COMMITMENTS AND CONTINGENCIES - Southbridge Landfill Environmental Remediation Liability (Details) - Southbridge Landfill - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	$ 4,596	$ 5,173
Accretion expense	30	34
Obligations incurred	27	0
Obligations settled	(12)	(141)
Ending balance	$ 4,641	$ 5,066

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.

+ References

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- Definition

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

+ References

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- Definition

Amount of cash outflow to settle environmental loss contingencies.

+ References

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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