Income Taxes (Textuals) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Accrued liabilities for interest and penalties	$ 0.1	$ 0.1
Total gross unrecognized tax benefits	3.2	6.2	$ 5.9
Unrecognized tax benefits that would impact effective tax rate	1.0
Estimated reduction in the liability for unrecognized tax benefits	1.3
Discrete tax benefit, share-based payments	33.1
Discrete tax charge, Tax Cuts and Jobs Act of 2017	48.8
Discrete tax charge, Transition Toll Tax	27.9
Discrete tax charge, net Transition Toll Tax	2.0
Discrete tax charge, change in enacted rate, domestic	11.4
Tax on undistributed foreign earnings	9.8	0.0
Restructuring and related charges	0.0	26.4	0.0
Discrete tax benefit, restructuring charges		9.0
Pension curtailment gain	0.0	2.1	0.0
Discrete tax charge, pension curtailment		0.8
Discrete tax charge, change in enacted rate, foreign		$ 1.0	0.8
Discrete tax benefit, executive retirement & related costs			4.0
Discrete tax benefit, pension settlement			$ 18.4
Undistributed earnings of foreign subsidiaries	$ 17.3