Business Segments and Revenue from Contracts with Customers - Revenue from Contracts with Customers (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Disaggregation of Revenue [Line Items]
Total contract revenue	$ 1,475	$ 1,415	$ 4,169	$ 4,055
Revenue (reduction) from other sources	468	387	1,390	1,238
Non-interest income (loss)	1,943	1,802	5,559	5,293
Operating segments | Credit Card
Disaggregation of Revenue [Line Items]
Total contract revenue	1,226	1,189	3,508	3,412
Revenue (reduction) from other sources	287	265	867	910
Non-interest income (loss)	1,513	1,454	4,375	4,322
Operating segments | Consumer Banking
Disaggregation of Revenue [Line Items]
Total contract revenue	141	124	408	360
Revenue (reduction) from other sources	1	5	18	(30)
Non-interest income (loss)	142	129	426	330
Operating segments | Commercial Banking
Disaggregation of Revenue [Line Items]
Total contract revenue	108	102	253	283
Revenue (reduction) from other sources	180	217	504	585
Non-interest income (loss)	288	319	757	868
Other
Disaggregation of Revenue [Line Items]
Total contract revenue	0	0	0	0
Revenue (reduction) from other sources	0	(100)	1	(227)
Non-interest income (loss)	0	(100)	1	(227)
Interchange fees, net
Disaggregation of Revenue [Line Items]
Total contract revenue	1,234	1,195	3,586	3,429
Interchange fees, net | Operating segments | Credit Card
Disaggregation of Revenue [Line Items]
Total contract revenue	1,115	1,085	3,251	3,115
Interchange fees, net | Operating segments | Consumer Banking
Disaggregation of Revenue [Line Items]
Total contract revenue	92	83	270	234
Interchange fees, net | Operating segments | Commercial Banking
Disaggregation of Revenue [Line Items]
Total contract revenue	27	27	64	79
Interchange fees, net | Other
Disaggregation of Revenue [Line Items]
Total contract revenue	0	0	1	1
Service charges and other customer-related fees
Disaggregation of Revenue [Line Items]
Total contract revenue	99	85	236	259
Service charges and other customer-related fees | Operating segments | Credit Card
Disaggregation of Revenue [Line Items]
Total contract revenue	0	0	0	0
Service charges and other customer-related fees | Operating segments | Consumer Banking
Disaggregation of Revenue [Line Items]
Total contract revenue	21	23	64	70
Service charges and other customer-related fees | Operating segments | Commercial Banking
Disaggregation of Revenue [Line Items]
Total contract revenue	78	62	173	190
Service charges and other customer-related fees | Other
Disaggregation of Revenue [Line Items]
Total contract revenue	0	0	(1)	(1)
Other
Disaggregation of Revenue [Line Items]
Total contract revenue	142	135	347	367
Other | Operating segments | Credit Card
Disaggregation of Revenue [Line Items]
Total contract revenue	111	104	257	297
Other | Operating segments | Consumer Banking
Disaggregation of Revenue [Line Items]
Total contract revenue	28	18	74	56
Other | Operating segments | Commercial Banking
Disaggregation of Revenue [Line Items]
Total contract revenue	3	13	16	14
Other | Other
Disaggregation of Revenue [Line Items]
Total contract revenue	$ 0	$ 0	$ 0	$ 0