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ASSET RETIREMENT OBLIGATIONS (Asset Retirement Obligations Operating Costs) (Details) - USD ($)
$ in Thousands
3 Months Ended 9 Months Ended
Sep. 30, 2021
Sep. 30, 2020
Sep. 30, 2021
Sep. 30, 2020
ASSET RETIREMENT OBLIGATIONS [Abstract]        
Accretion $ 3,341 $ 3,115 $ 9,796 $ 9,270
Depreciation 2,916 2,123 8,241 6,022
Total $ 6,257 $ 5,238 $ 18,037 $ 15,292