Note 7 - Income Taxes - Reconciliation of the Income Tax Benefit to the Statutory Federal Income Tax Rate (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Expected federal income tax benefit: (2019 & 2018 at 21%; 2017 at 34%)	$ (6,200)	$ (5,516)	$ (11,477)
Loss with no tax benefit provided	2,508	4,175	8,156
State income tax	6	6	4
Expiring carryforwards	2,427
Non-deductible expenses and other	1,265	1,341	3,321
Income tax expense	$ 6	$ 6	$ 4