Note 8 - Income Taxes - Provision for Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
U.S. Federal tax benefit at statutory rates, amount	$ (397)	$ (1,925)
U.S. Federal tax benefit at statutory rates, percent	21.00%	21.00%
Tax credits, amount	$ 109	$ (715)
Tax credits, percent	(5.80%)	7.80%
State income tax, amount	$ (53)	$ (108)
State income tax, percent	2.80%	1.20%
International operations, amount	$ (6)	$ 409
International operations, percent	0.30%	(4.50%)
Share-based compensation, amount	$ 317	$ 348
Share-based compensation, percent	(16.80%)	(3.80%)
Valuation allowance, amount	$ (1,224)	$ 1,471
Valuation allowance, percent	64.80%	(16.00%)
Expiration of tax attributes, amount	$ 1,330	$ 475
Expiration of tax attributes, percent	(70.40%)	(5.20%)
Other, net, amount	$ (76)	$ 61
Other, net, percent	4.00%	(0.70%)
Tax expense and effective tax rate, amount		$ 16
Tax expense and effective tax rate, percent	0.00%	(0.20%)