Quarterly report pursuant to Section 13 or 15(d)

Restricted Cash (Details)

v3.5.0.2
Restricted Cash (Details) - USD ($)
$ in Thousands
Jun. 30, 2016
Dec. 31, 2015
Restricted Cash    
Non-current restricted cash $ 7,557 $ 7,557
Surety Bond [Member]    
Restricted Cash    
Reclamation bonding requirement 27,400  
Certificate of deposit [Member]    
Restricted Cash    
Non-current restricted cash 100 100
Money Market Funds [Member]    
Restricted Cash    
Non-current restricted cash 7,457 $ 7,457
Money Market Funds [Member] | Surety Bond [Member]    
Restricted Cash    
Restricted cash pledged as collateral $ 7,500