Derivative Financial Instruments - Impact on Derivatives and Hedged Items on Consolidated Statement of Income (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Amount of Gain (Loss) on Derivative Recognized in Consolidated Statement of Income	$ 177	$ (668)	$ 280	$ (579)
Amount of Gain (Loss) on Hedged Item Recognized in Consolidated Statement of Income	(176)	666	(274)	566
Net unrealized gains (losses) on available-for-sale securities designated in fair value hedges, net of related taxes	5	5	3	23
Investment securities \| Processing fees and other revenue \| Foreign exchange contracts
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Amount of Gain (Loss) on Derivative Recognized in Consolidated Statement of Income	0	(30)	0	(43)
Amount of Gain (Loss) on Hedged Item Recognized in Consolidated Statement of Income	0	30	0	43
Foreign exchange deposit \| Processing fees and other revenue \| Foreign exchange contracts
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Amount of Gain (Loss) on Derivative Recognized in Consolidated Statement of Income	0	(601)	0	(353)
Amount of Gain (Loss) on Hedged Item Recognized in Consolidated Statement of Income	0	601	0	353
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	(8)	10	(11)	31
Amount of Gain (Loss) on Hedged Item Recognized in Consolidated Statement of Income	7	(9)	11	(30)
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	185	(47)	291	(214)
Amount of Gain (Loss) on Hedged Item Recognized in Consolidated Statement of Income	$ (183)	$ 44	$ (285)	$ 200

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

No definition available.

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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=109977999&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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