Note 5 - Net Income Per Share Basic and Diluted (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Numerator:
Net income	$ 11,198	$ 7,899	$ 21,773	$ 13,862
Denominator:
Weighted-average outstanding shares used to compute basic net income per share (in shares)	40,387	39,570	40,208	39,337
Effect of dilutive securities (in shares)	1,329	1,175	1,473	1,333
Weighted-average outstanding shares used to compute diluted net income per share (in shares)	41,716	40,745	41,681	40,670
Basic (in dollars per share)	$ 0.28	$ 0.20	$ 0.54	$ 0.35
Diluted (in dollars per share)	$ 0.27	$ 0.19	$ 0.52	$ 0.34