Other Income, Net (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Other Income and Expenses [Abstract]
Interest income	$ 0.2	$ 0.1
Net periodic postretirement benefit cost relating to Salaried VEBA	(1.6)	(1.5)
Realized gain on investments	1.2	1.6
All other income (expense), net	0.7	(0.1)
Other income, net	$ 0.5	$ 0.1