Basis of Preparation and Consolidation (Detail) - Details of financial line items reclassified (USD $) In Thousands	3 Months Ended
	Dec. 31, 2010 Previously Reported [Member]	Dec. 31, 2010 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)	$ 10
Additional paid in capital	9,993,006	8,993,016
Shareholders’ equity attributable to XL Group plc	10,610,753	9,610,753
Non-controlling interest in equity of consolidated subsidiaries	2,296	1,002,296
Non-controlling interests	(4)	(39,831)
Net income (loss) attributable to XL Group plc	643,377	603,550
Preference share dividends	(74,521)	(34,694)
Comprehensive income (loss)	$ 1,886,639	$ 1,846,812