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Landfill and Environmental Costs - Final Capping, Closure and Post-Closure Costs (Details) - USD ($)
$ in Millions
3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Activity in asset retirement obligation liabilities, which includes liabilities for final capping, closure and post-closure    
Asset retirement obligation liabilities, beginning of year $ 1,257.7 $ 1,224.6
Non-cash additions 10.3 10.6
Acquisitions, net of divestitures and other adjustments 0.1 (25.1)
Asset retirement obligation adjustments 0.3 0.6
Payments (7.3) (9.7)
Accretion expense 20.4 20.0
Asset retirement obligation liabilities, end of period 1,281.5 1,221.0
Less: current portion (76.8) (60.4)
Long-term portion $ 1,204.7 $ 1,160.6