Note 6 - Stockholders' Equity - Reconciliation of Activity in Stockholders' Equity Accounts (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Balance			$ 13,899				$ 13,899
Net income (loss)	$ (446)			$ (59)			432	$ 405
Balance	27,069						27,069
Common Stock [Member]
Balance	684	$ 294	294	294	$ 294	$ 294	294	294
Net income (loss)
Stock-based compensation expense
Issuance of common stock		390
Balance	684	684	294	294	294	294	684	294
Additional Paid-in Capital [Member]
Balance	29,696	17,391	17,370	17,328	17,306	17,285	17,370	17,285
Net income (loss)
Stock-based compensation expense	21	20	21	21	22	21
Issuance of common stock		12,285
Balance	29,717	29,696	17,391	17,349	17,328	17,306	29,717	17,349
Retained Earnings [Member]
Balance	(2,886)	(2,711)	(3,765)	(3,471)	(2,569)	(3,935)	(3,765)	(3,935)
Net income (loss)	(446)	(175)	1,054	(59)	(902)	1,366
Stock-based compensation expense
Issuance of common stock
Balance	$ (3,332)	$ (2,886)	$ (2,711)	$ (3,530)	$ (3,471)	$ (2,569)	$ (3,332)	$ (3,530)