Loans and Allowance for Loan Losses - Transactions in Allowance for Loan Losses (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
Mar. 31, 2015	Dec. 31, 2014
Allowance for loan losses:
Beginning balance	$ 22,572	$ 22,935
Provision	75	498
Charge-offs	(254)	(1,867)
Recoveries	105	1,006
Ending balance	22,498	22,572
Ending balance individually evaluated for impairment	1,405	1,631
Ending balance collectively evaluated for impairment	21,093	20,941
Ending balance loans acquired with deteriorated credit quality	0	0
Loans:
Ending balance	1,382,782	1,356,778
Ending balance individually evaluated for impairment	12,200	10,497
Ending balance collectively evaluated for impairment	1,370,582	1,346,281
Ending balance loans acquired with deteriorated credit quality	0	0
Residential 1-4 Family [Member]
Allowance for loan losses:
Beginning balance	5,582	4,935
Provision	29	1,059
Charge-offs	(64)	(468)
Recoveries	14	56
Ending balance	5,561	5,582
Ending balance individually evaluated for impairment	243	376
Ending balance collectively evaluated for impairment	5,318	5,206
Ending balance loans acquired with deteriorated credit quality	0	0
Loans:
Ending balance	352,539	350,758
Ending balance individually evaluated for impairment	1,737	3,061
Ending balance collectively evaluated for impairment	350,802	347,697
Ending balance loans acquired with deteriorated credit quality	0	0
Multifamily [Member]
Allowance for loan losses:
Beginning balance	172	77
Provision	51	95
Ending balance	223	172
Ending balance collectively evaluated for impairment	223	172
Ending balance loans acquired with deteriorated credit quality	0	0
Loans:
Ending balance	40,546	31,242
Ending balance collectively evaluated for impairment	40,546	31,242
Ending balance loans acquired with deteriorated credit quality	0	0
Commercial Real Estate [Member]
Allowance for loan losses:
Beginning balance	9,578	10,918
Provision	(935)	(378)
Charge-offs		(968)
Recoveries	1	6
Ending balance	8,644	9,578
Ending balance individually evaluated for impairment	1,110	1,135
Ending balance collectively evaluated for impairment	7,534	8,443
Ending balance loans acquired with deteriorated credit quality	0	0
Loans:
Ending balance	564,943	564,965
Ending balance individually evaluated for impairment	9,889	6,455
Ending balance collectively evaluated for impairment	555,054	558,510
Ending balance loans acquired with deteriorated credit quality	0	0
Construction [Member]
Allowance for loan losses:
Beginning balance	5,578	5,159
Provision	730	102
Charge-offs		(7)
Recoveries	7	324
Ending balance	6,315	5,578
Ending balance collectively evaluated for impairment	6,315	5,578
Ending balance loans acquired with deteriorated credit quality	0	0
Loans:
Ending balance	257,936	245,830
Ending balance collectively evaluated for impairment	257,936	245,830
Ending balance loans acquired with deteriorated credit quality	0	0
Farmland [Member]
Allowance for loan losses:
Beginning balance	795	618
Provision	(85)	176
Recoveries		1
Ending balance	710	795
Ending balance individually evaluated for impairment	52	120
Ending balance collectively evaluated for impairment	658	675
Ending balance loans acquired with deteriorated credit quality	0	0
Loans:
Ending balance	30,879	30,236
Ending balance individually evaluated for impairment	574	701
Ending balance collectively evaluated for impairment	30,305	29,535
Ending balance loans acquired with deteriorated credit quality	0	0
Second Mortgages [Member]
Allowance for loan losses:
Beginning balance	61	205
Provision	52	(164)
Charge-offs	(20)
Recoveries		20
Ending balance	93	61
Ending balance collectively evaluated for impairment	93	61
Ending balance loans acquired with deteriorated credit quality	0	0
Loans:
Ending balance	8,868	9,026
Ending balance individually evaluated for impairment		280
Ending balance collectively evaluated for impairment	8,868	8,746
Ending balance loans acquired with deteriorated credit quality	0	0
Equity Lines of Credit [Member]
Allowance for loan losses:
Beginning balance	304	300
Provision	35	3
Recoveries		1
Ending balance	339	304
Ending balance collectively evaluated for impairment	339	304
Ending balance loans acquired with deteriorated credit quality	0	0
Loans:
Ending balance	43,728	41,496
Ending balance collectively evaluated for impairment	43,728	41,496
Ending balance loans acquired with deteriorated credit quality	0	0
Commercial [Member]
Allowance for loan losses:
Beginning balance	176	395
Provision	76	(641)
Charge-offs		(37)
Recoveries	4	459
Ending balance	256	176
Ending balance collectively evaluated for impairment	256	176
Ending balance loans acquired with deteriorated credit quality	0	0
Loans:
Ending balance	30,357	30,000
Ending balance collectively evaluated for impairment	30,357	30,000
Ending balance loans acquired with deteriorated credit quality	0	0
Agricultural [Member]
Allowance for loan losses:
Beginning balance	326
Provision	122
Charge-offs	(170)
Recoveries	79
Ending balance	357
Ending balance collectively evaluated for impairment	357
Ending balance loans acquired with deteriorated credit quality	0
Loans:
Ending balance	52,986
Ending balance collectively evaluated for impairment	52,986
Ending balance loans acquired with deteriorated credit quality	0
Agricultural, Installment and Other [Member]
Allowance for loan losses:
Beginning balance		328
Provision		246
Charge-offs		(387)
Recoveries		139
Ending balance		326
Ending balance collectively evaluated for impairment		326
Ending balance loans acquired with deteriorated credit quality		0
Loans:
Ending balance	52,986	53,225
Ending balance collectively evaluated for impairment		53,225
Ending balance loans acquired with deteriorated credit quality		$ 0

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The balance of financing receivables that were acquired with deteriorated credit quality.

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The valuation allowance for financing receivables acquired with deteriorated credit quality.

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The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

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Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

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Amount of recovery of financing receivables doubtful of collection that were previously charged off.

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Amount of direct write-downs of financing receivables charged against the allowance.

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The balance of financing receivables that were collectively evaluated for impairment.

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Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

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Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

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Provision for (reversal of provision on) loan, lease and other losses

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