Loans - Schedule of Impairment by Class of Loans (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	$ 9,622	$ 10,617
Recorded Investment with no Allowance	896	1,975
Recorded Investment with Allowance	8,294	8,235
Total Recorded Investment	9,190	10,210
Related Allowance	919	779
Average Recorded Investment	8,945	9,456
Interest Income Recognized	282	337
Commercial [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	3,913	4,315
Recorded Investment with no Allowance	7
Recorded Investment with Allowance	3,902	4,329
Total Recorded Investment	3,909	4,329
Related Allowance	185	85
Average Recorded Investment	3,917	4,123
Interest Income Recognized	126	167
Commercial Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	3,767	4,906
Recorded Investment with no Allowance	306	1,723
Recorded Investment with Allowance	3,155	2,849
Total Recorded Investment	3,461	4,572
Related Allowance	442	522
Average Recorded Investment	3,730	4,396
Interest Income Recognized	125	152
Residential Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance	1,942	1,223
Recorded Investment with no Allowance	583	86
Recorded Investment with Allowance	1,237	1,057
Total Recorded Investment	1,820	1,143
Related Allowance	292	172
Average Recorded Investment	1,270	770
Interest Income Recognized	29	18
Construction & Land Development [Member]
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance		173
Recorded Investment with no Allowance		166
Recorded Investment with Allowance
Total Recorded Investment		166
Related Allowance
Average Recorded Investment	28	167
Interest Income Recognized	$ 2