Debt and Financing Activities - Commercial Paper (Details) - USD ($) $ in Millions	6 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	May 07, 2025	Mar. 31, 2025
Line of Credit Facility [Line Items]
Proceeds from issuance of commercial paper	$ 2,300	$ 6,900
Repayments of commercial paper	2,300	$ 6,900
Debt outstanding	7,758			$ 5,654
Commercial Paper
Line of Credit Facility [Line Items]
Credit facility, maximum borrowing capacity	5,000		$ 4,000
Debt outstanding	$ 0			$ 0