Derivatives, Hedging Activities and Interest Expense - Components of Interest Expense (Details) - USD ($) $ in Millions	3 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Derivative Instruments Gain Loss [Line Items]
Interest expense on debt	$ 389	$ 576
Interest expense on derivatives	66	109
Interest expense on debt and derivatives	455	685
Losses on debt denominated in foreign currencies	10	548
Losses (gains) on foreign currency swaps	25	(593)
Total interest expense	286	548
Interest Expense
Derivative Instruments Gain Loss [Line Items]
Gains on U.S. dollar interest rate swaps	$ (204)	$ (92)