Annual report pursuant to Section 13 and 15(d)

Asset Retirement Obligations (Details)

v3.6.0.2
Asset Retirement Obligations (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Change in estimated liability $ (534) $ 2,101
Lost Creek Property    
Estimated Future Cash Undiscounted Amount 15,000  
Change in estimated liability $ 338 2,391
Lost Creek Property | Minimum    
Discount Rate Of Asset Retirement Obligations 0.10%  
Lost Creek Property | Maximum    
Discount Rate Of Asset Retirement Obligations 3.20%  
Path Finder Mines [Member]    
Estimated Future Cash Undiscounted Amount $ 11,500  
Change in estimated liability $ (872) $ (290)
Path Finder Mines [Member] | Minimum    
Discount Rate Of Asset Retirement Obligations 2.16%  
Path Finder Mines [Member] | Maximum    
Discount Rate Of Asset Retirement Obligations 3.00%