Income Taxes - Valuation Allowances (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning of year				$ 62.8				$ 45.7	$ 62.8	$ 45.7	$ 40.1
Expiring tax credits									(0.4)	(0.4)	(0.3)
Acquisitions and dispositions									(3.4)	(0.3)	0.0
Changes in judgment about deferred tax assets(a)									(1.8)	2.6	1.5
Income from continuing operations	$ (52.0)	$ 19.9	$ 14.3	$ 34.7	$ 14.5	$ 24.5	$ 0.3	$ (3.1)	16.9	36.2	(9.1)
Other comprehensive loss									(18.8)	(15.8)	(103.4)
Foreign currency exchange effects									(2.4)	(8.5)	(4.3)
End of year	98.9				62.8				98.9	62.8	45.7
Retained earnings	564.9				$ 576.0				564.9	576.0
Valuation Allowance of Deferred Tax Assets
Movement in Valuation Allowances and Reserves [Roll Forward]
Income from continuing operations									43.9	20.5	8.4
Other comprehensive loss									0.2	0.7	0.3
Retained earnings									0.0	$ 2.5	$ 0.0
Retained earnings	$ 2.5								$ 2.5