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, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Earnings Per Share [Abstract]
Net income	$ 11,401	$ 6,604	$ 55,181	$ 23,507
Weighted average shares outstanding - basic (in shares)	5,124,478	5,122,206	5,123,321	5,120,490
Weighted average shares outstanding - diluted (in shares)	5,124,478	5,122,206	5,123,321	5,120,490
Net income per common share - basic (in usd per share)	$ 2.22	$ 1.29	$ 10.77	$ 4.59
Net income per common share - diluted (in usd per share)	$ 2.22	$ 1.29	$ 10.77	$ 4.59