Loans - Credit Card Loan Portfolio, Delinquency Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total retained loans	$ 1,084,850	$ 1,018,397	$ 1,089,598
Total gross charge-offs	1,451	$ 976
Credit card
Accounts, Notes, Loans and Financing Receivable [Line Items]
Revolving loans within the revolving period	179,279		184,379
Revolving loans converted to term loans	800		796
Total retained loans	$ 180,079		$ 185,175
% of 30 plus days past due to total retained loans, Revolving loans within the revolving period	1.63%		1.40%
% of 30 plus days past due to total retained loans, Revolving loans converted to term loans	12.25%		12.56%
% of 30 plus days past due to total retained loans	1.68%		1.45%
% of 90 plus days past due to total retained loans, Revolving loans within the revolving period	0.82%		0.67%
% of 90 plus days past due to total retained loans, Revolving loans converted to term loans	4.13%		4.52%
% of 90 plus days past due to total retained loans	0.83%		0.68%
Gross charge-offs originated within the revolving period	$ 1,075
Gross charge-offs originated converted to term loans	36
Total gross charge-offs	1,111
Credit card | Current and less than 30 days past due and still accruing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Revolving loans within the revolving period	176,353		$ 181,793
Revolving loans converted to term loans	702		696
Total retained loans	177,055		182,489
Credit card | 30–89 days past due and still accruing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Revolving loans within the revolving period	1,462		1,356
Revolving loans converted to term loans	65		64
Total retained loans	1,527		1,420
Credit card | 90 or more days past due and still accruing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Revolving loans within the revolving period	1,464		1,230
Revolving loans converted to term loans	33		36
Total retained loans	$ 1,497		$ 1,266