Income Taxes - Valuation Allowances (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning of year				$ 118.3				$ 100.7	$ 118.3	$ 100.7	$ 98.9
Expiring tax credits									(0.4)	(0.3)	(0.6)
Acquisitions and dispositions									4.9	3.1	(0.7)
Changes in judgment about deferred tax assets(a)									(2.4)	5.3	0.0
Income from continuing operations	$ 25.1	$ (23.8)	$ 13.7	$ 1.8	$ (3.8)	$ 5.8	$ 12.6	$ 13.7	16.8	28.3	(33.3)
Other comprehensive loss									(16.2)	3.9	(16.5)
Foreign currency exchange effects									(0.1)	(0.5)	(2.7)
End of year	$ 128.1				$ 118.3				128.1	118.3	100.7
Valuation Allowance of Deferred Tax Assets
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Income from continuing operations									8.1	10.0	6.1
Other comprehensive loss									$ (0.3)	$ 0.0	$ (0.3)