Income Taxes - Deductions Related to Valuation Allowance (Details) - Valuation Allowance of Deferred Tax Assets - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2022
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	$ 299.4	$ 290.3	$ 290.3
Additions Charged to Costs and Expenses	6.5	19.3	7.1
Deductions	(35.1)	(10.2)	(7.1)
Balance at End of Year	$ 270.8	$ 299.4	$ 290.3