-based equity awards fully vested	(454,440	)	(20.50		)
	Outstanding at end of period	619,428		$	27.51
Cash-equivalent stock awards [Member]	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Schedule of activity of cash equivalent awards	'
	The activity related to the Company's cash-equivalent RSUs and performance-based awards is as follows:
		RSU's					Performance-based Awards
	Nine Months Ended September 30, 2014	Number of Awards		Weighted Average Grant Date Fair Value			Number of Awards			Weighted Average Grant Date Fair Value
	Outstanding at beginning of period	2,049,084		$	24.69		1,031,961			23.67
	Granted	438,162		33.56			249,438			33.56
	Additional awards granted due to achievement of performance criteria	—		—			104,895			20.5
	Forfeited	(50,106	)	(26.75		)	(2,769	)		(25.28		)
	Fully vested	(752,668	)	(22.51		)	(454,440	)		(20.50		)
	Outstanding at end of period	1,684,472		$	27.98		929,085			$	27.51

Earnings_Per_Share_Tables

Earnings Per Share (Tables)	9 Months Ended
	Sep. 30, 2014
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:
		Three Months Ended				Nine Months Ended
		September 30,				September 30,
		2014		2013		2014		2013
	Basic earnings per share:
	Net income	$	30,915	$	122,843	$	359,750	$	279,973
	Weighted average common shares outstanding	96,458,231		101,974,077		97,926,378		103,020,681
	Basic earnings per share	$	0.32	$	1.2	$	3.67	$	2.72
		Three Months Ended				Nine Months Ended
		September 30,				September 30,
		2014		2013		2014		2013
	Diluted earnings per share:
	Net income	$	30,915	$	122,843	$	359,750	$	279,973
	Weighted average common shares outstanding	96,458,231		101,974,077		97,926,378		103,020,681
	Share equivalents:
	Stock options	1,430,243		1,500,342		1,449,641		1,492,374
	RSUs and performance-based equity awards	541,711		708,399		575,675		877,107
	Employee share purchase plan	14,053		1,761		13,602		3,114
	Weighted average common shares and common share equivalents outstanding - diluted	98,444,238		104,184,579		99,965,296		105,393,276
	Diluted earnings per share	$	0.31	$	1.18	$	3.6	$	2.66

Segment_Information_Tables

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2014
Segment Reporting [Abstract]	'
Summary of segment results	'
	The following tables provide a summary of the segment results:
	Three Months Ended September 30, 2014		U.S. Insurance				International				Reinsurance				Total
							Insurance
	Gross premiums written		$	386,681			$	144,236			$	176,967			$	707,884
	Net premiums written		321,713				87,820				159,209				568,742
	Net premiums earned		224,764				94,013				222,960				541,737
	Net losses and loss expenses		(153,010		)		(55,814		)		(127,266		)		(336,090		)
	Acquisition costs		(31,131		)		(1,209		)		(40,063		)		(72,403		)
	General and administrative expenses		(41,730		)		(27,993		)		(18,571		)		(88,294		)
	Underwriting (loss) income		(1,107		)		8,997				37,060				44,950
	Other insurance-related income		1,032				—				—				1,032
	Other insurance-related expenses		(1,270		)		(5,305		)		—				(6,575		)
	Segment (loss) income		$	(1,345	)		$	3,692			$	37,060			$	39,407
	Net investment income														43,412
	Net realized investment losses														(35,136		)
	Amortization of intangible assets														(633		)
	Interest expense														(14,325		)
	Foreign exchange loss														(278		)
	Income before income taxes														$	32,447
	Loss and loss expense ratio		68.1		%		59.4		%		57.1		%		62		%
	Acquisition cost ratio		13.9		%		1.3		%		18		%		13.4		%
	General and administrative expense ratio		18.6		%		29.8		%		8.3		%		16.3		%
	Expense ratio		32.5		%		31.1		%		26.3		%		29.7		%
	Combined ratio		100.6		%		90.5		%		83.4		%		91.7		%
	Three Months Ended September 30, 2013		U.S. Insurance				International				Reinsurance				Total
							Insurance
	Gross premiums written		$	308,709			$	132,881			$	139,303			$	580,893
	Net premiums written		238,792				75,632				138,653				453,077
	Net premiums earned		207,602				87,554				215,617				510,773
	Net losses and loss expenses		(141,222		)		(31,094		)		(104,654		)		(276,970		)
	Acquisition costs		(28,426		)		282				(36,970		)		(65,114		)
	General and administrative expenses		(41,616		)		(26,450		)		(20,487		)		(88,553		)
	Underwriting (loss) income		(3,662		)		30,292				53,506				80,136
	Other insurance-related income		—				—				—				—
	Other insurance-related expenses		—				—				—				—
	Segment (loss) income		$	(3,662	)		$	30,292			$	53,506			$	80,136
	Net investment income														39,271
	Net realized investment gains														27,487
	Amortization of intangible assets														(633		)
	Interest expense														(14,094		)
	Foreign exchange loss														(4,353		)
	Income before income taxes														$	127,814
	Loss and loss expense ratio		68		%		35.5		%		48.5		%		54.2		%
	Acquisition cost ratio		13.7		%		(0.3		)%		17.1		%		12.7		%
	General and administrative expense ratio		20		%		30.2		%		9.5		%		17.3		%
	Expense ratio		33.7		%		29.9		%		26.6		%		30		%
	Combined ratio		101.7		%		65.4		%		75.1		%		84.2		%
	Nine Months Ended September 30, 2014		U.S. Insurance				International				Reinsurance				Total
							Insurance
	Gross premiums written		$	998,051			$	483,079			$	888,552			$	2,369,682
	Net premiums written		746,403				285,450				862,427				1,894,280
	Net premiums earned		651,480				271,557				686,232				1,609,269
	Net losses and loss expenses		(440,491		)		(115,299		)		(370,441		)		(926,231		)
	Acquisition costs		(88,311		)		(835		)		(125,258		)		(214,404		)
	General and administrative expenses		(125,760		)		(82,164		)		(56,898		)		(264,822		)
	Underwriting (loss) income		(3,082		)		73,259				133,635				203,812
	Other insurance-related income		1,032				—				—				1,032
	Other insurance-related expenses		(1,270		)		(5,305		)		—				(6,575		)
	Segment (loss) income		$	(3,320	)		$	67,954			$	133,635			$	198,269
	Net investment income														127,824
	Net realized investment gains														104,286
	Amortization of intangible assets														(1,900		)
	Interest expense														(43,451		)
Foreign exchange loss														(978		)
Income before income taxes														$	384,050
Loss and loss expense ratio		67.6		%		42.5		%		54		%		57.6		%
Acquisition cost ratio		13.6		%		0.3		%		18.3		%		13.3		%
General and administrative expense ratio		19.3		%		30.3		%		8.3		%		16.5		%
Expense ratio		32.9		%		30.6		%		26.6		%		29.8		%
Combined ratio		100.5		%		73.1		%		80.6		%		87.4		%
Nine Months Ended September 30, 2013		U.S. Insurance				International				Reinsurance				Total
						Insurance
Gross premiums written		$	872,024			$	453,990			$	857,160			$	2,183,174
Net premiums written		652,464				259,771				817,116				1,729,351
Net premiums earned		593,477				258,809				628,986				1,481,272
Net losses and loss expenses		(398,910		)		(90,997		)		(317,369		)		(807,276		)
Acquisition costs		(78,824		)		1,489				(109,081		)		(186,416		)
General and administrative expenses		(119,514		)		(75,374		)		(56,930		)		(251,818		)
Underwriting (loss) income		(3,771		)		93,927				145,606				235,762
Other insurance-related income		—				—				—				—
Other insurance-related expenses		—				—				—				—
Segment (loss) income		$	(3,771	)		$	93,927			$	145,606			$	235,762
Net investment income														110,294
Net realized investment losses														(8,074		)
Amortization of intangible assets														(1,900		)
Interest expense														(42,416		)
Foreign exchange loss														(7,361		)
Income before income taxes														$	286,305
Loss and loss expense ratio		67.2		%		35.2		%		50.5		%		54.5		%
Acquisition cost ratio		13.3		%		(0.6		)%		17.3		%		12.6		%
General and administrative expense ratio		20.1		%		29.1		%		9.1		%		17		%
Expense ratio		33.4		%		28.5		%		26.4		%		29.6		%
Combined ratio		100.6		%		63.7		%		76.9		%		84.1		%
Analysis of gross written premium by geographic location	'
	The following table shows an analysis of the Company’s gross premiums written by geographic location of the Company’s subsidiaries and branches. All intercompany premiums have been eliminated.
		Three Months Ended								Nine Months Ended
		September 30,								September 30,
		2014				2013				2014				2013
	United States	$	483,992			$	377,618			$	1,447,652			$	1,296,212
	Bermuda	109,503				111,103				525,005				550,815
	Europe	64,947				52,004				245,931				198,747
	Asia Pacific	45,070				40,168				142,798				137,400
	Canada	4,372				—				8,296				—
	Total gross premiums written	$	707,884			$	580,893			$	2,369,682			$	2,183,174

