Allowance for Loan Losses - Allowance by Impairment Methodology and Loans by Impairment Methodology (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Allowance for loan losses:
Balance at beginning of year	$ 10,644	$ 13,075	$ 12,937
Charge-offs	(927)	(4,492)	(3,793)
Recoveries	851	2,486	376
Provision for (recovery of) loan losses	(3,850)us-gaap_ProvisionForLoanAndLeaseLosses	(425)us-gaap_ProvisionForLoanAndLeaseLosses	3,555us-gaap_ProvisionForLoanAndLeaseLosses
Balance at end of year	6,718	10,644	13,075
Ending Balance:
Allowance for loan losses, Individually evaluated for impairment	1,907	1,379	1,838
Allowance for loan losses, Collectively evaluated for impairment	4,811	9,265	11,237
Loans:
Ending Balance	378,410	357,093	383,594
Loans, Individually evaluated for impairment	13,922	21,694	16,980
Loans, Collectively evaluated for impairment	364,488	335,399	366,614
Construction and Land Development [Member]
Allowance for loan losses:
Balance at beginning of year	2,710	2,481	2,843
Charge-offs	(91)	(2,962)	(431)
Recoveries	80		1
Provision for (recovery of) loan losses	(1,296)	3,191	68
Balance at end of year	1,403	2,710	2,481
Ending Balance:
Allowance for loan losses, Individually evaluated for impairment	245	882	567
Allowance for loan losses, Collectively evaluated for impairment	1,158	1,828	1,914
Loans:
Ending Balance	29,475	34,060	43,524
Loans, Individually evaluated for impairment	3,205	6,862	2,516
Loans, Collectively evaluated for impairment	26,270	27,198	41,008
Secured by 1-4 Family Residential [Member]
Allowance for loan losses:
Balance at beginning of year	2,975	3,712	3,766
Charge-offs	(272)	(260)	(761)
Recoveries	15	823	68
Provision for (recovery of) loan losses	(1,514)	(1,300)	639
Balance at end of year	1,204	2,975	3,712
Ending Balance:
Allowance for loan losses, Individually evaluated for impairment	173	190	306
Allowance for loan losses, Collectively evaluated for impairment	1,031	2,785	3,406
Loans:
Ending Balance	163,727	141,961	134,964
Loans, Individually evaluated for impairment	3,414	3,431	3,776
Loans, Collectively evaluated for impairment	160,313	138,530	131,188
Other Real Estate [Member]
Allowance for loan losses:
Balance at beginning of year	4,418	6,163	5,192
Charge-offs	(203)	(1,070)	(2,154)
Recoveries	509	1,304	64
Provision for (recovery of) loan losses	(1,066)	(1,979)	3,061
Balance at end of year	3,658	4,418	6,163
Ending Balance:
Allowance for loan losses, Individually evaluated for impairment	1,456	263	930
Allowance for loan losses, Collectively evaluated for impairment	2,202	4,155	5,233
Loans:
Ending Balance	151,802	145,968	174,220
Loans, Individually evaluated for impairment	7,183	11,143	10,528
Loans, Collectively evaluated for impairment	144,619	134,825	163,692
Commercial and Industrial [Member]
Allowance for loan losses:
Balance at beginning of year	442	608	963
Charge-offs	(43)	(37)	(261)
Recoveries	18	179	35
Provision for (recovery of) loan losses	(107)	(308)	(129)
Balance at end of year	310	442	608
Ending Balance:
Allowance for loan losses, Individually evaluated for impairment	33	44	35
Allowance for loan losses, Collectively evaluated for impairment	277	398	573
Loans:
Ending Balance	21,166	22,803	23,071
Loans, Individually evaluated for impairment	120	258	160
Loans, Collectively evaluated for impairment	21,046	22,545	22,911
Consumer and Other Loans [Member]
Allowance for loan losses:
Balance at beginning of year	99	111	173
Charge-offs	(318)	(163)	(186)
Recoveries	229	180	208
Provision for (recovery of) loan losses	133	(29)	(84)
Balance at end of year	143	99	111
Ending Balance:
Allowance for loan losses, Collectively evaluated for impairment	143	99	111
Loans:
Ending Balance	12,240	12,301	7,815
Loans, Collectively evaluated for impairment	$ 12,240	$ 12,301	$ 7,815

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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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