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Landfill Accounting (Narrative) (Details)
 6 Months Ended 12 Months Ended
Jun. 30, 2019
USD ($)
site
$ / T
Jun. 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    
Property and equipment, net $ 5,318,196,000   $ 5,168,996,000
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 7    
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 $ 107,364,000 $ 97,156,000  
Average rate per ton consumed related to landfill depletion at owned landfills and landfills operated under life-of-site agreements | $ / T 4.77 4.56  
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 $ 7,063,000 $ 6,386,000  
Average rate per ton consumed related to final capping, closure and post-closure landfill accretion expense | $ / T 0.31 0.30  
Restricted cash $ 84,527,000   $ 84,661,000
Liabilities incurred 11,263,000    
Landfill [Member]      
Landfill Accounting [Line Items]      
Property and equipment, net 2,949,959,000    
Restricted cash 6,795,000   12,325,000
Restricted investments $ 51,902,000   $ 44,939,000
Landfill [Member] | Measurement Input, Discount Rate [Member]      
Landfill Accounting [Line Items]      
Asset retirement obligation, measurement input 4.75   4.75