Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ 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 available to common shareholders	$ 22,148	$ 18,251	$ 41,962	$ 47,249
Less: earnings allocated to participating securities	(206)	(180)	(385)	(463)
Net earnings allocated to common shareholders	21,942	18,071	41,577	46,786
Distributed earnings allocated to common stock	8,921	9,073	17,845	18,147
Undistributed earnings allocated to common stock	$ 13,021	$ 8,998	$ 23,732	$ 28,639
Average shares outstanding (in shares)	15,573	16,081	15,614	16,123
Effect of dilutive securities:
Employee stock awards (in shares)	21	16	26	19
Average common shares outstanding, diluted (in shares)	15,594	16,097	15,640	16,142
Basic earnings per common share (in dollars per share)	$ 1.41	$ 1.12	$ 2.66	$ 2.90
Diluted earnings per share (in dollars per share)	$ 1.41	$ 1.12	$ 2.66	$ 2.90