Loans - Wholesale Loan Portfolio, Financial Effect and Payment Status of FDMs (Details) - Wholesale - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2023
Secured by real estate
Financing Receivable, Modified [Line Items]
Amortized cost basis	$ 60	$ 125
Secured by real estate | Criticized nonaccrual
Financing Receivable, Modified [Line Items]
Amortized cost basis	0	8
Secured by real estate | Current and less than 30 days past due and still accruing
Financing Receivable, Modified [Line Items]
Amortized cost basis	60	117
Secured by real estate | 30–89 days past due and still accruing
Financing Receivable, Modified [Line Items]
Amortized cost basis	0	0
Secured by real estate | 90 or more days past due and still accruing
Financing Receivable, Modified [Line Items]
Amortized cost basis	0	0
Secured by real estate | Interest rate reduction
Financing Receivable, Modified [Line Items]
Amortized cost basis	$ 0	$ 5
% of loan modifications to total retained credit card loans	0.00%	0.00%
Weighted-average contractual interest rate reduction		3.50%
Secured by real estate | Term extension
Financing Receivable, Modified [Line Items]
Amortized cost basis	$ 60	$ 112
% of loan modifications to total retained credit card loans	0.04%	0.07%
Weighted-average term loan extensions	14 months	13 months
Secured by real estate | Other-than-insignificant payment delay
Financing Receivable, Modified [Line Items]
Amortized cost basis	$ 0	$ 2
% of loan modifications to total retained credit card loans	0.00%	0.00%
Secured by real estate | Interest rate reduction and term extension
Financing Receivable, Modified [Line Items]
Amortized cost basis	$ 0	$ 1
% of loan modifications to total retained credit card loans	0.00%	0.00%
Weighted-average contractual interest rate reduction		2.71%
Weighted-average term loan extensions		9 months
Secured by real estate | Other-than-insignificant payment delay and interest rate reduction
Financing Receivable, Modified [Line Items]
Amortized cost basis	$ 0	$ 5
% of loan modifications to total retained credit card loans	0.00%	0.00%
Weighted-average contractual interest rate reduction		1.84%
Commercial and industrial
Financing Receivable, Modified [Line Items]
Amortized cost basis	$ 715	$ 1,028
Commercial and industrial | Criticized nonaccrual
Financing Receivable, Modified [Line Items]
Amortized cost basis	201	315
Commercial and industrial | Current and less than 30 days past due and still accruing
Financing Receivable, Modified [Line Items]
Amortized cost basis	504	703
Commercial and industrial | 30–89 days past due and still accruing
Financing Receivable, Modified [Line Items]
Amortized cost basis	0	0
Commercial and industrial | 90 or more days past due and still accruing
Financing Receivable, Modified [Line Items]
Amortized cost basis	10	10
Commercial and industrial | Term extension
Financing Receivable, Modified [Line Items]
Amortized cost basis	$ 372	$ 669
% of loan modifications to total retained credit card loans	0.22%	0.40%
Weighted-average term loan extensions	21 months	19 months
Commercial and industrial | Other-than-insignificant payment delay
Financing Receivable, Modified [Line Items]
Amortized cost basis	$ 309	$ 310
% of loan modifications to total retained credit card loans	0.19%	0.19%
Commercial and industrial | Other-than-insignificant payment delay and term extension
Financing Receivable, Modified [Line Items]
Amortized cost basis	$ 32	$ 32
% of loan modifications to total retained credit card loans	0.02%	0.02%
Weighted-average term loan extensions	6 months	6 months
Commercial and industrial | Other-than-insignificant payment delay and interest rate reduction and term extension
Financing Receivable, Modified [Line Items]
Amortized cost basis	$ 2	$ 2
% of loan modifications to total retained credit card loans	0.00%	0.00%
Weighted-average contractual interest rate reduction	0.75%	0.75%
Weighted-average term loan extensions	31 months	31 months
Commercial and industrial | Term extension and principal forgiveness
Financing Receivable, Modified [Line Items]
Amortized cost basis	$ 0	$ 14
% of loan modifications to total retained credit card loans	0.00%	0.01%
Weighted-average term loan extensions		73 months
Reduction in amortized cost basis		$ 23
Commercial and industrial | Interest rate reduction and term extension
Financing Receivable, Modified [Line Items]
Amortized cost basis	$ 0	$ 1
% of loan modifications to total retained credit card loans	0.00%	0.00%
Weighted-average contractual interest rate reduction		1.36%
Weighted-average term loan extensions		18 months
Other
Financing Receivable, Modified [Line Items]
Amortized cost basis	$ 595	$ 837
Other | Criticized nonaccrual
Financing Receivable, Modified [Line Items]
Amortized cost basis	551	561
Other | Current and less than 30 days past due and still accruing
Financing Receivable, Modified [Line Items]
Amortized cost basis	16	248
Other | 30–89 days past due and still accruing
Financing Receivable, Modified [Line Items]
Amortized cost basis	28	28
Other | 90 or more days past due and still accruing
Financing Receivable, Modified [Line Items]
Amortized cost basis	0	0
Other | Interest rate reduction
Financing Receivable, Modified [Line Items]
Amortized cost basis	$ 0	$ 9
% of loan modifications to total retained credit card loans	0.00%	0.00%
Weighted-average contractual interest rate reduction		6.54%
Other | Term extension
Financing Receivable, Modified [Line Items]
Amortized cost basis	$ 100	$ 100
% of loan modifications to total retained credit card loans	0.03%	0.03%
Weighted-average term loan extensions	27 months	30 months
Other | Other-than-insignificant payment delay and term extension
Financing Receivable, Modified [Line Items]
Amortized cost basis	$ 0	$ 233
% of loan modifications to total retained credit card loans	0.00%	0.07%
Weighted-average term loan extensions		144 months
Other | Interest rate reduction and term extension
Financing Receivable, Modified [Line Items]
Amortized cost basis	$ 495	$ 495
% of loan modifications to total retained credit card loans	0.14%	0.14%
Weighted-average contractual interest rate reduction	17.08%	17.08%
Weighted-average term loan extensions	7 months	7 months