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Loans - TDR Disclosures in Progress Financial Impact of Modification (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Loans Modified	$ 292	$ 273
Credit Card
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Loans Modified	140	145
Consumer Banking
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Loans Modified	126	73
Consumer Banking | Auto
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Loans Modified	123	72
Consumer Banking | Retail banking
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Loans Modified	3	1
Commercial Banking
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Loans Modified	26	55
Commercial Banking | Total commercial lending
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Loans Modified		55
Commercial Banking | Commercial and multifamily real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Loans Modified	19	34
Commercial Banking | Commercial and industrial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Loans Modified	$ 7	21
Commercial Banking | Small-ticket commercial real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Loans Modified		$ 0
Reduced Interest Rate
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	56.00%	75.00%
Average Rate Reduction	17.87%	14.64%
Reduced Interest Rate | Credit Card
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	100.00%	100.00%
Average Rate Reduction	20.41%	20.04%
Reduced Interest Rate | Consumer Banking
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	20.00%	37.00%
Average Rate Reduction	3.36%	3.88%
Reduced Interest Rate | Consumer Banking | Auto
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	20.00%	37.00%
Average Rate Reduction	3.34%	3.83%
Reduced Interest Rate | Consumer Banking | Retail banking
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	1.00%	15.00%
Average Rate Reduction	12.50%	13.01%
Reduced Interest Rate | Commercial Banking
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	0.00%	61.00%
Average Rate Reduction	0.00%	0.00%
Reduced Interest Rate | Commercial Banking | Total commercial lending
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity		62.00%
Average Rate Reduction		0.00%
Reduced Interest Rate | Commercial Banking | Commercial and multifamily real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	0.00%	100.00%
Average Rate Reduction	0.00%	0.00%
Reduced Interest Rate | Commercial Banking | Commercial and industrial
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	0.00%	0.00%
Average Rate Reduction	0.00%	0.00%
Reduced Interest Rate | Commercial Banking | Small-ticket commercial real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity		0.00%
Average Rate Reduction		0.00%
Term Extension
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	46.00%	24.00%
Average Term Extension (Months)	6 months	7 months
Term Extension | Credit Card
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	0.00%	0.00%
Average Term Extension (Months)	0 months	0 months
Term Extension | Consumer Banking
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	92.00%	91.00%
Average Term Extension (Months)	5 months	7 months
Term Extension | Consumer Banking | Auto
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	94.00%	91.00%
Average Term Extension (Months)	5 months	7 months
Term Extension | Consumer Banking | Retail banking
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	0.00%	85.00%
Average Term Extension (Months)	4 months	6 months
Term Extension | Commercial Banking
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	73.00%	0.00%
Average Term Extension (Months)	12 months	0 months
Term Extension | Commercial Banking | Total commercial lending
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity		0.00%
Average Term Extension (Months)		0 months
Term Extension | Commercial Banking | Commercial and multifamily real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	100.00%	0.00%
Average Term Extension (Months)	12 months	0 months
Term Extension | Commercial Banking | Commercial and industrial
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	0.00%	0.00%
Average Term Extension (Months)	0 months	0 months
Term Extension | Commercial Banking | Small-ticket commercial real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity		0.00%
Average Term Extension (Months)		0 months
Domestic credit card: | Credit Card
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Loans Modified	$ 89	$ 98
Domestic credit card: | Reduced Interest Rate | Credit Card
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	100.00%	100.00%
Average Rate Reduction	16.45%	16.42%
Domestic credit card: | Term Extension | Credit Card
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	0.00%	0.00%
Average Term Extension (Months)	0 months	0 months
International card businesses: | Credit Card
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Loans Modified	$ 51	$ 47
International card businesses: | Reduced Interest Rate | Credit Card
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	100.00%	100.00%
Average Rate Reduction	27.32%	27.59%
International card businesses: | Term Extension | Credit Card
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	0.00%	0.00%
Average Term Extension (Months)	0 months	0 months

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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953676-111524

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