Earnings Per Share - Calculation of Basic Earnings Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Earnings Per Share [Abstract]
Net income		$ 3,222	$ 3,015	$ 9,284	$ 8,470
Less: distributed earnings allocated to participating securities		(12)	(10)	(33)	(27)
Less: undistributed earnings allocated to participating securities		(19)	(16)	(54)	(45)
Net earnings available to common shareholders		$ 3,191	$ 2,989	$ 9,197	$ 8,398
Weighted average common shares outstanding including participating securities		9,252,919	9,225,532	9,245,514	9,218,376
Less: average unvested restricted shares		(88,596)	(80,422)	(87,074)	(77,866)
Weighted average common shares outstanding		9,164,323	9,145,110	9,158,440	9,140,510
Basic earnings and diluted per share	[1]	$ 0.35	$ 0.33	$ 1.00	$ 0.92

[1] Share data has been adjusted to reflect a 2-for-1 stock split on September 20, 2017