Number of Loans and Leases which became Nonperforming and Modified in Proceeding 12-Month Period (Detail) (Nonperforming Financing Receivable, USD $)	3 Months Ended	9 Months Ended
	Sep. 30, 2011 Contract	Sep. 30, 2011 Contract
Financing Receivable, Modifications [Line Items]
Number of Loans and Leases	2	8
Recorded Investment	$ 300,000	$ 2,200,000
Unpaid Principal Balance	700,000	3,100,000
Commercial
Financing Receivable, Modifications [Line Items]
Number of Loans and Leases	1	1
Recorded Investment	200,000	200,000
Unpaid Principal Balance	600,000	600,000
Commercial | Commercial and Institutional
Financing Receivable, Modifications [Line Items]
Number of Loans and Leases	1	1
Recorded Investment	200,000	200,000
Unpaid Principal Balance	600,000	600,000
Personal
Financing Receivable, Modifications [Line Items]
Number of Loans and Leases	1	7
Recorded Investment	100,000	2,000,000
Unpaid Principal Balance	100,000	2,500,000
Personal | Residential Real Estate
Financing Receivable, Modifications [Line Items]
Number of Loans and Leases	1	7
Recorded Investment	100,000	2,000,000
Unpaid Principal Balance	$ 100,000	$ 2,500,000