Schedule II - Condensed Financial Information of Registrant - Condensed Balance Sheets (Details) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
ASSETS
Cash and cash equivalents	$ 2,521,814	$ 1,800,832	$ 2,618,378	$ 3,825,125
Other assets	750,872	693,810
Total assets	45,046,819	45,652,887
Liabilities:
Total liabilities	33,611,052	34,303,589
Commitments and Contingencies
Shareholders' equity:
Ordinary shares, 999,990,000 authorized, par value $0.01; issued and outstanding (2014, 255,182,955; 2013, 278,253,308)	2,552	2,783
Additional paid in capital	7,359,102	7,994,100
Accumulated other comprehensive income	1,484,458	736,657	1,520,020	583,065
Retained earnings	1,187,640	1,264,093
Shareholders' equity attributable to XL Group plc	10,033,752	9,997,633
Total liabilities and shareholders' equity	45,046,819	45,652,887
Parenthetical information:
Ordinary shares, shares authorized (in shares)	999,990,000	999,990,000
Ordinary shares, par value (in dollars per share)	$ 0.01	$ 0.01
Ordinary shares, shares issued (in shares)	255,182,955	278,253,308
Ordinary shares, shares outstanding (in shares)	255,182,955	278,253,308	298,682,000
XL Group PLC
ASSETS
Cash and cash equivalents	22,443	12,709	10,961	1,644
Investments in subsidiaries on an equity basis	10,195,445	10,187,614
Other assets	3,017	3,014
Total assets	10,220,905	10,203,337
Liabilities:
Amounts due to subsidiaries	166,782	190,601
Accounts payable and accrued liabilities	20,371	15,103
Total liabilities	187,153	205,704
Commitments and Contingencies
Shareholders' equity:
Ordinary shares, 999,990,000 authorized, par value $0.01; issued and outstanding (2014, 255,182,955; 2013, 278,253,308)	2,552	2,783
Additional paid in capital	7,359,102	7,994,100
Accumulated other comprehensive income	1,484,458	736,657
Retained earnings	1,187,640	1,264,093
Shareholders' equity attributable to XL Group plc	10,033,752	9,997,633
Total liabilities and shareholders' equity	$ 10,220,905	$ 10,203,337
Parenthetical information:
Ordinary shares, shares authorized (in shares)	999,990,000	999,990,000
Ordinary shares, par value (in dollars per share)	$ 0.01	$ 0.01
Ordinary shares, shares issued (in shares)	255,182,955	278,253,308
Ordinary shares, shares outstanding (in shares)	255,182,955	278,253,308