Note 10 - Net Income Per Share (Details) - Net Income Per Share Basic And Diluted - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Numerator:
Net income (in Dollars)	$ 10,110	$ 11,201	$ 7,899	$ 5,963	$ 8,860	$ 11,221	$ 6,397	$ 9,018	$ 35,172	$ 35,495	$ 22,898
Denominator:
Weighted-average outstanding shares used to compute basic net income per share									39,470	38,686	37,387
Effect of dilutive securities									1,399	1,107	1,233
Weighted-average outstanding shares used to compute diluted net income per share	41,445	40,689	40,745	40,596	40,321	39,727	39,608	39,517	40,869	39,793	38,620
Net income per share:
Basic (in Dollars per share)	$ 0.26	$ 0.28	$ 0.20	$ 0.15	$ 0.23	$ 0.29	$ 0.17	$ 0.23	$ 0.89	$ 0.92	$ 0.61
Diluted (in Dollars per share)	$ 0.24	$ 0.28	$ 0.19	$ 0.15	$ 0.22	$ 0.28	$ 0.16	$ 0.23	$ 0.86	$ 0.89	$ 0.59