Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Earnings Per Share [Abstract]
Outstanding stock options (in shares)	0	0	0	0
Distributed earnings allocated to common stock	$ 4,656	$ 4,299	$ 13,995	$ 12,888
Undistributed earnings allocated to common stock	9,515	9,499	28,260	29,748
Net earnings allocated to common stock	14,171	13,798	42,255	42,636
Net earnings allocated to participating securities	93	130	306	433
Net income allocated to common stock and participating securities	$ 14,264	$ 13,928	$ 42,561	$ 43,069
Weighted average shares outstanding for basic earnings per common share	25,867,169	26,164,646	25,881,360	26,211,630
Dilutive effect of stock compensation (in shares)	0	0	0	0
Weighted average shares outstanding for diluted earnings per common share	25,867,169	26,164,646	25,881,360	26,211,630
Basic earnings per common share (in dollars per share)	$ 0.55	$ 0.53	$ 1.63	$ 1.63
Diluted earnings per common share (in dollars per share)	$ 0.55	$ 0.53	$ 1.63	$ 1.63