Allowance for Loan Losses - Information Pertaining to Impaired Loans (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Financing Receivable, Allowance for Credit Losses [Line Items]
With no required reserve recorded, Carrying Value	$ 736	$ 838	$ 736	$ 838
With no required reserve recorded, Unpaid Balance Principal	775	1,577	775	1,577
With no required reserve recorded, Required Reserve
With no required reserve recorded, Average Carrying Value	625	865	668	1,162
With no required reserve recorded, Interest Income Recognized			1
With required reserve recorded, Carrying Value	7,830	5,720	7,830	5,720
With required reserve recorded, Unpaid Balance Principal	10,025	7,600	10,025	7,600
With required reserve recorded, Required Reserve	1,769	2,113	1,769	2,113
With required reserve recorded, Average Carrying Value	6,177	5,950	5,707	6,208
With required reserve recorded, Interest Income Recognized	38	53	101	120
Carrying Value	8,566	6,558	8,566	6,558
Unpaid Principal Balance	10,800	9,177	10,800	9,177
With required reserve recorded, Required Reserve	1,769	2,113	1,769	2,113
Average Carrying Value	6,802	6,815	6,375	7,370
Interest Income Recognized	38	53	102	120
Construction and Land Development [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
With no required reserve recorded, Required Reserve
With no required reserve recorded, Average Carrying Value				450
With required reserve recorded, Carrying Value	1,500	1,500	1,500	1,500
With required reserve recorded, Unpaid Balance Principal	3,292	3,292	3,292	3,292
With required reserve recorded, Required Reserve	1,000	1,000	1,000	1,000
With required reserve recorded, Average Carrying Value	1,500	1,500	1,500	1,050
Carrying Value	1,500	1,500	1,500	1,500
Unpaid Principal Balance	3,292	3,292	3,292	3,292
With required reserve recorded, Required Reserve	1,000	1,000	1,000	1,000
Average Carrying Value	1,500	1,500	1,500	1,500
Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
With no required reserve recorded, Carrying Value	264	635	264	635
With no required reserve recorded, Unpaid Balance Principal	294	1,346	294	1,346
With no required reserve recorded, Required Reserve
With no required reserve recorded, Average Carrying Value	239	473	390	382
With no required reserve recorded, Interest Income Recognized			1
With required reserve recorded, Carrying Value	868	1,247	868	1,247
With required reserve recorded, Unpaid Balance Principal	1,101	1,295	1,101	1,295
With required reserve recorded, Required Reserve	90	455	90	455
With required reserve recorded, Average Carrying Value	885	1,745	864	1,492
With required reserve recorded, Interest Income Recognized	12	12	29	35
Carrying Value	1,132	1,882	1,132	1,882
Unpaid Principal Balance	1,395	2,641	1,395	2,641
With required reserve recorded, Required Reserve	90	455	90	455
Average Carrying Value	1,124	2,218	1,254	1,874
Interest Income Recognized	12	12	30	35
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
With no required reserve recorded, Carrying Value	218	172	218	172
With no required reserve recorded, Unpaid Balance Principal	218	200	218	200
With no required reserve recorded, Required Reserve
With no required reserve recorded, Average Carrying Value	126	174	133	178
With required reserve recorded, Carrying Value	4,470	2,130	4,470	2,130
With required reserve recorded, Unpaid Balance Principal	4,558	2,170	4,558	2,170
With required reserve recorded, Required Reserve	445	434	445	434
With required reserve recorded, Average Carrying Value	2,796	2,138	2,394	3,027
With required reserve recorded, Interest Income Recognized	26	40	72	84
Carrying Value	4,688	2,302	4,688	2,302
Unpaid Principal Balance	4,776	2,370	4,776	2,370
With required reserve recorded, Required Reserve	445	434	445	434
Average Carrying Value	2,922	2,312	2,527	3,205
Interest Income Recognized	26	40	72	84
Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
With no required reserve recorded, Carrying Value	254	31	254	31
With no required reserve recorded, Unpaid Balance Principal	263	31	263	31
With no required reserve recorded, Required Reserve
With no required reserve recorded, Average Carrying Value	260	218	145	152
With required reserve recorded, Carrying Value	897	746	897	746
With required reserve recorded, Unpaid Balance Principal	979	746	979	746
With required reserve recorded, Required Reserve	139	127	139	127
With required reserve recorded, Average Carrying Value	901	494	853	610
With required reserve recorded, Interest Income Recognized		1		1
Carrying Value	1,151	777	1,151	777
Unpaid Principal Balance	1,242	777	1,242	777
With required reserve recorded, Required Reserve	139	127	139	127
Average Carrying Value	1,161	712	998	762
Interest Income Recognized		1		1
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
With no required reserve recorded, Carrying Value
With no required reserve recorded, Unpaid Balance Principal
With no required reserve recorded, Required Reserve
With no required reserve recorded, Average Carrying Value
With no required reserve recorded, Interest Income Recognized
With required reserve recorded, Carrying Value
With required reserve recorded, Unpaid Balance Principal
With required reserve recorded, Required Reserve
With required reserve recorded, Average Carrying Value
With required reserve recorded, Interest Income Recognized
Carrying Value
Unpaid Principal Balance
With required reserve recorded, Required Reserve
Average Carrying Value
Interest Income Recognized
Home Equity [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
With no required reserve recorded, Carrying Value
With no required reserve recorded, Unpaid Balance Principal
With no required reserve recorded, Required Reserve
With no required reserve recorded, Average Carrying Value
With no required reserve recorded, Interest Income Recognized
With required reserve recorded, Carrying Value	95	97	95	97
With required reserve recorded, Unpaid Balance Principal	95	97	95	97
With required reserve recorded, Required Reserve	95	97	95	97
With required reserve recorded, Average Carrying Value	95	73	96	29
Carrying Value	95	97	95	97
Unpaid Principal Balance	95	97	95	97
With required reserve recorded, Required Reserve	95	97	95	97
Average Carrying Value	$ 95	$ 73	$ 96	$ 29