Landfill and Environmental Costs - Environmental Remediation Liability (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Activity in environmental remediation liabilities
Environmental remediation liabilities, beginning of year	$ 540.2	$ 564.0
Net adjustments charged to expense	(10.5)	1.4
Payments	(7.2)	(11.2)
Accretion expense (non-cash interest expense)	4.8	5.1
Environmental remediation liabilities, end of period	527.3	559.3
Less: current portion	(58.6)	(63.6)
Long-term portion	$ 468.7	$ 495.7