Significant Accounting Policies, Short-term Investments, Property, Plant and Equipment and Assets Held for Sale (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Short-term investments [Abstract]
Short-term investments	$ 4.3	$ 5.7
Property, plant and equipment [Abstract]
Capital expenditures accrued	17.9	15.8	$ 12.5
Assets Held For Sale [Abstract]
Carrying value of assets held-for-sale	$ 1.1	$ 1.7