Earnings Per Share - Calculation of Basic Earnings Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Earnings Per Share [Abstract]
Net income	$ 6,776	$ 4,410	$ 4,804	$ 4,105	$ 4,723	$ 4,275	$ 6,180	$ 3,224	$ 20,095	$ 18,402	$ 14,949
Less: distributed earnings allocated to participating securities									(57)	(51)	(52)
Less: undistributed earnings allocated to participating securities									(96)	(87)	(98)
Net earnings available to common shareholders									$ 19,942	$ 18,264	$ 14,799
Weighted average common shares outstanding including participating securities									11,146,270	11,113,810	9,272,964
Less: average unvested restricted shares									(84,879)	(83,369)	(93,000)
Weighted average common shares outstanding	11,177,765	11,142,797	11,129,341	11,134,870	11,137,004	11,121,426	11,106,367	11,089,839	11,061,391	11,030,441	9,179,964
Basic and diluted earnings per share	$ 0.60	$ 0.40	$ 0.43	$ 0.37	$ 0.43	$ 0.38	$ 0.56	$ 0.29	$ 1.80	$ 1.66	$ 1.61