Loans - Analysis of Allowance for Credit Losses (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
ALLOWANCE FOR CREDIT LOSSES:
Beginning balance	$ 5,357	$ 5,386
Charge Offs	(778)	(1,262)	(891)
Recoveries	298	374	286
Provision	1,191	858
Other Non-interest expense related to unfunded	44	1
Ending Balance	6,112	5,357	5,386
Ending balance: individually evaluated for impairment	387	516
Ending balance: collectively evaluated for impairment	5,725	4,841
Ending balance: loans acquired with deteriorated credit quality	2	1
FINANCING RECEIVABLES:
Ending balance, net of deferred fees	621,926	576,113
Ending balance: individually evaluated for impairment	1,843	2,440
Ending balance: collectively evaluated for impairment	620,083	573,673
Ending balance: loans acquired with deteriorated credit quality	526	540
Consumer Real Estate [Member]
ALLOWANCE FOR CREDIT LOSSES:
Beginning balance	257	368
Charge Offs	(168)	(147)
Recoveries	34	20
Provision	414	16
Ending Balance	537	257
Ending balance: individually evaluated for impairment	36	78
Ending balance: collectively evaluated for impairment	501	179
Ending balance: loans acquired with deteriorated credit quality	2	1
FINANCING RECEIVABLES:
Ending balance, net of deferred fees	97,550	92,438
Ending balance: individually evaluated for impairment	301	300
Ending balance: collectively evaluated for impairment	97,249	92,138
Ending balance: loans acquired with deteriorated credit quality	526	540
Agricultural Real Estate [Member]
ALLOWANCE FOR CREDIT LOSSES:
Beginning balance	131	113
Provision	53	18
Ending Balance	184	131
Ending balance: individually evaluated for impairment		9
Ending balance: collectively evaluated for impairment	184	122
FINANCING RECEIVABLES:
Ending balance, net of deferred fees	50,895	44,301
Ending balance: individually evaluated for impairment		88
Ending balance: collectively evaluated for impairment	50,895	44,213
Agricultural [Member]
ALLOWANCE FOR CREDIT LOSSES:
Beginning balance	326	290
Recoveries	44	5
Provision	177	31
Ending Balance	547	326
Ending balance: individually evaluated for impairment	25
Ending balance: collectively evaluated for impairment	522	326
FINANCING RECEIVABLES:
Ending balance, net of deferred fees	74,611	65,449
Ending balance: individually evaluated for impairment	25
Ending balance: collectively evaluated for impairment	74,586	65,449
Commercial Real Estate [Member]
ALLOWANCE FOR CREDIT LOSSES:
Beginning balance	2,107	1,749
Charge Offs	(229)	(164)
Recoveries	4	23
Provision	485	499
Ending Balance	2,367	2,107
Ending balance: individually evaluated for impairment	111	295
Ending balance: collectively evaluated for impairment	2,256	1,812
FINANCING RECEIVABLES:
Ending balance, net of deferred fees	270,188	248,893
Ending balance: individually evaluated for impairment	1,179	1,675
Ending balance: collectively evaluated for impairment	269,009	247,218
Commercial and Industrial [Member]
ALLOWANCE FOR CREDIT LOSSES:
Beginning balance	1,359	2,183
Charge Offs		(513)
Recoveries	20	141
Provision	42	(452)
Ending Balance	1,421	1,359
Ending balance: individually evaluated for impairment	204	134
Ending balance: collectively evaluated for impairment	1,217	1,225
FINANCING RECEIVABLES:
Ending balance, net of deferred fees	104,824	103,856
Ending balance: individually evaluated for impairment	327	377
Ending balance: collectively evaluated for impairment	104,497	103,479
Consumer [Member]
ALLOWANCE FOR CREDIT LOSSES:
Beginning balance	292	268
Charge Offs	(381)	(438)
Recoveries	196	185
Provision	216	277
Ending Balance	323	292
Ending balance: individually evaluated for impairment	11
Ending balance: collectively evaluated for impairment	312	292
FINANCING RECEIVABLES:
Ending balance, net of deferred fees	23,858	21,176
Ending balance: individually evaluated for impairment	11
Ending balance: collectively evaluated for impairment	23,847	21,176
Unfunded Loan Commitment & Letters of Credit [Member]
ALLOWANCE FOR CREDIT LOSSES:
Beginning balance	163	162
Other Non-interest expense related to unfunded	44	1
Ending Balance	207	163
Ending balance: collectively evaluated for impairment	207	163
Unallocated [Member]
ALLOWANCE FOR CREDIT LOSSES:
Beginning balance	722	253
Provision	(196)	469
Ending Balance	526	722
Ending balance: collectively evaluated for impairment	$ 526	$ 722

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