Loans and Allowance for Loan and Lease Losses - Loan Portfolio Quality Indicators (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Financing Receivable, Recorded Investment [Line Items]
Total	$ 332,542	$ 321,025
Pass (Grades 1-5) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	311,136	299,629
Watch (Grade 6) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	9,481	9,470
Special Mention (Grade 7) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total		3,355
Substandard (Grade 8) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	4,098	4,106
Doubtful (Grade 9) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	7,827	4,465
Commercial Real Estate Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	116,472	111,455
Commercial Real Estate Loans [Member] | Pass (Grades 1-5) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	108,312	100,095
Commercial Real Estate Loans [Member] | Watch (Grade 6) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	3,897	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	163,467	163,839
Residential Real Estate Loans [Member] | Pass (Grades 1-5) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	153,754	157,518
Residential Real Estate Loans [Member] | Watch (Grade 6) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	3,633	327
Residential Real Estate Loans [Member] | Special Mention (Grade 7) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total		3,355
Residential Real Estate Loans [Member] | Substandard (Grade 8) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	423	427
Residential Real Estate Loans [Member] | Doubtful (Grade 9) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	5,657	2,212
Construction Real Estate Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	18,637	13,570
Construction Real Estate Loans [Member] | Pass (Grades 1-5) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	15,874	10,786
Construction Real Estate Loans [Member] | Watch (Grade 6) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	1,703	1,721
Construction Real Estate Loans [Member] | Substandard (Grade 8) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	224	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	30,196	29,358
Commercial Loans and Leases [Member] | Pass (Grades 1-5) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	29,513	28,516
Commercial Loans and Leases [Member] | Watch (Grade 6) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	248	325
Commercial Loans and Leases [Member] | Doubtful (Grade 9) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	435	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	1,875	2,018
Consumer Loans [Member] | Pass (Grades 1-5) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	1,788	1,929
Consumer Loans [Member] | Doubtful (Grade 9) [Member]
Financing Receivable, Recorded Investment [Line Items]
Total	$ 87	$ 89