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Summary of Significant Accounting Policies (Narrative) (Details)
$ in Millions
1 Months Ended 12 Months Ended
Apr. 30, 2020
USD ($)
Dec. 31, 2021
USD ($)
segment
pension_plan
landfill
Dec. 31, 2020
USD ($)
Dec. 31, 2019
USD ($)
Oct. 01, 2020
Concentration Risk [Line Items]          
Net book credit balances in our primary disbursement accounts   $ 39.0 $ 32.7    
Restricted cash and marketable securities   139.0 149.1 $ 179.4  
Capitalized interest   $ 5.0 $ 6.2 $ 7.2  
Post-closure period   30 years      
Number of closed landfills | landfill   124      
Asset retirement obligation, costs to discharge, inflation rate   1.70% 1.70% 1.70%  
Years of historical moving average increase of the U.S. Consumer Price Index used as our basis for inflation rate   10 years 10 years 10 years  
Number of operating segments | segment   3      
Future estimates of revenue and expense growth rate   3.00%      
Future estimated effective tax rates   27.00%      
Estimated discount rates, minimum range   6.00%      
Estimated discount rates, maximum range   8.00%      
Reporting unit, percentage of fair value in excess of carrying amount         150.00%
Impairment of assets     $ 42.6    
Number of qualified defined pension plans | pension_plan   1      
Amount committed to frontline employees and their families $ 20.0        
Minimum          
Concentration Risk [Line Items]          
Amortization period for other intangible assets   1 year      
Maximum          
Concentration Risk [Line Items]          
Amortization period for other intangible assets   15 years      
Insurance Programs For Workers' Compensation          
Concentration Risk [Line Items]          
Restricted cash and marketable securities   $ 84.2