Derivative Financial Instruments - Impact on Derivatives and Hedged Items on Consolidated Statement of Income (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Amount of Gain (Loss) on Derivative Recognized in Consolidated Statement of Income	$ 567	$ 262	$ (429)
Amount of Gain (Loss) on Hedged Item Recognized in Consolidated Statement of Income	(563)	(253)	419
Net unrealized gains (losses) on available-for-sale securities designated in fair value hedges, net of related taxes	3	18	24
Investment securities \| Software and processing fees \| Foreign exchange contracts
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Amount of Gain (Loss) on Derivative Recognized in Consolidated Statement of Income	0	0	(74)
Amount of Gain (Loss) on Hedged Item Recognized in Consolidated Statement of Income	0	0	74
Foreign exchange deposit \| Software and processing fees \| Foreign exchange contracts
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Amount of Gain (Loss) on Derivative Recognized in Consolidated Statement of Income	0	0	(328)
Amount of Gain (Loss) on Hedged Item Recognized in Consolidated Statement of Income	0	0	328
Investment securities available-for-sale \| Net interest income \| Interest rate contracts
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Amount of Gain (Loss) on Derivative Recognized in Consolidated Statement of Income	1	(4)	31
Amount of Gain (Loss) on Hedged Item Recognized in Consolidated Statement of Income	(4)	2	(32)
Long-term debt \| Net interest income \| Interest rate contracts
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Amount of Gain (Loss) on Derivative Recognized in Consolidated Statement of Income	566	266	(58)
Amount of Gain (Loss) on Hedged Item Recognized in Consolidated Statement of Income	$ (559)	$ (255)	$ 49

Other Comprehensive Income (Loss), Securities, Available-For-Sale, Designated In Fair Value Hedges, Unrealized Holding Gain (Loss) Arising During Period, After Tax

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- Definition

Amount of gain (loss) from the increase (decrease) in fair value of derivative and nonderivative instruments designated as fair value hedging instruments recognized in the income statement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 25
-Section 50
-Paragraph 1
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=121577467&loc=d3e76258-113986

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- Definition

Amount of the increase (decrease) in fair value of the hedged item in a fair value hedge recognized in the income statement.

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- Definition

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