Significant Accounting Policies, Short-term Investments, Property, Plant and Equipment and Assets Held for Sale (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2019
Short-Term Investments [Abstract]
Short-term investments	$ 3.7	$ 3.2
Property, Plant and Equipment [Abstract]
Accrued capital expenditures	7.9	8.7	$ 17.9
Assets Held For Sale [Abstract]
Impairment charges	166.8	$ 8.6	$ 0.4
Held for Sale [Member]
Assets Held For Sale [Abstract]
Impairment charges	166.8
Liabilities Held for Sale [Member]
Property, Plant and Equipment [Abstract]
Accrued capital expenditures	$ 2.7