Note 12 - Income Taxes - Net Deferred Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets, net:
Net operating loss carryforwards	$ 103,612	$ 100,631
Research and other credits	3,482	3,482
Other temporary differences	3,760	3,266
Deferred tax assets - before valuation allowance	110,854	107,379
Valuation allowance	(110,854)	(107,379)
Net deferred tax assets - after valuation allowance	$ 0	$ 0