Note 2 - Summary of Significant Accounting Policies - Calculation of EPS (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended																12 Months Ended
	Dec. 31, 2019		Sep. 30, 2019		Jun. 30, 2019		Mar. 31, 2019		Dec. 31, 2018		Sep. 30, 2018		Jun. 30, 2018		Mar. 31, 2018		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Net income (loss) - basic and diluted	$ (2,485)		$ (1,822)		$ 381		$ 426		$ 2,157		$ 2,322		$ 2,371		$ 1,777		$ (3,500)	$ 8,627	$ 8,905
Weighted average shares outstanding (in shares)																	58,833	58,358	56,933
Net income (loss) per share – basic (in dollars per share)	$ (0.04)	[1]	$ (0.03)	[1]	$ 0.01	[1]	$ 0.01	[1]	$ 0.04	[1]	$ 0.04	[1]	$ 0.04	[1]	$ 0.03	[1]	$ (0.06)	$ 0.15	$ 0.16
Weighted average shares outstanding (including dilutive CSEs) (in shares)																	58,833	59,407	58,250
Net income (loss) per share – diluted (in dollars per share)	$ (0.04)	[1]	$ (0.03)	[1]	$ 0.01	[1]	$ 0.01	[1]	$ 0.04	[1]	$ 0.04	[1]	$ 0.04	[1]	$ 0.03	[1]	$ (0.06)	$ 0.15	$ 0.15

[1] Quarterly net income per share does not add to full year net income per share due to rounding.