Condensed_Consolidated_Guarant1

Condensed Consolidated Guarantor Financial Statements (Tables)	9 Months Ended
	Sep. 30, 2014
Condensed Financial Information of Parent Company Only Disclosure [Abstract]	'
Schedule of condensed consolidating balance sheet	'
	Unaudited Condensed Consolidating Balance Sheet:
	As of September 30, 2014	Allied World			Allied World			Other Allied			Consolidating			Allied World
		Switzerland			Bermuda			World			Adjustments			Switzerland
		(Parent			(Subsidiary			Subsidiaries						Consolidated
		Guarantor)			Issuer)
	ASSETS:
	Investments	$	—		$	—		$	8,002,514		$	—		$	8,002,514
	Cash and cash equivalents	38,196			2,329			790,745			—			831,270
	Insurance balances receivable	—			—			926,183			—			926,183
	Funds held	—			—			405,703			—			405,703
	Reinsurance recoverable	—			—			1,349,009			—			1,349,009
	Net deferred acquisition costs	—			—			171,827			—			171,827
	Goodwill and intangible assets	—			—			325,016			—			325,016
	Balances receivable on sale of investments	—			—			60,122			—			60,122
	Investments in subsidiaries	3,644,932			4,255,136			—			(7,900,068		)	—
	Due from subsidiaries	18,497			407			15,508			(34,412		)	—
	Other assets	2,009			3,576			732,339			—			737,924
	Total assets	$	3,703,634		$	4,261,448		$	12,778,966		$	(7,934,480	)	$	12,809,568
	LIABILITIES:
	Reserve for losses and loss expenses	$	—		$	—		$	6,052,263		$	—		$	6,052,263
	Unearned premiums	—			—			1,716,927			—			1,716,927
	Reinsurance balances payable	—			—			203,428			—			203,428
	Balances due on purchases of investments	—			—			166,026			—			166,026
	Senior notes	—			798,725			—			—			798,725
	Due to subsidiaries	6,826			8,682			18,904			(34,412		)	—
	Other liabilities	23,209			12,513			162,878			—			198,600
	Total liabilities	30,035			819,920			8,320,426			(34,412		)	9,135,969
	Total shareholders’ equity	3,673,599			3,441,528			4,458,540			(7,900,068		)	3,673,599
	Total liabilities and shareholders’ equity	$	3,703,634		$	4,261,448		$	12,778,966		$	(7,934,480	)	$	12,809,568
	As of December 31, 2013	Allied World			Allied World			Other Allied			Consolidating			Allied World
		Switzerland			Bermuda			World			Adjustments			Switzerland
		(Parent			(Subsidiary			Subsidiaries						Consolidated
		Guarantor)			Issuer)
	ASSETS:
	Investments	$	—		$	—		$	7,712,036		$	—		$	7,712,036
	Cash and cash equivalents	10,790			2,775			518,371			—			531,936
	Insurance balances receivable	—			—			664,731			—			664,731
	Funds held	—			—			632,430			—			632,430
	Reinsurance recoverable	—			—			1,234,504			—			1,234,504
	Net deferred acquisition costs	—			—			126,661			—			126,661
	Goodwill and intangible assets	—			—			317,207			—			317,207
	Balances receivable on sale of investments	—			—			76,544			—			76,544
	Investments in subsidiaries	3,413,001			4,018,619			—			(7,431,620		)	—
	Due from subsidiaries	111,172			122,846			123,479			(357,497		)	—
	Other assets	1,757			4,671			643,353			—			649,781
	Total assets	$	3,536,720		$	4,148,911		$	12,049,316		$	(7,789,117	)	$	11,945,830
	LIABILITIES:
	Reserve for losses and loss expenses	$	—		$	—		$	5,766,529		$	—		$	5,766,529
	Unearned premiums	—			—			1,396,256			—			1,396,256
	Reinsurance balances payable	—			—			173,023			—			173,023
	Balances due on purchases of investments	—			—			104,740			—			104,740
	Senior notes	—			798,499			—			—			798,499
	Due to subsidiaries	12,945			110,534			234,018			(357,497		)	—
	Other liabilities	3,949			17,797			165,211			—			186,957
	Total liabilities	16,894			926,830			7,839,777			(357,497		)	8,426,004
	Total shareholders’ equity	3,519,826			3,222,081			4,209,539			(7,431,620		)	3,519,826
	Total liabilities and shareholders’ equity	$	3,536,720		$	4,148,911		$	12,049,316		$	(7,789,117	)	$	11,945,830
Schedule of condensed consolidating income statement	'
	Unaudited Condensed Consolidating Statement of Operations and Comprehensive Income:
	Three Months Ended September 30, 2014	Allied World			Allied World			Other Allied			Consolidating			Allied World
		Switzerland			Bermuda			World			Adjustments			Switzerland
		(Parent			(Subsidiary			Subsidiaries						Consolidated
		Guarantor)			Issuer)
	Net premiums earned	$	—		$	—		$	541,737		$	—		$	541,737
	Net investment income	2			—			43,410			—			43,412
	Net realized investment gains (losses)	—			—			(35,136		)	—			(35,136		)
	Other income	—			—			1,032			—			1,032
	Net losses and loss expenses	—			—			(336,090		)	—			(336,090		)
	Acquisition costs	—			—			(72,403		)	—			(72,403		)
	General and administrative expenses	(8,285		)	(182		)	(79,827		)	—			(88,294		)
	Other expense	—			—			(6,575		)	—			(6,575		)
	Amortization of intangible assets	—			—			(633		)	—			(633		)
	Interest expense	—			(13,855		)	(470		)	—			(14,325		)
	Foreign exchange gain (loss)	16			47			(341		)	—			(278		)
	Income tax (expense) benefit	—			—			(1,532		)	—			(1,532		)
	Equity in earnings of consolidated subsidiaries	39,182			49,491			—			(88,673		)	—
	NET INCOME (LOSS)	$	30,915		$	35,501		$	53,172		$	(88,673	)	$	30,915
	Other comprehensive income	—			—			—			—			—
	COMPREHENSIVE INCOME (LOSS)	$	30,915		$	35,501		$	53,172		$	(88,673	)	$	30,915
	Three Months Ended September 30, 2013	Allied World			Allied World			Other Allied			Consolidating			Allied World
		Switzerland			Bermuda			World			Adjustments			Switzerland
		(Parent			(Subsidiary			Subsidiaries						Consolidated
		Guarantor)			Issuer)
	Net premiums earned	$	—		$	—		$	510,773		$	—		$	510,773
	Net investment income	3			—			39,268			—			39,271
	Net realized investment gains (losses)	—			—			27,487			—			27,487
	Other income	—			—			—			—			—
	Net losses and loss expenses	—			—			(276,970		)	—			(276,970		)
	Acquisition costs	—			—			(65,114		)	—			(65,114		)
	General and administrative expenses	(7,323		)	(4,961		)	(76,269		)	—			(88,553		)
	Other expense	—			—			—			—			—
	Amortization of intangible assets	—			—			(633		)	—			(633		)
	Interest expense	—			(13,838		)	(256		)	—			(14,094		)
	Foreign exchange gain (loss)	(13		)	(212		)	(4,128		)	—			(4,353		)
	Income tax (expense) benefit	—			—			(4,971		)	—			(4,971		)
	Equity in earnings of consolidated subsidiaries	130,176			150,653			—			(280,829		)	—
	NET INCOME (LOSS)	$	122,843		$	131,642		$	149,187		$	(280,829	)	$	122,843
	Other comprehensive income	—			—			—			—			—
	COMPREHENSIVE INCOME (LOSS)	$	122,843		$	131,642		$	149,187		$	(280,829	)	$	122,843
	Nine Months Ended September 30, 2014	Allied World			Allied World			Other Allied			Consolidating			Allied World
		Switzerland			Bermuda			World			Adjustments			Switzerland
		(Parent			(Subsidiary			Subsidiaries						Consolidated
		Guarantor)			Issuer)
	Net premiums earned	$	—		$	—		$	1,609,269		$	—		$	1,609,269
	Net investment income	6			—			127,818			—			127,824
	Net realized investment gains (losses)	—			—			104,286			—			104,286
	Other income	—			—			1,032			—			1,032
	Net losses and loss expenses	—			—			(926,231		)	—			(926,231		)
	Acquisition costs	—			—			(214,404		)	—			(214,404		)
	General and administrative expenses	(28,012		)	(919		)	(235,891		)	—			(264,822		)
	Other expense	—			—			(6,575		)	—			(6,575		)
	Amortization of intangible assets	—			—			(1,900		)	—			(1,900		)
	Interest expense	—			(41,556		)	(1,895		)	—			(43,451		)
	Foreign exchange gain (loss)	12			68			(1,058		)	—			(978		)
	Income tax (expense) benefit	(86		)	—			(24,214		)	—			(24,300		)
	Equity in earnings of consolidated subsidiaries	387,830			419,294			—			(807,124		)	—
	NET INCOME (LOSS)	$	359,750		$	376,887		$	430,237		$	(807,124	)	$	359,750
	Other comprehensive income	—			—			—			—			—
	COMPREHENSIVE INCOME (LOSS)	$	359,750		$	376,887		$	430,237		$	(807,124	)	$	359,750
	Nine Months Ended September 30, 2013	Allied World			Allied World			Other Allied			Consolidating			Allied World
		Switzerland			Bermuda			World			Adjustments			Switzerland
(Parent			(Subsidiary			Subsidiaries						Consolidated
Guarantor)			Issuer)
Net premiums earned	$	—		$	—		$	1,481,272		$	—		$	1,481,272
Net investment income	11			4			110,279			—			110,294
Net realized investment gains (losses)	—			—			(8,074		)	—			(8,074		)
Other income	—			—			—			—			—
Net losses and loss expenses	—			—			(807,276		)	—			(807,276		)
Acquisition costs	—			—			(186,416		)	—			(186,416		)
General and administrative expenses	(26,875		)	(5,873		)	(219,070		)	—			(251,818		)
Other expense	—			—			—			—			—
Amortization of intangible assets	—			—			(1,900		)	—			(1,900		)
Interest expense	—			(41,503		)	(913		)	—			(42,416		)
Foreign exchange gain (loss)	261			(935		)	(6,687		)	—			(7,361		)
Income tax (expense) benefit	—			—			(6,332		)	—			(6,332		)
Equity in earnings of consolidated subsidiaries	306,576			353,280			—			(659,856		)	—
NET INCOME (LOSS)	$	279,973		$	304,973		$	354,883		$	(659,856	)	$	279,973
Other comprehensive income	—			—			—			—			—
COMPREHENSIVE INCOME (LOSS)	$	279,973		$	304,973		$	354,883		$	(659,856	)	$	279,973
Schedule of condensed consolidating statement of cash flows	'
	Unaudited Condensed Consolidating Statement of Cash Flows:
	Nine Months Ended September 30, 2014	Allied World			Allied World			Other Allied			Consolidating			Allied World
		Switzerland			Bermuda			World			Adjustments			Switzerland
		(Parent			(Subsidiary			Subsidiaries						Consolidated
		Guarantor)			Issuer)
	CASH FLOWS PROVIDED BY (USED IN) OPERATING ACTIVITIES	$	241,037		$	263,554		$	737,516		$	(575,000	)	$	667,107
	CASH FLOWS PROVIDED BY (USED IN) INVESTING ACTIVITIES:
	Purchases trading securities	—			—			(5,608,594		)	—			(5,608,594		)
	Purchases of other invested assets	—			—			(242,227		)	—			(242,227		)
	Sales of trading securities	—			—			5,500,176			—			5,500,176
	Sales of other invested assets	—			—			243,123			—			243,123
	Other	—			—			(46,620		)	—			(46,620		)
	Net cash provided by (used in) investing activities	—			—			(154,142		)	—			(154,142		)
	CASH FLOWS PROVIDED BY (USED IN) FINANCING ACTIVITIES:
	Dividends paid	(55,064		)	—			—			—			(55,064		)
	Intercompany dividends paid	—			(264,000		)	(311,000		)	575,000			—
	Proceeds from the exercise of stock options	7,640			—			—			—			7,640
	Share repurchases	(166,207		)	—			—			—			(166,207		)
	Net cash provided by (used in) financing activities	(213,631		)	(264,000		)	(311,000		)	575,000			(213,631		)
	NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	27,406			(446		)	272,374			—			299,334
	CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD	10,790			2,775			518,371			—			531,936
	CASH AND CASH EQUIVALENTS, END OF PERIOD	$	38,196		$	2,329		$	790,745		$	—		$	831,270
	Nine Months Ended September 30, 2013	Allied World			Allied World			Other Allied			Consolidating			Allied World
		Switzerland			Bermuda			World			Adjustments			Switzerland
		(Parent			(Subsidiary			Subsidiaries						Consolidated
		Guarantor)			Issuer)
	CASH FLOWS PROVIDED BY (USED IN) OPERATING ACTIVITIES:	$	177,859		$	226,564		$	431,127		$	(503,500	)	$	332,050
	CASH FLOWS PROVIDED BY (USED IN) INVESTING ACTIVITIES:
	Purchases of trading securities	—			—			(4,955,817		)	—			(4,955,817		)
	Purchases of other invested assets	—			—			(211,501		)	—			(211,501		)
	Sales of trading securities	—			—			5,137,280			—			5,137,280
	Sales of other invested assets	—			—			189,155			—			189,155
	Other	—			—			(78,203		)	—			(78,203		)
	Net cash provided by (used in) investing activities	—			—			80,914			—			80,914
	CASH FLOWS PROVIDED BY (USED IN) FINANCING ACTIVITIES:
	Dividends paid - partial par value reduction	(12,981		)	—			—			—			(12,981		)
	Dividends paid	(17,117		)	—			—			—			(17,117		)
	Intercompany dividends paid	—			(229,500		)	(274,000		)	503,500			—
	Proceeds from the exercise of stock options	8,465			—			—			—			8,465
	Share repurchases	(120,163		)	—			—			—			(120,163		)
	Net cash provided by (used in) financing activities	(141,796		)	(229,500		)	(274,000		)	503,500			(141,796		)
	NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	36,063			(2,936		)	238,041			—			271,168
	CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD	19,997			11,324			650,558			—			681,879
	CASH AND CASH EQUIVALENTS, END OF PERIOD	$	56,060		$	8,388		$	888,599		$	—		$	953,047

