Additional Detail of Troubled Debt Restructurings (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Sep. 30, 2013	Dec. 31, 2012
Financing Receivable, Modifications [Line Items]
Outstanding Record Investment Pre-Modification	$ 858	$ 924
Outstanding Record Investment Post-Modification	858	924
Number of loans	3	4
Interest income Recognized	24	42	100
Commercial installment
Financing Receivable, Modifications [Line Items]
Outstanding Record Investment Pre-Modification	0
Outstanding Record Investment Post-Modification	0
Number of loans	0	0
Interest income Recognized	0	0
Commercial real estate
Financing Receivable, Modifications [Line Items]
Outstanding Record Investment Pre-Modification	858	858
Outstanding Record Investment Post-Modification	858	858
Number of loans	3	3
Interest income Recognized	24	41	77
Consumer real estate
Financing Receivable, Modifications [Line Items]
Outstanding Record Investment Pre-Modification	0	66
Outstanding Record Investment Post-Modification	0	66
Number of loans	0	1
Interest income Recognized	0	1	12
Consumer installment
Financing Receivable, Modifications [Line Items]
Outstanding Record Investment Pre-Modification	0	0
Outstanding Record Investment Post-Modification	0	0
Number of loans	0	0
Interest income Recognized	$ 0	$ 0