Derivatives, Hedging Activities and Interest Expense - Components of Interest Expense (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2024	Dec. 31, 2023
Derivative Instruments Gain Loss [Line Items]
Interest expense on debt	$ 1,454	$ 1,306	$ 4,282	$ 3,581
Interest expense (income) on derivatives	51	(165)	(46)	(579)
Interest expense on debt and derivatives	1,505	1,141	4,236	3,002
(Gains) losses on debt denominated in foreign currencies	(775)	393	(382)	150
Losses (gains) on foreign currency swaps	798	(655)	201	(359)
(Gains) losses on U.S. dollar interest rate swaps	(114)	351	386	608
Total interest expense	$ 1,414	$ 1,230	$ 4,441	$ 3,401