Income Taxes - Summary of Difference in Effective Tax Rates and Statutory Federal Income Tax Rate of 21% (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Tax Disclosure [Abstract]
Tax at statutory rate, amount	$ 2,210	$ 2,172
Tax exempt income, amount	(60)	(34)
Life insurance, amount	(81)	(91)
Stock compensation, amount	(58)	(128)
Other, amount	(143)	(130)
Income tax provision, total amount	$ 1,868	$ 1,789
Tax at statutory rate, rate	21.00%	21.00%
Tax exempt income, rate	(0.57%)	(0.33%)
Life insurance, rate	(0.77%)	(0.88%)
Stock compensation, rate	(0.55%)	(1.24%)
Other, rate	(1.36%)	(1.26%)
Income tax provision, total rate	17.75%	17.29%