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Discontinued Operations - Schedule of Assets and Liabilities Associated with the Mining Segment (Details) - USD ($)
$ in Thousands
3 Months Ended 12 Months Ended
Dec. 31, 2015
Dec. 31, 2017
Dec. 31, 2016
Discontinued Operations and Disposal Groups [Abstract]      
Performance bonds   $ 114 $ 114
Undeveloped mining claims  
Mining equipment  
Less accumulated depreciation of mining equipment  
Less write-down due to impairment $ (22,620)
Net book value of assets conveyed  
Total assets of discontinued operations   114 114
Asset retirement obligations assumed by Purchaser $ 204