Acquisition and Disposals - Sale of Life Re Narrative (Details) (USD $)	3 Months Ended		0 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	May 30, 2014	May 01, 2014	Dec. 31, 2014
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Future policy benefit reserves	$ 4,375,863,000				$ 4,707,199,000
Future policy benefit reserves recoverable	3,933,589,000				4,265,678,000
Funds withheld on life retrocession arrangements (net of future policy benefit reserves recoverable)	1,138,652,000				1,155,016,000
Underwriting profit (loss)	139,207,000	97,231,000
Comprehensive income (loss)	220,712,000	210,004,000
XL Re Life (SAC) Ltd
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sale of subsidiary stock, percentage			100.00%
Consideration received			570,000,000
Quota share reinsurance percentage			100.00%
Future policy benefit reserves recoverable	3,900,000,000
Loss on disposal				621,300,000
Funds withheld asset	5,100,000,000
Comprehensive income (loss)	0
Life insurance product line | XL Re Life (SAC) Ltd
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Future policy benefit reserves			5,200,000,000
Future policy benefit reserves retained			400,000,000
Future policy benefit reserves recoverable			4,800,000,000
Life Funds Withheld Assets | XL Re Life (SAC) Ltd
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Underwriting profit (loss)	603,000
Comprehensive income (loss)	$ 603,000