GENERAL (Detail) - Details of financial line items reclassified (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Additional paid in capital	$ 8,938,678	$ 8,993,016
Shareholders’ equity attributable to XL Group plc	9,424,938	9,610,753
Non-controlling interest in equity of consolidated subsidiaries	1,344,472	1,002,296
Non-controlling interests	70,877	39,831	(104)
Net income (loss) attributable to XL Group plc	(474,760)	603,550	74,991
Preference share dividends	0	34,694	80,200
Comprehensive income (loss)	7,509	1,846,812	2,297,451
Previously Reported [Member]
Series E preference ordinary shares, 1,000,000 authorized, par value $0.01; Issued and outstanding: (2010, 1,000,000; 2009, 1,000,000)		10
Additional paid in capital		9,993,006
Shareholders’ equity attributable to XL Group plc		10,610,753
Non-controlling interest in equity of consolidated subsidiaries		2,296
Non-controlling interests		(4)
Net income (loss) attributable to XL Group plc		643,377
Preference share dividends		(74,521)
Comprehensive income (loss)		1,886,639
Revised [Member]
Series E preference ordinary shares, 1,000,000 authorized, par value $0.01; Issued and outstanding: (2010, 1,000,000; 2009, 1,000,000)		0
Additional paid in capital		8,993,016
Shareholders’ equity attributable to XL Group plc		9,610,753
Non-controlling interest in equity of consolidated subsidiaries		1,002,296
Non-controlling interests		(39,831)
Net income (loss) attributable to XL Group plc		603,550
Preference share dividends		(34,694)
Comprehensive income (loss)		$ 1,846,812