Income Taxes - Reconciliation of Income Tax Attributable to Pre-tax Income at Federal Statutory Tax Rates to Income Tax Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Tax at statutory rate, value	$ 9,699	$ 10,671	$ 11,336
Tax exempt income, net value	(2,054)	(1,816)	(1,684)
Bank owned life insurance, value	(379)	(418)	(364)
Merger costs, value	170	30	0
Other, value	(265)	(175)	26
Income tax expense	$ 7,171	$ 8,292	$ 9,314
Tax at statutory rate, percent	35.00%	35.00%	35.00%
Tax exempt income, net percent	(7.40%)	(6.00%)	(5.20%)
Bank owned life insurance, percent	(1.30%)	(1.40%)	(1.10%)
Merger costs, percent	0.60%	0.10%	0.00%
Other, percent	(1.00%)	(0.50%)	0.10%
Income tax expense, percent	25.90%	27.20%	28.80%