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Landfill Accounting (Narrative) (Details)
$ in Thousands
 9 Months Ended 12 Months Ended
Sep. 30, 2019
USD ($)
site
$ / T
Sep. 30, 2018
USD ($)
$ / T
Dec. 31, 2018
USD ($)
Landfill Accounting [Line Items]      
Number of landfills owned and operated by company | site 85    
Number of landfills operated, not owned, under life-of-site operating agreements | site 7    
Number of landfills operated under limited-term operating agreements | site 4    
Number of landfills in development stage | site 1    
Property and equipment, net $ 5,375,166   $ 5,168,996
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 6    
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 177 years    
Landfill depletion expense $ 169,064 $ 153,010  
Average rate per ton consumed related to landfill depletion at owned landfills and landfills operated under life-of-site agreements | $ / T 4.77 4.58  
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 $ 10,656 $ 9,583  
Average rate per ton consumed related to final capping, closure and post-closure landfill accretion expense | $ / T 0.30 0.29  
Restricted cash $ 92,050   $ 84,661
Liabilities incurred 15,573    
Landfill [Member]      
Landfill Accounting [Line Items]      
Property and equipment, net 2,961,560    
Restricted cash 11,538   12,325
Restricted investments $ 47,993   $ 44,939
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%