Condensed Consolidated Guarantor Financial Statements (Schedule Of Condensed Consolidating Income Statement) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Condensed Income Statements, Captions [Line Items]
Net premiums earned	$ 530,285	$ 463,228
Net investment income	47,619	33,388
Net realized investment gains (losses)	54,205	79,637
Net losses and loss expenses	(275,286)	(255,178)
Acquisition costs	(67,722)	(56,685)
General and administrative expenses	(80,340)	(82,680)
Amortization of intangible assets	(633)	(633)
Interest expense	(14,534)	(14,134)
Foreign exchange loss	(49)	(2,518)
Income tax (expense) benefit	(16,573)	(5,433)
Equity in earnings of consolidated subsidiaries	0	0
NET INCOME	176,972	158,992
Other comprehensive loss	0	0
COMPREHENSIVE INCOME (LOSS)	176,972	158,992
Consolidation, Eliminations [Member]
Condensed Income Statements, Captions [Line Items]
Net premiums earned	0	0
Net investment income	0	0
Net realized investment gains (losses)	0	0
Net losses and loss expenses	0	0
Acquisition costs	0	0
General and administrative expenses	0	0
Amortization of intangible assets	0	0
Interest expense	0	0
Foreign exchange loss	0	0
Income tax (expense) benefit	0	0
Equity in earnings of consolidated subsidiaries	(385,302)	(351,179)
NET INCOME	(385,302)	(351,179)
Other comprehensive loss	0	0
COMPREHENSIVE INCOME (LOSS)	(385,302)	(351,179)
Allied World Switzerland (Parent Guarantor) [Member]
Condensed Income Statements, Captions [Line Items]
Net premiums earned	0	0
Net investment income	2	7
Net realized investment gains (losses)	0	0
Net losses and loss expenses	0	0
Acquisition costs	0	0
General and administrative expenses	(8,914)	(10,986)
Amortization of intangible assets	0	0
Interest expense	0	0
Foreign exchange loss	(2)	272
Income tax (expense) benefit	(409)	0
Equity in earnings of consolidated subsidiaries	186,295	169,699
NET INCOME	176,972	158,992
Other comprehensive loss	0	0
COMPREHENSIVE INCOME (LOSS)	176,972	158,992
Allied World Bermuda (Subsidiary Issuer) [Member]
Condensed Income Statements, Captions [Line Items]
Net premiums earned	0	0
Net investment income	0	2
Net realized investment gains (losses)	0	0
Net losses and loss expenses	0	0
Acquisition costs	0	0
General and administrative expenses	(2,391)	(457)
Amortization of intangible assets	0	0
Interest expense	(13,848)	(13,830)
Foreign exchange loss	33	(95)
Income tax (expense) benefit	0	0
Equity in earnings of consolidated subsidiaries	199,007	181,480
NET INCOME	182,801	167,100
Other comprehensive loss	0	0
COMPREHENSIVE INCOME (LOSS)	182,801	167,100
Other Allied World Subsidiaries [Member]
Condensed Income Statements, Captions [Line Items]
Net premiums earned	530,285	463,228
Net investment income	47,617	33,379
Net realized investment gains (losses)	54,205	79,637
Net losses and loss expenses	(275,286)	(255,178)
Acquisition costs	(67,722)	(56,685)
General and administrative expenses	(69,035)	(71,237)
Amortization of intangible assets	(633)	(633)
Interest expense	(686)	(304)
Foreign exchange loss	(80)	(2,695)
Income tax (expense) benefit	(16,164)	(5,433)
Equity in earnings of consolidated subsidiaries	0	0
NET INCOME	202,501	184,079
Other comprehensive loss	0	0
COMPREHENSIVE INCOME (LOSS)	$ 202,501	$ 184,079