Summary of Subsequent Defaults (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2012
Financing Receivable, Modifications [Line Items]
Number of contracts	95	222
Recorded Investment Post Modification	$ 16	$ 33
Commercial Portfolio Segment | Commercial Mortgage Loans Owner Occupied [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	2	2
Recorded Investment Post Modification	1	1
Commercial Portfolio Segment | Commercial Mortgage Loans Non Owner Occupied [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	1	2
Recorded Investment Post Modification		1
Commercial Portfolio Segment | Commercial Construction
Financing Receivable, Modifications [Line Items]
Number of contracts		2
Recorded Investment Post Modification		3
Consumer Portfolio Segment | Home Equity
Financing Receivable, Modifications [Line Items]
Number of contracts	17	48
Recorded Investment Post Modification	1	3
Consumer Portfolio Segment | Automobile Loans
Financing Receivable, Modifications [Line Items]
Number of contracts	9	21
Consumer Portfolio Segment | Credit Card
Financing Receivable, Modifications [Line Items]
Number of contracts	4	21
Residential Mortgage Loans
Financing Receivable, Modifications [Line Items]
Number of contracts	62	126
Recorded Investment Post Modification	$ 14	$ 25