Revenues Contract with Customers (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Deferred Revenue Arrangement [Line Items]
Current	$ 29.6		$ 19.5
Noncurrent	17.1		14.9
Total	46.7		34.4
Contract with Customer, Liability, Revenue Recognized	6.3
Retained earnings	$ 603.7		$ 573.1
Contract with Customer, Expected Timing of Satisfaction, Period	4 years
Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
Deferred Revenue Arrangement [Line Items]
Retained earnings	$ 3.3	$ 3.2