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	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Derivative [Line Items]
Gain (loss) on derivative recognized in OCI, cash flow hedge	$ 9	$ (30)	$ 46	$ 168
Gain (loss) on derivative recognized in OCI, net investment hedge	111	(122)	222	(100)
Amount of Gain or (Loss) Recognized in Other Comprehensive Income on Derivative	120	(152)	268	68
Gain (loss) on hedges reclassified to income, cash flow hedge	24	24	70	52
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	24	24	$ 70	52
Floating-rate loans
Derivative [Line Items]
Term of debt instrument			5 years
Interest rate contracts
Derivative [Line Items]
Gain (loss) on derivative recognized in OCI, cash flow hedge	(3)	0	$ (9)	179
Interest rate contracts \| Net interest revenue
Derivative [Line Items]
Gain (loss) on hedges reclassified to income, cash flow hedge	22	18	62	32
Foreign exchange contracts
Derivative [Line Items]
Gain (loss) on derivative recognized in OCI, cash flow hedge	12	(30)	55	(11)
Gain (loss) on derivative recognized in OCI, net investment hedge	111	(122)	222	(100)
Foreign exchange contracts \| Net interest revenue
Derivative [Line Items]
Gain (loss) on hedges reclassified to income, cash flow hedge	2	6	8	20
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
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