Income Taxes (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Income Taxes
Income tax expense	$ 25,699us-gaap_IncomeTaxExpenseBenefit	$ 50,783us-gaap_IncomeTaxExpenseBenefit
Income (loss) before income taxes	(53,210)	125,752
Effective tax rate (as a percent)	(48.00%)	40.00%
Bermuda
Income Taxes
Income (loss) before income taxes	(13,662)	(5,315)
United States
Income Taxes
Income (loss) before income taxes	4,667	3,286
Effective tax rate (as a percent)	44.00%	45.00%
Foreign-other
Income Taxes
Income (loss) before income taxes	$ (44,215)	$ 127,781
Effective tax rate (as a percent)	0.00%
Statutory tax rate (as a percent)	0.00%
Ghana
Income Taxes
Effective tax rate (as a percent)	35.00%	35.00%

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Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Sum of operating profit and nonoperating income or expense before Income or Loss from equity method investments, income taxes, extraordinary items, and noncontrolling interest.

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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