Earnings Per Share (Calculation of Basic and Diluted EPS) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Earnings Per Share [Abstract]
Net income	$ 16,592	$ 13,236	$ 41,075	$ 32,457
Average Common Shares:
Basic (weighted-average outstanding shares)	11,586	11,460	11,535	11,424
Dilutive potential common shares from stock options (in shares)	122	135	131	127
Diluted (weighted-average outstanding shares)	11,708	11,595	11,666	11,551
Basic earnings per share (in dollars per share)	$ 1.43	$ 1.15	$ 3.56	$ 2.84
Diluted earnings per share (in dollars per share)	$ 1.42	$ 1.14	$ 3.52	$ 2.81