Sale of Life Reinsurance Subsidiary - Impact of Life Retro Arrangements (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended			7 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2014
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Underwriting profit (loss)	$ 585,907	$ 245,191	$ 3,968
Net investment income - Life Funds Withheld Assets	918,625	957,716	1,012,348
Exchange (gains) losses	37,568	28,243	(10,545)
Other income and expenses	(6,891)	(5,692)	3,768
Net realized and unrealized (gains) losses on derivative instruments	29,886	7,798	5,221
Net income (loss)	268,838	1,136,647	730,383
Change in adjustments related to future policy benefit reserves, net of tax	(400,456)	(44,660)	0
Change in cumulative translation adjustment - Life Funds Withheld Assets, net of tax	(25,729)	(54,858)	(8,156)
Comprehensive income (loss)	747,801	(783,363)	936,955
Life Funds Withheld Assets [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net investment income - Life Funds Withheld Assets	129,575	0	0
Net realized gains (losses) on investments sold	5,067	0	0
OTTI on investments - Life Funds Withheld Assets	20,587	0	0
Net realized and unrealized (gains) losses on derivative instruments	(488,222)	0	0
Change in net unrealized gains (losses) on investments, net of tax	274,083	0	0
Life Funds Withheld Assets [Member] | XL Re Life (SAC) Ltd [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Underwriting profit (loss)				11,649	[1]
Net investment income - Life Funds Withheld Assets				129,575
Net realized gains (losses) on investments sold				5,067
Net unrealized gains (losses) on investments - Trading				(9)
OTTI on investments - Life Funds Withheld Assets				20,587
Exchange (gains) losses				10,099
Other income and expenses				(1,610)
Net realized and unrealized (gains) losses on derivative instruments				(488,222)
Net income (loss)				(354,038)
Change in net unrealized gains (losses) on investments, net of tax				274,083
Change in adjustments related to future policy benefit reserves, net of tax				74,009
Change in cumulative translation adjustment - Life Funds Withheld Assets, net of tax				17,595
Total changes to other comprehensive income as a result of Life Retro Arrangements				365,687
Comprehensive income (loss)				$ 11,649	[1]

[1] The underwriting profit of $11.6 million relates to a premium adjustment relating to the Life Retro Arrangements transaction which was completed on May 30, 2014. Excluding this transaction, the impact to comprehensive income relating to the Life Retro Arrangements was nil for the year ended December 31, 2014.