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, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Disaggregation of Revenue [Line Items]
Total contract revenue	$ 1,407	$ 1,241	$ 2,640	$ 2,242
Revenue (reduction) from other sources	308	390	851	680
Non-interest income (loss)	1,715	1,631	3,491	2,922
Operating segments | Credit Card
Disaggregation of Revenue [Line Items]
Total contract revenue	1,191	1,019	2,223	1,832
Revenue (reduction) from other sources	219	234	645	450
Non-interest income (loss)	1,410	1,253	2,868	2,282
Operating segments | Consumer Banking
Disaggregation of Revenue [Line Items]
Total contract revenue	122	131	236	251
Revenue (reduction) from other sources	(26)	13	(35)	34
Non-interest income (loss)	96	144	201	285
Operating segments | Commercial Banking
Disaggregation of Revenue [Line Items]
Total contract revenue	94	91	181	159
Revenue (reduction) from other sources	178	166	368	338
Non-interest income (loss)	272	257	549	497
Other
Disaggregation of Revenue [Line Items]
Total contract revenue	0	0	0	0
Revenue (reduction) from other sources	(63)	(23)	(127)	(142)
Non-interest income (loss)	(63)	(23)	(127)	(142)
Interchange fees, net
Disaggregation of Revenue [Line Items]
Total contract revenue	1,201	1,016	2,234	1,833
Interchange fees, net | Operating segments | Credit Card
Disaggregation of Revenue [Line Items]
Total contract revenue	1,093	925	2,030	1,668
Interchange fees, net | Operating segments | Consumer Banking
Disaggregation of Revenue [Line Items]
Total contract revenue	80	67	151	124
Interchange fees, net | Operating segments | Commercial Banking
Disaggregation of Revenue [Line Items]
Total contract revenue	28	24	52	41
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	84	111	174	205
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	45	47	89
Service charges and other customer-related fees | Operating segments | Commercial Banking
Disaggregation of Revenue [Line Items]
Total contract revenue	63	66	128	116
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	122	114	232	204
Other | Operating segments | Credit Card
Disaggregation of Revenue [Line Items]
Total contract revenue	98	94	193	164
Other | Operating segments | Consumer Banking
Disaggregation of Revenue [Line Items]
Total contract revenue	21	19	38	38
Other | Operating segments | Commercial Banking
Disaggregation of Revenue [Line Items]
Total contract revenue	3	1	1	2
Other | Other
Disaggregation of Revenue [Line Items]
Total contract revenue	$ 0	$ 0	$ 0	$ 0