Loans - Credit Card: Net Charge-Offs (Detail) - Credit Card Portfolio Segment [Member] - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Loans and Leases Receivable Disclosure [Line Items]
Net charge-offs	$ 1,256	$ 949	$ 2,527	$ 1,899
Percentage annualized net charge-off by average loans held for investment	5.02%	4.02%	5.02%	4.05%
Geographic Distribution, Domestic [Member]
Loans and Leases Receivable Disclosure [Line Items]
Net charge-offs	$ 1,172	$ 874	$ 2,368	$ 1,761
Percentage annualized net charge-off by average loans held for investment	5.11%	4.07%	5.12%	4.12%
Geographic Distribution, Foreign [Member]
Loans and Leases Receivable Disclosure [Line Items]
Net charge-offs	$ 84	$ 75	$ 159	$ 138
Percentage annualized net charge-off by average loans held for investment	4.08%	3.54%	3.88%	3.39%