Taxation (Details) - Distribution of pre-tax income by jurisdiction and components of income tax (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Distribution of pre-tax income by jurisdiction:
U.S.	$ 52,258	$ (99,309)	$ 170,080
Non U.S.	712,158	(244,867)	636,038
Income (loss) before income taxes	764,416	(344,176)	806,118
Current expense:
U.S.	13,105	9,138	40,413
Non U.S.	44,475	87,220	35,113
Total current expense	57,580	96,358	75,526
Deferred expense (benefit):
U.S.	(56,646)	(5,550)	18,225
Non U.S.	33,094	(31,101)	68,986
Total deferred expense (benefit)	(23,552)	(36,651)	87,211
Total Tax Expense	$ 34,028	$ 59,707	$ 162,737