Derivatives, Hedging Activities and Interest Expense - Components of Interest Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2020
Derivative Instruments Gain Loss [Line Items]
Interest expense on debt	$ 1,498	$ 1,954	$ 2,488
Interest expense on derivatives	107	420	180
Interest expense on debt and derivatives	1,605	2,374	2,668
(Gains) losses on debt denominated in foreign currencies	(438)	1,402	(703)
Losses (gains) on foreign currency swaps	818	(1,351)	650
Total interest expense	1,401	2,302	2,834
Interest Expense
Derivative Instruments Gain Loss [Line Items]
(Gains) losses on U.S. dollar interest rate swaps	$ (584)	$ (123)	$ 219