Note 15 - Net Income Per Share - Basic and Diluted Net Income Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Net income	$ 10,791	$ 9,835
Average shares outstanding (in shares)	22,492	22,254
Dilutive securities (in shares)	510	338
Average shares outstanding including dilutive securities (in shares)	23,002	22,592
Net income per share, basic (in dollars per share)	$ 0.48	$ 0.44
Net income per share, diluted (in dollars per share)	$ 0.47	$ 0.44