Long-term Supply Contract (Details) - USD ($) $ in Thousands |
Dec. 31, 2017 |
Dec. 31, 2016 |
Jul. 30, 2014 |
|---|---|---|---|
| Commitments and Contingencies Disclosure [Abstract] | |||
| Supply agreement liability | $ 22,250 | $ 23,888 | $ 27,300 |
| X | ||||||||||
- Definition Long-term Supply Commitment, Amount No definition available.
|
| X | ||||||||||
- References No definition available.
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