Summary of Significant Accounting Policies - Interest and Other Income (Expense), Net (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Accounting Policies [Abstract]
Interest income	$ 0.6	$ 0.2
Pension and postretirement benefit (expense)	(0.7)	(1.2)
Gain (loss) on sale of joint venture interest	0.0	2.6
Other income (expense)	0.3	0.0
Interest and other income (expense), net	$ 0.2	$ 1.6