Income Taxes Income Taxes - Tax Cuts And Jobs Act Of 2017 Narrative (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended			13 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2018	Jun. 30, 2017
Tax Credit Carryforward [Line Items]
Effective income tax rate (as a percent)			9.50%	12.40%	28.70%
Provisional income tax expense (benefit)				$ 6.5		$ 6.6
Change in tax rate effect on deferred taxes				10.3		11.2
Transition tax for accumulated foreign earnings, income tax expense (benefit)				3.8		$ 4.6
Reclassification of the stranded tax effects related to the Tax Act (Note 10)				(10.9)
Measurement period tax benefit adjustment			$ 0.9
Measurement period adjustment to transition tax			0.8
Measurement period adjustment to GILTI tax	$ 0.6
Change in statutory tax rate, amount			$ (1.6)	(9.7)	$ 0.0
Measurement period adjustment				8.1
Deferred income tax benefit				1.6
Transition tax for accumulated foreign earnings				2.2
Retained Earnings
Tax Credit Carryforward [Line Items]
Reclassification of the stranded tax effects related to the Tax Act (Note 10)		$ 10.9		10.9
Federal Ministry of Finance, Germany
Tax Credit Carryforward [Line Items]
Elimination of foreign earnings repatriated							$ (4.1)
Change in statutory tax rate, amount				$ 0.6
Foreign Tax Authority
Tax Credit Carryforward [Line Items]
Change in statutory tax rate, amount	$ 0.1