Loans - Credit Card: Net Charge-Offs (Detail) - Credit Card Portfolio Segment [Member] - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Loans and Leases Receivable Disclosure [Line Items]
Net charge-offs	$ 1,271	$ 950
Percentage annualized net charge-off by average loans held for investment	5.02%	4.09%
Geographic Distribution, Domestic [Member]
Loans and Leases Receivable Disclosure [Line Items]
Net charge-offs	$ 1,196	$ 887
Percentage annualized net charge-off by average loans held for investment	5.14%	4.16%
Geographic Distribution, Foreign [Member]
Loans and Leases Receivable Disclosure [Line Items]
Net charge-offs	$ 75	$ 63
Percentage annualized net charge-off by average loans held for investment	3.69%	3.24%