Loans - Loan Receivable Components (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans held-for-investment	$ 1,610,475	$ 1,609,918	$ 1,577,898
Allowance for loan losses	(15,716)	(15,541)	(17,952)	$ (18,008)
Net loans held-for-investment	1,594,759	1,594,377
Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans held-for-investment	230,306	235,946	222,828
Allowance for loan losses	(2,254)	(2,153)	(2,694)	(2,921)
Commercial Real Estate Owner Occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans held-for-investment	261,971	231,348
Commercial Real Estate Non-Owner Occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans held-for-investment	729,102	742,662
Land and Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans held-for-investment	67,336	67,165	86,520
Allowance for loan losses	(588)	(604)	(1,365)	(1,058)
Home Equity Lines of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans held-for-investment	105,885	110,377
Home Equity Term Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans held-for-investment	8,405	9,104
Residential Real Estate Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans held-for-investment	205,573	210,874	241,891
Allowance for loan losses	(2,567)	(2,648)	$ (2,714)	$ (3,029)
Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans held-for-investment	1,897	2,442
Commercial Loans [Member] | Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans held-for-investment	230,306	235,946
Commercial Loans [Member] | Commercial Real Estate Owner Occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans held-for-investment	261,971	231,348
Commercial Loans [Member] | Commercial Real Estate Non-Owner Occupied
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans held-for-investment	729,102	742,662
Commercial Loans [Member] | Land and Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans held-for-investment	67,336	67,165
Consumer Loans [Member] | Home Equity Lines of Credit [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans held-for-investment	105,885	110,377
Consumer Loans [Member] | Home Equity Term Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans held-for-investment	8,405	9,104
Consumer Loans [Member] | Residential Real Estate Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans held-for-investment	205,573	210,874
Consumer Loans [Member] | Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans held-for-investment	$ 1,897	$ 2,442