Taxation (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Current income tax expense [abstract]
Current income tax expense									$ 144,865	$ 154,333	$ 64,886
Deferred income tax expense (benefit) [abstract]
Deferred income tax expense									55,457	(44,892)	51,726
Unrecognized tax expense (benefit) [abstract]
Unrecognized tax expense (benefit)	3,962				(40,469)				3,962	(40,469)	12,172
Total income tax expense (benefit) [Abstract]
Total income tax expense	22,800	64,100	50,100	67,200	3,300	41,800	50,100	(26,300)	204,284	68,972	128,784
Income (loss) before taxes
Income (loss) before taxes									1,338,798	(451,319)	981,336
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									14.60%	(7.20%)	14.90%
Impact of foreign exchange gains									(0.40%)	0.40%	(3.40%)
Unrecognized tax benefit									0.30%	9.00%	1.20%
Tax-exempt income and expenses not deductible									(0.30%)	(11.60%)	(0.70%)
Impact of enacted changes in tax rates									0.70%	0.00%	(1.90%)
Foreign branch tax									(0.70%)	(5.70%)	(0.20%)
Valuation allowance									1.20%	(1.90%)	2.00%
Other									(0.10%)	1.70%	1.20%
Actual tax rate									15.30%	(15.30%)	13.10%
[UsMember]
Current income tax expense [abstract]
Current income tax expense									29,196	82,065	28,180
Deferred income tax expense (benefit) [abstract]
Deferred income tax expense									48,740	(36,780)	46,988
Unrecognized tax expense (benefit) [abstract]
Unrecognized tax expense (benefit)	(623)				81				(623)	81	0
Total income tax expense (benefit) [Abstract]
Total income tax expense									77,313	45,366	75,168
[NonUsMember]
Current income tax expense [abstract]
Current income tax expense									115,669	72,268	36,706
Deferred income tax expense (benefit) [abstract]
Deferred income tax expense									6,717	(8,112)	4,738
Unrecognized tax expense (benefit) [abstract]
Unrecognized tax expense (benefit)	4,585				(40,550)				4,585	(40,550)	12,172
Total income tax expense (benefit) [Abstract]
Total income tax expense									126,971	23,606	53,616
[DomesticCountryMember]
Income (loss) before taxes
Income (loss) before taxes									661,648	(634,310)	441,074
[ForeignCountryMember]
Income (loss) before taxes
Income (loss) before taxes									$ 677,150	$ 182,991	$ 540,262