Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended				9 Months Ended		12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Mar. 31, 2018
Income Taxes [Abstract]
Effective income tax rate	32.00%			482.20%	(13.20%)	86.60%
Income Taxes [Abstract]
Provisional income tax expense (benefit) related to US Tax Reform				$ 35.7			$ 38.0
Income tax expense (benefit) related to US Tax Reform	$ 3.1				$ (7.7)
Deferred tax asset, Income tax expense (benefit)	(2.5)				(17.0)
Deferred tax assets - change in amount					(9.3)		(19.0)
Transition tax charge					(0.1)		$ 19.0
Transitional tax liability	18.9				18.9
Tax Credit Carryforward [Abstract]
Tax benefit from recognition of tax credits	(0.9)				(14.5)
Foreign Tax Jurisdiction [Member]
Net of valuation allowance, classification [Abstract]
Valuation allowance - deferred tax assets	33.9				33.9
Changes in deferred tax asset valuation allowances		$ 1.0	$ (2.0)
Domestic Tax Jurisdiction [Member]
Net of valuation allowance, classification [Abstract]
Valuation allowance - deferred tax assets	$ 7.0				7.0
Research Tax Credit Carryforward [Member]
Tax Credit Carryforward [Abstract]
Tax benefit from recognition of tax credits				$ (2.2)		$ (7.9)
Domestic Tax Jurisdiction [Member]
Income Taxes [Abstract]
Income tax expense (benefit) related to US Tax Reform					$ 1.7