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
Tax Credit Carryforward [Line Items]
Tax benefit from recognition of tax credits	$ (14.5)
Tax (benefit) from foreign development tax credit	(5.1)	$ 39.5	$ 5.9
Net of valuation allowance, classification [Abstract]
Income tax expense (benefit) related to US Tax Reform	(7.7)
Deferred tax asset, income tax expense (benefit)	2.5
Provisional income tax expense (benefit) related to US Tax Reform		38.0
Valuation allowance - deferred tax assets	43.4	48.9
Lapse of statute of limitations	(2.2)	(1.8)
Foreign Tax Jurisdictions [Member]
Net of valuation allowance, classification [Abstract]
Valuation allowance - deferred tax assets			2.0
Changes in deferred tax asset valuation allowances	(1.0)	(2.8)
Other Tax Jurisdictions [Member]
Net of valuation allowance, classification [Abstract]
Valuation allowance - deferred tax assets	$ 4.3
Changes in deferred tax asset valuation allowances			$ (1.8)
Hungarian Development Tax Credit [Member]
Tax Credit Carryforward [Line Items]
Tax (benefit) from foreign development tax credit		$ (9.0)