Leases - Components of lease costs (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2020
Leases [Abstract]
Short-term lease cost	$ 43	$ 32	$ 29
Operating lease cost	431	465	459
Amortization of right-of-use assets	33	23	14
Interest on lease liabilities	5	6	5
Total finance lease cost	38	29	19
Variable lease cost	127	125	125
Sublease income	(41)	(36)	(33)
Total lease cost	$ 598	$ 615	$ 599