Quarterly report pursuant to Section 13 or 15(d)

Restricted Cash (Details)

v3.3.0.814
Restricted Cash (Details) - USD ($)
$ in Thousands
Sep. 30, 2015
Dec. 31, 2014
Restricted Cash and Cash Equivalents Items [Line Items]    
Non-current restricted cash $ 7,557 $ 7,556
Surety Bond [Member]    
Restricted Cash and Cash Equivalents Items [Line Items]    
Reclamation bonding requirement 26,700  
Money Market Funds [Member]    
Restricted Cash and Cash Equivalents Items [Line Items]    
Non-current restricted cash 7,457 7,456
Money Market Funds [Member] | Surety Bond [Member]    
Restricted Cash and Cash Equivalents Items [Line Items]    
Restricted cash pledged as collateral 7,500  
Certificate of deposit [Member]    
Restricted Cash and Cash Equivalents Items [Line Items]    
Non-current restricted cash $ 100 $ 100