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, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Derivative [Line Items]
Gain (loss) on derivative recognized in OCI, cash flow hedge	$ (30)	$ 14	$ 168	$ 57
Gain (loss) on derivative recognized in OCI, net investment hedge	(122)	57	(100)	75
Amount of Gain or (Loss) Recognized in Other Comprehensive Income on Derivative	(152)	71	68	132
Gain (loss) on hedges reclassified to income, cash flow hedge	24	4	52	14
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	4	52	14
Interest rate contracts
Derivative [Line Items]
Gain (loss) on derivative recognized in OCI, cash flow hedge	0	2	179	33
Interest rate contracts \| Net interest income
Derivative [Line Items]
Gain (loss) on hedges reclassified to income, cash flow hedge	18	(3)	32	(7)
Foreign exchange contracts
Derivative [Line Items]
Gain (loss) on derivative recognized in OCI, cash flow hedge	(30)	12	(11)	24
Gain (loss) on derivative recognized in OCI, net investment hedge	(122)	57	(100)	75
Foreign exchange contracts \| Net interest income
Derivative [Line Items]
Gain (loss) on hedges reclassified to income, cash flow hedge	6	7	20	21
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
-Name Accounting Standards Codification
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Amount, before tax, of reclassification of gain (loss) from accumulated other comprehensive income (AOCI) for derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness.

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