Derivatives, Hedging Activities and Interest Expense - Components of Interest Expense (Details) - USD ($) $ in Millions	3 Months Ended				12 Months Ended
	Mar. 31, 2024	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2022
Derivative Instruments Gain Loss [Line Items]
Interest expense on debt					$ 4,936	$ 2,919	$ 1,498
Interest (income) expense on derivatives					(661)	(569)	107
Interest expense on debt and derivatives					4,275	2,350	1,605
Gains on debt denominated in foreign currencies					(80)	(614)	(438)
(Gains) losses on foreign currency swaps					(90)	805	818
Total interest expense	$ 1,304	$ 1,230	$ 1,272	$ 899	4,705	3,054	1,401
Interest Expense
Derivative Instruments Gain Loss [Line Items]
Losses (gains) on U.S. dollar interest rate swaps					$ 600	$ 513	$ (584)