Note 6 - Stockholders' Equity - Reconciliation of Activity in Stockholders' Equity Accounts (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Balance	$ 13,899
Net income (loss)	1,053	$ 1,366
Balance	14,973
Common Stock [Member]
Balance	294	294
Net income (loss)
Stock-based compensation expense
Balance	294	294
Additional Paid-in Capital [Member]
Balance	17,370	17,285
Net income (loss)
Stock-based compensation expense	21	21
Balance	17,391	17,306
Retained Earnings [Member]
Balance	(3,765)	(3,935)
Net income (loss)	1,054	1,366
Stock-based compensation expense
Balance	$ (2,711)	$ (2,569)