Loans and Allowance for Credit Losses - Summary of Impaired Loans by Portfolio Class (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Financing Receivable, Impaired [Line Items]
Period-end Recorded Investment	$ 7,659	$ 7,952
Unpaid Principal Balance	11,082	10,821
Valuation Allowance	838	1,005
Commitments to Lend Additional Funds	58	144
Commercial loan [Member]
Financing Receivable, Impaired [Line Items]
Period-end Recorded Investment	404	657
Unpaid Principal Balance	1,200	1,437
Valuation Allowance	40	62
Commitments to Lend Additional Funds	39	68
Commercial real estate [Member]
Financing Receivable, Impaired [Line Items]
Period-end Recorded Investment	1,077	1,436
Unpaid Principal Balance	2,251	2,503
Valuation Allowance	70	124
Commitments to Lend Additional Funds	4	25
Residential mortgages [Member]
Financing Receivable, Impaired [Line Items]
Period-end Recorded Investment	2,748	2,652
Unpaid Principal Balance	3,341	3,193
Valuation Allowance	415	482
Commitments to Lend Additional Funds		2
Credit card [Member]
Financing Receivable, Impaired [Line Items]
Period-end Recorded Investment	442	584
Unpaid Principal Balance	442	584
Valuation Allowance	153	219
Other retail [Member]
Financing Receivable, Impaired [Line Items]
Period-end Recorded Investment	443	188
Unpaid Principal Balance	486	197
Valuation Allowance	101	57
Commitments to Lend Additional Funds	3
Total loans, excluding GNMA and covered loans [Member]
Financing Receivable, Impaired [Line Items]
Period-end Recorded Investment	5,114	5,517
Unpaid Principal Balance	7,720	7,914
Valuation Allowance	779	944
Commitments to Lend Additional Funds	46	95
Loans purchased from GNMA [Member]
Financing Receivable, Impaired [Line Items]
Period-end Recorded Investment	1,778	1,265
Unpaid Principal Balance	1,778	1,265
Valuation Allowance	39	18
Covered loans [Member]
Financing Receivable, Impaired [Line Items]
Period-end Recorded Investment	767	1,170
Unpaid Principal Balance	1,584	1,642
Valuation Allowance	20	43
Commitments to Lend Additional Funds	$ 12	$ 49

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Amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 14A

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=7512638&loc=SL6953550-111524

+ Details

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- Definition

Amount of allowance for credit losses related to recorded investment.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 15

-Subparagraph (a)(3)

-URI http://asc.fasb.org/extlink&oid=7512638&loc=d3e5212-111524

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- Definition

Amount of unpaid principal balance of impaired financing receivables with related allowance for credit losses and without related allowance for credit losses.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 15

-Subparagraph (a)(4)

-URI http://asc.fasb.org/extlink&oid=7512638&loc=d3e5212-111524

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- Definition

Reflects the unfunded portion of contractual agreements to lend funds to borrowers for loans whose terms have been modified by troubled debt restructuring.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 40

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6951948&loc=d3e18794-111554

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 15

-Paragraph 40

-Subparagraph b.

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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