Loans - Trouble Debt Restructurings (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Loans Modified	$ 629	$ 160	$ 1,134	$ 422
Credit Card
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Loans Modified	$ 87	$ 60	$ 183	$ 143
Credit Card | Reduced Interest Rate
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	100.00%	100.00%	100.00%	100.00%
Average Rate Reduction	19.70%	21.22%	19.54%	21.43%
Consumer Banking
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Loans Modified	$ 280	$ 66	$ 520	$ 181
Consumer Banking | Term Extension
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	97.00%	91.00%	97.00%	94.00%
Average Term Extension (Months)	4 months	4 months	4 months	3 months
Consumer Banking | Reduced Interest Rate
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	49.00%	38.00%	52.00%	36.00%
Average Rate Reduction	8.56%	8.62%	8.68%	8.85%
Consumer Banking | Auto
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Loans Modified	$ 280	$ 65	$ 519	$ 180
Consumer Banking | Auto | Term Extension
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	97.00%	91.00%	97.00%	94.00%
Average Term Extension (Months)	4 months	4 months	4 months	3 months
Consumer Banking | Auto | Reduced Interest Rate
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	49.00%	39.00%	52.00%	36.00%
Average Rate Reduction	8.56%	8.62%	8.68%	8.87%
Consumer Banking | Retail banking
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Loans Modified		$ 1	$ 1	$ 1
Consumer Banking | Retail banking | Term Extension
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity		100.00%	100.00%	69.00%
Average Term Extension (Months)		41 months	12 months	28 months
Consumer Banking | Retail banking | Reduced Interest Rate
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity				31.00%
Average Rate Reduction				3.77%
Commercial Banking
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Loans Modified	$ 262	$ 34	$ 431	$ 98
Commercial Banking | Term Extension
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	62.00%	56.00%	64.00%	51.00%
Average Term Extension (Months)	14 months	17 months	13 months	11 months
Commercial Banking | Reduced Interest Rate
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity			2.00%
Average Rate Reduction			0.29%
Commercial Banking | Commercial and multifamily real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Loans Modified	$ 133		$ 264	$ 20
Commercial Banking | Commercial and multifamily real estate | Term Extension
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	91.00%		77.00%	100.00%
Average Term Extension (Months)	14 months		13 months	14 months
Commercial Banking | Commercial and multifamily real estate | Reduced Interest Rate
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity			4.00%
Average Rate Reduction			0.29%
Commercial Banking | Commercial And Industrial [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Loans Modified	$ 129	$ 34	$ 167	$ 78
Commercial Banking | Commercial And Industrial [Member] | Term Extension
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	33.00%	56.00%	45.00%	38.00%
Average Term Extension (Months)	13 months	17 months	12 months	8 months
Domestic credit card: | Credit Card
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Loans Modified	$ 57	$ 33	$ 119	$ 77
Domestic credit card: | Credit Card | Reduced Interest Rate
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	100.00%	100.00%	100.00%	100.00%
Average Rate Reduction	15.56%	16.07%	15.09%	16.10%
International card businesses: | Credit Card
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Loans Modified	$ 30	$ 27	$ 64	$ 66
International card businesses: | Credit Card | Reduced Interest Rate
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	100.00%	100.00%	100.00%	100.00%
Average Rate Reduction	27.65%	27.45%	27.83%	27.62%