Income Taxes, Unrecognized Tax Benefits, and Deferred Tax Asset Valuation Allowances (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Tax Credit Carryforward [Line Items]
Tax (benefit) from foreign development tax credit		$ 39.5	$ 5.9	$ (8.9)
Valuation Allowance [Line Items]
Valuation allowance - deferred tax assets		48.9	49.6
Foreign Tax Jurisdictions [Member]
Valuation Allowance [Line Items]
Valuation allowance - deferred tax assets			2.0
Valuation allowance - deferred tax assets change in amount		(2.8)		(3.0)
Other Tax Jurisdictions [Member]
Valuation Allowance [Line Items]
Valuation allowance - deferred tax assets change in amount			$ (1.8)	$ 5.0
Forecast [Member] | Foreign Tax Jurisdictions [Member]
Valuation Allowance [Line Items]
Valuation allowance - deferred tax assets change in amount	$ (3.0)
Hungarian Development Tax Credit [Member]
Tax Credit Carryforward [Line Items]
Tax (benefit) from foreign development tax credit		$ (9.0)