Note 16 - Income Taxes - Net Deferred Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Accruals and other	$ 3,672	$ 3,263
Research credits	7,275	7,275
Net operating loss carryforward	52,361	39,082
Section 59(e) R&D expenditures	8,933	10,387
Deferred revenue	21,324	20,689
Total deferred tax assets	93,565	80,696
Valuation allowance	(93,565)	(80,696)
Net deferred tax assets		$ 0