ASSET RETIREMENT OBLIGATIONS (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
ASSET RETIREMENT OBLIGATIONS
Surety bonds outstanding to performance of reclamation obligations	$ 88,700,000	$ 76,000,000
Estimated payments of asset retirement obligations:
2014	2,091,000
2015	2,630,000
2016	8,072,000
2017	447,000
2018	1,036,000
Thereafter	145,122,000
Aggregate undiscounted asset retirement obligations	159,398,000
Effect of discounting	(76,500,000)	70,700,000
Total asset retirement obligations	82,898,000	84,836,000	72,342,000
Less: current portion	(2,091,000)
Asset retirement obligations	$ 80,807,000	$ 81,644,000