Loans and Allowance for Credit Losses - Summary of Impaired Loans by Portfolio Class (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Financing Receivable, Impaired [Line Items]
Period-end Recorded Investment	$ 7,241	$ 7,659
Unpaid Principal Balance	10,139	11,082
Valuation Allowance	738	838
Commitments to Lend Additional Funds	49	58
Commercial [Member]
Financing Receivable, Impaired [Line Items]
Period-end Recorded Investment	384	404
Unpaid Principal Balance	1,030	1,200
Valuation Allowance	41	40
Commitments to Lend Additional Funds	24	39
Commercial Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Period-end Recorded Investment	918	1,077
Unpaid Principal Balance	1,832	2,251
Valuation Allowance	46	70
Commitments to Lend Additional Funds	10	4
Residential Mortgages [Member]
Financing Receivable, Impaired [Line Items]
Period-end Recorded Investment	2,769	2,748
Unpaid Principal Balance	3,424	3,341
Valuation Allowance	374	415
Commitments to Lend Additional Funds	3
Credit Card [Member]
Financing Receivable, Impaired [Line Items]
Period-end Recorded Investment	358	442
Unpaid Principal Balance	358	442
Valuation Allowance	114	153
Other Retail [Member]
Financing Receivable, Impaired [Line Items]
Period-end Recorded Investment	427	443
Unpaid Principal Balance	461	486
Valuation Allowance	106	101
Commitments to Lend Additional Funds	4	3
Total Impaired Loans, Excluding GNMA and Covered Loans [Member]
Financing Receivable, Impaired [Line Items]
Period-end Recorded Investment	4,856	5,114
Unpaid Principal Balance	7,105	7,720
Valuation Allowance	681	779
Commitments to Lend Additional Funds	41	46
Loans Purchased from GNMA Mortgage Pools [Member]
Financing Receivable, Impaired [Line Items]
Period-end Recorded Investment	1,851	1,778
Unpaid Principal Balance	1,851	1,778
Valuation Allowance	32	39
Covered Loans [Member]
Financing Receivable, Impaired [Line Items]
Period-end Recorded Investment	534	767
Unpaid Principal Balance	1,183	1,584
Valuation Allowance	25	20
Commitments to Lend Additional Funds	$ 8	$ 12