Earnings Per Share - Schedule of Earnings Per Share, Basic and Diluted (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
Earnings Per Share [Abstract]
Net income	$ 25,898	$ 12,331	$ 43,780	$ 16,903
Weighted average shares outstanding - basic (in shares)	5,123,255	5,120,548	5,122,733	5,119,623
Weighted average shares outstanding - diluted (in shares)	5,123,255	5,120,548	5,122,733	5,119,623
Net income per common share - basic (in usd per share)	$ 5.05	$ 2.41	$ 8.55	$ 3.30
Net income per common share - diluted (in usd per share)	$ 5.05	$ 2.41	$ 8.55	$ 3.30