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FAIR VALUE ACCOUNTING - Fair Value Measurements, Nonrecurring (Details)	Dec. 31, 2018 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
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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