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	6 Months Ended
Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Derivative [Line Items]
Gain (loss) on derivative recognized in OCI, cash flow hedge	$ 17	$ 30	$ 37	$ 198
Gain (loss) on derivative recognized in OCI, net investment hedge	(24)	(86)	111	22
Amount of Gain or (Loss) Recognized in Other Comprehensive Income on Derivative	(7)	(56)
Gain (loss) on hedges reclassified to income, cash flow hedge	25	21	46	28
Gain (loss) on hedges reclassified to income, net investment hedge	0	0	0	0
Amount of Gain or (Loss) Reclassified from Accumulated Other Comprehensive Income into Income	25	21	$ 46	28
Floating-rate loans
Derivative [Line Items]
Term of debt instrument			4 years 9 months 18 days
Interest rate contracts
Derivative [Line Items]
Gain (loss) on derivative recognized in OCI, cash flow hedge	10	21	$ (6)	179
Amount of Gain or (Loss) Recognized in Other Comprehensive Income on Derivative			148	220
Interest rate contracts \| Net interest revenue
Derivative [Line Items]
Gain (loss) on hedges reclassified to income, cash flow hedge	22	14	40	14
Foreign exchange contracts
Derivative [Line Items]
Gain (loss) on derivative recognized in OCI, cash flow hedge	7	9	43	19
Gain (loss) on derivative recognized in OCI, net investment hedge	(24)	(86)	111	22
Foreign exchange contracts \| Net interest revenue
Derivative [Line Items]
Gain (loss) on hedges reclassified to income, cash flow hedge	3	7	6	14
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	$ 0	$ 0

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Amount, before tax and reclassification, of gain (loss) from derivative instrument designated and qualifying cash flow hedge included in assessment of hedge effectiveness.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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