SIGNIFICANT ACCOUNTING POLICIES - Landfill Accounting (Details) $ in Millions	12 Months Ended
	Dec. 31, 2021 USD ($) cubic_yard cubicYard landfill_site	Dec. 31, 2020 USD ($) cubicYard cubic_yard landfill_site	Dec. 31, 2019 USD ($) cubicYard cubic_yard
Property, Plant and Equipment [Line Items]
Landfill sites | landfill_site	9
Permitted, but not highly probable airspace (cubic yards)	0	0
Remaining Airspace Capacity [Roll Forward]
Remaining capacity, beginning of period (cubic yards)	24,716,000	28,494,000	29,760,000
Changes in highly probable airspace, net (cubic yards)	0	(2,962,000)	0
Consumed (cubic yards)	(932,000)	(816,000)	(1,266,000)
Remaining capacity, end of period (cubic yards)	23,784,000	24,716,000	28,494,000
Number of landfill sites closed during period | landfill_site		2
Landfill final closure and post-closure liabilities | $	$ 53.4	$ 48.4
Regulatory post-closure period for landfill (in years)	30 years
Asset retirement obligations, inflation rate (as a percent)	1.02%	1.02%
Asset retirement obligations, risk free rate (as a percent)	4.84%	5.60%
Non-landfill closure and post-closure liabilities | $	$ 45.7	$ 39.5
Minimum
Remaining Airspace Capacity [Roll Forward]
Non-landfill closure and post-closure liabilities, period (in years)	10 years
Maximum
Remaining Airspace Capacity [Roll Forward]
Non-landfill closure and post-closure liabilities, period (in years)	30 years
Buttonwillow | California
Property, Plant and Equipment [Line Items]
Remaining Lives (Years)	21 years
Deer Park | Texas
Property, Plant and Equipment [Line Items]
Remaining Lives (Years)	1 year
Deer Trail | Colorado
Property, Plant and Equipment [Line Items]
Remaining Lives (Years)	26 years
Grassy Mountain | Utah
Property, Plant and Equipment [Line Items]
Remaining Lives (Years)	40 years
Kimball | Nebraska
Property, Plant and Equipment [Line Items]
Remaining Lives (Years)	5 years
Lambton | Ontario, Canada
Property, Plant and Equipment [Line Items]
Remaining Lives (Years)	48 years
Lone Mountain | Oklahoma
Property, Plant and Equipment [Line Items]
Remaining Lives (Years)	16 years
Ryley | Alberta, Canada
Property, Plant and Equipment [Line Items]
Remaining Lives (Years)	3 years
Sawyer | North Dakota
Property, Plant and Equipment [Line Items]
Remaining Lives (Years)	84 years
Altair
Remaining Airspace Capacity [Roll Forward]
Airspace consumed (in cubic yards) | cubicYard		25,000	132,000
Westmorland
Remaining Airspace Capacity [Roll Forward]
Airspace consumed (in cubic yards) | cubicYard	0	0	0
Landfill assets
Property, Plant and Equipment [Line Items]
Amortization | $	$ 13.7	$ 10.9	$ 12.3
Non-commercial landfills
Property, Plant and Equipment [Line Items]
Landfill sites | landfill_site	2
Permitted
Property, Plant and Equipment [Line Items]
Remaining highly probable airspace	23,784,000
Permitted | Buttonwillow | California
Property, Plant and Equipment [Line Items]
Remaining highly probable airspace	5,500,000
Permitted | Deer Park | Texas
Property, Plant and Equipment [Line Items]
Remaining highly probable airspace	32,000
Permitted | Deer Trail | Colorado
Property, Plant and Equipment [Line Items]
Remaining highly probable airspace	1,572,000
Permitted | Grassy Mountain | Utah
Property, Plant and Equipment [Line Items]
Remaining highly probable airspace	4,608,000
Permitted | Kimball | Nebraska
Property, Plant and Equipment [Line Items]
Remaining highly probable airspace	120,000
Permitted | Lambton | Ontario, Canada
Property, Plant and Equipment [Line Items]
Remaining highly probable airspace	4,534,000
Permitted | Lone Mountain | Oklahoma
Property, Plant and Equipment [Line Items]
Remaining highly probable airspace	3,617,000
Permitted | Ryley | Alberta, Canada
Property, Plant and Equipment [Line Items]
Remaining highly probable airspace	455,000
Permitted | Sawyer | North Dakota
Property, Plant and Equipment [Line Items]
Remaining highly probable airspace	3,346,000