Condensed Consolidated Guarantor Financial Statements (Schedule Of Condensed Consolidating Balance Sheet) (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013
ASSETS:
Investments	$ 8,143,974		$ 7,868,682
Cash and cash equivalents	661,847		589,339	$ 635,138		$ 531,936
Insurance balances receivable	944,539		664,815
Funds held	462,493		724,021
Reinsurance recoverable	1,433,109	$ 1,350,311	1,340,256	1,301,742	$ 1,280,525	1,234,504
Reinsurance recoverable on paid losses	88,421		86,075
Net deferred acquisition costs	208,034		151,546
Goodwill and intangible assets	494,097		324,556
Balances receivable on sale of investments	122,660		47,149
Investments in subsidiaries	0		0
Due from subsidiaries	0		0
Other assets	747,820		625,124
Total assets	13,306,994		12,421,563
LIABILITIES:
Reserve for losses and loss expenses	6,363,948	$ 5,905,110	5,881,165	5,935,678	$ 5,856,798	5,766,529
Unearned premiums	1,894,484		1,555,313
Reinsurance balances payable	231,350		180,060
Balances due on purchases of investments	205,430		5,428
Senior notes	798,962		798,802
Other long-term debt	24,472		19,213
Due to subsidiaries	0		0
Other liabilities	163,547		203,291
Total liabilities	9,682,193		8,643,272
Total shareholders’ equity	3,624,801		3,778,291	3,682,762		3,519,826
Total liabilities and shareholders’ equity	$ 13,306,994		12,421,563
Percentage ownership of Subsidiary Issuer	100.00%
Consolidating Adjustments [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
Reinsurance recoverable on paid losses	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	(7,824,543)		(7,847,329)
Due from subsidiaries	(44,010)		(180,658)
Other assets	0		0
Total assets	(7,868,553)		(8,027,987)
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
Other long-term debt	0		0
Due to subsidiaries	(44,010)		(180,658)
Other liabilities	0		0
Total liabilities	(44,010)		(180,658)
Total shareholders’ equity	(7,824,543)		(7,847,329)
Total liabilities and shareholders’ equity	(7,868,553)		(8,027,987)
Allied World Switzerland (Parent Guarantor) [Member]
ASSETS:
Investments	0		0
Cash and cash equivalents	29,095		32,579	40,976		10,790
Insurance balances receivable	0		0
Funds held	0		0
Reinsurance recoverable	0		0
Reinsurance recoverable on paid losses	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	3,621,020		3,629,301
Due from subsidiaries	8,373		147,072
Other assets	1,246		1,470
Total assets	3,659,734		3,810,422
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
Other long-term debt	0		0
Due to subsidiaries	9,787		7,599
Other liabilities	25,146		24,532
Total liabilities	34,933		32,131
Total shareholders’ equity	3,624,801		3,778,291
Total liabilities and shareholders’ equity	3,659,734		3,810,422
Allied World Bermuda (Subsidiary Issuer) [Member]
ASSETS:
Investments	0		0
Cash and cash equivalents	1,947		1,734	1,286		2,775
Insurance balances receivable	0		0
Funds held	0		0
Reinsurance recoverable	0		0
Reinsurance recoverable on paid losses	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	4,203,523		4,218,028
Due from subsidiaries	19,585		19,190
Other assets	2,592		3,192
Total assets	4,227,647		4,242,144
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	798,962		798,802
Other long-term debt	0		0
Due to subsidiaries	6,265		6,797
Other liabilities	19,910		19,618
Total liabilities	825,137		825,217
Total shareholders’ equity	3,402,510		3,416,927
Total liabilities and shareholders’ equity	4,227,647		4,242,144
Other Allied World Subsidiaries [Member]
ASSETS:
Investments	8,143,974		7,868,682
Cash and cash equivalents	630,805		555,026	$ 592,876		$ 518,371
Insurance balances receivable	944,539		664,815
Funds held	462,493		724,021
Reinsurance recoverable	1,433,109		1,340,256
Reinsurance recoverable on paid losses	88,421		86,075
Net deferred acquisition costs	208,034		151,546
Goodwill and intangible assets	494,097		324,556
Balances receivable on sale of investments	122,660		47,149
Investments in subsidiaries	0		0
Due from subsidiaries	16,052		14,396
Other assets	743,982		620,462
Total assets	13,288,166		12,396,984
LIABILITIES:
Reserve for losses and loss expenses	6,363,948		5,881,165
Unearned premiums	1,894,484		1,555,313
Reinsurance balances payable	231,350		180,060
Balances due on purchases of investments	205,430		5,428
Senior notes	0		0
Other long-term debt	24,472		19,213
Due to subsidiaries	27,958		166,262
Other liabilities	118,491		159,141
Total liabilities	8,866,133		7,966,582
Total shareholders’ equity	4,422,033		4,430,402
Total liabilities and shareholders’ equity	$ 13,288,166		$ 12,396,984