Taxation (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Current income tax expense [abstract]
Current income tax expense									$ 129,592	$ 144,865	$ 154,333
Deferred income tax expense (benefit) [abstract]
Deferred income tax (benefit) expense									(84,579)	55,457	(44,892)
Unrecognized tax expense (benefit) [abstract]
Unrecognized tax expense (benefit)	3,403				3,962				3,403	3,962	(40,469)
Total income tax expense [Abstract]
Total income tax expense	11,000	70,000	(75,000)	42,000	23,000	64,000	50,000	67,000	48,416	204,284	68,972
Income Before Taxes [Abstract]
Income (loss) before taxes									721,858	1,338,798	(451,319)
Reconciliation of effective tax rate (% of income (loss) before taxes)
Expected tax rate									0.00%	0.00%	0.00%
Foreign taxes at local expected tax rates									5.10%	14.60%	(7.20%)
Impact of foreign exchange (losses) gains									(1.10%)	(0.40%)	0.40%
Unrecognized tax benefit									0.50%	0.30%	9.00%
Tax-exempt income and expenses not deductible									(0.90%)	(0.30%)	(11.60%)
Impact of enacted changes in tax laws									1.80%	0.70%	0.00%
Foreign branch tax									(1.40%)	(0.70%)	(5.70%)
Valuation allowance									1.30%	1.20%	(1.90%)
Other									1.40%	(0.10%)	1.70%
Actual tax rate									6.70%	15.30%	(15.30%)
US [Member]
Current income tax expense [abstract]
Current income tax expense									55,993	29,196	82,065
Deferred income tax expense (benefit) [abstract]
Deferred income tax (benefit) expense									(13,693)	48,740	(36,780)
Unrecognized tax expense (benefit) [abstract]
Unrecognized tax expense (benefit)	(335)				(623)				(335)	(623)	81
Total income tax expense [Abstract]
Total income tax expense									41,965	77,313	45,366
Non-US [Member]
Current income tax expense [abstract]
Current income tax expense									73,599	115,669	72,268
Deferred income tax expense (benefit) [abstract]
Deferred income tax (benefit) expense									(70,886)	6,717	(8,112)
Unrecognized tax expense (benefit) [abstract]
Unrecognized tax expense (benefit)	3,738				4,585				3,738	4,585	(40,550)
Total income tax expense [Abstract]
Total income tax expense									6,451	126,971	23,606
Domestic (Bermuda)
Income Before Taxes [Abstract]
Income (loss) before taxes									611,900	661,648	(634,310)
Foreign
Income Before Taxes [Abstract]
Income (loss) before taxes									$ 109,958	$ 677,150	$ 182,991