General_Details

General (Details) (Hong Kong and Singapore Operations of Royal Sun Alliance Insurance Plc, USD $)	Sep. 30, 2014
In Thousands, unless otherwise specified
Hong Kong and Singapore Operations of Royal Sun Alliance Insurance Plc	'
Business Acquisition [Line Items]	'
Business Acquisition Preliminary Purchase Price	$211,000
Business Acquisition Expected Additional Capitalization	$90,000

Basis_of_Preparation_and_Conso2

Basis of Preparation and Consolidation (Details)	0 Months Ended
	1-May-14
Organization, Consolidation and Presentation of Financial Statements [Abstract]	'
Stockholders' Equity Note, Stock Split, Conversion Ratio	3

Investments_Narrative_Details

Investments (Narrative) (Details) (USD $)	3 Months Ended	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2014	Sep. 30, 2014	Sep. 30, 2014	Sep. 30, 2014
	Other invested assets [Member]	Minimum [Member]	Minimum [Member]	Maximum [Member]	Maximum [Member]
		Investments with redemption restrictions [Member]	Investments without redemption restrictions [Member]	Investments with redemption restrictions [Member]	Investments without redemption restrictions [Member]
			Hedge Funds [Member]		Hedge Funds [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]	'	'	'	'	'
Redemption notice period	'	'	'30 days	'	'
Redemption restriction period	'	'1 year	'	'3 years	'
Gate trigger, percentage	'	'	15.00%	'	25.00%
Loss on equity method investments	$9,348	'	'	'	'

Investments_Schedule_Of_Tradin

Investments (Schedule Of Trading Securities) (Details) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Equity securities and other invested assets [Member]	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'
Trading securities, Fair Value	$1,751,200	$1,463,927
Trading securities, Amortized Cost	1,603,094	1,305,984
Equity securities [Member]	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'
Trading securities, Fair Value	945,076	699,846
Trading securities, Amortized Cost	901,300	647,301
Other invested assets [Member]	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'
Trading securities, Fair Value	806,124	764,081
Trading securities, Amortized Cost	701,794	658,683
Fixed maturity investments [Member]	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'
Trading securities, Fair Value	6,128,237	6,100,798
Trading securities, Amortized Cost	6,074,752	6,065,350
U.S. Government And Government Agencies [Member]	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'
Trading securities, Fair Value	1,184,115	1,676,788
Trading securities, Amortized Cost	1,186,185	1,684,832
Non-U.S. Government And Government Agencies [Member]	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'
Trading securities, Fair Value	219,287	191,776
Trading securities, Amortized Cost	229,792	197,082
States, Municipalities And Political Subdivisions [Member]	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'
Trading securities, Fair Value	260,690	231,555
Trading securities, Amortized Cost	251,628	234,406
Corporate Debt, Financial Institutions [Member]	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'
Trading securities, Fair Value	1,194,949	958,794
Trading securities, Amortized Cost	1,185,637	943,518
Corporate Debt, Industrials [Member]	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'
Trading securities, Fair Value	1,202,906	1,174,047
Trading securities, Amortized Cost	1,201,341	1,165,448
Corporate Debt, Utilities [Member]	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'
Trading securities, Fair Value	125,513	69,426
Trading securities, Amortized Cost	125,202	69,658
Mortgage-Backed [Member]	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'
Trading securities, Fair Value	1,240,362	1,292,502
Trading securities, Amortized Cost	1,196,683	1,267,863
Asset-Backed [Member]	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'
Trading securities, Fair Value	700,415	505,910
Trading securities, Amortized Cost	$698,284	$502,543

Investments_Schedule_Of_Other_

Investments (Schedule Of Other Investments) (Details) (USD $)	9 Months Ended		12 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014		Dec. 31, 2013
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]	'		'
Other invested assets	929,201		911,392
Investment commitment	479,635		467,524
Investments with redemption restrictions [Member]	'		'
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]	'		'
Other invested assets	562,943		368,052
Investments without redemption restrictions [Member]	'		'
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]	'		'
Other invested assets	366,258		543,340
Hedge Funds [Member] | Investments without redemption restrictions [Member] | Minimum [Member]	'		'
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]	'		'
Redemption notice period	'30 days		'
Total Fair Value [Member]	'		'
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]	'		'
Other invested assets	806,124		764,081
Investment commitment	479,635		467,524
Total Fair Value [Member] | Investments with redemption restrictions [Member]	'		'
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]	'		'
Other invested assets	562,943		368,052
Total Fair Value [Member] | Investments without redemption restrictions [Member]	'		'
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]	'		'
Other invested assets	243,181		396,029
Total Fair Value [Member] | Private Equity Funds [Member]	'		'
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]	'		'
Other invested assets	303,111		216,825
Investment commitment	479,635		467,524
Total Fair Value [Member] | Private Equity Funds [Member] | Investments with redemption restrictions [Member]	'		'
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]	'		'
Other invested assets	303,111		216,825
Total Fair Value [Member] | Private Equity Funds [Member] | Investments without redemption restrictions [Member]	'		'
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]	'		'
Other invested assets	0		0
Total Fair Value [Member] | Private Equity [Member]	'		'
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]	'		'
Other invested assets	179,196		144,422
Investment commitment	223,030		263,519
Total Fair Value [Member] | Private Equity [Member] | Investments with redemption restrictions [Member]	'		'
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]	'		'
Other invested assets	179,196		144,422
Total Fair Value [Member] | Private Equity [Member] | Investments with redemption restrictions [Member] | Minimum [Member]	'		'
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]	'		'
Estimated remaining restriction period	'2 years		'2 years
Total Fair Value [Member] | Private Equity [Member] | Investments with redemption restrictions [Member] | Maximum [Member]	'		'
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]	'		'
Estimated remaining restriction period	'9 years		'9 years
Total Fair Value [Member] | Private Equity [Member] | Investments without redemption restrictions [Member]	'		'
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]	'		'
Other invested assets	0		0
Total Fair Value [Member] | Mezzanine Debt [Member]	'		'
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]	'		'
Other invested assets	114,399		64,627
Investment commitment	251,486		198,756
Total Fair Value [Member] | Mezzanine Debt [Member] | Investments with redemption restrictions [Member]	'		'
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]	'		'
Other invested assets	114,399		64,627
Total Fair Value [Member] | Mezzanine Debt [Member] | Investments with redemption restrictions [Member] | Minimum [Member]	'		'
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]	'		'
Estimated remaining restriction period	'5 years		'8 years
Total Fair Value [Member] | Mezzanine Debt [Member] | Investments with redemption restrictions [Member] | Maximum [Member]	'		'
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]	'		'
Estimated remaining restriction period	'9 years		'9 years
Total Fair Value [Member] | Mezzanine Debt [Member] | Investments without redemption restrictions [Member]	'		'
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]	'		'
Other invested assets	0		0
Total Fair Value [Member] | Distressed [Member]	'		'
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]	'		'
Other invested assets	9,516		7,776
Investment commitment	5,119		5,249
Total Fair Value [Member] | Distressed [Member] | Investments with redemption restrictions [Member]	'		'
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]	'		'
Other invested assets	9,516		7,776
Estimated remaining restriction period	'4 years		'4 years
Total Fair Value [Member] | Distressed [Member] | Investments without redemption restrictions [Member]	'		'
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]	'		'
Other invested assets	0		0
Total Fair Value [Member] | Hedge Funds [Member]	'		'
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]	'		'
Other invested assets	471,469		515,298
Investment commitment	0		0
Total Fair Value [Member] | Hedge Funds [Member] | Investments with redemption restrictions [Member]	'		'
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]	'		'
Other invested assets	259,832		151,227
Total Fair Value [Member] | Hedge Funds [Member] | Investments without redemption restrictions [Member]	'		'
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]	'		'
Other invested assets	211,637		364,071
Total Fair Value [Member] | Distressed Funds [Member]	'		'
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]	'		'
Other invested assets	173,111		151,227
Investment commitment	0		0
Total Fair Value [Member] | Distressed Funds [Member] | Investments with redemption restrictions [Member]	'		'
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]	'		'
Other invested assets	173,111		151,227
Estimated remaining restriction period	'1 year		'
Total Fair Value [Member] | Distressed Funds [Member] | Investments with redemption restrictions [Member] | Minimum [Member]	'		'
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]	'		'
Estimated remaining restriction period	'		'1 year
Total Fair Value [Member] | Distressed Funds [Member] | Investments with redemption restrictions [Member] | Maximum [Member]	'		'
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]	'		'
Estimated remaining restriction period	'		'2 years
Total Fair Value [Member] | Distressed Funds [Member] | Investments without redemption restrictions [Member]	'		'
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]	'		'
Other invested assets	0		0
Total Fair Value [Member] | Equity Long/Short [Member]	'		'
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]	'		'
Other invested assets	111,627		99,365
Investment commitment	0		0
Total Fair Value [Member] | Equity Long/Short [Member] | Investments with redemption restrictions [Member]	'		'
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]	'		'
Other invested assets	86,721		0
Estimated remaining restriction period	'1 year		'
Total Fair Value [Member] | Equity Long/Short [Member] | Investments without redemption restrictions [Member]	'		'
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]	'		'
Other invested assets	24,906		99,365
Redemption frequency	'Quarterly	[1]	'Quarterly	[1]
Total Fair Value [Member] | Equity Long/Short [Member] | Investments without redemption restrictions [Member] | Minimum [Member]	'		'
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]	'		'
Redemption notice period	'30 days	[1]	'30 days	[1]
Total Fair Value [Member] | Equity Long/Short [Member] | Investments without redemption restrictions [Member] | Maximum [Member]	'		'
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]	'		'
Redemption notice period	'60 days	[1]	'60 days	[1]
Total Fair Value [Member] | Multi-Strategy Funds [Member]	'		'
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]	'		'
Other invested assets	81,576		136,958
Investment commitment	0		0
Total Fair Value [Member] | Multi-Strategy Funds [Member] | Investments with redemption restrictions [Member]	'		'
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]	'		'
Other invested assets	0		0
Total Fair Value [Member] | Multi-Strategy Funds [Member] | Investments without redemption restrictions [Member]	'		'
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]	'		'
Other invested assets	81,576		136,958
Redemption frequency	'Quarterly	[1]	'Quarterly	[1]
Total Fair Value [Member] | Multi-Strategy Funds [Member] | Investments without redemption restrictions [Member] | Minimum [Member]	'		'
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]	'		'
Redemption notice period	'45 days	[1]	'45 days	[1]
Total Fair Value [Member] | Multi-Strategy Funds [Member] | Investments without redemption restrictions [Member] | Maximum [Member]	'		'
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]	'		'
Redemption notice period	'90 days	[1]	'90 days	[1]
Total Fair Value [Member] | Event Driven Funds [Member]	'		'
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]	'		'
Other invested assets	'		14,018
Investment commitment	'		0
Total Fair Value [Member] | Event Driven Funds [Member] | Investments with redemption restrictions [Member]	'		'
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]	'		'
Other invested assets	'		0
Total Fair Value [Member] | Event Driven Funds [Member] | Investments without redemption restrictions [Member]	'		'
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]	'		'
Other invested assets	'		14,018
Redemption frequency	'		'Annual	[1]
Redemption notice period	'		'60 days	[1]
Total Fair Value [Member] | Relative Value Credit [Member]	'		'
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]	'		'
Other invested assets	105,155		113,730
Investment commitment	0		0
Total Fair Value [Member] | Relative Value Credit [Member] | Investments with redemption restrictions [Member]	'		'
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]	'		'
Other invested assets	0		0
Total Fair Value [Member] | Relative Value Credit [Member] | Investments without redemption restrictions [Member]	'		'
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]	'		'
Other invested assets	105,155		113,730
Redemption frequency	'Quarterly	[1]	'Quarterly	[1]
Redemption notice period	'60 days	[1]	'60 days
Total Fair Value [Member] | High Yield Loan Fund [Member]	'		'
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]	'		'
Other invested assets	31,544		31,958
Investment commitment	0		0
Total Fair Value [Member] | High Yield Loan Fund [Member] | Investments with redemption restrictions [Member]	'		'
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]	'		'
Other invested assets	0		0
Total Fair Value [Member] | High Yield Loan Fund [Member] | Investments without redemption restrictions [Member]	'		'
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]	'		'
Other invested assets	31,544		31,958
Redemption frequency	'Monthly	[1]	'Monthly	[1]
Redemption notice period	'30 days	[1]	'30 days	[1]
Carrying Value [Member] | Other Private Securities [Member]	'		'
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]	'		'
Other invested assets	123,077		147,311
Investment commitment	0		0
Carrying Value [Member] | Other Private Securities [Member] | Investments with redemption restrictions [Member]	'		'
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]	'		'
Other invested assets	0		0
Carrying Value [Member] | Other Private Securities [Member] | Investments without redemption restrictions [Member]	'		'
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]	'		'
Other invested assets	123,077		147,311
[1]	The redemption frequency and notice periods only apply to the investments without redemption restrictions. Some or all of these investments may be subject to a gate as described below.

