Sale of Life Reinsurance Subsidiary - Narrative (Details) (USD $)	3 Months Ended		9 Months Ended			0 Months Ended					3 Months Ended	4 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	May 01, 2014 XL Re Life (SAC) Ltd [Member]	Sep. 30, 2014 XL Re Life (SAC) Ltd [Member]	May 30, 2014 XL Re Life (SAC) Ltd [Member]	Sep. 30, 2014 Life Insurance Product Line [Member] XL Re Life (SAC) Ltd [Member]	May 30, 2014 Life Insurance Product Line [Member] XL Re Life (SAC) Ltd [Member]	Sep. 30, 2014 Life Funds Withheld Assets XL Re Life (SAC) Ltd [Member]	Sep. 30, 2014 Life Funds Withheld Assets XL Re Life (SAC) Ltd [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sale of Subsidiary Stock, Percentage						100.00%
Disposal Group, Including Discontinued Operation, Consideration						$ 570,000,000
Quota Share Reinsurance Percentage						100.00%
Pro Forma Effect of Sale, After Tax Net Loss						621,300,000
Future policy benefit reserves	4,965,907,000		4,965,907,000		4,803,816,000				4,966,000,000	5,200,000,000
Estimated Future Policy Benefit Reserve Retention							400,000,000
Future policy benefit reserves recoverable	4,560,388,000		4,560,388,000		0		4,600,000,000	4,800,000,000
Funds withheld on life retrocession arrangements (net of future policy benefit reserves recoverable)	914,773,000		914,773,000		0
Estimated Assets Funds Withheld							5,500,000,000
Underwriting profit (loss)	$ 139,138,000	$ 26,265,000	$ 371,443,000	$ 194,439,000							$ 3,711,000	$ 3,711,000