Quarterly report pursuant to Section 13 or 15(d)

Mineral Properties - rollforward (Details)

v3.19.3
Mineral Properties - rollforward (Details) - USD ($)
$ in Thousands
 9 Months Ended 12 Months Ended
Sep. 30, 2019
Dec. 31, 2018
Balance at beginning of period $ 45,805  
Acquisition costs 8  
Change in estimated reclamation costs (59) $ 2,840
Property write-offs (11)  
Amortization (1,952)  
Balance at end of period 43,791 45,805
Lost Creek Project    
Balance at beginning of period 12,644  
Property write-offs 16  
Amortization (1,952)  
Balance at end of period 10,708 12,644
Pathfinder properties    
Balance at beginning of period 19,964  
Change in estimated reclamation costs (59)  
Balance at end of period 19,905 19,964
Other U.S. Properties [Member]    
Balance at beginning of period 13,197  
Acquisition costs 8  
Property write-offs (27)  
Balance at end of period $ 13,178 $ 13,197