Earnings per Common Share - Computation of Basic and Diluted Earnings per Common Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Basic
Net income	$ 9,164	$ 6,504	$ 19,922	$ 14,337
Less allocation of earnings and dividends to participating securities	42	22	76	38
Net income available to common shareholders—basic	$ 9,122	$ 6,482	$ 19,846	$ 14,299
Weighted average common shares outstanding	15,602,329	16,044,125	15,734,226	16,280,935
Less average participating securities	72,563	54,274	59,995	43,693
Weighted average number of shares outstanding used in the calculation of basic earnings per common share	15,529,766	15,989,851	15,674,231	16,237,242
Earnings per common share:
Basic	$ 0.59	$ 0.41	$ 1.27	$ 0.88
Diluted	$ 0.59	$ 0.41	$ 1.27	$ 0.88