Net Income per Share (Computation Of Basic And Diluted Net Income Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Numerator for basic and diluted net income per share:
Net income	$ 2,124	$ 9,063	$ 24,067	$ 45,398
Denominator for basic net income per share:
Weighted-average common shares outstanding (in shares)	39,853	39,641	39,843	38,028
Basic net income per share (in dollars per share)	$ 0.05	$ 0.23	$ 0.60	$ 1.19
Denominator for diluted net income per share:
Dilutive stock options and restricted stock units (in shares)	639	623	620	1,078
Diluted weighted-average common shares outstanding (in shares)	40,492	40,264	40,463	39,106
Diluted net income per share (in dollars per share)	$ 0.05	$ 0.23	$ 0.59	$ 1.16