Leases - Components of Lease Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2022
Operating lease expense
Operating lease cost	$ 353	$ 404	$ 484
Short-term lease cost	28	35	40
Variable lease cost	61	73	73
Sublease income	(19)	(18)	(32)
Total operating costs	423	494	565
Finance lease expense
Amortization of right-of-use assets	137	218	346
Interest on lease liabilities	15	17	27
Total finance lease cost	$ 152	$ 235	$ 373