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FAIR VALUE ACCOUNTING - Fair Value Measurements, Nonrecurring (Details) - USD ($) | 12 Months Ended |
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Dec. 31, 2017 | Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
United States Inflation Rate | 2.00% | 2.00%
Level 3 | Nichols Ranch Project and mineral properties in the ISR and Conventional segments |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Discount Rate | 10.00% |
United States Inflation Rate | 2.00% |
Level 3 | Nichols Ranch Project |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Discount Rate | 10.00% |
United States Inflation Rate | 2.00% |
Level 3 | Minimum | Nichols Ranch Project and mineral properties in the ISR and Conventional segments |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Short and Long Term Uranium Price | $ 38.90 |
Level 3 | Minimum | Nichols Ranch Project |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Short and Long Term Uranium Price | 37.95 |
Level 3 | Maximum | Nichols Ranch Project and mineral properties in the ISR and Conventional segments |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Short and Long Term Uranium Price | 62.10 |
Level 3 | Maximum | Nichols Ranch Project |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Short and Long Term Uranium Price | $ 65.00 |

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- Definition Interest rate used to find the present value of an amount to be paid or received in the future as an input to measure fair value. For example, but not limited to, weighted average cost of capital (WACC), cost of capital, cost of equity and cost of debt. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (bbb) -URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258 + Details
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