Fair Value Measurements (Assets and Liabilities Required to be Carried at Fair Value on a Recurring Basis) (Details) - USD ($) $ in Millions	Sep. 30, 2021	Mar. 31, 2021
Assets:
Interest rate swaps	$ 27.2	$ 50.8
Other Non-Current Assets
Assets:
Interest rate swaps	27.3	50.8
Other Non-Current Assets | Interest rate swaps, financing element
Liabilities:
Financing element of certain hybrid instruments	93.1	98.2
Fair Value, Measurements, Recurring
Assets:
Available-for-sale equity securities	0.7	1.8
Forward exchange contracts	2.1	1.5
Interest rate swaps	120.4	149.0
Liabilities:
Forward exchange contracts	(2.6)	(2.6)
Interest rate swaps	(72.9)	(78.4)
Fair Value, Measurements, Recurring | Level 1
Assets:
Available-for-sale equity securities	0.7	1.8
Forward exchange contracts	0.0	0.0
Interest rate swaps	0.0	0.0
Liabilities:
Forward exchange contracts	0.0	0.0
Interest rate swaps	0.0	0.0
Fair Value, Measurements, Recurring | Level 2
Assets:
Available-for-sale equity securities	0.0	0.0
Forward exchange contracts	2.1	1.5
Interest rate swaps	120.4	149.0
Liabilities:
Forward exchange contracts	(2.6)	(2.6)
Interest rate swaps	$ (72.9)	$ (78.4)