Loans - Credit Card Loan Portfolio, Delinquency Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Loans and Leases Receivable Disclosure [Line Items]
Total retained loans	$ 1,280,870	$ 1,089,598	$ 1,010,206
Total gross charge-offs	7,653	4,326	$ 4,564
Credit card
Loans and Leases Receivable Disclosure [Line Items]
Revolving loans within revolving period	210,117	184,379
Revolving loans converted to term loans	1,006	796
Total retained loans	$ 211,123	$ 185,175
% of 30 plus days past due to total retained loans, Revolving loans within the revolving period	2.09%	1.40%
% of 30 plus days past due to total retained loans, Revolving loans converted to term loans	12.33%	12.56%
% of 30 plus days past due to total retained loans	2.14%	1.45%
% of 90 plus days past due to total retained loans, Revolving loans within the revolving period	1.03%	0.67%
% of 90 plus days past due to total retained loans, Revolving loans converted to term loans	3.98%	4.52%
% of 90 plus days past due to total retained loans	1.05%	0.68%
Gross charge-offs originated within the revolving period	$ 5,325
Gross charge-offs originated converted to term loans	166
Total gross charge-offs	5,491
Credit card | Current and less than 30 days past due and still accruing
Loans and Leases Receivable Disclosure [Line Items]
Revolving loans within revolving period	205,731	$ 181,793
Revolving loans converted to term loans	882	696
Total retained loans	206,613	182,489
Credit card | 30–89 days past due and still accruing
Loans and Leases Receivable Disclosure [Line Items]
Revolving loans within revolving period	2,217	1,356
Revolving loans converted to term loans	84	64
Total retained loans	2,301	1,420
Credit card | 90 or more days past due and still accruing
Loans and Leases Receivable Disclosure [Line Items]
Revolving loans within revolving period	2,169	1,230
Revolving loans converted to term loans	40	36
Total retained loans	$ 2,209	$ 1,266