Summary of Subsequent Defaults (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended
	Sep. 30, 2011 number	Sep. 30, 2011 years number
Financing Receivable, Modifications [Line Items]
Number of contracts	150	514
Recorded Investment Post Modification	$ 30	$ 88
Commercial Portfolio Segment | CommercialAndIndustrialLoansMember [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	1	7
Recorded Investment Post Modification	13	20
Commercial Portfolio Segment | Commercial Mortgage Loans Owner Occupied [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	0	3
Recorded Investment Post Modification	0	1
Commercial Portfolio Segment | Commercial Mortgage Loans Non Owner Occupied [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	2	7
Recorded Investment Post Modification	1	5
Commercial Portfolio Segment | Commercial Construction
Financing Receivable, Modifications [Line Items]
Number of contracts	1	5
Recorded Investment Post Modification	1	7
Commercial Portfolio Segment | Commercial Leases [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	0	5
Recorded Investment Post Modification	0	3
Consumer Portfolio Segment | Home Equity
Financing Receivable, Modifications [Line Items]
Number of contracts	49	172
Recorded Investment Post Modification	3	11
Consumer Portfolio Segment | Automobile Loans
Financing Receivable, Modifications [Line Items]
Number of contracts	8	20
Recorded Investment Post Modification	0	1
Consumer Portfolio Segment | Credit Card
Financing Receivable, Modifications [Line Items]
Number of contracts	14	60
Recorded Investment Post Modification	0	1
Residential Mortgage Loans
Financing Receivable, Modifications [Line Items]
Number of contracts	75	235
Recorded Investment Post Modification	$ 12	$ 39