Investments_Schedule_Of_Net_In

Investments (Schedule Of Net Investment Income) (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Net Investment Income [Line Items]	'	'	'	'
Net investment income	$43,412	$39,271	$127,824	$110,294
Fixed maturity investments [Member]	'	'	'	'
Net Investment Income [Line Items]	'	'	'	'
Net investment income	38,762	31,179	110,998	96,366
Equity securities [Member]	'	'	'	'
Net Investment Income [Line Items]	'	'	'	'
Net investment income	3,711	6,110	12,876	13,718
Other invested assets - hedge funds and private equity [Member]	'	'	'	'
Net Investment Income [Line Items]	'	'	'	'
Net investment income	2,249	3,812	8,767	6,001
Other invested assets - other private securities [Member]	'	'	'	'
Net Investment Income [Line Items]	'	'	'	'
Net investment income	3,292	1,997	7,291	5,115
Cash and cash equivalents [Member]	'	'	'	'
Net Investment Income [Line Items]	'	'	'	'
Net investment income	552	302	1,562	1,319
Expenses [Member]	'	'	'	'
Net Investment Income [Line Items]	'	'	'	'
Net investment income	($5,154)	($4,129)	($13,670)	($12,225)

Investments_Components_Of_Real

Investments (Components Of Realized Gains And Losses) (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Gain (Loss) on Investments [Line Items]	'	'	'	'
Gross realized gains on sale of invested assets	$28,773	$51,915	$146,780	$154,387
Gross realized losses on sale of invested assets	-9,955	-40,770	-26,228	-82,812
Net realized and unrealized gains (losses) on derivatives	2,171	-4,169	-24,469	3,392
Net realized investment (losses) gains	-35,136	27,487	104,286	-8,074
Fixed maturity investments, trading [Member]	'	'	'	'
Gain (Loss) on Investments [Line Items]	'	'	'	'
Mark-to-market (losses) gains	-40,843	30,383	18,039	-101,205
Equity securities, trading [Member]	'	'	'	'
Gain (Loss) on Investments [Line Items]	'	'	'	'
Mark-to-market (losses) gains	-8,479	-17,198	-8,768	-18,555
Other invested assets [Member]	'	'	'	'
Gain (Loss) on Investments [Line Items]	'	'	'	'
Mark-to-market (losses) gains	($6,803)	$7,326	($1,068)	$36,719

Investments_Pledged_Assets_Det

Investments (Pledged Assets) (Details) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Compliance With Reinsurance Contract Provisions Or Insurance Laws [Member]	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'
Restricted cash, cash equivalents and investments	$3,082,601	$2,894,401
Pledged As Collateral For Letter Of Credit Facilities [Member]	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'
Restricted cash, cash equivalents and investments	$543,828	$1,053,632

Derivative_Instruments_Locatio

Derivative Instruments (Location and Amounts of Derivative Fair Values On The Condensed Consolidated Balance Sheets) (Details) (Not Designated as Hedging Instrument, USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Derivatives, Fair Value [Line Items]	'	'
Asset Derivative Notional Amount	$604,540	$786,188
Asset Derivative Fair Value	1,228	13,083
Liability Derivative Notional Amount	2,355	162,439
Liability Derivative Fair Value	22	5,390
Foreign exchange contracts | Other assets	'	'
Derivatives, Fair Value [Line Items]	'	'
Asset Derivative Notional Amount	38,940	294,788
Asset Derivative Fair Value	814	6,254
Foreign exchange contracts | Accounts payable and accrued liabilities	'	'
Derivatives, Fair Value [Line Items]	'	'
Liability Derivative Notional Amount	2,355	122,439
Liability Derivative Fair Value	22	1,176
Interest rate swaps | Other assets	'	'
Derivatives, Fair Value [Line Items]	'	'
Asset Derivative Notional Amount	565,600	491,400
Asset Derivative Fair Value	414	6,829
Interest rate swaps | Accounts payable and accrued liabilities	'	'
Derivatives, Fair Value [Line Items]	'	'
Liability Derivative Notional Amount	0	40,000
Liability Derivative Fair Value	$0	$4,214

Derivative_Instruments_Locatio1

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 Instrument, USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Derivative Instruments, Gain (Loss) [Line Items]	'	'	'	'
Realized and unrealized gains (losses) on derivatives	$4,057	($6,505)	($25,048)	$2,301
Foreign exchange gain (loss)	'	'	'	'
Derivative Instruments, Gain (Loss) [Line Items]	'	'	'	'
Realized and unrealized gains (losses) on derivatives	1,886	-2,336	-580	-1,091
Foreign exchange gain (loss) | Foreign exchange contracts	'	'	'	'
Derivative Instruments, Gain (Loss) [Line Items]	'	'	'	'
Realized and unrealized gains (losses) on derivatives	1,886	-2,336	-580	-1,091
Net realized investment gains (losses)	'	'	'	'
Derivative Instruments, Gain (Loss) [Line Items]	'	'	'	'
Realized and unrealized gains (losses) on derivatives	2,171	-4,169	-24,468	3,392
Net realized investment gains (losses) | Put options	'	'	'	'
Derivative Instruments, Gain (Loss) [Line Items]	'	'	'	'
Realized and unrealized gains (losses) on derivatives	0	0	0	-3,822
Net realized investment gains (losses) | Foreign exchange contracts	'	'	'	'
Derivative Instruments, Gain (Loss) [Line Items]	'	'	'	'
Realized and unrealized gains (losses) on derivatives	1,701	-4,164	857	1,925
Net realized investment gains (losses) | Interest rate futures and swaps	'	'	'	'
Derivative Instruments, Gain (Loss) [Line Items]	'	'	'	'
Realized and unrealized gains (losses) on derivatives	$470	($5)	($25,325)	$5,289

