Loans - Credit Card: Net Charge-Offs (Detail) - Credit Card Portfolio Segment [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Loans and Leases Receivable Disclosure [Line Items]
Net charge-offs	$ 3,953	$ 2,918	$ 2,728
Percentage annualized net charge-off by average loans held for investment	4.09%	3.36%
Geographic Distribution, Domestic [Member]
Loans and Leases Receivable Disclosure [Line Items]
Net charge-offs	$ 3,681	$ 2,718
Percentage annualized net charge-off by average loans held for investment	4.16%	3.45%
Geographic Distribution, Foreign [Member]
Loans and Leases Receivable Disclosure [Line Items]
Net charge-offs	$ 272	$ 200
Percentage annualized net charge-off by average loans held for investment	3.33%	2.50%