Business Segments and Revenue from Contracts with Customers - Revenue from Contracts with Customers (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Disaggregation of Revenue [Line Items]
Total contract revenue	$ 1,233	$ 1,001
Revenue (reduction) from other sources	543	290
Non-interest income (loss)	1,776	1,291
Operating segments | Credit Card
Disaggregation of Revenue [Line Items]
Total contract revenue	1,032	813
Revenue (reduction) from other sources	426	216
Non-interest income (loss)	1,458	1,029
Operating segments | Consumer Banking
Disaggregation of Revenue [Line Items]
Total contract revenue	114	120
Revenue (reduction) from other sources	(9)	21
Non-interest income (loss)	105	141
Operating segments | Commercial Banking
Disaggregation of Revenue [Line Items]
Total contract revenue	87	68
Revenue (reduction) from other sources	190	172
Non-interest income (loss)	277	240
Other
Disaggregation of Revenue [Line Items]
Total contract revenue	0	0
Revenue (reduction) from other sources	(64)	(119)
Non-interest income (loss)	(64)	(119)
Interchange fees, net
Disaggregation of Revenue [Line Items]
Total contract revenue	1,033	817
Interchange fees, net | Operating segments | Credit Card
Disaggregation of Revenue [Line Items]
Total contract revenue	937	743
Interchange fees, net | Operating segments | Consumer Banking
Disaggregation of Revenue [Line Items]
Total contract revenue	71	57
Interchange fees, net | Operating segments | Commercial Banking
Disaggregation of Revenue [Line Items]
Total contract revenue	24	17
Interchange fees, net | Other
Disaggregation of Revenue [Line Items]
Total contract revenue	1	0
Service charges and other customer-related fees
Disaggregation of Revenue [Line Items]
Total contract revenue	90	94
Service charges and other customer-related fees | Operating segments | Credit Card
Disaggregation of Revenue [Line Items]
Total contract revenue	0	0
Service charges and other customer-related fees | Operating segments | Consumer Banking
Disaggregation of Revenue [Line Items]
Total contract revenue	26	44
Service charges and other customer-related fees | Operating segments | Commercial Banking
Disaggregation of Revenue [Line Items]
Total contract revenue	65	50
Service charges and other customer-related fees | Other
Disaggregation of Revenue [Line Items]
Total contract revenue	(1)	0
Other
Disaggregation of Revenue [Line Items]
Total contract revenue	110	90
Other | Operating segments | Credit Card
Disaggregation of Revenue [Line Items]
Total contract revenue	95	70
Other | Operating segments | Consumer Banking
Disaggregation of Revenue [Line Items]
Total contract revenue	17	19
Other | Operating segments | Commercial Banking
Disaggregation of Revenue [Line Items]
Total contract revenue	(2)	1
Other | Other
Disaggregation of Revenue [Line Items]
Total contract revenue	$ 0	$ 0