Derivatives, Hedging Activities and Interest Expense - Components of Interest Expense (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2023	Dec. 31, 2022
Derivative Instruments Gain Loss [Line Items]
Interest expense on debt	$ 1,306	$ 845	$ 3,581	$ 1,914
Interest income on derivatives	(165)	(186)	(579)	(368)
Interest expense on debt and derivatives	1,141	659	3,002	1,546
Losses (gains) on debt denominated in foreign currencies	393	532	150	(649)
(Gains) losses on foreign currency swaps	(655)	(509)	(359)	947
Total interest expense	1,230	765	3,401	2,033
Interest Expense
Derivative Instruments Gain Loss [Line Items]
Losses on U.S. dollar interest rate swaps	$ 351	$ 83	$ 608	$ 189