Derivative Financial Instruments - Schedule of Differences Between the Gains (Losses) on the Derivative and The Gains (Losses) on the Hedged Item (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Derivative [Line Items]
Gain (loss) on derivative recognized in OCI, cash flow hedge	$ 20	$ 168
Gain (loss) on derivative recognized in OCI, net investment hedge	135	108
Amount of Gain or (Loss) Recognized in Other Comprehensive Income on Derivative	155	276
Gain (loss) on hedges reclassified to income, cash flow hedge	21	7
Gain (loss) on hedges reclassified to income, net investment hedge	0	0
Amount of Gain or (Loss) Reclassified from Accumulated Other Comprehensive Income into Income	$ 21	7
Floating-rate loans
Derivative [Line Items]
Term of debt instrument	3 years 4 months 24 days
Interest rate contracts
Derivative [Line Items]
Gain (loss) on derivative recognized in OCI, cash flow hedge	$ (16)	158
Interest rate contracts | Net interest revenue
Derivative [Line Items]
Gain (loss) on hedges reclassified to income, cash flow hedge	18	0
Foreign exchange contracts
Derivative [Line Items]
Gain (loss) on derivative recognized in OCI, cash flow hedge	36	10
Gain (loss) on derivative recognized in OCI, net investment hedge	135	108
Foreign exchange contracts | Net interest revenue
Derivative [Line Items]
Gain (loss) on hedges reclassified to income, cash flow hedge	3	7
Foreign exchange contracts | Gains (Losses) related to investment securities, net
Derivative [Line Items]
Gain (loss) on hedges reclassified to income, net investment hedge	$ 0	$ 0