Earnings Per Share (Calculation of Basic and Diluted EPS) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Earnings Per Share [Abstract]
Net income	$ 14,583	$ 12,167
Average Common Shares:
Basic (weighted-average outstanding shares)	11,606	11,472
Dilutive potential common shares from stock options (in shares)	133	148
Diluted (weighted-average outstanding shares)	11,739	11,620
Basic earnings per share (in dollars per share)	$ 1.26	$ 1.06
Diluted earnings per share (in dollars per share)	$ 1.24	$ 1.05