Fair_Value_Of_Financial_Instru2

Fair Value Of Financial Instruments (Schedule Of Fair Value Of Financial Instruments) (Details) (USD $)	Sep. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Trading fixed maturity investments	$6,128,237	$6,100,798
Equity securities	945,076	699,846
Other invested assets	929,201	911,392
Total investments	8,002,514	7,712,036
Senior notes	798,725	798,499
Fair Value, Measurements, Recurring [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Trading fixed maturity investments	6,128,237	6,100,798
Equity securities	945,076	699,846
Other invested assets	806,124	764,081
Total investments	7,879,437	7,564,725
Senior notes	798,725	798,499
Fair Value, Measurements, Recurring [Member] | Foreign exchange contracts	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Derivative assets	814	6,254
Derivative liabilities	22	1,176
Fair Value, Measurements, Recurring [Member] | Interest rate swaps	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Derivative assets	414	6,829
Derivative liabilities	0	4,214
Fair Value, Measurements, Recurring [Member] | U.S. Government And Government Agencies [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Trading fixed maturity investments	1,184,115	1,676,788
Fair Value, Measurements, Recurring [Member] | Non-U.S. Government And Government Agencies [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Trading fixed maturity investments	219,287	191,776
Fair Value, Measurements, Recurring [Member] | States, Municipalities And Political Subdivisions [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Trading fixed maturity investments	260,690	231,555
Fair Value, Measurements, Recurring [Member] | Corporate Debt [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Trading fixed maturity investments	2,523,368	2,202,267
Fair Value, Measurements, Recurring [Member] | Mortgage-Backed [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Trading fixed maturity investments	1,240,362	1,292,502
Fair Value, Measurements, Recurring [Member] | Asset-Backed [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Trading fixed maturity investments	700,415	505,910
Fair Value, Measurements, Recurring [Member] | Total Fair Value [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Trading fixed maturity investments	6,128,237	6,100,798
Equity securities	945,076	699,846
Other invested assets	806,124	764,081
Total investments	7,879,437	7,564,725
Senior notes	888,370	897,601
Fair Value, Measurements, Recurring [Member] | Total Fair Value [Member] | Foreign exchange contracts	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Derivative assets	814	6,254
Derivative liabilities	22	1,176
Fair Value, Measurements, Recurring [Member] | Total Fair Value [Member] | Interest rate swaps	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Derivative assets	414	6,829
Derivative liabilities	0	4,214
Fair Value, Measurements, Recurring [Member] | Total Fair Value [Member] | U.S. Government And Government Agencies [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Trading fixed maturity investments	1,184,115	1,676,788
Fair Value, Measurements, Recurring [Member] | Total Fair Value [Member] | Non-U.S. Government And Government Agencies [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Trading fixed maturity investments	219,287	191,776
Fair Value, Measurements, Recurring [Member] | Total Fair Value [Member] | States, Municipalities And Political Subdivisions [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Trading fixed maturity investments	260,690	231,555
Fair Value, Measurements, Recurring [Member] | Total Fair Value [Member] | Corporate Debt [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Trading fixed maturity investments	2,523,368	2,202,267
Fair Value, Measurements, Recurring [Member] | Total Fair Value [Member] | Mortgage-Backed [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Trading fixed maturity investments	1,240,362	1,292,502
Fair Value, Measurements, Recurring [Member] | Total Fair Value [Member] | Asset-Backed [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Trading fixed maturity investments	700,415	505,910
Fair Value, Measurements, Recurring [Member] | Level 1 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Trading fixed maturity investments	998,487	1,370,088
Equity securities	907,041	625,942
Other invested assets	0	0
Total investments	1,905,528	1,996,030
Senior notes	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | 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 [Member] | Level 1 [Member] | Interest rate swaps	'	'
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 [Member] | Level 1 [Member] | U.S. Government And Government Agencies [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Trading fixed maturity investments	998,487	1,370,088
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Non-U.S. Government And Government Agencies [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Trading fixed maturity investments	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | States, Municipalities And Political Subdivisions [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Trading fixed maturity investments	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Corporate Debt [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Trading fixed maturity investments	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Mortgage-Backed [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Trading fixed maturity investments	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Asset-Backed [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Trading fixed maturity investments	0	0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Trading fixed maturity investments	4,918,472	4,489,959
Equity securities	0	0
Other invested assets	0	0
Total investments	4,918,472	4,489,959
Senior notes	888,370	897,601
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Foreign exchange contracts	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Derivative assets	814	6,254
Derivative liabilities	22	1,176
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Interest rate swaps	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Derivative assets	414	6,829
Derivative liabilities	0	4,214
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | U.S. Government And Government Agencies [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Trading fixed maturity investments	185,628	306,700
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Non-U.S. Government And Government Agencies [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Trading fixed maturity investments	219,287	191,776
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | States, Municipalities And Political Subdivisions [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Trading fixed maturity investments	260,690	231,555
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Corporate Debt [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Trading fixed maturity investments	2,523,368	2,202,267
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Mortgage-Backed [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Trading fixed maturity investments	1,120,454	1,145,164
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Asset-Backed [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Trading fixed maturity investments	609,045	412,497
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Trading fixed maturity investments	211,278	240,751
Equity securities	38,035	73,904
Other invested assets	806,124	764,081
Total investments	1,055,437	1,078,736
Senior notes	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | 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 [Member] | Level 3 [Member] | Interest rate swaps	'	'
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 [Member] | Level 3 [Member] | U.S. Government And Government Agencies [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Trading fixed maturity investments	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Non-U.S. Government And Government Agencies [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Trading fixed maturity investments	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | States, Municipalities And Political Subdivisions [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Trading fixed maturity investments	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Corporate Debt [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Trading fixed maturity investments	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Mortgage-Backed [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Trading fixed maturity investments	119,908	147,338
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Asset-Backed [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Trading fixed maturity investments	$91,370	$93,413

Fair_Value_Of_Financial_Instru3

Fair Value Of Financial Instruments (Schedule Of Fair Value Measurement Using Significant Unobservable Inputs Level Three) (Details) (USD $)	3 Months Ended				9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Other invested assets [Member]	'		'		'		'
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]	'		'		'		'
Opening balance	$804,505		$714,391		$764,081		$655,888
Realized and unrealized gains (losses) included in net income	6,797		9,403		51,921		53,365
Purchases	78,629		67,554		267,549		237,506
Sales	-83,807		-24,277		-277,427		-179,688
Transfers into Level 3 from Level 2	0		0		0		0
Transfers out of Level 3 to Level 2	0	[1]	0	[1]	0	[1]	0	[1]
Ending balance	806,124		767,071		806,124		767,071
Mortgage-Backed [Member]	'		'		'		'
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]	'		'		'		'
Opening balance	146,801		198,003		147,338		167,825
Realized and unrealized gains (losses) included in net income	-882		464		3,654		-5,910
Purchases	16,311		69,775		34,187		102,369
Sales	-28,761		-79,001		-65,038		-69,968
Transfers into Level 3 from Level 2	1,628		13		1,253		5,073
Transfers out of Level 3 to Level 2	-15,189	[1]	0	[1]	-1,486	[1]	-10,135	[1]
Ending balance	119,908		189,254		119,908		189,254
Asset-Backed [Member]	'		'		'		'
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]	'		'		'		'
Opening balance	71,232		61,285		93,413		62,246
Realized and unrealized gains (losses) included in net income	-253		-313		-659		-791
Purchases	18,021		16,969		35,526		42,956
Sales	-9,970		-1,302		-19,871		-26,728
Transfers into Level 3 from Level 2	17,863		3,394		13,923		2,350
Transfers out of Level 3 to Level 2	-5,523	[1]	0	[1]	-30,962	[1]	0	[1]
Ending balance	91,370		80,033		91,370		80,033
Equity securities [Member]	'		'		'		'
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]	'		'		'		'
Opening balance	34,863		53,499		73,904		54,680
Realized and unrealized gains (losses) included in net income	3,172		3,972		-6,572		2,791
Purchases	0		10,000		0		10,000
Sales	0		0		-29,297		0
Transfers into Level 3 from Level 2	0		0		0		0
Transfers out of Level 3 to Level 2	0	[1]	0	[1]	0	[1]	0	[1]
Ending balance	$38,035		$67,471		$38,035		$67,471
[1]	Transfers out of Level 3 are primarily attributable to the availability of market observable information.

Reserve_For_Losses_And_Loss_Ex2

Reserve For Losses And Loss Expenses (Schedule Of Reserve For Losses And Loss Expenses) (Details) (USD $)	Sep. 30, 2014	Jun. 30, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Insurance Loss Reserves [Abstract]	'	'	'	'	'	'
Outstanding loss reserves	$1,585,900	'	$1,520,867	'	'	'
Reserves for losses incurred but not reported	4,466,363	'	4,245,662	'	'	'
Reserve for losses and loss expenses	$6,052,263	$5,935,678	$5,766,529	$5,780,781	$5,696,865	$5,645,549

Reserve_For_Losses_And_Loss_Ex3

Reserve For Losses And Loss Expenses (Schedule Of Reconciliation Of Unpaid Losses And Loss Expenses) (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Insurance Loss Reserves [Abstract]	'	'	'	'
Gross liability at beginning of year	$5,935,678	$5,696,865	$5,766,529	$5,645,549
Reinsurance recoverable at beginning of year	-1,301,742	-1,179,525	-1,234,504	-1,141,110
Net liability at beginning of year	4,633,936	4,517,340	4,532,025	4,504,439
Net losses incurred related to:	'	'	'	'
Current year	382,970	338,420	1,067,111	961,224
Prior years	-46,880	-61,450	-140,880	-153,948
Total incurred	336,090	276,970	926,231	807,276
Net paid losses related to:	'	'	'	'
Current year	53,596	30,399	80,401	54,983
Prior years	202,626	213,252	666,555	696,137
Total paid	256,222	243,651	746,956	751,120
Foreign exchange revaluation	-10,550	4,088	-8,046	-5,848
Net liability at end of year	4,703,254	4,554,747	4,703,254	4,554,747
Reinsurance recoverable at end of year	1,349,009	1,226,034	1,349,009	1,226,034
Gross liability at end of year	$6,052,263	$5,780,781	$6,052,263	$5,780,781

Shareholders_Equity_Issued_Sha

Shareholders' Equity (Issued Share Capital) (Details)	Sep. 30, 2014	Sep. 30, 2014	Dec. 31, 2013	Dec. 31, 2013
In Thousands, except Share data, unless otherwise specified	USD ($)	CHF	USD ($)	CHF
Stockholders' Equity Note [Abstract]	'	'	'	'
Common shares issued and fully paid, 2014: CHF 4.10 per share; 2013: CHF 4.10 per share	100,775,256	100,775,256	103,477,452	103,477,452
Common shares, par value	'	4.1	'	4.1
Total share capital	$407,990	'	$418,988	'

Shareholders_Equity_Schedule_O

Shareholders' Equity (Schedule Of Common Stock Outstanding Roll Forward) (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]	'	'	'	'	'
Shares issued at beginning of period, shares	'	'	103,477,452	'	'
Shares cancelled, shares	'	'	-2,702,196	'	'
Shares issued at end of period, shares	100,775,256	'	100,775,256	'	'
Treasury Stock Transactions, Excluding Value of Shares Reissued [Abstract]	'	'	'	'	'
Treasury shares issued at beginning of period, shares	'	'	3,223,806	'	'
Shares repurchased, shares	654,851	1,282,164	4,616,543	4,103,499	'
Shares issued out of treasury, shares	'	'	-745,135	'	'
Shares cancelled, shares	'	'	-2,702,196	'	'
Total treasury shares at end of period, shares	4,393,018	'	4,393,018	'	'
Total shares outstanding at end of year	96,382,238	'	96,382,238	'	100,253,646

