Loans and Allowance for Loan and Lease Losses - Loan Portfolio Quality Indicators (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Financing Receivable, Recorded Investment [Line Items]
Total	$ 324,723	$ 321,025
Pass (Grades 1-5) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	303,315	299,629
Watch (Grade 6) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	9,365	9,470
Special Mention (Grade 7) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	3,329	3,355
Substandard (Grade 8) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	4,101	4,106
Doubtful (Grade 9) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	4,613	4,465
Commercial Real Estate Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	114,131	111,455
Commercial Real Estate Loans [Member] | Pass (Grades 1-5) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	102,866	100,095
Commercial Real Estate Loans [Member] | Watch (Grade 6) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	7,002	7,097
Commercial Real Estate Loans [Member] | Substandard (Grade 8) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	3,451	3,451
Commercial Real Estate Loans [Member] | Doubtful (Grade 9) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	812	812
Residential Real Estate Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	160,980	163,839
Residential Real Estate Loans [Member] | Pass (Grades 1-5) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	154,487	157,518
Residential Real Estate Loans [Member] | Watch (Grade 6) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	324	327
Residential Real Estate Loans [Member] | Special Mention (Grade 7) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	3,329	3,355
Residential Real Estate Loans [Member] | Substandard (Grade 8) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	425	427
Residential Real Estate Loans [Member] | Doubtful (Grade 9) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	2,415	2,212
Construction Real Estate Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	18,394	13,570
Construction Real Estate Loans [Member] | Pass (Grades 1-5) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	15,621	10,786
Construction Real Estate Loans [Member] | Watch (Grade 6) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	1,712	1,721
Construction Real Estate Loans [Member] | Substandard (Grade 8) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	225	228
Construction Real Estate Loans [Member] | Doubtful (Grade 9) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	836	835
Commercial Loans and Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	27,350	29,358
Commercial Loans and Leases [Member] | Pass (Grades 1-5) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	26,528	28,516
Commercial Loans and Leases [Member] | Watch (Grade 6) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	327	325
Commercial Loans and Leases [Member] | Doubtful (Grade 9) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	495	517
Municipal Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	1,895	785
Municipal Loans [Member] | Pass (Grades 1-5) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	1,895	785
Consumer Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	1,973	2,018
Consumer Loans [Member] | Pass (Grades 1-5) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	1,918	1,929
Consumer Loans [Member] | Doubtful (Grade 9) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	$ 55	$ 89