Other (expense), net (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Intercompany Foreign Currency Balance [Line Items]
Postretirement expense	$ (225.1)	$ (24.2)	$ (392.8)	$ (46.9)
Loss on debt extinguishment	0.0	(28.5)	0.0	(28.5)
Foreign exchange gains (losses)	2.0	0.7	(0.9)	(14.9)
Environmental costs and other, net	(4.7)	(1.7)	(16.7)	(11.5)
Total other (expense), net	(227.8)	(53.7)	(410.4)	(101.8)
Liquidation of Foreign Subsidiaries
Intercompany Foreign Currency Balance [Line Items]
Foreign exchange gains (losses)	0.7	0.6	(1.6)	(18.4)
Pension Plans
Intercompany Foreign Currency Balance [Line Items]
Settlement losses	$ 210.7	$ 0.0	$ 368.7	$ 0.0