Note 13 - Income Taxes (Details Textual) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Income Tax Expense (Benefit), Total	$ 48	$ 38
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount	(4,055)	992
Deferred Tax Assets, Valuation Allowance, Total	70,066	74,121
Operating Loss Carryforwards, Subject to Expiration	260,598	$ 227,781
Operating Loss Carry Forwards Annual Limit	$ 14,284
Rights [Member]
Term of Extended Rights Plan (Year)	3 years
Threshold Percentage of Beneficial Ownership for Significant Dilution in Ownership Interest	4.90%
Class of Warrant or Right Number of Rights Per Common Stock Share	1
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right (in shares)	0.001
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)	$ 4.25
Class of Warrant or Right Current Beneficial Ownership Percentage That Will Not Trigger Preferred Share Purchase Rights	4.90%