COMMITMENTS AND CONTINGENCIES (Details) - USD ($) $ in Millions |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2020 |
Dec. 31, 2019 |
Dec. 31, 2018 |
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| Commitments and Contingencies Disclosure [Abstract] | |||
| Undelivered feedstock | $ 9.2 | $ 12.4 | |
| Shortfall fee expenses | 1.1 | 0.6 | $ 0.5 |
| Mine closure and environmental | $ 0.9 | $ 0.9 | $ 0.7 |
| X | ||||||||||
- Definition Shortfall Fee Expenses No definition available.
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| X | ||||||||||
- References No definition available.
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| X | ||||||||||
- Definition The charge against earnings in the period for known or estimated future costs arising from requirements to perform environmental remediation activities. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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| X | ||||||||||
- Definition Amount of the unrecorded obligation to transfer funds in the future for fixed or minimum amounts or quantities of goods or services at fixed or minimum prices (for example, as in take-or-pay contracts or throughput contracts). Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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