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COMMITMENTS AND CONTINGENCIES - Environmental Remediation Liability (Details) - Southbridge Landfill - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	$ 4,261	$ 4,596
Accretion expense	28	30
Obligations incurred	0	27
Obligations settled	0	(12)
Ending balance	$ 4,289	$ 4,641

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- Definition

Accrual For Environmental Loss Contingencies, Obligations Incurred

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- Definition

Total costs accrued as of the balance sheet date for environmental loss contingencies.

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Amount of expense for newly incurred environmental loss contingencies. Includes, but is not limited to, remediation expense and interest accretion.

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Amount of cash outflow to settle environmental loss contingencies.

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