Guarantor Financial Information Income Statement (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Revenues:
Net premiums earned		$ 2,532,212	$ 2,082,053	$ 4,886,822	$ 3,416,053
Net investment income		215,388	223,204	421,274	431,717
Total net realized gains (losses) on investments		104,617	49,967	197,367	102,858
Net realized and unrealized gains (losses) on derivative instruments		906	48,509	(2,716)	65,030
Income (loss) from investment fund affiliates		13,179	31,377	8,600	66,706
Fee income and other		10,862	11,012	19,124	15,740
Total revenues		2,647,422	2,685,296	5,064,649	4,107,911
Expenses:
Net losses and loss expenses incurred		1,632,386	1,151,195	3,014,871	1,921,022
Claims and policy benefits		5,482	22,081	10,419	41,468
Acquisition costs	[1]	420,520	341,617	823,787	495,313
Operating expenses		522,521	507,354	1,037,902	833,010
Exchange (gains) losses		(19,100)	10,374	(52,919)	37,764
Interest expense		55,738	49,667	108,041	101,105
Total expenses		2,617,547	2,082,288	4,942,101	3,429,682
Income (loss) before income tax and income (loss) from operating affiliates		29,875	603,008	122,548	678,229
Income (loss) from operating affiliates		21,418	9,462	34,068	32,130
Gain on sale of operating affiliate		0	340,407	0	340,407
Equity in net earnings (losses) of subsidiaries		0	0	0	0
Provision (benefit) for income tax		2,467	32,959	24,762	57,177
Net income (loss)		48,826	919,918	131,854	993,589
Non-controlling interests		5,044	4,879	66,187	42,269
Net income (loss) attributable to ordinary shareholders		43,782	915,039	65,667	951,320
Comprehensive income (loss)		357,812	286,043	787,638	543,036
Consolidating Adjustments and Eliminations
Revenues:
Net premiums earned		0	0	0	0
Net investment income		481	464	1,162	2,248
Total net realized gains (losses) on investments		367	2,479	1,900	1,264
Net realized and unrealized gains (losses) on derivative instruments		0	0	0	0
Income (loss) from investment fund affiliates		0	0	0	0
Fee income and other		0	0	0	0
Total revenues		848	2,943	3,062	3,512
Expenses:
Net losses and loss expenses incurred		0	0	0	0
Claims and policy benefits		0	0	0	0
Acquisition costs		0	0	0	0
Operating expenses		0	0	0	0
Exchange (gains) losses		0	0	0	0
Interest expense		0	0	0	0
Total expenses		0	0	0	0
Income (loss) before income tax and income (loss) from operating affiliates		848	2,943	3,062	3,512
Income (loss) from operating affiliates		0	0	0	0
Gain on sale of operating affiliate		0	0	0	0
Equity in net earnings (losses) of subsidiaries		(120,854)	(1,794,694)	(240,071)	(2,007,605)
Provision (benefit) for income tax		0	0	0	0
Net income (loss)		(120,006)	(1,791,751)	(237,009)	(2,004,093)
Non-controlling interests		0	0	0	0
Net income (loss) attributable to ordinary shareholders		(120,006)	(1,791,751)	(237,009)	(2,004,093)
Comprehensive income (loss)		(748,066)	(533,759)	(1,680,951)	(1,187,525)
XL- Ireland
Revenues:
Net premiums earned		0	0	0	0
Net investment income		64	54	177	134
Total net realized gains (losses) on investments		0	0	0	0
Net realized and unrealized gains (losses) on derivative instruments		0	0	0	0
Income (loss) from investment fund affiliates		0	0	0	0
Fee income and other		0	0	0	0
Total revenues		64	54	177	134
Expenses:
Net losses and loss expenses incurred		0	0	0	0
Claims and policy benefits		0	0	0	0
Acquisition costs		0	0	0	0
Operating expenses		(499)	2,954	2,775	5,716
Exchange (gains) losses		(470)	(9)	(453)	(271)
Interest expense		(9)	1	(15)	1
Total expenses		(978)	2,946	2,307	5,446
Income (loss) before income tax and income (loss) from operating affiliates		1,042	(2,892)	(2,130)	(5,312)
Income (loss) from operating affiliates		0	0	0	0
Gain on sale of operating affiliate		0	0	0	0
Equity in net earnings (losses) of subsidiaries		42,740	917,931	67,177	956,416
Provision (benefit) for income tax		0	0	(620)	(216)
Net income (loss)		43,782	915,039	65,667	951,320
Non-controlling interests		0	0	0	0
