STOCK BASED COMPENSATION (Details)
 0 Months Ended 1 Months Ended 12 Months Ended 12 Months Ended 0 Months Ended 12 Months Ended
Oct. 19, 2006
Jan. 31, 2013
USD ($)
Dec. 31, 2013
USD ($)
Dec. 31, 2012
USD ($)
Dec. 31, 2011
USD ($)
Dec. 31, 2010
USD ($)
Jan. 19, 2012
Oct. 03, 2005
Oct. 02, 2005
Dec. 31, 2013
Minimum
Dec. 31, 2011
Minimum
Dec. 31, 2013
Maximum
Dec. 31, 2011
Maximum
Jan. 24, 2012
Minera Andes
CAD
Dec. 31, 2013
Minera Andes
USD ($)
Dec. 31, 2012
Minera Andes
USD ($)
Dec. 31, 2013
Certain employees and directors
USD ($)
Dec. 31, 2012
Certain employees and directors
USD ($)
Dec. 31, 2011
Certain employees and directors
USD ($)
STOCK BASED COMPENSATION                                      
Number of shares of common stock reserved for issuance 9,000,000           13,500,000 5,000,000 3,500,000                    
Number of shares increased under the US Gold Plan 4,000,000                                    
Maximum number of shares that may be subject to grants of options to an individual in a calendar year 1,000,000                                    
Shares                                      
Balance at the beginning of the period (in shares)   3,561,000 3,561,000 3,870,000 3,086,000                            
Granted (in shares)     1,728,000 300,000 947,000                       1,700,000 300,000 900,000
Exercised (in shares)   (1,000,000) (48,000) (445,000) (163,000)                 (45,000)          
Forfeited (in shares)     (400,000) (128,000)                              
Expired (in shares)       (36,000)                              
Balance at the end of the period (in shares)     4,841,000 3,561,000 3,870,000 3,086,000                          
Exercisable at the end of the period (in shares)     2,795,000                                
Weighted Average Exercise Price                                      
Balance at the beginning of the period (in dollars per share)   $ 3.47 $ 3.47 $ 3.24 $ 2.02                            
Granted (in dollars per share)     $ 2.26 $ 5.80 $ 7.10                       $ 2.26 $ 5.80 $ 7.10
Exercised (in dollars per share)     $ 1.97 $ 1.84 $ 2.52                 1.80          
Forfeited (in dollars per share)     $ 4.57 $ 6.27                              
Expired (in dollars per share)       $ 7.96                              
Balance at the end of the period (in dollars per share)     $ 2.96 $ 3.47 $ 3.24 $ 2.02                          
Exercisable (in dollars per share)     $ 2.83                                
Weighted Average Remaining Contractual Life                                      
Outstanding at the end of the period     5 years 2 months 12 days 6 years 7 months 6 days 7 years 3 months 18 days 7 years 7 months 6 days                          
Exercisable at the end of the period     5 years 3 months 18 days                                
Intrinsic Value                                      
Exercised (in dollars)     $ 47,000 $ 596,000 $ 864,000                            
Outstanding at the end of the period (in dollars)     1,190,000                                
Exercisable at the end of the period (in dollars)     1,190,000                                
Stock options granted (in shares)     1,728,000 300,000 947,000                       1,700,000 300,000 900,000
Exercise price of options granted (in dollars per share)     $ 2.26 $ 5.80 $ 7.10                       $ 2.26 $ 5.80 $ 7.10
Vesting period of options                                 3 years    
Exercise period of options                                 5 years 10 years 10 years
Principal assumptions used in applying the Black-Scholes option pricing model for the awards                                      
Risk-free interest rate (as a percent)       0.97%           0.50% 1.74% 0.86% 2.33%            
Volatility factor of the expected market price of common stock (as a percent)       75.00%           66.00% 90.00% 69.00% 100.00%            
Weighted-average expected life of option     3 years 6 months 6 years 6 years 7 months 6 days                            
Weighted-average grant date fair value (in dollars per share)     $ 1.02 $ 3.80 $ 4.86                            
Stock option expense     1,400,000 3,400,000 2,700,000                   200,000 1,300,000      
Additional disclosures                                      
Unrecognized compensation expense on non-vested stock options (in dollars)     $ 1,100,000                                
Non-vested stock options outstanding (in shares)     2,000,000                                
Weighted-average period of recognition     1 year 4 months 24 days