Annual report pursuant to Section 13 and 15(d)

Mineral Properties - rollforward (Details)

v3.6.0.2
Mineral Properties - rollforward (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Balance at beginning of period $ 50,610 $ 52,750  
Change in estimated reclamation costs (Note 13) (534) 2,101  
Write-off of mineral properties (note 7) (62)   $ (483)
Amortization (2,985) (4,241)  
Balance at end of period 47,029 50,610 52,750
Lost Creek Property      
Balance at beginning of period 16,662 18,512  
Change in estimated reclamation costs (Note 13) 338 2,391  
Amortization (2,985) (4,241)  
Balance at end of period 14,015 16,662 18,512
Path Finder Mines [Member]      
Balance at beginning of period 20,738 21,028  
Change in estimated reclamation costs (Note 13) (872) (290)  
Balance at end of period 19,866 20,738 21,028
Other U.S. Properties [Member]      
Balance at beginning of period 13,210 13,210  
Write-off of mineral properties (note 7) (62)    
Balance at end of period $ 13,148 $ 13,210 $ 13,210