Note 12 - Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets
Net operating loss carryforwards and credits	$ 15,064	$ 5,302
Share-based compensation expense	3,441	3,548
Property, plant and equipment	1,025	1,399
Common stock warrant liabilities	524
Operating lease liabilities	147
Other	21	51
Less: valuation allowance	(19,802)	(10,300)
Total deferred tax assets	420
Deferred tax liabilities
Operating lease right-of-use assets	(420)
Total deferred tax liabilities	(420)
Net deferred tax assets (liabilities)