Guarantor Financial Information Income Statement (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2017		Mar. 31, 2016
Revenues:
Net premiums earned		$ 2,522,791		$ 2,354,610
Net investment income		200,532		205,886
Total net realized gains (losses) on investments		37,286		92,750
Net realized and unrealized gains (losses) on derivative instruments		(7,069)		(3,622)
Income (loss) from investment fund affiliates		38,261		(4,579)
Fee income and other		13,661		8,262
Total revenues		2,755,361		2,417,227
Expenses:
Net losses and loss expenses incurred		1,583,456		1,382,485
Claims and policy benefits		7,291		4,937
Acquisition costs		435,869		403,267
Operating expenses		468,038		515,381
Exchange (gains) losses		(3,336)		(33,819)
Loss (gain) on sale of subsidiary		0
Interest expense		50,711		52,303
Total expenses		2,542,029		2,324,554
Income (loss) before income tax and income (loss) from operating affiliates		213,332		92,673
Income (loss) from operating affiliates		13,609		12,650
Gain on sale of operating affiliate		0		0
Equity in net earnings (losses) of subsidiaries		0		0
Provision (benefit) for income tax		13,092		22,295
Net income (loss)		213,849		83,028
Non-controlling interests		61,006		61,143
Net income (loss) attributable to common shareholders		152,843		21,885
Comprehensive income (loss)		282,271		429,826
Life Funds Withheld Assets
Revenues:
Net investment income		33,364		41,560
Net realized and unrealized gains (losses) on derivative instruments		(50,101)		(236,080)
Consolidating Adjustments and Eliminations
Revenues:
Net premiums earned		0		0
Net investment income		(83)		681
Total net realized gains (losses) on investments		0		1,533
Net realized and unrealized gains (losses) on derivative instruments		0		0
Income (loss) from investment fund affiliates		0		0
Fee income and other		0		0
Total revenues		(83)		2,214
Expenses:
Net losses and loss expenses incurred		0		0
Claims and policy benefits		0		0
Acquisition costs		0		0
Operating expenses		0		0
Exchange (gains) losses		0		0
Loss (gain) on sale of subsidiary		0
Interest expense		0		0
Total expenses		0		0
Income (loss) before income tax and income (loss) from operating affiliates		(83)		2,214
Income (loss) from operating affiliates		0		0
Gain on sale of operating affiliate		0		0
Equity in net earnings (losses) of subsidiaries		(408,642)		(119,217)
Provision (benefit) for income tax		0		0
Net income (loss)		(408,725)		(117,003)
Non-controlling interests		(83)		0
Net income (loss) attributable to common shareholders		(408,642)		(117,003)
Comprehensive income (loss)		(667,498)		(932,885)
Consolidating Adjustments and Eliminations | Life Funds Withheld Assets
Revenues:
Net realized and unrealized gains (losses) on derivative instruments		0		0
XL- Bermuda/Ireland
Revenues:
Net premiums earned		0	[1]	0
Net investment income		83	[1]	113
Total net realized gains (losses) on investments		0	[1]	0
Net realized and unrealized gains (losses) on derivative instruments		0	[1]	0
Income (loss) from investment fund affiliates		0	[1]	0
Fee income and other		0	[1]	0
Total revenues		83	[1]	113
Expenses:
Net losses and loss expenses incurred		0	[1]	0
Claims and policy benefits		0	[1]	0
Acquisition costs		0	[1]	0
Operating expenses		16,180	[1]	3,274
Exchange (gains) losses		176	[1]	17
Loss (gain) on sale of subsidiary	[1]	0
Interest expense		0	[1]	(6)
Total expenses		16,356	[1]	3,285
Income (loss) before income tax and income (loss) from operating affiliates		(16,273)	[1]	(3,172)
Income (loss) from operating affiliates		0	[1]	0
Gain on sale of operating affiliate		0	[1]	0
Equity in net earnings (losses) of subsidiaries		169,116	[1]	24,437
Provision (benefit) for income tax		0	[1]	(620)
Net income (loss)		152,843	[1]	21,885
Non-controlling interests		0	[1]	0
Net income (loss) attributable to common shareholders		152,843	[1]	21,885
Comprehensive income (loss)		282,271	[1]	429,826
XL- Bermuda/Ireland | Life Funds Withheld Assets
Revenues:
Net realized and unrealized gains (losses) on derivative instruments		0	[1]	0
XL-Cayman
Revenues:
Net premiums earned		0		0
Net investment income		2,313		1,785
Total net realized gains (losses) on investments		(777)		277
Net realized and unrealized gains (losses) on derivative instruments		0		0
Income (loss) from investment fund affiliates		0		0
Fee income and other		0		0
Total revenues		1,536		2,062
Expenses:
Net losses and loss expenses incurred		0		0
Claims and policy benefits		0		0
Acquisition costs		0		0
Operating expenses		509		1,495
Exchange (gains) losses		1		(36)
Loss (gain) on sale of subsidiary		0
Interest expense		35,147		35,169
Total expenses		35,657		36,628
Income (loss) before income tax and income (loss) from operating affiliates		(34,121)		(34,566)
Income (loss) from operating affiliates		0		0
Gain on sale of operating affiliate		0		0
Equity in net earnings (losses) of subsidiaries		239,526		94,780
Provision (benefit) for income tax		0		0
Net income (loss)		205,405		60,214
Non-controlling interests		36,289		35,777
Net income (loss) attributable to common shareholders		169,116		24,437
Comprehensive income (loss)		298,544		432,378
XL-Cayman | Life Funds Withheld Assets
Revenues:
Net realized and unrealized gains (losses) on derivative instruments		0		0
Other XL Subsidiaries
Revenues:
Net premiums earned		2,522,791		2,354,610
Net investment income		198,219		203,307
Total net realized gains (losses) on investments		38,063		90,940
Net realized and unrealized gains (losses) on derivative instruments		(7,069)		(3,622)
Income (loss) from investment fund affiliates		38,261		(4,579)
Fee income and other		13,661		8,262
Total revenues		2,753,825		2,412,838
Expenses:
Net losses and loss expenses incurred		1,583,456		1,382,485
Claims and policy benefits		7,291		4,937
Acquisition costs		435,869		403,267
Operating expenses		451,349		510,612
Exchange (gains) losses		(3,513)		(33,800)
Loss (gain) on sale of subsidiary		0
Interest expense		15,564		17,140
Total expenses		2,490,016		2,284,641
Income (loss) before income tax and income (loss) from operating affiliates		263,809		128,197
Income (loss) from operating affiliates		13,609		12,650
Gain on sale of operating affiliate		0		0
Equity in net earnings (losses) of subsidiaries		0		0
Provision (benefit) for income tax		13,092		22,915
Net income (loss)		264,326		117,932
Non-controlling interests		24,800		25,366
Net income (loss) attributable to common shareholders		239,526		92,566
Comprehensive income (loss)		368,954		500,507
Other XL Subsidiaries | Life Funds Withheld Assets
Revenues:
Net realized and unrealized gains (losses) on derivative instruments		$ (50,101)		$ (236,080)

[1] Results for the period include XL-Ireland, which prior to the Redomestication was the ultimate parent and is now in liquidation proceedings as outlined in Note 1, "Significant Accounting Policies." The Company expects the net assets of XL-Ireland to ultimately be distributed to XL-Bermuda upon completion of the liquidation.