Noninterest Revenue and Noninterest Expense - Card Income (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Total card income	$ 1,366	$ 1,020	$ 2,640	$ 2,295
Interchange and merchant processing income
Disaggregation of Revenue [Line Items]
Total card income	5,184	4,723	9,905	9,082
Rewards costs and partner payments
Disaggregation of Revenue [Line Items]
Total card income	(3,610)	(3,527)	(6,846)	(6,411)
Adjustment to credit card rewards liability		330		330
Other card income
Disaggregation of Revenue [Line Items]
Total card income	$ (208)	$ (176)	$ (419)	$ (376)
Deferred revenues, recognition period	12 months		12 months