STOCK BASED COMPENSATION - Stock Options (Details) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($) CAD / shares $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares	Dec. 31, 2014 USD ($) $ / shares shares	Dec. 31, 2013 USD ($) $ / shares shares	Dec. 31, 2012 $ / shares shares
STOCK BASED COMPENSATION
Stock options granted (in shares)		2,733,000	1,731,000	1,728,000
Exercise price of options granted (in dollars per share) | $ / shares		$ 1.03	$ 2.90	$ 2.26
Exercisable period of options		3 years 8 months 12 days
Number of shares of common stock reserved for issuance	17,500,000	17,500,000
Shares
Balance at the beginning of the period (in shares)		4,651,000	4,841,000	3,561,000
Granted (in shares)		2,733,000	1,731,000	1,728,000
Exercised (in shares)		(272,000)	(1,499,000)	(48,000)
Forfeited (in shares)		(158,000)	(422,000)	(400,000)
Balance at the end of the period (in shares)		6,954,000	4,651,000	4,841,000	3,561,000
Exercisable at the end of the period (in shares)	2,772,000	2,772,000
Weighted Average Exercise Price
Balance at the beginning of the period (in dollars per share) | $ / shares		$ 3.35	$ 2.96	$ 3.47
Granted (in dollars per share) | $ / shares		1.03	2.90	2.26
Exercised (in dollars per share) | $ / shares		1.29	1.29	1.97
Forfeited (in dollars per share) | $ / shares		2.82	4.39	4.57
Expired (in dollars per share) | $ / shares		2.12
Balance at the end of the period (in dollars per share) | $ / shares		2.49	$ 3.35	$ 2.96	$ 3.47
Exercisable (in dollars per share) | $ / shares	$ 3.80	$ 3.80
Weighted Average Remaining Contractual Life
Outstanding at the end of the period		4 years 1 month 6 days	4 years 4 months 24 days	5 years 2 months 12 days	6 years 7 months 6 days
Exercisable period of options		3 years 8 months 12 days
Intrinsic Value
Exercised (in dollars) | $			$ 438	$ 47
Outstanding at the end of the period (in dollars) | $	$ 98	$ 98
Exercisable at the end of the period (in dollars) | $	8	$ 8
Granted (in shares)		2,733,000	1,731,000	1,728,000
Principal assumptions used in applying the Black-Scholes option pricing model for the awards
Risk-free interest rate, low end of range (as a percent)		1.10%		0.50%
Risk-free interest rate, high end of range (as a percent)		1.79%		0.86%
Dividend yield (as a percent)			0.00%	0.00%
Volatility factor of the expected market price of common stock, low end of range (as a percent)		73.00%		66.00%
Volatility factor of the expected market price of common stock, high end of range (as a percent)		74.00%		69.00%
Risk-free interest rate (as a percent)		1.01%
Volatility factor of the expected market price of common stock (as a percent)			70.00%
Weighted-average expected life of option			3 years 6 months	3 years 6 months
Weighted-average grant date fair value (in dollars per share) | $ / shares		$ 0.49	$ 1.45	$ 1.02
Stock option expense | $		$ 1,300	$ 1,300	$ 1,400
Additional disclosures
Unrecognized compensation expense on non-vested stock options (in dollars) | $	$ 1,600	$ 1,600	$ 1,800
Non-vested stock options outstanding (in shares)		4,200,000	2,700,000
Weighted-average period of recognition		1 year 7 months 6 days	1 year 7 months 6 days	1 year 4 months 24 days
Minimum
Principal assumptions used in applying the Black-Scholes option pricing model for the awards
Dividend yield (as a percent)		0.00%
Weighted-average expected life of option		3 years 6 months
Maximum
STOCK BASED COMPENSATION
Maximum number of shares that may be subject to grants of options to an individual in a calendar year		1,000,000
Principal assumptions used in applying the Black-Scholes option pricing model for the awards
Dividend yield (as a percent)		1.15%
Minera Andes
Shares
Exercised (in shares)		(198,000)
Weighted Average Exercise Price
Exercised (in dollars per share) | CAD / shares	$ 1.96
Certain employees and directors
STOCK BASED COMPENSATION
Stock options granted (in shares)		2,700,000	1,700,000	1,700,000
Exercise price of options granted (in dollars per share) | $ / shares		$ 1.03	$ 2.90	$ 2.26
Shares
Granted (in shares)		2,700,000	1,700,000	1,700,000
Weighted Average Exercise Price
Granted (in dollars per share) | $ / shares		$ 1.03	$ 2.90	$ 2.26
Intrinsic Value
Granted (in shares)		2,700,000	1,700,000	1,700,000
Vesting period of options		3 years
Exercise period of options		5 years