Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Earnings Per Share [Abstract]
Outstanding stock options (in shares)	0	0
Distributed earnings allocated to common stock	$ 5,704	$ 4,663
Undistributed earnings allocated to common stock	13,278	11,422
Net earnings allocated to common stock	18,982	16,085
Net earnings allocated to participating securities	134	121
Net income allocated to common stock and participating securities	$ 19,116	$ 16,206
Weighted average shares outstanding for basic earnings per common share	25,950,386	25,903,397
Dilutive effect of stock compensation (in shares)	0	0
Weighted average shares outstanding for diluted earnings per common share	25,950,386	25,903,397
Basic earnings per common share (in dollars per share)	$ 0.73	$ 0.62
Diluted earnings per common share (in dollars per share)	$ 0.73	$ 0.62