SCHEDULE IICONDENSED FINANCIAL INFORMATION OF REGISTRANTCONDENSED BALANCE SHEETS - PARENT COMPANY ONLY (Detail) - STATEMENT OF INCOME AND COMPREHENSIVE INCOME (USD $) In Thousands, unless otherwise specified	12 Months Ended			6 Months Ended	12 Months Ended	6 Months Ended		12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2010 Segment, Continuing Operations [Member]	Dec. 31, 2011 Segment, Continuing Operations [Member]	Jun. 30, 2010 Segment, Discontinued Operations [Member]		Dec. 31, 2009 Segment, Discontinued Operations [Member]
Net investment income	$ 1,063,199	$ 1,116,530	$ 1,215,173	$ 0	$ 2	$ 44,636	[1]	$ 20,245	[1]
Net realized gains (losses) on investments sold	(28,187)	(65,670)	(108,979)	0	0	25,177	[1]	(5,453)	[1]
Other-than-temporary impairments on investments	(174,102)	(170,643)	(992,202)	0	0	(11,670)	[1]	(8,468)	[1]
Other-than-temporary impairments on investments transferred to other comprehensive income	13,930	(34,490)	179,744	0	0	4	[1]	1,319	[1]
Total net realized gains (losses) on investments	(188,359)	(270,803)	(921,437)	0	0	13,511	[1]	(12,602)	[1]
Net realized and unrealized gains (losses) on derivative instruments	(10,738)	(33,843)	(33,647)	0	0	(4,087)	[1]	(8,830)	[1]
Equity in net earnings (losses) of subsidiaries (Dividends were $183,029 in 2011 $197,326 and $448,400 in 2010 and $2,091,474 in 2009)				275,629	(400,612)	384,311	[1]	310,490	[1]
Equity in net earnings of affiliates				0	0	2	[1]	1,221	[1]
Total revenues	6,696,803	6,398,582	6,193,647	275,629	(400,610)	438,373	[1]	310,524	[1]
Operating expenses	1,082,479	971,105	1,055,823	9,930	74,422	48,256	[1]	107,211	[1]
Foreign exchange (gains) losses	(40,640)	(10,161)	84,813	34	(275)	1,003	[1]	(122)	[1]
Interest expense	205,592	213,643	216,504	0	3	51,431	[1]	122,662	[1]
Total expenses	7,117,765	5,713,836	6,058,933	9,964	74,150	100,690	[1]	229,751	[1]
Income (loss) before income tax				265,665	(474,760)	337,683	[1]	80,773	[1]
Provision for income tax	59,707	162,737	120,307	0	0	(202)	[1]	5,782	[1]
Net income (loss)	(403,883)	643,381	74,887	265,665	(474,760)	337,885	[1]	74,991	[1]
Preference share dividends	0	34,694	80,200	0	0	(34,694)	[1]	(80,200)	[1]
Gain on redemption of Redeemable Series C preference ordinary shares	0	16,616	211,816	0	0	16,616	[1]	211,816	[1]
Net income (loss) attributable to ordinary shareholders	(474,760)	585,472	206,607	265,665	(474,760)	319,807	[1]	206,607	[1]
Net income (loss)	(403,883)	643,381	74,887	265,665	(474,760)	337,885	[1]	74,991	[1]
Impact of adoption of new authoritative OTTI guidance, net of taxes	0	0	229,670	0	0	0	[1]	(229,670)	[1]
Impact of adoption of new authoritative embedded derivative guidance, net of taxes	0	(31,917)	0	31,917	0	0	[1]	0	[1]
Change in net unrealized gains (losses) on investment portfolio, net of tax	446,427	997,066	2,376,556	161,048	471,696	880,332	[1]	2,391,020	[1]
Change in OTTI losses recognized in other comprehensive income, net of tax	39,456	124,906	(123,343)	93,269	39,456	31,637	[1]	(123,343)	[1]
Change in underfunded pension liability	2,622	2,619	3,427	(6,186)	(2,622)	3,567	[1]	(3,427)	[1]
Change in value of cash flow hedge	(439)	(439)	(438)	219	439	220	[1]	438	[1]
Change in net unrealized gains (losses) on future policy benefit reserves	0	(3,714)	6,554	0	0	(3,714)	[1]	6,554	[1]
Foreign currency translation adjustments	(26,700)	50,953	180,888	159,261	(26,700)	(108,308)	[1]	180,888	[1]
Comprehensive income (loss)	$ 7,509	$ 1,846,812	$ 2,297,451	$ 705,193	$ 7,509	$ 1,141,619	[1]	$ 2,297,451	[1]

[1] As part of the Redomestication on July 1, 2010, XL-Cayman became a wholly-owned subsidiary of XL-Ireland, and as such, certain of the above financial data with respect to periods prior to the Redomestication are not comparable for periods subsequent to the Redomestication.