REMEDIAL LIABILITIES (Changes in Remedial Liabilities) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Changes to remedial liabilities
Balance at the beginning of the period	$ 114,173	$ 121,017
Accretion	4,398	4,535
Changes in estimates recorded to consolidated statement of operations	4,130	(3,017)
Expenditures	(8,203)	(8,862)
Currency translation and other	315	500
Balance at the end of the period	114,813	114,173
Remedial Liabilities for Landfill Sites
Changes to remedial liabilities
Balance at the beginning of the period	1,851	1,838
Accretion	90	88
Changes in estimates recorded to consolidated statement of operations	(15)	(17)
Expenditures	(61)	(59)
Currency translation and other	0	1
Balance at the end of the period	1,865	1,851
Remedial Liabilities for Inactive Sites
Changes to remedial liabilities
Balance at the beginning of the period	61,991	65,315
Accretion	2,607	2,639
Changes in estimates recorded to consolidated statement of operations	2,873	(913)
Expenditures	(4,332)	(5,079)
Currency translation and other	(79)	29
Balance at the end of the period	63,060	61,991
Remedial Liabilities (Including Superfund) for Non-Landfill Operations
Changes to remedial liabilities
Balance at the beginning of the period	50,331	53,864
Accretion	1,701	1,808
Changes in estimates recorded to consolidated statement of operations	1,272	(2,087)
Expenditures	(3,810)	(3,724)
Currency translation and other	394	470
Balance at the end of the period	$ 49,888	$ 50,331