Environmental Obligations - Recoveries and Reserves (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Recorded Recoveries [Roll Forward]
Expected recoveries recorded, beginning	$ 38.4	$ 46.2
Increase (Decrease) in Recoveries	2.9	(2.9)
Cash Received	(4.3)	(4.9)
Other	0.3
Expected recoveries recorded, ending	37.3	38.4	$ 46.2
Transfer to environmental obligations (from) asset retirement obligations			2.6
Accrual for Environmental Loss Contingencies, Balance Sheet Classification [Abstract]
Environmental reserves, current, net of recoveries	115.3	63.0
Environmental reserves, long-term continuing and discontinued, net of recoveries	470.5	458.5
Total environmental reserves, net of recoveries	585.8	521.5	411.8	$ 360.4
Net Environmental Provisions [Abstract]
Continuing operations	108.7	21.7	16.2
Discontinued operations	29.8	153.9	76.1
Net environmental provision	138.5	175.6	92.3
Net Environmental Provisions, Assets and Liabilities [Abstract]
Environmental reserves	138.8	178.2	105.6
Other assets	(0.3)	(2.6)	(13.3)
Net environmental provision	138.5	175.6	92.3
Environmental liabilities, continuing and discontinued
Recorded Recoveries [Roll Forward]
Expected recoveries recorded, beginning	7.9	13.9
Increase (Decrease) in Recoveries	2.6	(5.5)
Cash Received	(0.5)	(0.5)
Other	0.0
Expected recoveries recorded, ending	10.0	7.9	13.9
Other assets
Recorded Recoveries [Roll Forward]
Expected recoveries recorded, beginning	30.5	32.3
Increase (Decrease) in Recoveries	0.3	2.6
Cash Received	(3.8)	(4.4)
Other	0.3
Expected recoveries recorded, ending	$ 27.3	$ 30.5	$ 32.3