Loans and Allowance for Credit Losses - Summary of Impaired Loans by Portfolio Class (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Financing Receivable, Impaired [Line Items]
Period-end Recorded Investment	$ 7,019	$ 7,659
Unpaid Principal Balance	9,876	11,082
Valuation Allowance	647	838
Commitments to Lend Additional Funds	51	58
Commercial [Member]
Financing Receivable, Impaired [Line Items]
Period-end Recorded Investment	375	404
Unpaid Principal Balance	857	1,200
Valuation Allowance	38	40
Commitments to Lend Additional Funds	25	39
Commercial Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Period-end Recorded Investment	721	1,077
Unpaid Principal Balance	1,570	2,251
Valuation Allowance	36	70
Commitments to Lend Additional Funds	14	4
Residential Mortgages [Member]
Financing Receivable, Impaired [Line Items]
Period-end Recorded Investment	2,762	2,748
Unpaid Principal Balance	3,404	3,341
Valuation Allowance	323	415
Commitments to Lend Additional Funds	2
Credit Card [Member]
Financing Receivable, Impaired [Line Items]
Period-end Recorded Investment	335	442
Unpaid Principal Balance	335	442
Valuation Allowance	101	153
Commitments to Lend Additional Funds
Other Retail [Member]
Financing Receivable, Impaired [Line Items]
Period-end Recorded Investment	408	443
Unpaid Principal Balance	609	486
Valuation Allowance	86	101
Commitments to Lend Additional Funds	3	3
Total Impaired Loans, Excluding GNMA and Covered Loans [Member]
Financing Receivable, Impaired [Line Items]
Period-end Recorded Investment	4,601	5,114
Unpaid Principal Balance	6,775	7,720
Valuation Allowance	584	779
Commitments to Lend Additional Funds	44	46
Loans Purchased from GNMA Mortgage Pools [Member]
Financing Receivable, Impaired [Line Items]
Period-end Recorded Investment	1,915	1,778
Unpaid Principal Balance	1,915	1,778
Valuation Allowance	29	39
Commitments to Lend Additional Funds
Covered Loans [Member]
Financing Receivable, Impaired [Line Items]
Period-end Recorded Investment	503	767
Unpaid Principal Balance	1,186	1,584
Valuation Allowance	34	20
Commitments to Lend Additional Funds	$ 7	$ 12