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Landfill Accounting - Summary of Liabilities for Final Closure and Post-Closure Costs (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]      
Beginning balance $ 248.0 $ 225.9  
Increase in retirement obligation 11.0 9.7  
Accretion of closure and post-closure costs 18.0 17.0 $ 15.4
Acquisition 0.0 4.9  
Asset retirement obligation adjustments 6.9 10.7  
Costs incurred (19.7) (20.2)  
Ending balance 264.2 248.0 $ 225.9
Less: Current portion (28.0) (18.6)  
Noncurrent portion of retirement obligation $ 236.2 $ 229.4