v3.19.1

COMMITMENTS AND CONTINGENCIES (Narrative) (Details) - USD ($) | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Loss Contingencies [Line Items] |  |  |
loss contingency recorded | $ 0 |  |
Future Operating Lease Commitments |  |  |
Operating Lease, Contract Term, Maximum (in years) | 20 years |  |
Reclamation Deposits and Surety Bonds |  |  |
Security placed with the State of Utah and the BLM | $ 19,000,000 | $ 18,800,000 |
Long-term restricted cash deposits | 482,000 | 481,000 | $ 3,481,000
Surety bonds issued by an insurer | 18,500,000 | $ 18,300,000 |
Minimum [Member] |  |  |
Loss Contingencies [Line Items] |  |  |
Estimate of possible Loss | 22,000,000 |  |
Maximum [Member] |  |  |
Loss Contingencies [Line Items] |  |  |
Estimate of possible Loss | $ 28,000,000 |  |

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