Summary of Subsequent Defaults (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Financing Receivable, Modifications [Line Items]
Number of contracts	138	150	360	514
Recorded Investment Post Modification	$ 19	$ 30	$ 52	$ 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	1		3	3
Recorded Investment Post Modification	1		2	1
Commercial Portfolio Segment | Commercial Mortgage Loans Non Owner Occupied [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts		2	2	7
Recorded Investment Post Modification		1	1	5
Commercial Portfolio Segment | Commercial Construction
Financing Receivable, Modifications [Line Items]
Number of contracts		1	2	5
Recorded Investment Post Modification		1	3	7
Commercial Portfolio Segment | Commercial Leases [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts				5
Recorded Investment Post Modification				3
Consumer Portfolio Segment | Home Equity
Financing Receivable, Modifications [Line Items]
Number of contracts	19	49	67	172
Recorded Investment Post Modification	2	3	5	11
Consumer Portfolio Segment | Automobile Loans
Financing Receivable, Modifications [Line Items]
Number of contracts	15	8	36	20
Recorded Investment Post Modification				1
Consumer Portfolio Segment | Credit Card
Financing Receivable, Modifications [Line Items]
Number of contracts	5	14	26	60
Recorded Investment Post Modification				1
Residential Mortgage Loans
Financing Receivable, Modifications [Line Items]
Number of contracts	98	75	224	235
Recorded Investment Post Modification	$ 16	$ 12	$ 41	$ 39