Loans and Allowance for Credit Losses - Impaired Loans Average Recorded Investment and Interest Income Recognized (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	$ 5,839	$ 6,193	$ 5,898	$ 6,294
Interest Income Recognized	65	73	130	142
Commercial [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	842	335	756	323
Interest Income Recognized	3	4	4	6
Commercial Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	302	445	314	497
Interest Income Recognized	3	7	6	10
Residential Mortgages [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	2,452	2,688	2,496	2,696
Interest Income Recognized	31	33	63	66
Other Retail [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	297	342	301	348
Interest Income Recognized	3	3	6	7
Credit Card [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	212	222	211	228
Interest Income Recognized	1	1	2	3
Total Loans, Excluding GNMA and Covered Loans [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	4,105	4,032	4,078	4,092
Interest Income Recognized	41	48	81	92
Covered Loans [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	38	42	38	42
Interest Income Recognized	1		1
Government National Mortgage Association [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	1,696	2,119	1,782	2,160
Interest Income Recognized	$ 23	$ 25	$ 48	$ 50