Loans - Credit Card: Net Charge-Offs (Detail) - Credit Card - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Loans and Leases Receivable Disclosure [Line Items]
Net charge-offs	$ 1,364	$ 1,377
Net charge-offs rate	4.90%	5.03%
Domestic credit card
Loans and Leases Receivable Disclosure [Line Items]
Net charge-offs	$ 1,294	$ 1,321
Net charge-offs rate	5.04%	5.26%
International card business
Loans and Leases Receivable Disclosure [Line Items]
Net charge-offs	$ 70	$ 56
Net charge-offs rate	3.20%	2.49%