Noninterest Revenue and Noninterest Expense - Card Income (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Total card income	$ 1,283	$ 1,328	$ 3,923	$ 3,623
Interchange and merchant processing income
Disaggregation of Revenue [Line Items]
Total card income	5,127	4,781	15,032	13,863
Rewards costs and partner payments
Disaggregation of Revenue [Line Items]
Total card income	(3,669)	(3,276)	(10,515)	(9,687)
Adjustment to credit card rewards liability		330		330
Other card income
Disaggregation of Revenue [Line Items]
Total card income	$ (175)	$ (177)	$ (594)	$ (553)
Deferred revenues, recognition period	12 months		12 months