Noninterest Revenue and Noninterest Expense - Card Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disaggregation of Revenue [Line Items]
Credit cost amortization period	12 months
Direct loan origination costs amortization period	12 months
Total card income	$ 4,784	$ 4,420	$ 5,102
Interchange and merchant processing income
Disaggregation of Revenue [Line Items]
Total card income	31,021	28,085	23,592
Reward costs and partner payments
Disaggregation of Revenue [Line Items]
Total card income	(24,601)	(22,162)	(17,868)
All other
Disaggregation of Revenue [Line Items]
Total card income	$ (1,636)	$ (1,503)	$ (622)
Deferred revenues, recognition period	12 months
Minimum
Disaggregation of Revenue [Line Items]
Credit card revenue sharing agreement terms	5 years
Maximum
Disaggregation of Revenue [Line Items]
Credit card revenue sharing agreement terms	10 years