Business Segments and Revenue from Contracts with Customers - Revenue from Contracts with Customers (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Disaggregation of Revenue [Line Items]
Total contract revenue	$ 1,390	$ 1,278
Revenue (reduction) from other sources	524	439
Total non-interest income (loss)	1,914	1,717
Operating segments | Credit Card
Disaggregation of Revenue [Line Items]
Total contract revenue	1,141	1,080
Revenue (reduction) from other sources	335	283
Total non-interest income (loss)	1,476	1,363
Operating segments | Consumer Banking
Disaggregation of Revenue [Line Items]
Total contract revenue	146	126
Revenue (reduction) from other sources	13	9
Total non-interest income (loss)	159	135
Operating segments | Commercial Banking
Disaggregation of Revenue [Line Items]
Total contract revenue	103	72
Revenue (reduction) from other sources	178	140
Total non-interest income (loss)	281	212
Other
Disaggregation of Revenue [Line Items]
Total contract revenue	0	0
Revenue (reduction) from other sources	(2)	7
Total non-interest income (loss)	(2)	7
Interchange fees, net
Disaggregation of Revenue [Line Items]
Total contract revenue	1,145	1,139
Interchange fees, net | Operating segments | Credit Card
Disaggregation of Revenue [Line Items]
Total contract revenue	1,020	1,025
Interchange fees, net | Operating segments | Consumer Banking
Disaggregation of Revenue [Line Items]
Total contract revenue	98	86
Interchange fees, net | Operating segments | Commercial Banking
Disaggregation of Revenue [Line Items]
Total contract revenue	27	27
Interchange fees, net | Other
Disaggregation of Revenue [Line Items]
Total contract revenue	0	1
Service charges and other customer-related fees
Disaggregation of Revenue [Line Items]
Total contract revenue	78	60
Service charges and other customer-related fees | Operating segments | Credit Card
Disaggregation of Revenue [Line Items]
Total contract revenue	0	0
Service charges and other customer-related fees | Operating segments | Consumer Banking
Disaggregation of Revenue [Line Items]
Total contract revenue	4	21
Service charges and other customer-related fees | Operating segments | Commercial Banking
Disaggregation of Revenue [Line Items]
Total contract revenue	74	40
Service charges and other customer-related fees | Other
Disaggregation of Revenue [Line Items]
Total contract revenue	0	(1)
Other
Disaggregation of Revenue [Line Items]
Total contract revenue	167	79
Other | Operating segments | Credit Card
Disaggregation of Revenue [Line Items]
Total contract revenue	121	55
Other | Operating segments | Consumer Banking
Disaggregation of Revenue [Line Items]
Total contract revenue	44	19
Other | Operating segments | Commercial Banking
Disaggregation of Revenue [Line Items]
Total contract revenue	2	5
Other | Other
Disaggregation of Revenue [Line Items]
Total contract revenue	$ 0	$ 0