Loans and Allowance for Credit Losses - Additional Information on Impaired Loans (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	$ 7,560	$ 7,914
Interest Income Recognized	95	63
Commercial [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	391	569
Interest Income Recognized	10	3
Commercial real estate [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	1,055	1,524
Interest Income Recognized	11	7
Residential mortgages [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	2,728	2,638
Interest Income Recognized	34	26
Credit card [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	418	548
Interest Income Recognized	4	8
Other retail [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	443	180
Interest Income Recognized	6	2
Total loans, excluding GNMA and covered loans [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	5,035	5,459
Interest Income Recognized	65	46
Loans purchased from GNMA mortgage pools [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	1,844	1,277
Interest Income Recognized	23	15
Covered loans [Member]
Financing Receivable, Impaired [Line Items]
Average Recorded Investment	681	1,178
Interest Income Recognized	$ 7	$ 2