Supplemental Financial Information - Deductions Related to Valuation Allowance (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Supplemental Cash Flow Information [Abstract]
Cash paid for income taxes	$ 77.6	$ 25.9	$ 48.4
Cash paid for interest on borrowings	347.9	85.3	82.5
Valuation Allowance of Deferred Tax Assets
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	204.5	210.1	161.8
Additions Charged to Costs and Expenses	16.2	36.2	15.2
Additions Charged to Other Accounts	175.8	0.0	37.6
Deductions	(64.4)	(41.8)	(4.5)
Balance at End of Year	332.1	204.5	210.1
Allowance for Doubtful Accounts
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	2.2	2.1	2.5
Additions Charged to Costs and Expenses	0.0	0.2	0.2
Deductions	(0.2)	(0.1)	(0.6)
Balance at End of Year	$ 2.0	$ 2.2	$ 2.1