Summary of Loans Modified in a TDR (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended	3 Months Ended	6 Months Ended	3 Months Ended	6 Months Ended	3 Months Ended	6 Months Ended	3 Months Ended	6 Months Ended	3 Months Ended	6 Months Ended	3 Months Ended	6 Months Ended	3 Months Ended	6 Months Ended	3 Months Ended	6 Months Ended	3 Months Ended
Jun. 30, 2012	Jun. 30, 2012 Quarterly [Member]	Jun. 30, 2012 Commercial Portfolio Segment CommercialAndIndustrialLoansMember [Member]	Jun. 30, 2012 Commercial Portfolio Segment CommercialAndIndustrialLoansMember [Member] Quarterly [Member]	Jun. 30, 2012 Commercial Portfolio Segment Commercial Mortgage Loans Owner Occupied [Member]	Jun. 30, 2012 Commercial Portfolio Segment Commercial Mortgage Loans Owner Occupied [Member] Quarterly [Member]	Jun. 30, 2012 Commercial Portfolio Segment Commercial Mortgage Loans Non Owner Occupied [Member]	Jun. 30, 2012 Commercial Portfolio Segment Commercial Mortgage Loans Non Owner Occupied [Member] Quarterly [Member]	Jun. 30, 2012 Commercial Portfolio Segment Commercial Construction	Jun. 30, 2012 Commercial Portfolio Segment Commercial Construction Quarterly [Member]	Jun. 30, 2012 Consumer Portfolio Segment Home Equity	Jun. 30, 2012 Consumer Portfolio Segment Home Equity Quarterly [Member]	Jun. 30, 2012 Consumer Portfolio Segment Automobile Loans	Jun. 30, 2012 Consumer Portfolio Segment Automobile Loans Quarterly [Member]	Jun. 30, 2012 Consumer Portfolio Segment Credit Card	Jun. 30, 2012 Consumer Portfolio Segment Credit Card Quarterly [Member]	Jun. 30, 2012 Residential Mortgage Loans	Jun. 30, 2012 Residential Mortgage Loans Quarterly [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans Modified in a TDR During the Period	8,128	4,159	41	11	36	9	40	10	11		670	359	561	222	5,732	2,991	1,037	557
Recorded Investment in Loans Modified in a TDR During the Period	$ 401	$ 171	$ 25	$ 10	$ 15	$ 7	$ 67	$ 16	$ 36		$ 42	$ 23	$ 9	$ 4	$ 38	$ 20	$ 169	$ 91
Increase (Decrease) to ALLL Upon Modification	$ 3	$ (4)	$ (9)	$ (6)	$ (3)	$ (1)	$ (5)	$ (6)	$ (4)	$ (4)	$ 2	$ 1	$ 2	$ 1	$ 5	$ 3	$ 15	$ 8

Reflects the net amount of other additions and reductions in the reserve for credit losses.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.7(d))

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 114

-Paragraph 20

-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.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 9

-Section 03

-Paragraph 7

-Subparagraph d

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 15

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6965416&loc=d3e5212-111524

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration