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	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Derivative [Line Items]
Gain (loss) on derivative recognized in OCI, cash flow hedge	$ 154	$ 51	$ (24)
Gain (loss) on derivative recognized in OCI, net investment hedge	(250)	30	81
Amount of Gain or (Loss) Recognized in Other Comprehensive Income on Derivative	(96)	81	57
Gain (loss) on hedges reclassified to income, cash flow hedge	72	17	26
Gain (loss) on hedges reclassified to income, net investment hedge	0	0	0
Amount of Gain or (Loss) Reclassified from Accumulated Other Comprehensive Income into Income	72	17	26
Interest rate contracts
Derivative [Line Items]
Gain (loss) on derivative recognized in OCI, cash flow hedge	176	8	(12)
Interest rate contracts \| Net interest revenue
Derivative [Line Items]
Gain (loss) on hedges reclassified to income, cash flow hedge	49	(10)	(1)
Foreign exchange contracts
Derivative [Line Items]
Gain (loss) on derivative recognized in OCI, cash flow hedge	(22)	43	(12)
Gain (loss) on derivative recognized in OCI, net investment hedge	(250)	30	81
Foreign exchange contracts \| Net interest revenue
Derivative [Line Items]
Gain (loss) on hedges reclassified to income, cash flow hedge	23	27	27
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

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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
-Name Accounting Standards Codification
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