Income Taxes - U.S. Tax Reform effects (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Dec. 31, 2017	Sep. 30, 2018
Effect Of Tax Cuts And Jobs Act Of 2017, Accounting Incomplete, Provisional [Abstract]
Estimated expense on accumulated undistributed foreign earnings		$ (1.2)
Estimated benefit due to remeasurement of net deferred tax liabilities		(1.0)
Net expense (benefit)	$ 7.8	$ (0.2)