Noninterest Revenue and Noninterest Expense - Card Income (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Disaggregation of Revenue [Line Items]
Total card income	$ 1,274	$ 1,275
Interchange and merchant processing income
Disaggregation of Revenue [Line Items]
Total card income	4,721	4,359
Rewards costs and partner payments
Disaggregation of Revenue [Line Items]
Total card income	(3,236)	(2,884)
Other card income
Disaggregation of Revenue [Line Items]
Total card income	$ (211)	$ (200)
Deferred revenues, recognition period	12 months