Earnings Per Share (Details 2) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Earnings Per Share [Abstract]
Distributed earnings allocated to common stock	$ 18,707	$ 17,582	$ 17,091
Undistributed earnings allocated to common stock	38,670	39,336	40,249
Net earnings allocated to common stock	57,377	56,918	57,340
Net earnings allocated to participating securities	409	568	729
Net income available to common shareholders	$ 57,786	$ 57,486	$ 58,069
Weighted average shares outstanding for basic earnings per common share	25,879,397	26,173,351	26,434,769
Dilutive effect of stock compensation (in shares)	0	0	0
Weighted average shares outstanding for diluted earnings per common share	25,879,397	26,173,351	26,434,769
Basic earnings per common share (in dollars per share)	$ 2.22	$ 2.17	$ 2.17
Diluted earnings per common share (in dollars per share)	$ 2.22	$ 2.17	$ 2.17