Earnings Per Share - Schedule of Earnings Per Share, Basic and Diluted (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Earnings Per Share [Abstract]
Net income	$ 6,604	$ 16,493	$ 23,507	$ 45,641
Weighted average shares outstanding - basic and diluted (in shares)	5,122,206	5,118,698	5,120,490	5,118,030
Net income per common share - basic and diluted (in usd per share)	$ 1.29	$ 3.22	$ 4.59	$ 8.92