Loans and Allowance for Credit Losses - Summary of Impaired Loans by Portfolio Class (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Financing Receivable, Impaired [Line Items]
Period-end Recorded Investment	$ 7,457	$ 7,659
Unpaid Principal Balance	10,728	11,082
Valuation Allowance	774	838
Commitments to Lend Additional Funds	57	58
Commercial [Member]
Financing Receivable, Impaired [Line Items]
Period-end Recorded Investment	377	404
Unpaid Principal Balance	1,108	1,200
Valuation Allowance	32	40
Commitments to Lend Additional Funds	34	39
Commercial real estate [Member]
Financing Receivable, Impaired [Line Items]
Period-end Recorded Investment	1,033	1,077
Unpaid Principal Balance	2,015	2,251
Valuation Allowance	56	70
Commitments to Lend Additional Funds	11	4
Residential mortgages [Member]
Financing Receivable, Impaired [Line Items]
Period-end Recorded Investment	2,708	2,748
Unpaid Principal Balance	3,344	3,341
Valuation Allowance	385	415
Credit card [Member]
Financing Receivable, Impaired [Line Items]
Period-end Recorded Investment	393	442
Unpaid Principal Balance	393	442
Valuation Allowance	132	153
Other retail [Member]
Financing Receivable, Impaired [Line Items]
Period-end Recorded Investment	443	443
Unpaid Principal Balance	512	486
Valuation Allowance	114	101
Commitments to Lend Additional Funds	3	3
Total loans, excluding GNMA and covered loans [Member]
Financing Receivable, Impaired [Line Items]
Period-end Recorded Investment	4,954	5,114
Unpaid Principal Balance	7,372	7,720
Valuation Allowance	719	779
Commitments to Lend Additional Funds	48	46
Loans purchased from GNMA mortgage pools [Member]
Financing Receivable, Impaired [Line Items]
Period-end Recorded Investment	1,909	1,778
Unpaid Principal Balance	1,909	1,778
Valuation Allowance	32	39
Covered loans [Member]
Financing Receivable, Impaired [Line Items]
Period-end Recorded Investment	594	767
Unpaid Principal Balance	1,447	1,584
Valuation Allowance	23	20
Commitments to Lend Additional Funds	$ 9	$ 12