Loans - Trouble Debt Restructurings (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Loans Modified	$ 812	$ 1,489	$ 998
Credit Card
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Loans Modified	277	411	524
Consumer Banking
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Loans Modified	374	541	275
Consumer Banking | Auto
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Loans Modified	371	536	268
Consumer Banking | Retail banking
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Loans Modified	3	5	7
Commercial Banking
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Loans Modified	161	537	199
Commercial Banking | Total commercial lending
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Loans Modified			198
Commercial Banking | Commercial and multifamily real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Loans Modified	49	98	39
Commercial Banking | Commercial And Industrial [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Loans Modified	$ 112	$ 439	159
Commercial Banking | Small-ticket commercial real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Loans Modified			$ 1
Reduced Interest Rate
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	55.00%	33.00%	67.00%
Average Rate Reduction	16.26%	18.06%	16.37%
Reduced Interest Rate | Credit Card
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	100.00%	100.00%	100.00%
Average Rate Reduction	21.15%	20.61%	20.12%
Reduced Interest Rate | Consumer Banking
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	42.00%	11.00%	38.00%
Average Rate Reduction	8.70%	5.73%	3.68%
Reduced Interest Rate | Consumer Banking | Auto
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	43.00%	11.00%	39.00%
Average Rate Reduction	8.72%	5.68%	3.63%
Reduced Interest Rate | Consumer Banking | Retail banking
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	13.00%	11.00%	11.00%
Average Rate Reduction	2.94%	10.86%	10.66%
Reduced Interest Rate | Commercial Banking
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	6.00%	3.00%	19.00%
Average Rate Reduction	1.19%	0.14%	0.04%
Reduced Interest Rate | Commercial Banking | Total commercial lending
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity			19.00%
Average Rate Reduction			0.04%
Reduced Interest Rate | Commercial Banking | Commercial and multifamily real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	21.00%	0.00%	87.00%
Average Rate Reduction	1.19%	0.00%	0.00%
Reduced Interest Rate | Commercial Banking | Commercial And Industrial [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	0.00%	4.00%	3.00%
Average Rate Reduction	0.00%	0.14%	0.33%
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	52.00%	55.00%	28.00%
Average Term Extension (Months)	5 months	8 months	7 months
Term Extension | Credit Card
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	0.00%	0.00%	0.00%
Average Term Extension (Months)	0 months	0 months	0 months
Term Extension | Consumer Banking
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	93.00%	94.00%	89.00%
Average Term Extension (Months)	4 months	3 months	7 months
Term Extension | Consumer Banking | Auto
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	93.00%	95.00%	90.00%
Average Term Extension (Months)	4 months	3 months	7 months
Term Extension | Consumer Banking | Retail banking
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	30.00%	20.00%	54.00%
Average Term Extension (Months)	42 months	8 months	3 months
Term Extension | Commercial Banking
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	46.00%	58.00%	18.00%
Average Term Extension (Months)	9 months	17 months	7 months
Term Extension | Commercial Banking | Total commercial lending
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity			18.00%
Average Term Extension (Months)			7 months
Term Extension | Commercial Banking | Commercial and multifamily real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	85.00%	86.00%	13.00%
Average Term Extension (Months)	11 months	5 months	1 month
Term Extension | Commercial Banking | Commercial And Industrial [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	30.00%	52.00%	20.00%
Average Term Extension (Months)	6 months	21 months	8 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
Principal Forgiveness
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	0.00%	1.00%	0.00%
Gross Balance Reduction	$ 1	$ 8	$ 1
Principal Forgiveness | Credit Card
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	0.00%	0.00%	0.00%
Gross Balance Reduction	$ 0	$ 0	$ 0
Principal Forgiveness | Consumer Banking
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	0.00%	0.00%	2.00%
Gross Balance Reduction	$ 1	$ 1	$ 1
Principal Forgiveness | Consumer Banking | Auto
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	0.00%	0.00%	1.00%
Gross Balance Reduction	$ 1	$ 1	$ 1
Principal Forgiveness | Consumer Banking | Retail banking
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	0.00%	0.00%	33.00%
Gross Balance Reduction	$ 0	$ 0	$ 0
Principal Forgiveness | Commercial Banking
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	0.00%	3.00%	0.00%
Gross Balance Reduction	$ 0	$ 7	$ 0
Principal Forgiveness | Commercial Banking | Total commercial lending
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity			0.00%
Gross Balance Reduction			$ 0
Principal Forgiveness | Commercial Banking | Commercial and multifamily real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	0.00%	0.00%	0.00%
Gross Balance Reduction	$ 0	$ 0	$ 0
Principal Forgiveness | Commercial Banking | Commercial And Industrial [Member]
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	0.00%	4.00%	0.00%
Gross Balance Reduction	$ 0	$ 7	$ 0
Principal Forgiveness | Commercial Banking | Small-ticket commercial real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity			0.00%
Gross Balance Reduction			$ 0
Domestic credit card: | Credit Card
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Loans Modified	$ 154	$ 243	$ 351
Domestic credit card: | Reduced Interest Rate | Credit Card
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	100.00%	100.00%	100.00%
Average Rate Reduction	15.90%	15.94%	16.60%
Domestic credit card: | Term Extension | Credit Card
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	0.00%	0.00%	0.00%
Average Term Extension (Months)	0 months	0 months	0 months
Domestic credit card: | Principal Forgiveness | Credit Card
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	0.00%	0.00%	0.00%
Gross Balance Reduction	$ 0	$ 0	$ 0
International card businesses: | Credit Card
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total Loans Modified	$ 123	$ 168	$ 173
International card businesses: | Reduced Interest Rate | Credit Card
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	100.00%	100.00%	100.00%
Average Rate Reduction	27.70%	27.38%	27.28%
International card businesses: | Term Extension | Credit Card
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	0.00%	0.00%	0.00%
Average Term Extension (Months)	0 months	0 months	0 months
International card businesses: | Principal Forgiveness | Credit Card
Financing Receivable, Troubled Debt Restructuring [Line Items]
% of TDR Activity	0.00%	0.00%	0.00%
Gross Balance Reduction	$ 0	$ 0	$ 0