Loans and Allowance for Credit Losses - Impaired Loans Average Recorded Investment and Interest Income (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	$ 6,092	$ 7,325	$ 6,227	$ 7,514
Interest Income Recognized	65	81	207	260
Commercial [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	408	425	351	430
Interest Income Recognized	3	4	9	8
Commercial Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	388	541	461	598
Interest Income Recognized	3	4	13	17
Residential Mortgages [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	2,669	2,740	2,687	2,744
Interest Income Recognized	31	33	97	105
Credit Card [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	216	264	224	281
Interest Income Recognized	1	1	4	7
Other Retail [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	329	373	342	381
Interest Income Recognized	3	5	10	13
Total Impaired Loans, Excluding GNMA and Covered Loans [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	4,010	4,343	4,065	4,434
Interest Income Recognized	41	47	133	150
Covered Loans [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	42	335	42	389
Interest Income Recognized		5		15
Government National Mortgage Association [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	2,040	2,647	2,120	2,691
Interest Income Recognized	$ 24	$ 29	$ 74	$ 95