Goodwill and Other Intangibles (Narrative) (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
	Jun. 30, 2018	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill		$ 672.7		$ 672.7		$ 605.6
Other Intangible Assets
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization expense related to other intangible assets		4.3	$ 2.3	13.2	$ 7.0
Estimated future amortization expense for 2018		4.3		4.3
Estimated future amortization expense for 2019		17.0		17.0
Estimated future amortization expense for 2020		17.0		17.0
Estimated future amortization expense for 2021		14.5		14.5
Estimated future amortization expense for 2022		9.9		9.9
Omnium Technology
Acquired Finite-Lived Intangible Assets [Line Items]
Purchase price	$ 73.0
Goodwill	$ 71.4
Intangibles acquired		$ 1.6		$ 1.6