Schedule II - Condensed Financial Information of Registrant (Statement of Cash Flows) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended			6 Months Ended			12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Jun. 30, 2010 XLIT Ltd.		Dec. 31, 2010 Xl Group PLC	Dec. 31, 2012 Xl Group PLC	Dec. 31, 2011 Xl Group PLC
Condensed Financial Statements Captions [Line Items]
Net income (loss) attributable to XL Group plc	$ 651,134	$ (474,760)	$ 603,550	$ 337,885	[1]	$ 265,665	$ 651,134	$ (474,760)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Net realized gains losses on investments and derivative instruments				(9,423)
Equity in net earnings of subsidiaries				(384,311)	[1]	(275,629)	(662,280)	400,612
(Income) loss from investment and operating affiliates	(114,314)	(103,039)	(172,474)	(2)	[1]	0	0	0
Share based compensation	47,472	41,225	44,057	21,901		22,157	47,472	41,225
Amortization of premiums (discounts) on fixed maturities	169,353	120,130	60,869	(9,791)		0	0	0
Accretion of notes payable and debt				341		0	0	0
Accounts payable and accrued liabilities				(24,973)		0	0	0
Amount due to subsidiaries				(183,273)		125,052	166,853	(205,893)
Dividends received from subsidiaries				197,326		448,400	0	183,029
Other	(58,254)	(51,970)	(82,039)	24,621		1,462	(3,296)	10,956
Total adjustments	325,718	731,085	(48,625)	(367,584)		321,442	(451,251)	429,929
Net cash provided by (used in) operating activities	1,056,106	327,202	594,756	(29,699)		587,107	199,883	(44,831)
Cash flows provided by (used in) investing activities: [Abstract]
Proceeds from sale of fixed maturities and short-term investments	3,604,792	5,091,375	5,206,690	369,752		0	0	0
Proceeds from redemption of fixed maturities and short-term investments	4,579,651	3,595,922	2,851,815	575,326		0	0	0
Proceeds from sale of equity securities	221,617	205,736	115,839	238		0	0	0
Purchases of fixed maturities and short term investments	(8,902,879)	(7,529,962)	(8,098,862)	(919,840)		0	0	0
Investment in subsidiaries				298,119		0	341,750	272,398
Investment in affiliates				5		0	0	0
Investment in limited partnerships				95		0	0	0
Net cash provided by (used in) investing activities	(942,593)	832,103	261,481	323,695		0	341,750	272,398
Cash flows provided by (used in) financing activities:
Proceeds from issuance of ordinary shares and exercise of stock options	5,413	576,333	1,182	0		1,182	5,413	576,333
Repurchase of preference ordinary shares				(94,157)		0		0
Dividends paid	(134,799)	(138,050)	(133,748)	(106,471)		(65,350)	(134,799)	(138,050)
Buybacks of ordinary shares	(402,930)	(667,022)	(522,024)	(1,840)		(520,184)	(402,930)	(667,022)
Net cash provided by (used in) financing activities	(1,344,753)	(358,716)	(1,473,343)	(202,468)		(584,352)	(532,316)	(228,739)
Net change in cash and cash equivalents	(1,206,747)	802,257	(620,829)	91,528		2,755	9,317	(1,172)
Cash and cash equivalents beginning of year	3,825,125	3,022,868	3,643,697	600,993		61	1,644	2,816
Cash and cash equivalents end of year	$ 2,618,378	$ 3,825,125	$ 3,022,868	$ 692,521		$ 2,816	$ 10,961	$ 1,644

[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.