Fair Value Measurements (Details) - Recurring basis - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Fair value of assets and liabilities measured on recurring basis
Short-term investments	$ 17.9	$ 12.4
Forward contracts		2.4
Forward contracts	(0.2)
Contingent consideration	(75.0)
Total	(57.3)	14.8
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair value of assets and liabilities measured on recurring basis
Short-term investments	17.9	12.4
Total	17.9	12.4
Significant Observable Inputs (Level 2)
Fair value of assets and liabilities measured on recurring basis
Forward contracts		2.4
Forward contracts	(0.2)
Total	(0.2)	$ 2.4
Significant Unobservable Inputs (Level 3)
Fair value of assets and liabilities measured on recurring basis
Contingent consideration	(75.0)
Total	$ (75.0)