Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ 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 available to common shareholders	$ 22,732	$ 20,126	$ 64,694	$ 67,374
Less: earnings allocated to participating securities	(220)	(198)	(618)	(658)
Net earnings allocated to common shareholders	22,512	19,928	64,076	66,716
Distributed earnings allocated to common stock	8,726	8,944	26,177	26,832
Undistributed earnings allocated to common stock	$ 13,786	$ 10,984	$ 37,899	$ 39,884
Average shares outstanding (in shares)	15,279	15,950	15,501	16,065
Effect of dilutive securities:
Employee stock awards (in shares)	23	20	25	19
Average shares outstanding, diluted (in shares)	15,302	15,970	15,526	16,084
Basic earnings per common share (in dollars per share)	$ 1.47	$ 1.25	$ 4.13	$ 4.15
Diluted earnings per share (in dollars per share)	$ 1.47	$ 1.25	$ 4.13	$ 4.15