Landfill Accounting (Narrative) (Details) $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2020 USD ($) site $ / T	Sep. 30, 2019 USD ($) $ / T	Dec. 31, 2019 USD ($)
Landfill Accounting [Line Items]
Number of landfills owned and operated by company | site	83
Number of landfills operated, not owned, under life-of-site operating agreements | site	6
Number of landfills operated under limited-term operating agreements | site	4
Number of landfills in development stage | site	1
Property and equipment, net	$ 5,193,378		$ 5,516,347
Average remaining landfill life based on permitted capacity and projected annual disposal volumes	28 years
Number of owned landfills the company is seeking to expand | site	10
Number of landfills operated under life-of-site operating agreements that the company is seeking to expand | site	3
Average remaining landfill life based on permitted capacity, projected annual disposal volumes and probable expansion capacity	32 years
Life of Company's owned landfills and landfills operated under life-of-site operating agreements min range	1 year
Life of Company's owned landfills and landfills operated under life of site operating agreements max range	204 years
Landfill depletion expense	$ 149,988	$ 169,064
Average rate per ton consumed related to landfill depletion at owned landfills and landfills operated under life-of-site agreements | $ / T	4.51	4.77
Accretion expense associated with landfill obligations	$ 11,174	$ 10,656
Average rate per ton consumed related to final capping, closure and post-closure landfill accretion expense | $ / T	0.34	0.30
Restricted cash	$ 96,519		96,483
Restricted investments	47,161		$ 51,179
Liabilities incurred	1,861
Landfill [Member]
Landfill Accounting [Line Items]
Property and equipment, net	$ 2,645,221
Inflation rate for purposes of computing layers for final capping, closure and post-closure obligations	2.50%		2.50%
Restricted cash	$ 17,589		$ 12,324
Restricted investments	$ 44,558		$ 48,590
Landfill [Member] | Measurement Input, Discount Rate [Member]
Landfill Accounting [Line Items]
Discount rate for purposes of computing layers for final capping, closure and post-closure obligations	4.75%		4.75%