Allowance for Loan Losses - Performing and Nonperforming Loans (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment [Line Items]
Performing	$ 199,500	$ 187,760
Nonperforming	12	38
Total	199,512	187,798
Residential Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Performing	177,266	165,048
Nonperforming		37
Total	177,266	165,085
Real Estate Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Performing	5,251	6,254
Total	5,251	6,254
Consumer and Other [Member]
Financing Receivable, Recorded Investment [Line Items]
Performing	16,983	16,458
Nonperforming	12	1
Total	$ 16,995	$ 16,459