DEBT (Summary of Standby Letters Of Credit) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Line of Credit Facility [Line Items]
Risk management insurance	$ 44,618	$ 43,731
Reclamation/restoration requirements	226,594	$ 226,565	$ 228,234
Standby Letters of Credit [Member]
Line of Credit Facility [Line Items]
Risk management insurance	33,111
Reclamation/restoration requirements	5,753
Total	$ 38,864