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, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Earnings Per Share [Abstract]
Net income	$ 12,331	$ 11,283	$ 16,903	$ 29,148
Weighted average shares outstanding - basic and diluted (in shares)	5,120,548	5,118,030	5,119,623	5,117,690
Net income per common share - basic and diluted (in usd per share)	$ 2.41	$ 2.20	$ 3.30	$ 5.70