Loans - Schedule of Allowances for Loan Losses by Portfolio Segment (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	$ 5,065	$ 4,804	$ 5,085	$ 4,580
Provision for possible loan losses	150	210	335	420
Charge-offs	(163)	(95)	(380)	(111)
Recoveries	11	26	23	56
Net charge-offs	(152)	(69)	(357)	(55)
Ending balance	5,063	4,945	5,063	4,945
Commercial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	1,141	1,176	1,219	933
Provision for possible loan losses	182	171	113	413
Charge-offs	(5)	(32)	(18)	(38)
Recoveries	4	1	8	8
Net charge-offs	(1)	(31)	(10)	(30)
Ending balance	1,322	1,316	1,322	1,316
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	2,192	1,824	1,872	1,902
Provision for possible loan losses	51	42	568	(36)
Charge-offs	(156)	(51)	(353)	(51)
Net charge-offs	(156)	(51)	(353)	(51)
Ending balance	2,087	1,815	2,087	1,815
Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	1,054	1,282	1,205	1,096
Provision for possible loan losses	102	(110)	(49)	67
Charge-offs	(2)		(6)
Recoveries	3	2	7	11
Net charge-offs	1	2	1	11
Ending balance	1,157	1,174	1,157	1,174
Construction & Land Development [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	145	134	178	253
Provision for possible loan losses	(94)	28	(127)	(91)
Ending balance	51	162	51	162
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	77	68	91	76
Provision for possible loan losses	(37)	65	(52)	53
Charge-offs		(12)	(3)	(22)
Recoveries	4	23	8	37
Net charge-offs	4	11	5	15
Ending balance	44	144	44	144
Unallocated [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Beginning balance	456	320	520	320
Provision for possible loan losses	(54)	14	(118)	14
Ending balance	$ 402	$ 334	$ 402	$ 334