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HEALTH, SAFETY AND ENVIRONMENTAL MATTERS Table 2 - Accruals for Environmental Matters (Details) - USD ($)
$ in Thousands
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Accrual for Environmental Loss Contingencies, Balance Sheet Classification [Abstract]      
Accrued liabilities $ 5,371 $ 4,837  
Other long-term liabilities 3,002 3,101  
Accruals for environmental matters $ 8,373 $ 7,938 $ 7,753