Allowance for Loan Losses - Aging Analysis of Past Due Loans (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	$ 3,725	$ 3,288
60-89 Days Past Due	767	985
90 Days or Greater	4,578	5,321
Total Past Due	9,070	9,594
Current	975,035	905,263
Total Loans	984,105	914,857
Past Due 90 Days and Accruing	0	0
Commercial and Agriculture [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	171	58
60-89 Days Past Due	444
90 Days or Greater	321	187
Total Past Due	936	245
Current	119,214	113,941
Total Loans	120,150	114,186
Past Due 90 Days and Accruing	0	0
Commercial Real Estate Owner Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	338	622
60-89 Days Past Due	57	251
90 Days or Greater	654	657
Total Past Due	1,049	1,530
Current	164,458	141,484
Total Loans	165,507	143,014
Past Due 90 Days and Accruing	0	0
Commercial Real Estate Non Owner Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	157	521
60-89 Days Past Due		5
90 Days or Greater	1,965	2,103
Total Past Due	2,122	2,629
Current	316,911	306,037
Total Loans	319,033	308,666
Past Due 90 Days and Accruing	0	0
Residential Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	2,875	1,923
60-89 Days Past Due	222	721
90 Days or Greater	1,620	2,347
Total Past Due	4,717	4,991
Current	279,818	263,519
Total Loans	284,535	268,510
Past Due 90 Days and Accruing	0	0
Real Estate Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due		33
90 Days or Greater		8
Total Past Due		41
Current	75,082	65,411
Total Loans	75,082	65,452
Past Due 90 Days and Accruing	0	0
Consumer and Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	184	131
60-89 Days Past Due	44	8
90 Days or Greater	18	19
Total Past Due	246	158
Current	19,552	14,871
Total Loans	19,798	15,029
Past Due 90 Days and Accruing	$ 0	$ 0

Financing receivables that are less than 60 days past due but more than 29 days past due.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 7A

-URI http://asc.fasb.org/extlink&oid=35738203&loc=SL6953401-111524

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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-Section 45

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