CLOSURE AND POST-CLOSURE LIABILITIES (Changes in Post-Closure Liabilities) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Changes to post-closure liabilities
Balance at the beginning of the period	$ 69,931	$ 61,037
Liabilities assumed in acquisitions	220	685
New asset retirement obligations	2,705	2,518
Accretion	5,601	5,104
Changes in estimates recorded to consolidated statement of operations	2,685	1,460
Changes in estimates recorded to consolidated balance sheet	3,865	1,931
Expenditures	(9,839)	(2,281)
Currency translation and other	483	(523)
Balance at the end of the period	75,651	69,931
Increase in facility closure costs	2,300	1,200
Landfill Retirement Liability
Changes to post-closure liabilities
Balance at the beginning of the period	37,809	32,382
Liabilities assumed in acquisitions	0	0
New asset retirement obligations	2,705	2,518
Accretion	2,772	2,537
Changes in estimates recorded to consolidated statement of operations	248	(37)
Changes in estimates recorded to consolidated balance sheet	3,303	1,867
Expenditures	(7,718)	(1,224)
Currency translation and other	282	(234)
Balance at the end of the period	39,401	37,809
Non-Landfill Retirement Liability
Changes to post-closure liabilities
Balance at the beginning of the period	32,122	28,655
Liabilities assumed in acquisitions	220	685
New asset retirement obligations	0	0
Accretion	2,829	2,567
Changes in estimates recorded to consolidated statement of operations	2,437	1,497
Changes in estimates recorded to consolidated balance sheet	562	64
Expenditures	(2,121)	(1,057)
Currency translation and other	201	(289)
Balance at the end of the period	$ 36,250	$ 32,122