Shareholders_Equity_Schedule_O1

Shareholders' Equity (Schedule Of Dividends Paid) (Details) (USD $)	3 Months Ended		9 Months Ended		0 Months Ended				1 Months Ended		0 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Jul. 02, 2014	1-May-14	Apr. 03, 2014	Jan. 02, 2014	Oct. 31, 2013	Jul. 31, 2013	Oct. 02, 2014
					Common shares	Common shares	Common shares	Common shares	Common shares	Common shares	Subsequent event
											Common shares
Dividends, Common Stock [Abstract]	'	'	'	'	'	'	'	'	'	'	'
Dividends paid per common share	$0.23	$0.17	$0.56	$0.29	$0.23	'	$0.17	$0.17	$0.17	$0.17	$0.23
Payment of quarterly dividends	'	'	'	'	$21,870	'	$16,495	$16,732	'	'	'
Dividends declared per share	'	'	'	'	'	$0.23	'	'	'	'	'

Shareholders_Equity_Schedule_O2

Shareholders' Equity (Schedule Of Share Repurchases) (Details) (USD $)	0 Months Ended	3 Months Ended		9 Months Ended
In Thousands, except Share data, unless otherwise specified	1-May-14	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Stockholders' Equity Note [Abstract]	'	'	'	'	'
Stock Repurchase Program, Authorized Amount	$500,000	'	'	'	'
Shares repurchased, shares	'	654,851	1,282,164	4,616,543	4,103,499
Cost of shares repurchased	'	$24,996	$40,574	$164,528	$123,145
Shares repurchased, average price per share	'	$38.17	$31.64	$35.64	$30.01
Treasury shares held for issuance pursuant to equity-based compensation plans	3,000,000	'	'	'	'

Employee_Benefit_Plans_Restric

Employee Benefit Plans (Restricted Stock Units) (Details) (USD $)	9 Months Ended
	Sep. 30, 2014
Restricted Stock Units (RSUs) [Member]	'
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]	'
Vesting period	'4 years
Rsus Other Than Performance Based Rsus [Member]	'
Activity:	'
Outstanding, beginning of period, shares	143,697
Granted, shares	454,176
Forfeited, shares	-8,061
Fully vested, shares	-77,700
Outstanding, end of period, shares	512,112
Weighted average grant date fair value:	'
Outstanding, beginning of period - weighted average grant date fair value	21.69
Granted - weighted average grant date fair value	33.56
Forfeited - weighted average grant date fair value	-31.71
Vested - weighted average grant date fair value	-21.68
Outstanding, end of period - weighted average grant date fair value	32.06
Performance Based Rsus [Member]	'
Activity:	'
Outstanding, beginning of period, shares	804,519
Granted, shares	166,302
Additional awards granted due to achievement of performance criteria, shares	104,895
Forfeited, shares	-1,848
Fully vested, shares	-454,440
Outstanding, end of period, shares	619,428
Weighted average grant date fair value:	'
Outstanding, beginning of period - weighted average grant date fair value	23.21
Granted - weighted average grant date fair value	33.56
Additional awards granted due to achievement of performance criteria - weighted average grant date fair value	20.5
Forfeited - weighted average grant date fair value	-25.28
Vested - weighted average grant date fair value	-20.5
Outstanding, end of period - weighted average grant date fair value	27.51
Awards 2014 [Member] | Performance Based Rsus [Member]	'
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]	'
The rate at which performance awards are expensed	100.00%
Awards 2013 [Member] | Performance Based Rsus [Member]	'
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]	'
The rate at which performance awards are expensed	100.00%
Awards 2012 [Member] | Performance Based Rsus [Member]	'
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]	'
The rate at which performance awards are expensed	135.00%

Employee_Benefit_Plans_CashEqu

Employee Benefit Plans (Cash-Equivalent Stock Awards) (Details) (USD $)	9 Months Ended
	Sep. 30, 2014
Cash Equivalent Stock Awards Rsus [Member]	'
Activity:	'
Outstanding, beginning of period, shares	2,049,084
Granted, shares	438,162
Additional awards granted due to achievement of performance criteria, shares	0
Forfeited, shares	-50,106
Fully vested, shares	-752,668
Outstanding, end of period, shares	1,684,472
Weighted average grant date fair value:	'
Outstanding, beginning of period - weighted average grant date fair value	$24.69
Granted - weighted average grant date fair value	$33.56
Additional awards granted due to achievement of performance criteria - weighted average grant date fair value	$0
Forfeited - weighted average grant date fair value	($26.75)
Vested - weighted average grant date fair value	($22.51)
Outstanding, end of period - weighted average grant date fair value	$27.98
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 period, shares	1,031,961
Granted, shares	249,438
Additional awards granted due to achievement of performance criteria, shares	104,895
Forfeited, shares	-2,769
Fully vested, shares	-454,440
Outstanding, end of period, shares	929,085
Weighted average grant date fair value:	'
Outstanding, beginning of period - weighted average grant date fair value	$23.67
Granted - weighted average grant date fair value	$33.56
Additional awards granted due to achievement of performance criteria - weighted average grant date fair value	$20.50
Forfeited - weighted average grant date fair value	($25.28)
Vested - weighted average grant date fair value	($20.50)
Outstanding, end of period - weighted average grant date fair value	$27.51
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 $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Share-based compensation expense	$11,624	$16,416	$36,752	$43,949
Stock options [Member]	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Share-based compensation expense	424	647	1,564	2,662
RSUs and performance-based equity awards [Member]	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Share-based compensation expense	2,767	2,070	9,258	6,621
Cash-equivalent stock awards [Member]	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Share-based compensation expense	$8,433	$13,699	$25,930	$34,666

Earnings_Per_Share_Narrative_D

Earnings Per Share (Narrative) (Details) (Stock Compensation Plan [Member])	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Stock Compensation Plan [Member]	'	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'	'	'
Anti-dilutive securities excluded from computation of earnings per share	0	0	0	0

Earnings_Per_Share_Comparison_

Earnings Per Share (Comparison Of Basic And Diluted Earnings Per Share) (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, except Share data, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Earnings Per Share, Basic [Abstract]	'	'	'	'
Net income	$30,915	$122,843	$359,750	$279,973
Weighted average common shares outstanding	96,458,231	101,974,077	97,926,378	103,020,681
Basic earnings per share	$0.32	$1.20	$3.67	$2.72
Earnings Per Share, Diluted [Abstract]	'	'	'	'
Net income	$30,915	$122,843	$359,750	$279,973
Weighted average common shares outstanding	96,458,231	101,974,077	97,926,378	103,020,681
Share equivalents:	'	'	'	'
Warrants and options	1,430,243	1,500,342	1,449,641	1,492,374
RSUs and LTIP awards	541,711	708,399	575,675	877,107
Employee share purchase plan	14,053	1,761	13,602	3,114
Weighted average common shares and common share equivalents outstanding - diluted	98,444,238	104,184,579	99,965,296	105,393,276
Diluted earnings per share	$0.31	$1.18	$3.60	$2.66

Segment_Information_Summary_Of

Segment Information (Summary Of Segment Results) (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
			segments
Segment Reporting Information [Line Items]	'	'	'	'
Gross premiums written	$707,884	$580,893	$2,369,682	$2,183,174
Net premiums written	568,742	453,077	1,894,280	1,729,351
Net premiums earned	541,737	510,773	1,609,269	1,481,272
Net losses and loss expenses	-336,090	-276,970	-926,231	-807,276
Acquisition costs	-72,403	-65,114	-214,404	-186,416
General and administrative expenses	-88,294	-88,553	-264,822	-251,818
Underwriting (loss) income	44,950	80,136	203,812	235,762
Other insurance-related income	1,032	0	1,032	0
Other insurance-related expenses	-6,575	0	-6,575	0
Segment (loss) income	39,407	80,136	198,269	235,762
Net investment income	43,412	39,271	127,824	110,294
Net realized investment (losses) gains	-35,136	27,487	104,286	-8,074
Amortization of intangible assets	-633	-633	-1,900	-1,900
Interest expense	-14,325	-14,094	-43,451	-42,416
Foreign exchange loss	-278	-4,353	-978	-7,361
Income before income taxes	32,447	127,814	384,050	286,305
Loss and loss expense ratio	62.00%	54.20%	57.60%	54.50%
Acquisition cost ratio	13.40%	12.70%	13.30%	12.60%
General and administrative expense ratio	16.30%	17.30%	16.50%	17.00%
Expense ratio	29.70%	30.00%	29.80%	29.60%
Combined ratio	91.70%	84.20%	87.40%	84.10%
Number of operating segments	'	'	3	'
Operating Segments [Member] | U S Insurance [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Gross premiums written	386,681	308,709	998,051	872,024
Net premiums written	321,713	238,792	746,403	652,464
Net premiums earned	224,764	207,602	651,480	593,477
Net losses and loss expenses	-153,010	-141,222	-440,491	-398,910
Acquisition costs	-31,131	-28,426	-88,311	-78,824
General and administrative expenses	-41,730	-41,616	-125,760	-119,514
Underwriting (loss) income	-1,107	-3,662	-3,082	-3,771
Other insurance-related income	1,032	0	1,032	0
Other insurance-related expenses	-1,270	0	-1,270	0
Segment (loss) income	-1,345	-3,662	-3,320	-3,771
Loss and loss expense ratio	68.10%	68.00%	67.60%	67.20%
Acquisition cost ratio	13.90%	13.70%	13.60%	13.30%
General and administrative expense ratio	18.60%	20.00%	19.30%	20.10%
Expense ratio	32.50%	33.70%	32.90%	33.40%
Combined ratio	100.60%	101.70%	100.50%	100.60%
Operating Segments [Member] | International Insurance [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Gross premiums written	144,236	132,881	483,079	453,990
Net premiums written	87,820	75,632	285,450	259,771
Net premiums earned	94,013	87,554	271,557	258,809
Net losses and loss expenses	-55,814	-31,094	-115,299	-90,997
Acquisition costs	-1,209	282	-835	1,489
General and administrative expenses	-27,993	-26,450	-82,164	-75,374
Underwriting (loss) income	8,997	30,292	73,259	93,927
Other insurance-related income	0	0	0	0
Other insurance-related expenses	-5,305	0	-5,305	0
Segment (loss) income	3,692	30,292	67,954	93,927
Loss and loss expense ratio	59.40%	35.50%	42.50%	35.20%
Acquisition cost ratio	1.30%	-0.30%	0.30%	-0.60%
General and administrative expense ratio	29.80%	30.20%	30.30%	29.10%
Expense ratio	31.10%	29.90%	30.60%	28.50%
Combined ratio	90.50%	65.40%	73.10%	63.70%
Operating Segments [Member] | Reinsurance [Member]	'	'	'	'
Segment Reporting Information [Line Items]	'	'	'	'
Gross premiums written	176,967	139,303	888,552	857,160
Net premiums written	159,209	138,653	862,427	817,116
Net premiums earned	222,960	215,617	686,232	628,986
Net losses and loss expenses	-127,266	-104,654	-370,441	-317,369
Acquisition costs	-40,063	-36,970	-125,258	-109,081
General and administrative expenses	-18,571	-20,487	-56,898	-56,930
Underwriting (loss) income	37,060	53,506	133,635	145,606
Other insurance-related income	0	0	0	0
Other insurance-related expenses	0	0	0	0
Segment (loss) income	$37,060	$53,506	$133,635	$145,606
Loss and loss expense ratio	57.10%	48.50%	54.00%	50.50%
Acquisition cost ratio	18.00%	17.10%	18.30%	17.30%
General and administrative expense ratio	8.30%	9.50%	8.30%	9.10%
Expense ratio	26.30%	26.60%	26.60%	26.40%
Combined ratio	83.40%	75.10%	80.60%	76.90%

