Statutory Capital and Surplus (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Statutory Accounting Practices [Line Items]
Amount of Restricted Net Assets for Consolidated and Unconsolidated Subsidiaries	$ 2,715,774
Bermuda
Statutory Accounting Practices [Line Items]
Statutory Capital and Surplus	3,208,776	3,272,786
Minimum Required Statutory Capital and Surplus	806,012	718,344
Statutory Net Income (Loss)	467,283	528,712	197,624
Statutory Amount Available for Dividend Payments	802,194
United States
Statutory Accounting Practices [Line Items]
Statutory Capital and Surplus	1,187,023	1,110,468
Minimum Required Statutory Capital and Surplus	205,699	173,078
Statutory Net Income (Loss)	36,744	25,390	44,974
Statutory Amount Available for Dividend Payments	103,789
Ireland
Statutory Accounting Practices [Line Items]
Removal of Regulatory Restrictions Percentage	20.00%
Statutory Capital and Surplus	407,600	412,480
Minimum Required Statutory Capital and Surplus	27,098	19,513
Statutory Net Income (Loss)	(4,880)	9,325	14,590
Statutory Amount Available for Dividend Payments	20,502
Switzerland
Statutory Accounting Practices [Line Items]
Statutory Capital and Surplus	167,840	174,259
Minimum Required Statutory Capital and Surplus	22,905	19,945
Statutory Net Income (Loss)	(6,418)	10,657	(637)
Statutory Amount Available for Dividend Payments	1,858
United Kingdom
Statutory Accounting Practices [Line Items]
Statutory Capital and Surplus	229,745	224,854
Minimum Required Statutory Capital and Surplus	229,689	224,531
Statutory Net Income (Loss)	9,362	1,800	(10,320)
Statutory Amount Available for Dividend Payments	$ 0