CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (USD $) In Thousands	Total	Noncontrolling Interest [Member]	Preferred Stock [Member]	Common Stock [Member] Common Class A [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Retained Earnings [Member]
Balance at Dec. 31, 2009		$ 2,305	$ 10	$ 3,421	$ 10,474,688	$ (1,142,467)	$ 94,460
Net income (loss) attributable to XL Group plc	337,885						337,885
Dividends on preference ordinary shares							(34,694)
Dividends on ordinary shares							(68,636)
Gain on redemption of Redeemable Series C preference ordinary shares	16,616						16,616
Change in net unrealized gains (losses) on investments, net of tax						863,940
Change in net unrealized gains (losses) on affiliate and other investments, net of tax	16,392					16,392
Change in OTTI losses recognized in other comprehensive income, net of tax						31,637
Change in underfunded pension liability	(3,567)					3,567
Change in value of cash flow hedge	(220)					220
Foreign currency translation adjustments	108,308					(108,308)
Change in net unrealized gain (loss) on future policy benefit reserves	(3,714)					(3,714)
Issuance of ordinary shares					1,095
Exercise of stock options				1	104
Share based compensation expense					20,628
Buybacks of ordinary shares				(1)	(1,840)
Non-controlling interests	(81)	(81)
Non-controlling interest share in change in accumulated other comprehensive (income) loss		4
Balance at Jun. 30, 2010	10,507,232	2,228	10	3,421	10,494,675	(338,733)	345,631
Balance at Dec. 31, 2010	10,613,049	1,002,296		3,165	8,993,016	100,795	513,777
Net income (loss) attributable to XL Group plc	(1,621)						(1,621)
Dividends on ordinary shares							(68,529)
Change in net unrealized gains (losses) on investments, net of tax						181,206
Change in net unrealized gains (losses) on affiliate and other investments, net of tax	32,666					32,666
Change in OTTI losses recognized in other comprehensive income, net of tax						24,124
Change in underfunded pension liability	397					(397)
Change in value of cash flow hedge	(220)					220
Foreign currency translation adjustments	(84,357)					84,357
Issuance of ordinary shares				3	976
Exercise of stock options					1,087
Share based compensation expense					20,008
Buybacks of ordinary shares				(116)	(258,787)
Non-controlling interests	35,438	1
Non-controlling interest share in change in accumulated other comprehensive (income) loss		(16)
Purchase of Series E preference ordinary shares		(500)
Balance at Jun. 30, 2011	$ 10,627,731	$ 1,001,781		$ 3,052	$ 8,756,300	$ 422,971	$ 443,627