Landfill Accounting (Narrative) (Details) $ in Thousands	6 Months Ended		12 Months Ended
	Jun. 30, 2018 USD ($) site $ / T	Jun. 30, 2017 USD ($) $ / T	Dec. 31, 2017 USD ($)
Landfill Accounting [Line Items]
Number of landfills owned and operated by company | site	81
Number of landfills operated, not owned, under life-of-site operating agreements | site	8
Number of landfills operated under limited-term operating agreements | site	4
Property and equipment, net	$ 5,024,868		$ 4,820,934
Average remaining landfill life based on permitted capacity and projected annual disposal volumes	27 years
Number of owned landfills the company is seeking to expand | site	11
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	30 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	158 years
Landfill depletion expense	$ 97,156	$ 93,968
Average rate per ton consumed related to landfill depletion at owned landfills and landfills operated under life-of-site agreements | $ / T	4.56	4.51
Inflation rate for purposes of computing layers for final capping, closure and post-closure obligations	2.50%		2.50%
Accretion expense associated with landfill obligations	$ 6,386	$ 5,775
Average rate per ton consumed related to final capping, closure and post-closure landfill accretion expense | $ / T	0.30	0.27
Restricted asset balance for purposes of securing our performance of future final capping, closure and post-closure obligations	$ 56,824		$ 56,090
Liabilities incurred	7,810
Landfill [Member]
Landfill Accounting [Line Items]
Property and equipment, net	$ 2,855,105
Fair value discount rate	4.75%		4.75%