Computation of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Earnings Per Share [Abstract]
Net income	$ 6,721	$ 3,728	$ 40,984	$ 16,621
Weighted average shares outstanding – basic	14,202,859	14,100,180	14,181,530	14,082,698
Net income per share	$ 0.47	$ 0.26	$ 2.89	$ 1.18
Weighted average shares outstanding – diluted	14,327,757	14,346,585	14,328,861	14,321,113
Net income per share	$ 0.47	$ 0.26	$ 2.86	$ 1.16