Net income (loss) attributable to ordinary shareholders		43,782	915,039	65,667	951,320
Comprehensive income (loss)		357,812	286,043	787,638	543,036
XL-Cayman
Revenues:
Net premiums earned		0	0	0	0
Net investment income		3,096	2,668	4,881	5,700
Total net realized gains (losses) on investments		976	2,532	1,253	3,801
Net realized and unrealized gains (losses) on derivative instruments		0	76,065	0	12,365
Income (loss) from investment fund affiliates		0	0	0	0
Fee income and other		0	0	0	0
Total revenues		4,072	81,265	6,134	21,866
Expenses:
Net losses and loss expenses incurred		0	0	0	0
Claims and policy benefits		0	0	0	0
Acquisition costs		0	0	0	0
Operating expenses		1,071	2,442	2,566	5,442
Exchange (gains) losses		(136)	(51)	(172)	(18)
Interest expense		35,177	34,701	70,346	72,474
Total expenses		36,112	37,092	72,740	77,898
Income (loss) before income tax and income (loss) from operating affiliates		(32,040)	44,173	(66,606)	(56,032)
Income (loss) from operating affiliates		0	0	0	0
Gain on sale of operating affiliate		0	0	0	0
Equity in net earnings (losses) of subsidiaries		78,114	876,763	172,894	1,051,189
Provision (benefit) for income tax		0	0	0	245
Net income (loss)		46,074	920,936	106,288	994,912
Non-controlling interests		3,334	3,005	39,111	38,496
Net income (loss) attributable to ordinary shareholders		42,740	917,931	67,177	956,416
Comprehensive income (loss)		356,770	288,935	789,148	548,132
Other XL-Ireland Subsidiaries
Revenues:
Net premiums earned		2,532,212	2,082,053	4,886,822	3,416,053
Net investment income		211,747	220,018	415,054	423,635
Total net realized gains (losses) on investments		103,274	44,956	194,214	97,793
Net realized and unrealized gains (losses) on derivative instruments		906	(27,556)	(2,716)	52,665
Income (loss) from investment fund affiliates		13,179	31,377	8,600	66,706
Fee income and other		10,862	11,012	19,124	15,740
Total revenues		2,642,438	2,601,034	5,055,276	4,082,399
Expenses:
Net losses and loss expenses incurred		1,632,386	1,151,195	3,014,871	1,921,022
Claims and policy benefits		5,482	22,081	10,419	41,468
Acquisition costs		420,520	341,617	823,787	495,313
Operating expenses		521,949	501,958	1,032,561	821,852
Exchange (gains) losses		(18,494)	10,434	(52,294)	38,053
Interest expense		20,570	14,965	37,710	28,630
Total expenses		2,582,413	2,042,250	4,867,054	3,346,338
Income (loss) before income tax and income (loss) from operating affiliates		60,025	558,784	188,222	736,061
Income (loss) from operating affiliates		21,418	9,462	34,068	32,130
Gain on sale of operating affiliate		0	340,407	0	340,407
Equity in net earnings (losses) of subsidiaries		0	0	0	0
Provision (benefit) for income tax		2,467	32,959	25,382	57,148
Net income (loss)		78,976	875,694	196,908	1,051,450
Non-controlling interests		1,710	1,874	27,076	3,773
Net income (loss) attributable to ordinary shareholders		77,266	873,820	169,832	1,047,677
Comprehensive income (loss)		391,296	244,824	891,803	639,393
Life Funds Withheld Assets
Revenues:
Net investment income		39,146	46,864	80,706	97,283
Net realized and unrealized gains (losses) on derivative instruments		(229,742)	239,174	(465,822)	9,807
Life Funds Withheld Assets | Consolidating Adjustments and Eliminations
Revenues:
Net realized and unrealized gains (losses) on derivative instruments		0	0		0
Life Funds Withheld Assets | XL- Ireland
Revenues:
Net realized and unrealized gains (losses) on derivative instruments		0	0		0
Life Funds Withheld Assets | XL-Cayman
Revenues:
Net realized and unrealized gains (losses) on derivative instruments		0	0		0
Life Funds Withheld Assets | Other XL-Ireland Subsidiaries
Revenues:
Net realized and unrealized gains (losses) on derivative instruments		$ (229,742)	$ 239,174	$ (465,822)	$ 9,807

[1] The Company has reflected the amortization of certain fair value adjustments recorded in conjunction with the Catlin Acquisition within the respective segments.