Summary of Loans Modified in a TDR (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012 number
Financing Receivable, Modifications [Line Items]
Number of Loans Modified in a TDR During the Period	3,969
Recorded Investment in Loans Modified in a TDR During the Period	$ 230
Increase (Decrease) to ALLL Upon Modification	7
Commercial Portfolio Segment | CommercialAndIndustrialLoansMember [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans Modified in a TDR During the Period	30
Recorded Investment in Loans Modified in a TDR During the Period	15
Increase (Decrease) to ALLL Upon Modification	(3)
Commercial Portfolio Segment | Commercial Mortgage Loans Owner Occupied [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans Modified in a TDR During the Period	27
Recorded Investment in Loans Modified in a TDR During the Period	8
Increase (Decrease) to ALLL Upon Modification	(2)
Commercial Portfolio Segment | Commercial Mortgage Loans Non Owner Occupied [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans Modified in a TDR During the Period	30
Recorded Investment in Loans Modified in a TDR During the Period	51
Increase (Decrease) to ALLL Upon Modification	1
Commercial Portfolio Segment | Commercial Construction
Financing Receivable, Modifications [Line Items]
Number of Loans Modified in a TDR During the Period	11
Recorded Investment in Loans Modified in a TDR During the Period	36
Consumer Portfolio Segment | Home Equity
Financing Receivable, Modifications [Line Items]
Number of Loans Modified in a TDR During the Period	311
Recorded Investment in Loans Modified in a TDR During the Period	19
Increase (Decrease) to ALLL Upon Modification	1
Consumer Portfolio Segment | Automobile Loans
Financing Receivable, Modifications [Line Items]
Number of Loans Modified in a TDR During the Period	339
Recorded Investment in Loans Modified in a TDR During the Period	5
Increase (Decrease) to ALLL Upon Modification	1
Consumer Portfolio Segment | Credit Card
Financing Receivable, Modifications [Line Items]
Number of Loans Modified in a TDR During the Period	2,741
Recorded Investment in Loans Modified in a TDR During the Period	18
Increase (Decrease) to ALLL Upon Modification	2
Residential Mortgage Loans
Financing Receivable, Modifications [Line Items]
Number of Loans Modified in a TDR During the Period	480
Recorded Investment in Loans Modified in a TDR During the Period	78
Increase (Decrease) to ALLL Upon Modification	$ 7