Condensed Consolidated Guarantor Financial Statements (Schedule Of Condensed Consolidating Cash Flows) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Condensed Cash Flow Statements, Captions [Line Items]
CASH FLOWS PROVIDED BY (USED IN) OPERATING ACTIVITIES:	$ 407,790	$ 106,109	$ 628,856
CASH FLOWS USED IN INVESTING ACTIVITIES:
Purchases of trading securities	(7,630,034)	(7,527,670)	(8,006,237)
Purchases of other invested assets	(307,955)	(276,926)	(333,031)
Sales of available for sale securities	0	0	236,978
Sales of trading securities	7,536,936	7,540,194	7,892,907
Sales of other invested assets	267,885	187,477	53,741
Capital contribution to subsidiary			0
Other	6,201	28,782	(104,091)
Net cash used in investing activities	(126,967)	(48,143)	(259,733)
CASH FLOWS USED IN FINANCING ACTIVITIES:
Partial par value reduction	0awh_PartialParValueReduction	(12,981)awh_PartialParValueReduction	(67,825)awh_PartialParValueReduction
Dividends paid	(76,750)us-gaap_PaymentsOfDividendsCommonStock	(34,059)us-gaap_PaymentsOfDividendsCommonStock	0us-gaap_PaymentsOfDividendsCommonStock
Intercompany dividends paid	0	0	0
Proceeds from the exercise of stock options	10,027	12,137	10,527
Proceeds from other long-term debt	19,213	0	0
Share repurchases	(175,910)	(173,006)	(263,942)
Capital contribution from parent			0us-gaap_ProceedsFromContributedCapital
Net cash used in financing activities	(223,420)	(207,909)	(321,240)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	57,403	(149,943)	47,883
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD	531,936	681,879	633,996
CASH AND CASH EQUIVALENTS, END OF PERIOD	589,339	531,936	681,879
Consolidating Adjustments
Condensed Cash Flow Statements, Captions [Line Items]
CASH FLOWS PROVIDED BY (USED IN) OPERATING ACTIVITIES:	(643,250)	(596,500)	(770,000)
CASH FLOWS USED IN INVESTING ACTIVITIES:
Purchases of trading securities	0	0	0
Purchases of other invested assets	0	0	0
Sales of available for sale securities			0
Sales of trading securities	0	0	0
Sales of other invested assets	0	0	0
Capital contribution to subsidiary			110,000
Other	0	0	0
Net cash used in investing activities	0	0	110,000
CASH FLOWS USED IN FINANCING ACTIVITIES:
Partial par value reduction		0	0
Dividends paid	0	0
Intercompany dividends paid	643,250	596,500	770,000
Proceeds from the exercise of stock options	0	0	0
Proceeds from other long-term debt	0
Share repurchases	0	0	0
Capital contribution from parent			(110,000)
Net cash used in financing activities	643,250	596,500	660,000
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	0	0	0
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD	0	0	0
CASH AND CASH EQUIVALENTS, END OF PERIOD	0	0	0
Allied World Switzerland (Parent Guarantor)
Condensed Cash Flow Statements, Captions [Line Items]
CASH FLOWS PROVIDED BY (USED IN) OPERATING ACTIVITIES:	264,422	198,702	338,565
CASH FLOWS USED IN INVESTING ACTIVITIES:
Purchases of trading securities	0	0	0
Purchases of other invested assets	0	0	0
Sales of available for sale securities			0
Sales of trading securities	0	0	0
Sales of other invested assets	0	0	0
Capital contribution to subsidiary			(110,000)
Other	0	0	0
Net cash used in investing activities	0	0	(110,000)
CASH FLOWS USED IN FINANCING ACTIVITIES:
Partial par value reduction		(12,981)	(67,825)
Dividends paid	(76,750)	(34,059)
Intercompany dividends paid	0	0	0
Proceeds from the exercise of stock options	10,027	12,137	10,527
Proceeds from other long-term debt	0
Share repurchases	(175,910)	(173,006)	(263,942)
Capital contribution from parent			0
Net cash used in financing activities	(242,633)	(207,909)	(321,240)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	21,789	(9,207)	(92,675)
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD	10,790	19,997	112,672
CASH AND CASH EQUIVALENTS, END OF PERIOD	32,579	10,790	19,997
Allied World Bermuda (Subsidiary Issuer)
Condensed Cash Flow Statements, Captions [Line Items]
CASH FLOWS PROVIDED BY (USED IN) OPERATING ACTIVITIES:	292,959	265,951	357,438
CASH FLOWS USED IN INVESTING ACTIVITIES:
Purchases of trading securities	0	0	0
Purchases of other invested assets	0	0	0
Sales of available for sale securities			0
Sales of trading securities	0	0	0
Sales of other invested assets	0	0	0
Capital contribution to subsidiary			0
Other	0	0	0
Net cash used in investing activities	0	0	0
CASH FLOWS USED IN FINANCING ACTIVITIES:
Partial par value reduction		0	0
Dividends paid	0	0
Intercompany dividends paid	(294,000)	(274,500)	(355,000)
Proceeds from the exercise of stock options	0	0	0
Proceeds from other long-term debt	0
Share repurchases	0	0	0
Capital contribution from parent			0
Net cash used in financing activities	(294,000)	(274,500)	(355,000)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	(1,041)	(8,549)	2,438
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD	2,775	11,324	8,886
CASH AND CASH EQUIVALENTS, END OF PERIOD	1,734	2,775	11,324
Other Allied World Subsidiaries
Condensed Cash Flow Statements, Captions [Line Items]
CASH FLOWS PROVIDED BY (USED IN) OPERATING ACTIVITIES:	493,659	237,956	702,853
CASH FLOWS USED IN INVESTING ACTIVITIES:
Purchases of trading securities	(7,630,034)	(7,527,670)	(8,006,237)
Purchases of other invested assets	(307,955)	(276,926)	(333,031)
Sales of available for sale securities			236,978
Sales of trading securities	7,536,936	7,540,194	7,892,907
Sales of other invested assets	267,885	187,477	53,741
Capital contribution to subsidiary			0
Other	6,201	28,782	(104,091)
Net cash used in investing activities	(126,967)	(48,143)	(259,733)
CASH FLOWS USED IN FINANCING ACTIVITIES:
Partial par value reduction		0	0
Dividends paid	0	0
Intercompany dividends paid	(349,250)	(322,000)	(415,000)
Proceeds from the exercise of stock options	0	0	0
Proceeds from other long-term debt	19,213
Share repurchases	0	0	0
Capital contribution from parent			110,000
Net cash used in financing activities	(330,037)	(322,000)	(305,000)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	36,655	(132,187)	138,120
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD	518,371	650,558	512,438
CASH AND CASH EQUIVALENTS, END OF PERIOD	$ 555,026	$ 518,371	$ 650,558

The net cash from (used in) all of the entity's operating activities, including those of discontinued operations, of the reporting entity. Operating activities generally involve producing and delivering goods and providing services. Operating activity cash flows include transactions, adjustments, and changes in value that are not defined as investing or financing activities and the effect of exchange rate changes on cash balances held in foreign currencies.

No definition available.