Summary of Subsequent Defaults (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012 number		Dec. 31, 2011 number
Financing Receivable, Modifications [Line Items]
Number of contracts	512	[1]	657	[1]
Recorded Investment in Loans Modified in a TDR During the Period	$ 73	[1]	$ 86	[1]
Commercial Portfolio Segment | CommercialAndIndustrialLoansMember [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	2	[1]	8	[1]
Recorded Investment in Loans Modified in a TDR During the Period	3	[1]	4	[1]
Commercial Portfolio Segment | Commercial Mortgage Loans Owner Occupied [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	3	[1]	4	[1]
Recorded Investment in Loans Modified in a TDR During the Period	2	[1]	5	[1]
Commercial Portfolio Segment | Commercial Mortgage Loans Non Owner Occupied [Member]
Financing Receivable, Modifications [Line Items]
Number of contracts	2	[1]	4	[1]
Recorded Investment in Loans Modified in a TDR During the Period	1	[1]	3	[1]
Commercial Portfolio Segment | Commercial Construction
Financing Receivable, Modifications [Line Items]
Number of contracts	2	[1]	3	[1]
Recorded Investment in Loans Modified in a TDR During the Period	3	[1]	4	[1]
Consumer Portfolio Segment | Home Equity
Financing Receivable, Modifications [Line Items]
Number of contracts	101	[1]	206	[1]
Recorded Investment in Loans Modified in a TDR During the Period	7	[1]	13	[1]
Consumer Portfolio Segment | Automobile Loans
Financing Receivable, Modifications [Line Items]
Number of contracts	42	[1]	28	[1]
Recorded Investment in Loans Modified in a TDR During the Period			1	[1]
Consumer Portfolio Segment | Credit Card
Financing Receivable, Modifications [Line Items]
Number of contracts	28	[1]	67	[1]
Recorded Investment in Loans Modified in a TDR During the Period			1	[1]
Residential Mortgage Loans
Financing Receivable, Modifications [Line Items]
Number of contracts	332	[1]	337	[1]
Recorded Investment in Loans Modified in a TDR During the Period	$ 57	[1]	$ 55	[1]

[1] Excludes all loans and leases held for sale and loans acquired with deteriorated credit quality.