Acquisition and Disposals - Impact of Life Retro arrangements (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Underwriting profit (loss)		$ 203,331	$ 135,075	$ 342,538	$ 232,306
Net investment income		223,204	232,773	431,717	465,962
Exchange (gains) losses		(10,374)	(21,141)	(37,764)	(31,582)
Other income and expenses	[1]	(1,364)	(2,858)	(7,872)	(3,352)
Net realized and unrealized gains (losses) on life retrocession embedded derivative		48,509	11,599	65,030	13,409
Net income (loss)		919,918	(275,578)	993,589	15,898
Change in adjustments related to future policy benefit reserves, net of tax		26,328	(440,461)	86,684	(474,465)
Change in cumulative translation adjustment		(34,423)	(9,602)	1,680	(13,482)
Comprehensive income (loss)		(628,996)	260,373	(408,284)	470,377
XL Re Life (SAC) Ltd
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Comprehensive income (loss)		0
Life Funds Withheld Assets
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net investment income		46,864	19,165	97,283	19,165
Net realized gains (losses) on investments sold		68,037	624	120,775	624
Net unrealized gains (losses) on investments, trading securities		(19,543)	0	(18,783)	0
OTTI on investments		(2,878)	(8,771)	(8,087)	(8,771)
Net realized and unrealized gains (losses) on life retrocession embedded derivative		239,174	(17,546)	9,807	(17,546)
Change in net unrealized gains (losses) on investments, net of tax		(321,046)	12,297	(283,931)	12,297
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)	[2]	0	0	603	0
Net investment income		46,864	19,165	97,283	19,165
Net realized gains (losses) on investments sold		68,037	624	120,775	624
Net unrealized gains (losses) on investments, trading securities		(19,543)	0	(18,783)	0
OTTI on investments		(2,878)	(8,771)	(8,087)	(8,771)
Exchange (gains) losses		(18,370)	0	(14,686)	0
Other income and expenses		3,773	(19)	2,475	(19)
Net realized and unrealized gains (losses) on life retrocession embedded derivative		239,174	(17,546)	9,807	(17,546)
Net income (loss)		317,057	(6,547)	189,387	(6,547)
Change in net unrealized gains (losses) on investments, net of tax		(321,046)	12,297	(283,931)	12,297
Change in adjustments related to future policy benefit reserves, net of tax		26,328	0	86,684	0
Change in cumulative translation adjustment		(22,339)	(5,750)	8,463	(5,750)
Total changes to other comprehensive income as a result of Life Retro Arrangements		(317,057)	6,547	(188,784)	6,547
Comprehensive income (loss)		$ 0	$ 0	$ 603	$ 0

[1] Net fee income and other includes operating expenses from the Company's loss prevention consulting services business.

[2] The underwriting profit of $0.6 million relates to a premium adjustment during the six months ended June 30, 2015 relating to the Life Retro Arrangements transaction. Excluding this transaction, the impact to comprehensive income relating to the Life Retro Arrangements was nil for the three and six months ended June 30, 2015.