Condensed Consolidated Guarantor Financial Statements (Schedule Of Condensed Consolidating Balance Sheet) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013	Dec. 31, 2012
ASSETS:
Investments	$ 7,893,350	$ 7,712,036
Cash and cash equivalents	565,802	531,936	662,581	681,879
Insurance balances receivable	839,630	664,731
Funds held	447,801	632,430
Reinsurance recoverable	1,280,525	1,234,504	1,163,503	1,141,110
Net deferred acquisition costs	167,104	126,661
Goodwill and intangible assets	316,574	317,207
Balances receivable on sale of investments	198,640	76,544
Investments in subsidiaries	0	0
Due from subsidiaries	0	0
Other assets	624,739	649,781
Total assets	12,334,165	11,945,830
LIABILITIES:
Reserve for losses and loss expenses	5,856,798	5,766,529	5,673,220	5,645,549
Unearned premiums	1,627,658	1,396,256
Reinsurance balances payable	160,041	173,023
Balances due on purchases of investments	171,442	104,740
Senior notes	798,573	798,499
Due to subsidiaries	0	0
Other liabilities	102,975	186,957
Total liabilities	8,717,487	8,426,004
Total shareholders’ equity	3,616,678	3,519,826	3,431,963	3,326,335
Total liabilities and shareholders’ equity	12,334,165	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	(7,460,727)	(7,431,620)
Due from subsidiaries	(238,891)	(357,497)
Other assets	0	0
Total assets	(7,699,618)	(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	(238,891)	(357,497)
Other liabilities	0	0
Total liabilities	(238,891)	(357,497)
Total shareholders’ equity	(7,460,727)	(7,431,620)
Total liabilities and shareholders’ equity	(7,699,618)	(7,789,117)
Allied World Switzerland (Parent Guarantor) [Member]
ASSETS:
Investments	0	0
Cash and cash equivalents	22,557	10,790	33,015	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	3,434,192	3,413,001
Due from subsidiaries	187,571	111,172
Other assets	2,079	1,757
Total assets	3,646,399	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	10,565	12,945
Other liabilities	19,156	3,949
Total liabilities	29,721	16,894
Total shareholders’ equity	3,616,678	3,519,826
Total liabilities and shareholders’ equity	3,646,399	3,536,720
Allied World Bermuda (Subsidiary Issuer) [Member]
ASSETS:
Investments	0	0
Cash and cash equivalents	1,047	2,775	17,183	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	4,026,535	4,018,619
Due from subsidiaries	30,569	122,846
Other assets	4,321	4,671
Total assets	4,062,472	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	798,573	798,499
Due to subsidiaries	10,186	110,534
Other liabilities	14,583	17,797
Total liabilities	823,342	926,830
Total shareholders’ equity	3,239,130	3,222,081
Total liabilities and shareholders’ equity	4,062,472	4,148,911
Other Allied World Subsidiaries [Member]
ASSETS:
Investments	7,893,350	7,712,036
Cash and cash equivalents	542,198	518,371	612,383	650,558
Insurance balances receivable	839,630	664,731
Funds held	447,801	632,430
Reinsurance recoverable	1,280,525	1,234,504
Net deferred acquisition costs	167,104	126,661
Goodwill and intangible assets	316,574	317,207
Balances receivable on sale of investments	198,640	76,544
Investments in subsidiaries	0	0
Due from subsidiaries	20,751	123,479
Other assets	618,339	643,353
Total assets	12,324,912	12,049,316
LIABILITIES:
Reserve for losses and loss expenses	5,856,798	5,766,529
Unearned premiums	1,627,658	1,396,256
Reinsurance balances payable	160,041	173,023
Balances due on purchases of investments	171,442	104,740
Senior notes	0	0
Due to subsidiaries	218,140	234,018
Other liabilities	69,236	165,211
Total liabilities	8,103,315	7,839,777
Total shareholders’ equity	4,221,597	4,209,539
Total liabilities and shareholders’ equity	$ 12,324,912	$ 12,049,316