Schedule of Loans Restructured by Class (Detail) (Troubled Debt Restructuring, USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012 Contract	Sep. 30, 2011 Contract	Sep. 30, 2012 Contract	Sep. 30, 2011 Contract
Composition of Loan Portfolio [Line Items]
Number of Contracts	4	1	6	5
Pre-Modification Outstanding Recorded Investment	$ 853	$ 162	$ 3,785	$ 3,918
Post-Modification Outstanding Recorded Investment	821	162	3,760	3,974
Commercial
Composition of Loan Portfolio [Line Items]
Number of Contracts	4		6	1
Pre-Modification Outstanding Recorded Investment	853		3,785	250
Post-Modification Outstanding Recorded Investment	821		3,760	250
Real estate - commercial
Composition of Loan Portfolio [Line Items]
Number of Contracts				2
Pre-Modification Outstanding Recorded Investment				2,806
Post-Modification Outstanding Recorded Investment				2,862
Real estate - residential
Composition of Loan Portfolio [Line Items]
Number of Contracts		1		2
Pre-Modification Outstanding Recorded Investment		162		862
Post-Modification Outstanding Recorded Investment		$ 162		$ 862