Shareholders' Equity (Narrative) (Details) In Thousands, except Share data, unless otherwise specified	3 Months Ended	12 Months Ended				12 Months Ended	0 Months Ended			12 Months Ended	0 Months Ended
	Mar. 31, 2013	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)	Dec. 31, 2012 CHF	Dec. 31, 2013 CHF	Dec. 31, 2013 Allied World Switzerland (Parent Guarantor) [Member]	Jul. 09, 2013 Nonvoting common stock	Jul. 30, 2012 Nonvoting common stock	Jul. 09, 2013 Common Shares Repurchased And Constructively Retired [Member]	Dec. 31, 2012 Common Shares Repurchased And Constructively Retired [Member]	Jul. 30, 2012 Voting common stock	Dec. 31, 2013 Voting common stock
Class of Stock [Line Items]
Stock Repurchased and Retired During Period, Shares	1,848,144
Common stock, shares outstanding		33,417,882	34,797,781	34,797,781
Shares cancelled, shares		1,877,384	3,633,774	3,633,774			29,240	173,100	1,538,686	1,133,774	2,326,900
Maximum authorized value increase of registered share capital					92,259
Maximum authorized increased voting shares												7,500,728
Total share capital		418,988	454,980
Common shares, par value				12.64	12.3
Maximum percentage of registered capital in treasury shares		10.00%
Shares cancelled, value		$ 0
Threshold for dividend restrictions						20.00%
Minimum Annual Profit Percentage Required						5.00%