Business Segments and Revenue from Contracts with Customers - Revenue from Contracts with Customers (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Disaggregation of Revenue [Line Items]
Total contract revenue	$ 1,416	$ 1,407	$ 2,694	$ 2,640
Revenue (reduction) from other sources	483	308	922	851
Non-interest income (loss)	1,899	1,715	3,616	3,491
Operating segments | Credit Card
Disaggregation of Revenue [Line Items]
Total contract revenue	1,202	1,191	2,282	2,223
Revenue (reduction) from other sources	297	219	580	645
Non-interest income (loss)	1,499	1,410	2,862	2,868
Operating segments | Consumer Banking
Disaggregation of Revenue [Line Items]
Total contract revenue	141	122	267	236
Revenue (reduction) from other sources	8	(26)	17	(35)
Non-interest income (loss)	149	96	284	201
Operating segments | Commercial Banking
Disaggregation of Revenue [Line Items]
Total contract revenue	73	94	145	181
Revenue (reduction) from other sources	184	178	324	368
Non-interest income (loss)	257	272	469	549
Other
Disaggregation of Revenue [Line Items]
Total contract revenue	0	0	0	0
Revenue (reduction) from other sources	(6)	(63)	1	(127)
Non-interest income (loss)	(6)	(63)	1	(127)
Interchange fees, net
Disaggregation of Revenue [Line Items]
Total contract revenue	1,213	1,201	2,352	2,234
Interchange fees, net | Operating segments | Credit Card
Disaggregation of Revenue [Line Items]
Total contract revenue	1,111	1,093	2,136	2,030
Interchange fees, net | Operating segments | Consumer Banking
Disaggregation of Revenue [Line Items]
Total contract revenue	92	80	178	151
Interchange fees, net | Operating segments | Commercial Banking
Disaggregation of Revenue [Line Items]
Total contract revenue	10	28	37	52
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	77	84	137	174
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	22	21	43	47
Service charges and other customer-related fees | Operating segments | Commercial Banking
Disaggregation of Revenue [Line Items]
Total contract revenue	55	63	95	128
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	126	122	205	232
Other | Operating segments | Credit Card
Disaggregation of Revenue [Line Items]
Total contract revenue	91	98	146	193
Other | Operating segments | Consumer Banking
Disaggregation of Revenue [Line Items]
Total contract revenue	27	21	46	38
Other | Operating segments | Commercial Banking
Disaggregation of Revenue [Line Items]
Total contract revenue	8	3	13	1
Other | Other
Disaggregation of Revenue [Line Items]
Total contract revenue	$ 0	$ 0	$ 0	$ 0