Fair Value Measurement - Carrying Amount and Fair Values of Financial Instruments (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015	Sep. 30, 2015	Dec. 31, 2014
Financial Assets:
Cash and due from financial institutions	$ 33,229	$ 35,561	$ 33,619	$ 29,858
Securities available for sale	200,967	196,249
Loans, net of allowance for loan losses	1,033,516	987,166
Other securities	13,926	13,452
Bank owned life insurance	24,404	20,104
Accrued interest receivable	4,547	3,902
Financial Liabilities:
Securities sold under agreement to repurchase	21,713	25,040
Carrying Amount [Member]
Financial Assets:
Cash and due from financial institutions	33,229	35,561
Securities available for sale	200,967	196,249
Loans, held for sale	2,827	2,698
Loans, net of allowance for loan losses	1,033,516	987,166
Other securities	13,926	13,452
Bank owned life insurance	24,404	20,104
Accrued interest receivable	4,547	3,902
Swap asset	3,705
Swap asset		1,962
Financial Liabilities:
Nonmaturing deposits	915,360	840,984
Time deposits	218,793	211,049
Short-term FHLB advances	17,500	53,700
Long-term FHLB advances	17,500	17,500
Securities sold under agreement to repurchase	21,713	25,040
Subordinated debentures	29,427	29,427
Accrued interest payable	137	120
Swap liability	3,705
Swap liability		1,962
Total Fair Value [Member]
Financial Assets:
Cash and due from financial institutions	33,229	35,561
Securities available for sale	200,967	196,249
Loans, held for sale	2,827	2,698
Loans, net of allowance for loan losses	1,037,955	986,848
Other securities	13,926	13,452
Bank owned life insurance	24,404	20,104
Accrued interest receivable	4,547	3,902
Swap asset	3,705
Swap asset		1,962
Financial Liabilities:
Nonmaturing deposits	915,360	840,984
Time deposits	219,345	212,006
Short-term FHLB advances	17,394	52,906
Long-term FHLB advances	17,710	17,687
Securities sold under agreement to repurchase	21,713	25,040
Subordinated debentures	30,367	25,572
Accrued interest payable	137	120
Swap liability	3,705	1,962
(Level 1) [Member]
Financial Assets:
Cash and due from financial institutions	33,229	35,561
Loans, held for sale	2,827	2,698
Other securities	13,926	13,452
Bank owned life insurance	24,404	20,104
Accrued interest receivable	4,547	3,902
Financial Liabilities:
Nonmaturing deposits	915,360	840,984
Short-term FHLB advances	17,394	52,906
Securities sold under agreement to repurchase	21,713	25,040
Accrued interest payable	137	120
(Level 2) [Member]
Financial Assets:
Securities available for sale	200,967	196,249
Swap asset	3,705
Swap asset		1,962
Financial Liabilities:
Swap liability	3,705	1,962
(Level 3) [Member]
Financial Assets:
Loans, net of allowance for loan losses	1,037,955	986,848
Financial Liabilities:
Time deposits	219,345	212,006
Long-term FHLB advances	17,710	17,687
Subordinated debentures	$ 30,367	$ 25,572