Note 12 - Income Taxes - Net Deferred Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Net operating loss carryforwards	$ 109,813	$ 103,612
Research and other credits	3,482	3,482
Operating lease assets	(170)
Operating lease liabilities	198
Other temporary differences	4,851	3,760
Deferred tax assets	118,175	110,854
Valuation allowance	(118,175)	(110,854)
Net deferred tax assets