Income Taxes (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Income Taxes
Income tax expense	$ 46,253	$ 22,521	$ 90,344	$ 38,807
Income (loss) before income taxes	(24,563)	(2,322)	39,622	(23,577)
Effective tax rate (as a percent)	(188.00%)	(970.00%)	228.00%	(165.00%)
Bermuda
Income Taxes
Income (loss) before income taxes	(6,663)	(3,251)	(13,440)	(6,419)
United States
Income Taxes
Income (loss) before income taxes	2,903	3,035	5,273	6,347
Effective tax rate (as a percent)	274.00%	277.00%	167.00%	152.00%
Foreign-other
Income Taxes
Income (loss) before income taxes	$ (20,803)	$ (2,106)	$ 47,789	$ (23,505)
Effective tax rate (as a percent)			0.00%
Statutory rate (as a percent)			0.00%
Ghana
Income Taxes
Effective tax rate (as a percent)	34.00%	38.00%	36.00%	36.00%