Goodwill and Other Intangible Assets - Intangible Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Amortization of Intangible Assets	$ 10.0	$ 10.0	$ 10.0
Gross carrying amount	191.7	191.7
Accumulated amortization	(53.7)	(43.5)
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
2018	10.0
2019	10.0
2020	10.0
2021	10.0
2022	10.0
Technology [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	91.4	91.4
Accumulated amortization	(27.4)	(23.0)
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	35.7	35.7
Accumulated amortization	(9.1)	(7.6)
Trademarks [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	64.6	64.6
Accumulated amortization	$ (17.2)	$ (12.9)