Earnings Per Common Share - Computation of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Basic earnings per common share computation:
Net income per consolidated statements of income	$ 12,915	$ 8,246	$ 26,021	$ 17,059
Net earnings allocated to participating securities	(47)	(29)	(92)	(59)
Net earnings allocated to common stock	$ 12,868	$ 8,217	$ 25,929	$ 17,000
Weighted average common shares outstanding, including shares considered participating securities (in shares)	16,885,000	15,393,000	16,870,000	15,365,000
Less: Average participating securities (in shares)	(60,000)	(52,000)	(58,000)	(52,000)
Weighted average shares (in shares)	16,825,000	15,341,000	16,812,000	15,313,000
Basic earnings per common share (in dollar per share)	$ 0.76	$ 0.54	$ 1.54	$ 1.11
Diluted earnings per common share computation:
Net earnings allocated to common stock	$ 12,868	$ 8,217	$ 25,929	$ 17,000
Weighted average common shares outstanding for basic earnings per common share (in shares)	16,825,000	15,341,000	16,812,000	15,313,000
Add: Dilutive effects of performance based-shares (in shares)	0	0	0	0
Weighted average shares and dilutive potential common shares (in shares)	16,825,000	15,341,000	16,812,000	15,313,000
Diluted earnings per common share (in dollar per share)	$ 0.76	$ 0.54	$ 1.54	$ 1.11
Distributed earnings allocated to common stock
Basic earnings per common share computation:
Net earnings allocated to common stock	$ 2,859	$ 2,608	$ 5,718	$ 5,216
Undistributed earnings allocated to common stock
Basic earnings per common share computation:
Net earnings allocated to common stock	$ 10,009	$ 5,609	$ 20,211	$ 11,784