Note 9 - Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Federal research credits	$ 1,600
Change in valuation allowance attributable to operations	(298)	$ (3,114)
Internal Revenue Service (IRS)
Operating Loss Carryforwards	162,300
Internal Revenue Service (IRS) \| No Expire
Operating Loss Carryforwards	0
State and Local Jurisdiction
State research credits	800
State and Local Jurisdiction \| Expire On Various Dates
Operating Loss Carryforwards	$ 23,900

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