Fair Value Measurements Unobservable Inputs Rollforward (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Adjustment to contingent consideration fair value	$ 0.0	$ 0.0	$ 0.2
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	4.8	5.8
Included in other comprehensive income	1.2	(1.0)
Ending balance	$ 6.0	$ 4.8	$ 5.8