Condensed Consolidated Guarantor Financial Statements (Schedule Of Condensed Consolidating Balance Sheet) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012
ASSETS:
Investments	$ 8,027,840		$ 7,712,036
Cash and cash equivalents	635,138		531,936	674,103		681,879
Insurance balances receivable	976,441		664,731
Funds held	414,445		632,430
Reinsurance recoverable	1,301,742	1,280,525	1,234,504	1,179,525	1,163,503	1,141,110
Net deferred acquisition costs	163,259		126,661
Goodwill and intangible assets	325,325		317,207
Balances receivable on sale of investments	164,713		76,544
Investments in subsidiaries	0		0
Due from subsidiaries	0		0
Other assets	660,744		649,781
Total assets	12,669,647		11,945,830
LIABILITIES:
Reserve for losses and loss expenses	5,935,678	5,856,798	5,766,529	5,696,865	5,673,220	5,645,549
Unearned premiums	1,703,684		1,396,256
Reinsurance balances payable	224,182		173,023
Balances due on purchases of investments	180,378		104,740
Senior notes	798,648		798,499
Due to subsidiaries	0		0
Other liabilities	144,315		186,957
Total liabilities	8,986,885		8,426,004
Total shareholders’ equity	3,682,762		3,519,826	3,373,229		3,326,335
Total liabilities and shareholders’ equity	12,669,647		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	(7,801,785)		(7,431,620)
Due from subsidiaries	(110,208)		(357,497)
Other assets	0		0
Total assets	(7,911,993)		(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	(110,208)		(357,497)
Other liabilities	0		0
Total liabilities	(110,208)		(357,497)
Total shareholders’ equity	(7,801,785)		(7,431,620)
Total liabilities and shareholders’ equity	(7,911,993)		(7,789,117)
Allied World Switzerland (Parent Guarantor) [Member]
ASSETS:
Investments	0		0
Cash and cash equivalents	40,976		10,790	3,676		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	3,600,731		3,413,001
Due from subsidiaries	75,813		111,172
Other assets	1,090		1,757
Total assets	3,718,610		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	8,373		12,945
Other liabilities	27,475		3,949
Total liabilities	35,848		16,894
Total shareholders’ equity	3,682,762		3,519,826
Total liabilities and shareholders’ equity	3,718,610		3,536,720
Allied World Bermuda (Subsidiary Issuer) [Member]
ASSETS:
Investments	0		0
Cash and cash equivalents	1,286		2,775	8,299		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	4,201,054		4,018,619
Due from subsidiaries	18,859		122,846
Other assets	4,026		4,671
Total assets	4,225,225		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	798,648		798,499
Due to subsidiaries	7,163		110,534
Other liabilities	17,976		17,797
Total liabilities	823,787		926,830
Total shareholders’ equity	3,401,438		3,222,081
Total liabilities and shareholders’ equity	4,225,225		4,148,911
Other Allied World Subsidiaries [Member]
ASSETS:
Investments	8,027,840		7,712,036
Cash and cash equivalents	592,876		518,371	662,128		650,558
Insurance balances receivable	976,441		664,731
Funds held	414,445		632,430
Reinsurance recoverable	1,301,742		1,234,504
Net deferred acquisition costs	163,259		126,661
Goodwill and intangible assets	325,325		317,207
Balances receivable on sale of investments	164,713		76,544
Investments in subsidiaries	0		0
Due from subsidiaries	15,536		123,479
Other assets	655,628		643,353
Total assets	12,637,805		12,049,316
LIABILITIES:
Reserve for losses and loss expenses	5,935,678		5,766,529
Unearned premiums	1,703,684		1,396,256
Reinsurance balances payable	224,182		173,023
Balances due on purchases of investments	180,378		104,740
Senior notes	0		0
Due to subsidiaries	94,672		234,018
Other liabilities	98,864		165,211
Total liabilities	8,237,458		7,839,777
Total shareholders’ equity	4,400,347		4,209,539
Total liabilities and shareholders’ equity	$ 12,637,805		$ 12,049,316