Condensed Consolidated Guarantor Financial Statements (Schedule Of Condensed Consolidating Balance Sheet) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Jun. 30, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Dec. 31, 2012
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