Schedule II - Condensed Financial Information of Registrant - Statement of Income and Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Condensed Financial Statements Captions [Line Items]
Net investment income									$ 872,370	$ 918,625	$ 957,716
Total revenues									9,308,926	6,602,267	7,541,234
Operating expenses									1,966,939	1,341,315	1,213,178
Foreign exchange (gains) losses									22,504	(37,568)	(28,243)
Interest expense									205,215	134,106	155,462
Total expenses									8,399,895	6,343,750	6,446,886
Provision for income tax									(19,161)	96,897	77,505
Net income (loss) attributable to ordinary shareholders									1,207,152	188,340	1,059,916
Net income (loss)	$ 228,550	$ 27,282	$ 915,039	$ 36,281	$ 139,499	$ 72,384	$ (279,260)	$ 255,717
Unrealized gains on held to maturity investment portfolio at time of transfer to available for sale, net of tax									0	424,861	0
Cumulative adjustments recorded to value of future policy benefit reserves, amount									170,688	(400,456)	(44,660)
Change in net unrealized gains (losses) on affiliate and other investments, net of tax									(6,074)	35,143	26,637
Change in OTTI losses recognized in other comprehensive income, net of tax									18,545	13,143	32,181
Change in underfunded pension liability									(3,852)	(7,550)	7,653
Change in value of cash flow hedge									(200)	255	439
Foreign currency translation adjustments									(25,315)	(25,729)	(54,858)
Comprehensive income (loss)									409,310	936,141	276,553
XL Group PLC
Condensed Financial Statements Captions [Line Items]
Net investment income									169	275	24
Total revenues									169	275	24
Operating expenses									46,340	9,646	11,699
Foreign exchange (gains) losses									(345)	127	243
Interest expense									11	5	2
Total expenses									46,006	9,778	11,944
Income (loss) before income tax									(45,837)	(9,503)	(11,920)
Equity in net earnings (losses) of subsidiaries (dividends were: 2015: $764,277; 2014: $858,521; 2013: $617,719)									1,253,609	197,843	1,071,836
Provision for income tax									620	0	0
Net income (loss) attributable to ordinary shareholders									1,207,152	188,340	1,059,916
Net income (loss)									1,207,152	188,340	1,059,916
Unrealized gains on held to maturity investment portfolio at time of transfer to available for sale, net of tax									0	424,861	0
Change in net unrealized gains (losses) on affiliate and other investments, net of tax									(6,074)	35,143	26,637
Change in OTTI losses recognized in other comprehensive income, net of tax									18,545	13,143	32,181
Change in underfunded pension liability									(3,852)	(7,550)	7,653
Change in value of cash flow hedge									(200)	255	439
Foreign currency translation adjustments									(25,315)	(25,729)	(54,858)
Comprehensive income (loss)									409,310	936,141	276,553
Parenthetical information, dividends:
Dividends received from subsidiaries									764,277	858,521	617,719
Dividends and Return of Capital Received From Subsidiary									829,000	940,000	702,000
Life Funds Withheld Assets [Member]
Condensed Financial Statements Captions [Line Items]
Net investment income									187,489	129,575	0
Change in net unrealized gains (losses) on investments, net of tax									(421,604)	274,083	0
Life Funds Withheld Assets [Member] | XL Group PLC
Condensed Financial Statements Captions [Line Items]
Change in net unrealized gains (losses) on investments, net of tax									(421,604)	274,083	0
Exclude Life Funds Withheld Assets [Member]
Condensed Financial Statements Captions [Line Items]
Net investment income									684,881	789,050	957,716
Change in net unrealized gains (losses) on investments, net of tax									(530,030)	434,051	(750,755)
Exclude Life Funds Withheld Assets [Member] | XL Group PLC
Condensed Financial Statements Captions [Line Items]
Change in net unrealized gains (losses) on investments, net of tax									(530,030)	434,051	(750,755)
Unrealized Gains (Losses) on Investments
Condensed Financial Statements Captions [Line Items]
Cumulative adjustments recorded to value of future policy benefit reserves, amount									170,700
Unrealized Gains (Losses) on Investments | XL Group PLC
Condensed Financial Statements Captions [Line Items]
Cumulative adjustments recorded to value of future policy benefit reserves, amount									$ 170,688	$ (400,456)	$ (44,660)