| Significant Accounting Policies - Schedule of Other Liabilities (Long-term) (Details) - USD ($) $ in Thousands | Dec. 31, 2018 | Dec. 31, 2017 | 
|---|---|---|
| Other Liabilities Disclosure [Abstract] | ||
| Apache lawsuit | $ 49,500 | $ 49,500 | 
| Uncertain tax positions including interest/penalties | 11,523 | 11,015 | 
| Dispute related to royalty deductions | 4,787 | |
| Dispute related to royalty-in-kind | 2,135 | 914 | 
| Other | 745 | 5,437 | 
| Total other liabilities (long-term) | $ 68,690 | $ 66,866 | 
| X | ||||||||||
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- Definition Amount recognized for uncertainty in income taxes classified as noncurrent. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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- Definition Amount of loss contingency liability. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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| X | ||||||||||
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- Definition Amount of expenses incurred but not yet paid classified as other, due after one year or the normal operating cycle, if longer. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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- References No definition available. 
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- Definition Amount of liabilities classified as other, due after one year or the normal operating cycle, if longer. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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| X | ||||||||||
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- Definition Dispute related to royalty deductions noncurrent. No definition available. 
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| X | ||||||||||
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- Definition Dispute related to royalty-in-kind non current. No definition available. 
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