Additional Financial Information - Lease Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Mar. 31, 2023
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows for operating leases	$ 68.4	$ 45.1	$ 40.3
Right-of-use assets obtained in exchange for new lease obligations:
Operating leases	7.4	172.1	11.3
Increase in right-of-use assets and lease liability due to a reassessment event:
Operating leases - increase in right-of-use assets	2.8	103.6	17.4
Operating leases - increase in lease liability	$ 2.8	$ 103.6	$ 17.4