Accumulated Other Comprehensive (Loss) Income (Components of accumulated comprehensive loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Increase (Decrease) in Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	$ 357.9	$ 349.6
Other comprehensive income (loss)	(4.1)	(16.1)
Ending balance	359.1	331.6
Cumulative Translation Adjustment
Increase (Decrease) in Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(8.3)	(22.4)
Other comprehensive income (loss)	(4.3)	(16.6)
Ending balance	(12.6)	(39.0)
Pension and Postretirement Benefits
Increase (Decrease) in Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(9.8)	(14.6)
Other comprehensive income (loss)	0.2	0.5
Ending balance	(9.6)	(14.1)
Accumulated Other Comprehensive Loss
Increase (Decrease) in Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(18.1)	(37.0)
Ending balance	$ (22.2)	$ (53.1)