Business Segments and Revenue from Contracts with Customers - Revenue from Contracts with Customers (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disaggregation of Revenue [Line Items]
Total contract revenue (loss)	$ 5,645	$ 5,417	$ 4,780
Revenue (reduction) from other sources	1,901	1,719	1,484
Total non-interest income	7,546	7,136	6,264
Operating segments | Credit Card
Disaggregation of Revenue [Line Items]
Total contract revenue (loss)	4,746	4,573	3,880
Revenue (reduction) from other sources	1,194	1,198	926
Total non-interest income	5,940	5,771	4,806
Operating segments | Consumer Banking
Disaggregation of Revenue [Line Items]
Total contract revenue (loss)	555	485	513
Revenue (reduction) from other sources	34	(16)	41
Total non-interest income	589	469	554
Operating segments | Commercial Banking
Disaggregation of Revenue [Line Items]
Total contract revenue (loss)	344	361	388
Revenue (reduction) from other sources	658	768	760
Total non-interest income	1,002	1,129	1,148
Other
Disaggregation of Revenue [Line Items]
Total contract revenue (loss)	0	(2)	(1)
Revenue (reduction) from other sources	15	(231)	(243)
Total non-interest income	15	(233)	(244)
Interchange fees, net
Disaggregation of Revenue [Line Items]
Total contract revenue (loss)	4,793	4,606	3,860
Customer reward expenses	8,200	7,600	6,400
Interchange fees, net | Operating segments | Credit Card
Disaggregation of Revenue [Line Items]
Total contract revenue (loss)	4,333	4,178	3,497
Interchange fees, net | Operating segments | Consumer Banking
Disaggregation of Revenue [Line Items]
Total contract revenue (loss)	367	320	267
Interchange fees, net | Operating segments | Commercial Banking
Disaggregation of Revenue [Line Items]
Total contract revenue (loss)	91	109	96
Interchange fees, net | Other
Disaggregation of Revenue [Line Items]
Total contract revenue (loss)	2	(1)	0
Service charges and other customer-related fees
Disaggregation of Revenue [Line Items]
Total contract revenue (loss)	306	327	457
Service charges and other customer-related fees | Operating segments | Credit Card
Disaggregation of Revenue [Line Items]
Total contract revenue (loss)	0	0	0
Service charges and other customer-related fees | Operating segments | Consumer Banking
Disaggregation of Revenue [Line Items]
Total contract revenue (loss)	86	91	171
Service charges and other customer-related fees | Operating segments | Commercial Banking
Disaggregation of Revenue [Line Items]
Total contract revenue (loss)	222	236	287
Service charges and other customer-related fees | Other
Disaggregation of Revenue [Line Items]
Total contract revenue (loss)	(2)	0	(1)
Other
Disaggregation of Revenue [Line Items]
Total contract revenue (loss)	546	484	463
Other | Operating segments | Credit Card
Disaggregation of Revenue [Line Items]
Total contract revenue (loss)	413	395	383
Other | Operating segments | Consumer Banking
Disaggregation of Revenue [Line Items]
Total contract revenue (loss)	102	74	75
Other | Operating segments | Commercial Banking
Disaggregation of Revenue [Line Items]
Total contract revenue (loss)	31	16	5
Other | Other
Disaggregation of Revenue [Line Items]
Total contract revenue (loss)	$ 0	$ (1)	$ 0