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ASSET RETIREMENT OBLIGATIONS (Asset Retirement Obligations Operating Costs) (Details) - USD ($)
$ in Thousands
3 Months Ended
Mar. 31, 2017
Mar. 31, 2016
ASSET RETIREMENT OBLIGATIONS [Abstract]    
Accretion $ 2,882 $ 2,755
Depreciation 1,632 1,693
Total $ 4,514 $ 4,448