Note 6 - Net Income per Share (Details) - Net Income per Share Basic and Diluted - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Numerator:
Net income (in Dollars)	$ 11,201	$ 11,221	$ 25,063	$ 26,635
Denominator:
Weighted-average outstanding shares used to compute basic net income per share	39,592	38,785	39,422	38,646
Effect of dilutive securities	1,097	942	1,254	972
Weighted-average outstanding shares used to compute diluted net income per share	40,689	39,727	40,676	39,618
Net income per share:
Basic (in Dollars per share)	$ 0.28	$ 0.29	$ 0.64	$ 0.69
Diluted (in Dollars per share)	$ 0.28	$ 0.28	$ 0.62	$ 0.67