Allowance for Loan Losses - Allowance by Impairment Methodology and Loans by Impairment Methodology (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Allowance for loan losses:
Beginning Balance	$ 6,718	$ 10,644	$ 10,644
Charge-offs	(112)	(239)	(927)
Recoveries	165	78	851
Provision for (recovery of) loan losses		(200)us-gaap_ProvisionForLoanAndLeaseLosses	(3,850)us-gaap_ProvisionForLoanAndLeaseLosses
Ending Balance	6,771	10,283	6,718
Ending Balance:
Allowance for loan losses, Individually evaluated for impairment	1,901	1,538	1,907
Allowance for loan losses, Collectively evaluated for impairment	4,870	8,745	4,811
Loans:
Ending Balance	398,517	359,533	378,410
Loans, Individually evaluated for impairment	13,034	21,238	13,922
Loans, Collectively evaluated for impairment	385,483	338,295	364,488
Construction and Land Development [Member]
Allowance for loan losses:
Beginning Balance	1,403	2,710	2,710
Charge-offs			(91)
Recoveries	1		80
Provision for (recovery of) loan losses	197	(458)	(1,296)
Ending Balance	1,601	2,252	1,403
Ending Balance:
Allowance for loan losses, Individually evaluated for impairment	341	862	245
Allowance for loan losses, Collectively evaluated for impairment	1,260	1,390	1,158
Loans:
Ending Balance	33,344	33,876	29,475
Loans, Individually evaluated for impairment	3,071	6,568	3,205
Loans, Collectively evaluated for impairment	30,273	27,308	26,270
Secured by 1-4 Family Residential [Member]
Allowance for loan losses:
Beginning Balance	1,204	2,975	2,975
Charge-offs	(47)	(71)	(272)
Recoveries	34	4	15
Provision for (recovery of) loan losses	(239)	42	(1,514)
Ending Balance	952	2,950	1,204
Ending Balance:
Allowance for loan losses, Individually evaluated for impairment	85	126	173
Allowance for loan losses, Collectively evaluated for impairment	867	2,824	1,031
Loans:
Ending Balance	172,874	147,541	163,727
Loans, Individually evaluated for impairment	2,747	3,468	3,414
Loans, Collectively evaluated for impairment	170,127	144,073	160,313
Other Real Estate [Member]
Allowance for loan losses:
Beginning Balance	3,658	4,418	4,418
Charge-offs			(203)
Recoveries	1	1	509
Provision for (recovery of) loan losses	137	89	(1,066)
Ending Balance	3,796	4,508	3,658
Ending Balance:
Allowance for loan losses, Individually evaluated for impairment	1,447	505	1,456
Allowance for loan losses, Collectively evaluated for impairment	2,349	4,003	2,202
Loans:
Ending Balance	158,896	142,719	151,802
Loans, Individually evaluated for impairment	7,103	11,030	7,183
Loans, Collectively evaluated for impairment	151,793	131,689	144,619
Commercial and Industrial [Member]
Allowance for loan losses:
Beginning Balance	310	442	442
Charge-offs		(36)	(43)
Recoveries	60	1	18
Provision for (recovery of) loan losses	(82)	36	(107)
Ending Balance	288	443	310
Ending Balance:
Allowance for loan losses, Individually evaluated for impairment	28	45	33
Allowance for loan losses, Collectively evaluated for impairment	260	398	277
Loans:
Ending Balance	21,420	23,381	21,166
Loans, Individually evaluated for impairment	113	172	120
Loans, Collectively evaluated for impairment	21,307	23,209	21,046
Consumer and Other Loans [Member]
Allowance for loan losses:
Beginning Balance	143	99	99
Charge-offs	(65)	(132)	(318)
Recoveries	69	72	229
Provision for (recovery of) loan losses	(13)	91	133
Ending Balance	134	130	143
Ending Balance:
Allowance for loan losses, Collectively evaluated for impairment	134	130	143
Loans:
Ending Balance	11,983	12,016	12,240
Loans, Collectively evaluated for impairment	$ 11,983	$ 12,016	$ 12,240

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Amount of loans and leases that have been written off from both loan receivables and allowance reserve for credit loss.

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Amount of recovery of loans and lease receivables which had previously been fully or partially written-off as bad debts.

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

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The balance of financing receivables that were individually 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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Amount of expense related to estimated loss from loan and lease transactions.

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