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SUPPLEMENTAL FINANCIAL INFORMATION - Schedule of Other Nonoperating Income (Expense) (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract] |  |  |
Interest income | $ 482 | $ 336 | $ 161
Change in value of investments accounted for at fair value | (153) | 769 | 509
Change in value of warrant liabilities | 3,726 | (3,469) | 784
Change in value of Convertible Debentures | 291 | (612) | (940)
Foreign exchange loss | (46) | 0 | 0
Sales and property tax refunds | 0 | 341 | 0
Sale of surplus assets | 0 | 293 | 1,913
Other | (322) | 14 | 142
Other income (loss) | $ 3,978 | $ (2,328) | $ 2,569

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