Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Earnings Per Share [Abstract]
Net income available to common shareholders	$ 29,000	$ 21,619
Undistributed Earnings (Loss) Allocated to Participating Securities, Basic	(263)	(186)
Distributed earnings allocated to common stock	9,117	8,661
Undistributed earnings allocated to common stock	19,620	12,772
Net earnings allocated to common shareholders	$ 28,737	$ 21,433
Average shares outstanding (in shares)	16,080	16,411
Effect of dilutive securities:
Employee stock awards (in shares)	21	18
Average common shares outstanding, diluted (in shares)	16,101	16,429
Basic earnings per common share (in dollars per share)	$ 1.79	$ 1.31
Diluted earnings per share (in dollars per share)	$ 1.78	$ 1.30