Segment_Information_Gross_Prem

Segment Information (Gross Premiums Written By Geographic Location) (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'	'	'
Gross premiums written	$707,884	$580,893	$2,369,682	$2,183,174
United States	'	'	'	'
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'	'	'
Gross premiums written	483,992	377,618	1,447,652	1,296,212
Bermuda	'	'	'	'
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'	'	'
Gross premiums written	109,503	111,103	525,005	550,815
Europe	'	'	'	'
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'	'	'
Gross premiums written	64,947	52,004	245,931	198,747
Asia Pacific	'	'	'	'
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'	'	'
Gross premiums written	45,070	40,168	142,798	137,400
Canada	'	'	'	'
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'	'	'
Gross premiums written	4,372	0	8,296	0
Switzerland	'	'	'	'
Revenues from External Customers and Long-Lived Assets [Line Items]	'	'	'	'
Gross premiums written	$11,130	$10,509	$65,684	$57,183

Segment_Information_Narrative_

Segment Information (Narrative) (Details) (Operating Segments [Member], U S Insurance [Member], USD $)	1 Months Ended
In Thousands, unless otherwise specified	31-May-14
Operating Segments [Member] | U S Insurance [Member]	'
Segment Reporting Information [Line Items]	'
Goodwill, Acquired During Period	$9,709

Condensed_Consolidated_Guarant2

Condensed Consolidated Guarantor Financial Statements (Schedule Of Condensed Consolidating Balance Sheet) (Details) (USD $)	Sep. 30, 2014	Jun. 30, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
ASSETS:	'	'	'	'	'	'
Investments	$8,002,514	'	$7,712,036	'	'	'
Cash and cash equivalents	831,270	'	531,936	953,047	'	681,879
Insurance balances receivable	926,183	'	664,731	'	'	'
Funds held	405,703	'	632,430	'	'	'
Reinsurance recoverable	1,349,009	1,301,742	1,234,504	1,226,034	1,179,525	1,141,110
Net deferred acquisition costs	171,827	'	126,661	'	'	'
Goodwill and intangible assets	325,016	'	317,207	'	'	'
Balances receivable on sale of investments	60,122	'	76,544	'	'	'
Investments in subsidiaries	0	'	0	'	'	'
Due from subsidiaries	0	'	0	'	'	'
Other assets	737,924	'	649,781	'	'	'
Total assets	12,809,568	'	11,945,830	'	'	'
LIABILITIES:	'	'	'	'	'	'
Reserve for losses and loss expenses	6,052,263	5,935,678	5,766,529	5,780,781	5,696,865	5,645,549
Unearned premiums	1,716,927	'	1,396,256	'	'	'
Reinsurance balances payable	203,428	'	173,023	'	'	'
Balances due on purchases of investments	166,026	'	104,740	'	'	'
Senior notes	798,725	'	798,499	'	'	'
Due to subsidiaries	0	'	0	'	'	'
Other liabilities	198,600	'	186,957	'	'	'
Total liabilities	9,135,969	'	8,426,004	'	'	'
Total shareholders’ equity	3,673,599	'	3,519,826	3,443,928	'	3,326,335
Total liabilities and shareholders’ equity	12,809,568	'	11,945,830	'	'	'
Percentage ownership of Subsidiary Issuer	100.00%	'	'	'	'	'
Consolidation, Eliminations [Member]	'	'	'	'	'	'
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	'	'	'
Net deferred acquisition costs	0	'	0	'	'	'
Goodwill and intangible assets	0	'	0	'	'	'
Balances receivable on sale of investments	0	'	0	'	'	'
Investments in subsidiaries	-7,900,068	'	-7,431,620	'	'	'
Due from subsidiaries	-34,412	'	-357,497	'	'	'
Other assets	0	'	0	'	'	'
Total assets	-7,934,480	'	-7,789,117	'	'	'
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	0	'	0	'	'	'
Due to subsidiaries	-34,412	'	-357,497	'	'	'
Other liabilities	0	'	0	'	'	'
Total liabilities	-34,412	'	-357,497	'	'	'
Total shareholders’ equity	-7,900,068	'	-7,431,620	'	'	'
Total liabilities and shareholders’ equity	-7,934,480	'	-7,789,117	'	'	'
Allied World Switzerland (Parent Guarantor) [Member]	'	'	'	'	'	'
ASSETS:	'	'	'	'	'	'
Investments	0	'	0	'	'	'
Cash and cash equivalents	38,196	'	10,790	56,060	'	19,997
Insurance balances receivable	0	'	0	'	'	'
Funds held	0	'	0	'	'	'
Reinsurance recoverable	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	3,644,932	'	3,413,001	'	'	'
Due from subsidiaries	18,497	'	111,172	'	'	'
Other assets	2,009	'	1,757	'	'	'
Total assets	3,703,634	'	3,536,720	'	'	'
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	0	'	0	'	'	'
Due to subsidiaries	6,826	'	12,945	'	'	'
Other liabilities	23,209	'	3,949	'	'	'
Total liabilities	30,035	'	16,894	'	'	'
Total shareholders’ equity	3,673,599	'	3,519,826	'	'	'
Total liabilities and shareholders’ equity	3,703,634	'	3,536,720	'	'	'
Allied World Bermuda (Subsidiary Issuer) [Member]	'	'	'	'	'	'
ASSETS:	'	'	'	'	'	'
Investments	0	'	0	'	'	'
Cash and cash equivalents	2,329	'	2,775	8,388	'	11,324
Insurance balances receivable	0	'	0	'	'	'
Funds held	0	'	0	'	'	'
Reinsurance recoverable	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	4,255,136	'	4,018,619	'	'	'
Due from subsidiaries	407	'	122,846	'	'	'
Other assets	3,576	'	4,671	'	'	'
Total assets	4,261,448	'	4,148,911	'	'	'
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	798,725	'	798,499	'	'	'
Due to subsidiaries	8,682	'	110,534	'	'	'
Other liabilities	12,513	'	17,797	'	'	'
Total liabilities	819,920	'	926,830	'	'	'
Total shareholders’ equity	3,441,528	'	3,222,081	'	'	'
Total liabilities and shareholders’ equity	4,261,448	'	4,148,911	'	'	'
Other Allied World Subsidiaries [Member]	'	'	'	'	'	'
ASSETS:	'	'	'	'	'	'
Investments	8,002,514	'	7,712,036	'	'	'
Cash and cash equivalents	790,745	'	518,371	888,599	'	650,558
Insurance balances receivable	926,183	'	664,731	'	'	'
Funds held	405,703	'	632,430	'	'	'
Reinsurance recoverable	1,349,009	'	1,234,504	'	'	'
Net deferred acquisition costs	171,827	'	126,661	'	'	'
Goodwill and intangible assets	325,016	'	317,207	'	'	'
Balances receivable on sale of investments	60,122	'	76,544	'	'	'
Investments in subsidiaries	0	'	0	'	'	'
Due from subsidiaries	15,508	'	123,479	'	'	'
Other assets	732,339	'	643,353	'	'	'
Total assets	12,778,966	'	12,049,316	'	'	'
LIABILITIES:	'	'	'	'	'	'
Reserve for losses and loss expenses	6,052,263	'	5,766,529	'	'	'
Unearned premiums	1,716,927	'	1,396,256	'	'	'
Reinsurance balances payable	203,428	'	173,023	'	'	'
Balances due on purchases of investments	166,026	'	104,740	'	'	'
Senior notes	0	'	0	'	'	'
Due to subsidiaries	18,904	'	234,018	'	'	'
Other liabilities	162,878	'	165,211	'	'	'
Total liabilities	8,320,426	'	7,839,777	'	'	'
Total shareholders’ equity	4,458,540	'	4,209,539	'	'	'
Total liabilities and shareholders’ equity	$12,778,966	'	$12,049,316	'	'	'

