Schedule II - Condensed Financial Information of Registrant - Condensed Balance Sheets (Details) - USD ($) $ / shares in Units, $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
ASSETS
Cash and cash equivalents	$ 3,256,236	$ 2,521,814	$ 1,800,832	$ 2,618,378
Other assets	937,199	750,872
Total assets	58,682,938	45,046,819
Liabilities:
Total liabilities	$ 45,028,475	$ 33,611,053
Commitments and Contingencies
Shareholders' equity:
Class A ordinary shares, 999,990,000 authorized, par value $0.01; issued and outstanding (2015, 294,745,045; 2014, 255,182,955)	$ 2,947	$ 2,552
Additional paid in capital	8,910,167	7,359,102
Accumulated other comprehensive income	686,616	1,484,458	$ 736,657	1,520,020
Retained earnings	2,077,349	1,187,639
Shareholders' equity attributable to XL Group plc	11,677,079	10,033,751
Total liabilities and shareholders' equity	$ 58,682,938	$ 45,046,819
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)	294,745,045	255,182,955
Ordinary shares, shares outstanding (in shares)	294,745,045	255,182,955	278,253,000
XL Group PLC
ASSETS
Cash and cash equivalents	$ 11,557	$ 22,443	$ 12,709	$ 10,961
Amounts due from subsidiaries	33,417	0
Investments in subsidiaries on an equity basis	11,648,673	10,195,445
Other assets	2,748	3,017
Total assets	11,696,395	10,220,905
Liabilities:
Amounts due to subsidiaries	0	166,782
Accounts payable and accrued liabilities	19,316	20,372
Total liabilities	$ 19,316	$ 187,154
Commitments and Contingencies
Shareholders' equity:
Class A ordinary shares, 999,990,000 authorized, par value $0.01; issued and outstanding (2015, 294,745,045; 2014, 255,182,955)	$ 2,947	$ 2,552
Additional paid in capital	8,910,167	7,359,102
Accumulated other comprehensive income	686,616	1,484,458
Retained earnings	2,077,349	1,187,639
Shareholders' equity attributable to XL Group plc	11,677,079	10,033,751
Total liabilities and shareholders' equity	$ 11,696,395	$ 10,220,905
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)	294,745,045	255,182,955
Ordinary shares, shares outstanding (in shares)	294,745,045	255,182,955