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Loans - TDR - Subsequent Defaults (Detail) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020 USD ($) Contract	Sep. 30, 2019 USD ($) Contract	Sep. 30, 2020 USD ($) Contract	Sep. 30, 2019 USD ($) Contract
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | Contract	18,541	29,175	76,520	92,103
Total Loans | $	$ 63	$ 66	$ 233	$ 207
Credit Card
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | Contract	17,227	27,723	73,060	88,222
Total Loans | $	$ 31	$ 48	$ 125	$ 159
Consumer Banking
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | Contract	1,310	1,452	3,449	3,881
Total Loans | $	$ 16	$ 18	$ 43	$ 48
Consumer Banking | Auto
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | Contract	1,307	1,446	3,442	3,863
Total Loans | $	$ 15	$ 18	$ 42	$ 47
Consumer Banking | Retail banking
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | Contract	3	6	7	18
Total Loans | $	$ 1	$ 0	$ 1	$ 1
Commercial Banking
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | Contract	4	0	11	0
Total Loans | $	$ 16	$ 0	$ 65	$ 0
Commercial Banking | Commercial and industrial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | Contract	4	0	11	0
Total Loans | $	$ 16	$ 0	$ 65	$ 0
Domestic credit card: | Credit Card
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | Contract	6,554	10,619	27,022	36,227
Total Loans | $	$ 14	$ 22	$ 57	$ 77
International card businesses: | Credit Card
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | Contract	10,673	17,104	46,038	51,995
Total Loans | $	$ 17	$ 26	$ 68	$ 82

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+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 34
-URI http://asc.fasb.org/extlink&oid=121611835&loc=SL6953682-111524

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 34
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=121611835&loc=SL6953682-111524

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