Condensed_Consolidated_Guarant3

Condensed Consolidated Guarantor Financial Statements (Schedule Of Condensed Consolidating Income Statement) (Details) (USD $)	3 Months Ended		9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Condensed Income Statements, Captions [Line Items]	'	'	'	'
Net premiums earned	$541,737	$510,773	$1,609,269	$1,481,272
Net investment income	43,412	39,271	127,824	110,294
Net realized investment gains (losses)	-35,136	27,487	104,286	-8,074
Other income	1,032	0	1,032	0
Net losses and loss expenses	-336,090	-276,970	-926,231	-807,276
Acquisition costs	-72,403	-65,114	-214,404	-186,416
General and administrative expenses	-88,294	-88,553	-264,822	-251,818
Other expense	-6,575	0	-6,575	0
Amortization of intangible assets	-633	-633	-1,900	-1,900
Interest expense	-14,325	-14,094	-43,451	-42,416
Foreign exchange gain (loss)	-278	-4,353	-978	-7,361
Income tax (expense) benefit	-1,532	-4,971	-24,300	-6,332
Equity in earnings of consolidated subsidiaries	0	0	0	0
NET INCOME	30,915	122,843	359,750	279,973
Other comprehensive income	0	0	0	0
COMPREHENSIVE INCOME (LOSS)	30,915	122,843	359,750	279,973
Consolidation, Eliminations [Member]	'	'	'	'
Condensed Income Statements, Captions [Line Items]	'	'	'	'
Net premiums earned	0	0	0	0
Net investment income	0	0	0	0
Net realized investment gains (losses)	0	0	0	0
Other income	0	0	0	0
Net losses and loss expenses	0	0	0	0
Acquisition costs	0	0	0	0
General and administrative expenses	0	0	0	0
Other expense	0	0	0	0
Amortization of intangible assets	0	0	0	0
Interest expense	0	0	0	0
Foreign exchange gain (loss)	0	0	0	0
Income tax (expense) benefit	0	0	0	0
Equity in earnings of consolidated subsidiaries	-88,673	-280,829	-807,124	-659,856
NET INCOME	-88,673	-280,829	-807,124	-659,856
Other comprehensive income	0	0	0	0
COMPREHENSIVE INCOME (LOSS)	-88,673	-280,829	-807,124	-659,856
Allied World Switzerland (Parent Guarantor) [Member]	'	'	'	'
Condensed Income Statements, Captions [Line Items]	'	'	'	'
Net premiums earned	0	0	0	0
Net investment income	2	3	6	11
Net realized investment gains (losses)	0	0	0	0
Other income	0	0	0	0
Net losses and loss expenses	0	0	0	0
Acquisition costs	0	0	0	0
General and administrative expenses	-8,285	-7,323	-28,012	-26,875
Other expense	0	0	0	0
Amortization of intangible assets	0	0	0	0
Interest expense	0	0	0	0
Foreign exchange gain (loss)	16	-13	12	261
Income tax (expense) benefit	0	0	-86	0
Equity in earnings of consolidated subsidiaries	39,182	130,176	387,830	306,576
NET INCOME	30,915	122,843	359,750	279,973
Other comprehensive income	0	0	0	0
COMPREHENSIVE INCOME (LOSS)	30,915	122,843	359,750	279,973
Allied World Bermuda (Subsidiary Issuer) [Member]	'	'	'	'
Condensed Income Statements, Captions [Line Items]	'	'	'	'
Net premiums earned	0	0	0	0
Net investment income	0	0	0	4
Net realized investment gains (losses)	0	0	0	0
Other income	0	0	0	0
Net losses and loss expenses	0	0	0	0
Acquisition costs	0	0	0	0
General and administrative expenses	-182	-4,961	-919	-5,873
Other expense	0	0	0	0
Amortization of intangible assets	0	0	0	0
Interest expense	-13,855	-13,838	-41,556	-41,503
Foreign exchange gain (loss)	47	-212	68	-935
Income tax (expense) benefit	0	0	0	0
Equity in earnings of consolidated subsidiaries	49,491	150,653	419,294	353,280
NET INCOME	35,501	131,642	376,887	304,973
Other comprehensive income	0	0	0	0
COMPREHENSIVE INCOME (LOSS)	35,501	131,642	376,887	304,973
Other Allied World Subsidiaries [Member]	'	'	'	'
Condensed Income Statements, Captions [Line Items]	'	'	'	'
Net premiums earned	541,737	510,773	1,609,269	1,481,272
Net investment income	43,410	39,268	127,818	110,279
Net realized investment gains (losses)	-35,136	27,487	104,286	-8,074
Other income	1,032	0	1,032	0
Net losses and loss expenses	-336,090	-276,970	-926,231	-807,276
Acquisition costs	-72,403	-65,114	-214,404	-186,416
General and administrative expenses	-79,827	-76,269	-235,891	-219,070
Other expense	-6,575	0	-6,575	0
Amortization of intangible assets	-633	-633	-1,900	-1,900
Interest expense	-470	-256	-1,895	-913
Foreign exchange gain (loss)	-341	-4,128	-1,058	-6,687
Income tax (expense) benefit	-1,532	-4,971	-24,214	-6,332
Equity in earnings of consolidated subsidiaries	0	0	0	0
NET INCOME	53,172	149,187	430,237	354,883
Other comprehensive income	0	0	0	0
COMPREHENSIVE INCOME (LOSS)	$53,172	$149,187	$430,237	$354,883

Condensed_Consolidated_Guarant4

Condensed Consolidated Guarantor Financial Statements (Schedule Of Condensed Consolidating Cash Flows) (Details) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013
Condensed Cash Flow Statements, Captions [Line Items]	'	'
CASH FLOWS PROVIDED BY (USED IN) OPERATING ACTIVITIES:	$667,107	$332,050
CASH FLOWS (USED IN) PROVIDED BY INVESTING ACTIVITIES:	'	'
Purchases of trading securities	-5,608,594	-4,955,817
Purchases of other invested assets	-242,227	-211,501
Sales of trading securities	5,500,176	5,137,280
Sales of other invested assets	243,123	189,155
Other	-46,620	-78,203
Net cash (used in) provided by investing activities	-154,142	80,914
CASH FLOWS PROVIDED BY (USED IN) FINANCING ACTIVITIES:	'	'
Dividends paid - par value reduction	0	-12,981
Dividends paid	-55,064	-17,117
Intercompany dividends paid	0	0
Proceeds from the exercise of stock options	7,640	8,465
Share repurchases	-166,207	-120,163
Net cash used in financing activities	-213,631	-141,796
NET INCREASE IN CASH AND CASH EQUIVALENTS	299,334	271,168
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD	531,936	681,879
CASH AND CASH EQUIVALENTS, END OF PERIOD	831,270	953,047
Consolidation, Eliminations [Member]	'	'
Condensed Cash Flow Statements, Captions [Line Items]	'	'
CASH FLOWS PROVIDED BY (USED IN) OPERATING ACTIVITIES:	-575,000	-503,500
CASH FLOWS (USED IN) PROVIDED BY INVESTING ACTIVITIES:	'	'
Purchases of trading securities	0	0
Purchases of other invested assets	0	0
Sales of trading securities	0	0
Sales of other invested assets	0	0
Other	0	0
Net cash (used in) provided by investing activities	0	0
CASH FLOWS PROVIDED BY (USED IN) FINANCING ACTIVITIES:	'	'
Dividends paid - par value reduction	'	0
Dividends paid	0	0
Intercompany dividends paid	575,000	503,500
Proceeds from the exercise of stock options	0	0
Share repurchases	0	0
Net cash used in financing activities	575,000	503,500
NET INCREASE IN CASH AND CASH EQUIVALENTS	0	0
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD	0	0
CASH AND CASH EQUIVALENTS, END OF PERIOD	0	0
Allied World Switzerland (Parent Guarantor) [Member]	'	'
Condensed Cash Flow Statements, Captions [Line Items]	'	'
CASH FLOWS PROVIDED BY (USED IN) OPERATING ACTIVITIES:	241,037	177,859
CASH FLOWS (USED IN) PROVIDED BY INVESTING ACTIVITIES:	'	'
Purchases of trading securities	0	0
Purchases of other invested assets	0	0
Sales of trading securities	0	0
Sales of other invested assets	0	0
Other	0	0
Net cash (used in) provided by investing activities	0	0
CASH FLOWS PROVIDED BY (USED IN) FINANCING ACTIVITIES:	'	'
Dividends paid - par value reduction	'	-12,981
Dividends paid	-55,064	-17,117
Intercompany dividends paid	0	0
Proceeds from the exercise of stock options	7,640	8,465
Share repurchases	-166,207	-120,163
Net cash used in financing activities	-213,631	-141,796
NET INCREASE IN CASH AND CASH EQUIVALENTS	27,406	36,063
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD	10,790	19,997
CASH AND CASH EQUIVALENTS, END OF PERIOD	38,196	56,060
Allied World Bermuda (Subsidiary Issuer) [Member]	'	'
Condensed Cash Flow Statements, Captions [Line Items]	'	'
CASH FLOWS PROVIDED BY (USED IN) OPERATING ACTIVITIES:	263,554	226,564
CASH FLOWS (USED IN) PROVIDED BY INVESTING ACTIVITIES:	'	'
Purchases of trading securities	0	0
Purchases of other invested assets	0	0
Sales of trading securities	0	0
Sales of other invested assets	0	0
Other	0	0
Net cash (used in) provided by investing activities	0	0
CASH FLOWS PROVIDED BY (USED IN) FINANCING ACTIVITIES:	'	'
Dividends paid - par value reduction	'	0
Dividends paid	0	0
Intercompany dividends paid	-264,000	-229,500
Proceeds from the exercise of stock options	0	0
Share repurchases	0	0
Net cash used in financing activities	-264,000	-229,500
NET INCREASE IN CASH AND CASH EQUIVALENTS	-446	-2,936
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD	2,775	11,324
CASH AND CASH EQUIVALENTS, END OF PERIOD	2,329	8,388
Other Allied World Subsidiaries [Member]	'	'
Condensed Cash Flow Statements, Captions [Line Items]	'	'
CASH FLOWS PROVIDED BY (USED IN) OPERATING ACTIVITIES:	737,516	431,127
CASH FLOWS (USED IN) PROVIDED BY INVESTING ACTIVITIES:	'	'
Purchases of trading securities	-5,608,594	-4,955,817
Purchases of other invested assets	-242,227	-211,501
Sales of trading securities	5,500,176	5,137,280
Sales of other invested assets	243,123	189,155
Other	-46,620	-78,203
Net cash (used in) provided by investing activities	-154,142	80,914
CASH FLOWS PROVIDED BY (USED IN) FINANCING ACTIVITIES:	'	'
Dividends paid - par value reduction	'	0
Dividends paid	0	0
Intercompany dividends paid	-311,000	-274,000
Proceeds from the exercise of stock options	0	0
Share repurchases	0	0
Net cash used in financing activities	-311,000	-274,000
NET INCREASE IN CASH AND CASH EQUIVALENTS	272,374	238,041
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD	518,371	650,558
CASH AND CASH EQUIVALENTS, END OF PERIOD	$790,745	$888,599

Condensed_Consolidated_Guarant5

Condensed Consolidated Guarantor Financial Statements (Notes to Consolidated Guarantor Financial Statements) (Details) (USD $)	9 Months Ended
In Thousands, unless otherwise specified	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	Dec. 31, 2012
Investments in subsidiaries	$0	'	$0	'
Total shareholders’ equity	3,673,599	3,443,928	3,519,826	3,326,335
Cash Dividends Paid to Parent Company by Consolidated Subsidiaries	264,000	229,500	'	'
Allied World Bermuda (Subsidiary Issuer) [Member]	'	'	'	'
Investments in subsidiaries	4,255,136	'	4,018,619	'
Total shareholders’ equity	3,441,528	'	3,222,081	'
Adjustment to correct for miscalculation | Restatement Adjustment | Allied World Bermuda (Subsidiary Issuer) [Member]	'	'	'	'
Investments in subsidiaries	'	'	776,000	'
Total shareholders’ equity	'	'	$0	'

Subsequent_Events_Details

Subsequent Events (Details) (USD $)

3 Months Ended

9 Months Ended

0 Months Ended

1 Months Ended

0 Months Ended

In Thousands, except Per Share data, unless otherwise specified

Sep. 30, 2014

Sep. 30, 2013

Sep. 30, 2014

Sep. 30, 2013

Dec. 31, 2013

Oct. 22, 2014

Jul. 02, 2014

Apr. 03, 2014

Jan. 02, 2014

Oct. 31, 2013

Jul. 31, 2013

Oct. 02, 2014

Subsequent event

Common shares

Common shares

Common shares

Common shares

Common shares

Common shares

Subsequent event

Subsequent Event [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

Dividends paid per common share

$0.23

$0.17

$0.56

$0.29

'

'

$0.23

$0.17

$0.17

$0.17

$0.17

$0.23

Investment commitment

$479,635

'

$479,635

'

$467,524

$225,000

'

'

'

'

'

'