Note 13 - Income Taxes - Significant Components of Deferred Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Net operating loss carryforwards	$ 16,688	$ 31,759
Capitalized start up costs	3,225	3,555
Research and development credits	527	951
Accruals and reserves	532	1,272
Fixed assets and depreciation	(128)	(69)
Total deferred tax assets	21,100	37,606
Valuation allowance	(21,100)	(37,606)
Net deferred tax assets