Debt and Financing Activities - Commercial Paper (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2022
Debt Instrument [Line Items]
Commercial paper issuances	$ 20,000	$ 8,500	$ 11,200
Commercial paper repaid	20,000	8,500	$ 11,200
Total debt	5,629	5,594
Commercial Paper
Debt Instrument [Line Items]
Credit facility borrowing capacity (up to)	4,000
Total debt	$ 0	$ 0