Loans and Allowance for Credit Losses - Impaired Loans Average Recorded Investment and Interest Income (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	$ 6,395	$ 7,615
Interest Income Recognized	69	91
Commercial [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	311	417
Interest Income Recognized	2	2
Commercial Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	550	660
Interest Income Recognized	3	9
Residential Mortgages [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	2,703	2,753
Interest Income Recognized	33	35
Credit Card [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	233	300
Interest Income Recognized	2	3
Other Retail [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	355	388
Interest Income Recognized	4	4
Total Impaired Loans, Excluding GNMA and Covered Loans [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	4,152	4,518
Interest Income Recognized	44	53
Loans Purchased from GNMA Mortgage Pools [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	2,201	2,662
Interest Income Recognized	25	33
Covered Loans [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	42	435
Interest Income Recognized		$ 5