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, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Disaggregation of Revenue [Line Items]
Total contract revenue	$ 1,415	$ 1,251	$ 4,055	$ 3,493
Revenue (reduction) from other sources	387	423	1,238	1,103
Non-interest income (loss)	1,802	1,674	5,293	4,596
Operating segments | Credit Card
Disaggregation of Revenue [Line Items]
Total contract revenue	1,189	1,028	3,412	2,860
Revenue (reduction) from other sources	265	235	910	685
Non-interest income (loss)	1,454	1,263	4,322	3,545
Operating segments | Consumer Banking
Disaggregation of Revenue [Line Items]
Total contract revenue	124	127	360	378
Revenue (reduction) from other sources	5	0	(30)	34
Non-interest income (loss)	129	127	330	412
Operating segments | Commercial Banking
Disaggregation of Revenue [Line Items]
Total contract revenue	102	96	283	255
Revenue (reduction) from other sources	217	210	585	548
Non-interest income (loss)	319	306	868	803
Other
Disaggregation of Revenue [Line Items]
Total contract revenue	0	0	0	0
Revenue (reduction) from other sources	(100)	(22)	(227)	(164)
Non-interest income (loss)	(100)	(22)	(227)	(164)
Interchange fees, net
Disaggregation of Revenue [Line Items]
Total contract revenue	1,195	1,022	3,429	2,855
Interchange fees, net | Operating segments | Credit Card
Disaggregation of Revenue [Line Items]
Total contract revenue	1,085	930	3,115	2,598
Interchange fees, net | Operating segments | Consumer Banking
Disaggregation of Revenue [Line Items]
Total contract revenue	83	68	234	192
Interchange fees, net | Operating segments | Commercial Banking
Disaggregation of Revenue [Line Items]
Total contract revenue	27	24	79	65
Interchange fees, net | Other
Disaggregation of Revenue [Line Items]
Total contract revenue	0	0	1	0
Service charges and other customer-related fees
Disaggregation of Revenue [Line Items]
Total contract revenue	85	113	259	318
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	23	42	70	131
Service charges and other customer-related fees | Operating segments | Commercial Banking
Disaggregation of Revenue [Line Items]
Total contract revenue	62	71	190	187
Service charges and other customer-related fees | Other
Disaggregation of Revenue [Line Items]
Total contract revenue	0	0	(1)	0
Other
Disaggregation of Revenue [Line Items]
Total contract revenue	135	116	367	320
Other | Operating segments | Credit Card
Disaggregation of Revenue [Line Items]
Total contract revenue	104	98	297	262
Other | Operating segments | Consumer Banking
Disaggregation of Revenue [Line Items]
Total contract revenue	18	17	56	55
Other | Operating segments | Commercial Banking
Disaggregation of Revenue [Line Items]
Total contract revenue	13	1	14	3
Other | Other
Disaggregation of Revenue [Line Items]
Total contract revenue	$ 0	$ 0	$ 0	$ 0