Allowance for Loan Losses - Information Pertaining to Impaired Loans (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Financing Receivable, Allowance for Credit Losses [Line Items]
With no required reserve recorded, Carrying Value	$ 751	$ 158	$ 751	$ 158
With no required reserve recorded, Unpaid Principal Balance	1,025	242	1,025	242
With no required reserve recorded, Required Reserve	0	0	0	0
With no required reserve recorded, Average Carrying Value Recognized	489	372	352	451
With no required reserve recorded, Interest Income	18	2	26	4
With required reserve recorded, Carrying Value	3,706	3,275	3,706	3,275
With required reserve recorded, Unpaid Principal Balance	3,832	3,580	3,832	3,580
With required reserve recorded, Required Reserve	174	295	174	295
With required reserve recorded, Average Carrying Value Recognized	2,802	4,463	2,905	5,022
With required reserve recorded, Interest Income	26	23	45	51
Carrying Value	4,457	3,433	4,457	3,433
Unpaid Principal Balance	4,857	3,822	4,857	3,822
With required reserve recorded, Required Reserve	174	295	174	295
Average Carrying Value Recognized	3,291	4,835	3,257	5,473
Interest Income	44	25	71	55
Construction and Land Development [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
With no required reserve recorded, Required Reserve	0	0	0	0
With required reserve recorded, Carrying Value	96	101	96	101
With required reserve recorded, Unpaid Principal Balance	108	108	108	108
With required reserve recorded, Required Reserve	6	12	6	12
With required reserve recorded, Average Carrying Value Recognized	97	102	97	102
Carrying Value	96	101	96	101
Unpaid Principal Balance	108	108	108	108
With required reserve recorded, Required Reserve	6	12	6	12
Average Carrying Value Recognized	97	102	97	102
Commercial and Industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
With no required reserve recorded, Carrying Value	52	32	52	32
With no required reserve recorded, Unpaid Principal Balance	239	32	239	32
With no required reserve recorded, Required Reserve	0	0	0	0
With no required reserve recorded, Average Carrying Value Recognized	54	47	56	40
With required reserve recorded, Carrying Value	358	563	358	563
With required reserve recorded, Unpaid Principal Balance	373	765	373	765
With required reserve recorded, Required Reserve	10	43	10	43
With required reserve recorded, Average Carrying Value Recognized	370	644	374	722
With required reserve recorded, Interest Income	5	5	9	11
Carrying Value	410	595	410	595
Unpaid Principal Balance	612	797	612	797
With required reserve recorded, Required Reserve	10	43	10	43
Average Carrying Value Recognized	424	691	430	762
Interest Income	5	5	9	11
Municipal [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
With required reserve recorded, Required Reserve	0		0
With required reserve recorded, Required Reserve	0		0
Municipal [Member] | Municipal [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
With no required reserve recorded, Required Reserve	0	0	0	0
Commercial Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
With no required reserve recorded, Carrying Value	596		596
With no required reserve recorded, Unpaid Principal Balance	596		596
With no required reserve recorded, Required Reserve	0	0	0	0
With no required reserve recorded, Average Carrying Value Recognized	329	196	188	280
With no required reserve recorded, Interest Income	16		22
With required reserve recorded, Carrying Value	3,140	1,705	3,140	1,705
With required reserve recorded, Unpaid Principal Balance	3,239	1,801	3,239	1,801
With required reserve recorded, Required Reserve	151	108	151	108
With required reserve recorded, Average Carrying Value Recognized	2,030	2,809	1,878	3,286
With required reserve recorded, Interest Income	20	17	33	33
Carrying Value	3,736	1,705	3,736	1,705
Unpaid Principal Balance	3,835	1,801	3,835	1,801
With required reserve recorded, Required Reserve	151	108	151	108
Average Carrying Value Recognized	2,359	3,005	2,066	3,566
Interest Income	36	17	55	33
Residential Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
With no required reserve recorded, Carrying Value	103	126	103	126
With no required reserve recorded, Unpaid Principal Balance	190	210	190	210
With no required reserve recorded, Required Reserve	0	0	0	0
With no required reserve recorded, Average Carrying Value Recognized	106	129	108	131
With no required reserve recorded, Interest Income	2	2	4	4
With required reserve recorded, Carrying Value	112	815	112	815
With required reserve recorded, Unpaid Principal Balance	112	815	112	815
With required reserve recorded, Required Reserve	7	41	7	41
With required reserve recorded, Average Carrying Value Recognized	283	817	505	820
With required reserve recorded, Interest Income	1	1	3	7
Carrying Value	215	941	215	941
Unpaid Principal Balance	302	1,025	302	1,025
With required reserve recorded, Required Reserve	7	41	7	41
Average Carrying Value Recognized	389	946	613	951
Interest Income	3	3	7	11
Consumer [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
With no required reserve recorded, Required Reserve	0	0	0	0
Home Equity [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
With no required reserve recorded, Required Reserve	0	0	0	0
With required reserve recorded, Carrying Value		91		91
With required reserve recorded, Unpaid Principal Balance		91		91
With required reserve recorded, Required Reserve		91		91
With required reserve recorded, Average Carrying Value Recognized	22	91	51	92
Carrying Value		91		91
Unpaid Principal Balance		91		91
With required reserve recorded, Required Reserve		91		91
Average Carrying Value Recognized	$ 22	$ 91	$ 51	$ 92