Business Segments and Revenue from Contracts with Customers - Revenue from Contracts with Customers (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Total contract revenue	$ 4,780	$ 3,737	$ 3,820
Revenue (reduction) from other sources	1,484	1,873	1,433
Non-interest income (loss)	6,264	5,610	5,253
Operating segments | Credit Card
Disaggregation of Revenue [Line Items]
Total contract revenue	3,880	3,062	3,045
Revenue (reduction) from other sources	926	761	843
Non-interest income (loss)	4,806	3,823	3,888
Operating segments | Consumer Banking
Disaggregation of Revenue [Line Items]
Total contract revenue	513	436	604
Revenue (reduction) from other sources	41	30	39
Non-interest income (loss)	554	466	643
Operating segments | Commercial Banking
Disaggregation of Revenue [Line Items]
Total contract revenue	388	242	178
Revenue (reduction) from other sources	760	681	653
Non-interest income (loss)	1,148	923	831
Other
Disaggregation of Revenue [Line Items]
Total contract revenue	(1)	(3)	(7)
Revenue (reduction) from other sources	(243)	401	(102)
Non-interest income (loss)	(244)	398	(109)
Interchange fees, net
Disaggregation of Revenue [Line Items]
Total contract revenue	3,860	3,017	3,179
Customer reward expenses	6,400	4,900	4,900
Interchange fees, net | Operating segments | Credit Card
Disaggregation of Revenue [Line Items]
Total contract revenue	3,497	2,747	2,925
Interchange fees, net | Operating segments | Consumer Banking
Disaggregation of Revenue [Line Items]
Total contract revenue	267	209	205
Interchange fees, net | Operating segments | Commercial Banking
Disaggregation of Revenue [Line Items]
Total contract revenue	96	63	55
Interchange fees, net | Other
Disaggregation of Revenue [Line Items]
Total contract revenue	0	(2)	(6)
Service charges and other customer-related fees
Disaggregation of Revenue [Line Items]
Total contract revenue	457	362	417
Service charges and other customer-related fees | Operating segments | Credit Card
Disaggregation of Revenue [Line Items]
Total contract revenue	0	0	0
Service charges and other customer-related fees | Operating segments | Consumer Banking
Disaggregation of Revenue [Line Items]
Total contract revenue	171	188	298
Service charges and other customer-related fees | Operating segments | Commercial Banking
Disaggregation of Revenue [Line Items]
Total contract revenue	287	175	120
Service charges and other customer-related fees | Other
Disaggregation of Revenue [Line Items]
Total contract revenue	(1)	(1)	(1)
Other
Disaggregation of Revenue [Line Items]
Total contract revenue	463	358	224
Other | Operating segments | Credit Card
Disaggregation of Revenue [Line Items]
Total contract revenue	383	315	120
Other | Operating segments | Consumer Banking
Disaggregation of Revenue [Line Items]
Total contract revenue	75	39	101
Other | Operating segments | Commercial Banking
Disaggregation of Revenue [Line Items]
Total contract revenue	5	4	3
Other | Other
Disaggregation of Revenue [Line Items]
Total contract revenue	$ 0	$ 0	$ 0