Loans - Aging of Recorded Investment in Past Due Loans (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	$ 5,083	$ 6,019
60-89 Days Past Due	2,144	2,447
Greater Than 90 Days Past Due	8,901	11,766
Total Past Due	16,128	20,232
Loans Not Past Due	1,343,468	1,279,027
Total	1,359,596	1,299,259
Commercial, Industrial, and Agricultural [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	888	1,236
60-89 Days Past Due	588	542
Greater Than 90 Days Past Due	294	3,952
Total Past Due	1,770	5,730
Loans Not Past Due	426,688	421,985
Total	428,458	427,715
Commercial Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	20	233
60-89 Days Past Due	1,351	713
Greater Than 90 Days Past Due	4,323	4,139
Total Past Due	5,694	5,085
Loans Not Past Due	347,058	338,380
Total	352,752	343,465
Residential Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	2,719	4,216
60-89 Days Past Due	1,191	114
Greater Than 90 Days Past Due	3,239	2,539
Total Past Due	7,149	6,869
Loans Not Past Due	495,168	452,245
Total	502,317	459,114
Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	265	334
60-89 Days Past Due	122	1,049
Greater Than 90 Days Past Due	1,045	1,112
Total Past Due	1,432	2,495
Loans Not Past Due	68,216	60,996
Total	69,648	63,491
Credit Cards [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	0	0
60-89 Days Past Due	83	29
Greater Than 90 Days Past Due	0	24
Total Past Due	83	53
Loans Not Past Due	5,150	5,012
Total	5,233	5,065
Overdrafts [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	0	0
60-89 Days Past Due	0	0
Greater Than 90 Days Past Due	0	0
Total Past Due	0	0
Loans Not Past Due	1,188	409
Total	$ 1,188	$ 409

Financing receivable recorded investment loans not past due.

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- Definition

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

+ References

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

+ Details

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- Definition

Financing receivables that are less than 90 days past due but more than 59 days past due.

+ References

+ Details

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- Definition

Financing receivables that are equal to or greater than 90 days past due.

+ References

+ Details

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- Definition

Recorded Investment in financing receivables that are past due at the balance sheet date.

+ References

+ Details

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- Definition

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=28367877&loc=d3e4428-111522

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