| Income Taxes - Components of Income Tax Expense (Benefit) (Details) - USD ($) $ in Thousands | 12 Months Ended | ||
|---|---|---|---|
| Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015 | |
| Components of Income Tax Expense (Benefit), Continuing Operations [Abstract] | |||
| Current | $ (12,786) | $ (71,768) | $ 288 | 
| Deferred | 217 | 28,392 | (203,272) | 
| Total income tax (benefit) | $ (12,569) | $ (43,376) | $ (202,984) | 
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- References No definition available. 
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- Definition Amount of current income tax expense (benefit) pertaining to taxable income (loss) from continuing operations. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition Amount of deferred income tax expense (benefit) pertaining to income (loss) from continuing operations. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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| X | ||||||||||
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- Definition Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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