Note 1 - Organization and Significant Accounting Policies - Calculation of Basic and Diluted Net Income Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Numerator:
Net income	$ 574	$ 17,028	$ 13,100
Denominator (in thousands):
Basic weighted-average common stock outstanding (in shares)	22,034	21,771	20,850
Effect of stock-based awards (in shares)	469	790	715
Diluted weighted-average common stock outstanding (in shares)	22,503	22,561	21,565
Basic net income per share (in dollars per share)	$ 0.03	$ 0.78	$ 0.63
Diluted net income per share (in dollars per share)	$ 0.03	$ 0.75	$ 0.61