Earnings Per Share (Computation of Basic and Diluted) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Numerator:
Net income	$ 13,540	$ 10,902	$ 27,167	$ 25,482
Denominator:
Weighted-average shares outstanding - basic (shares)	18,627	18,158	18,551	18,055
Effect of dilutive stock options (shares)	429	531	452	564
Weighted-average shares outstanding - diluted (shares)	19,056	18,689	19,003	18,619
Basic earnings per share (in dollars per share)	$ 0.73	$ 0.60	$ 1.46	$ 1.41
Diluted earnings per share (in dollars per share)	$ 0.71	$ 0.58	$ 1.43	$ 1.37