Earnings Per Share - Calculation of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Earnings Per Share Basic [Abstract]
Net income	$ 19,312	$ 10,800
Basic weighted average common shares	19,311,710	19,266,016
Basic earnings per common share	$ 1.00	$ 0.56
Net income	$ 19,312	$ 10,800
Weighted average common shares	19,311,710	19,266,016
Restricted stock and stock options	97,094	86,229
Diluted weighted average common shares	19,408,804	19,352,245
Diluted earnings per common share	$ 0.99	$ 0.56