Taxation (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Current income tax expense (benefit) [abstract]
Current income tax									$ 154,333	$ 64,886	$ 91,000
Deferred income tax expense (benefit) [abstract]
Deferred income tax									(44,892)	51,726	170,420
Unrecognized tax expense (benefit)	(40,469)				12,172				(40,469)	12,172	670
Total income tax expense (benefit) [Abstract]
Total income tax expense (benefit)	3,300	41,800	50,100	(26,300)	10,900	72,600	17,800	27,600	68,972	128,784	262,090
Income Before Taxes [Abstract]
(Loss) income before taxes									(451,319)	981,336	1,798,944
Reconciliation of effective tax rate (% of (loss) income before taxes)
Expected tax rate									0.00%	0.00%	0.00%
Foreign taxes at local expected tax rates									(7.20%)	14.90%	14.20%
Impact of foreign exchange gains									0.40%	(3.40%)	(0.40%)
Unrecognized tax benefit									9.00%	1.20%	0.00%
Tax-exempt income and expenses not deductible									(11.60%)	(0.70%)	(1.20%)
Impact of enacted changes in tax rates									0.00%	(1.90%)	(0.10%)
Foreign branch tax									(5.70%)	(0.20%)	1.80%
Valuation allowance									(1.90%)	2.00%	0.00%
Other									1.70%	1.20%	0.30%
Actual tax rate									(15.30%)	13.10%	14.60%
[UsMember]
Current income tax expense (benefit) [abstract]
Current income tax									82,065	28,180	43,020
Deferred income tax expense (benefit) [abstract]
Deferred income tax									(36,780)	46,988	83,583
Unrecognized tax expense (benefit)	81				0				81	0	(461)
Total income tax expense (benefit) [Abstract]
Total income tax expense (benefit)									45,366	75,168	126,142
[NonUsMember]
Current income tax expense (benefit) [abstract]
Current income tax									72,268	36,706	47,980
Deferred income tax expense (benefit) [abstract]
Deferred income tax									(8,112)	4,738	86,837
Unrecognized tax expense (benefit)	(40,550)				12,172				(40,550)	12,172	1,131
Total income tax expense (benefit) [Abstract]
Total income tax expense (benefit)									23,606	53,616	135,948
[DomesticCountryMember]
Income Before Taxes [Abstract]
(Loss) income before taxes									(634,310)	441,074	895,663
[ForeignCountryMember]
Income Before Taxes [Abstract]
(Loss) income before taxes									$ 182,991	$ 540,262	$ 903,281