Note 7 - Income Taxes (Details Textual) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Income Tax Expense (Benefit), Total	$ 0	$ 0
Deferred Tax Assets, Valuation Allowance, Total			$ 84,100
Deferred Income Tax Assets, Net, Total			800
Deferred Tax Assets, Tax Credit Carryforwards, Alternative Minimum Tax			$ 800
Unrecognized Tax Benefits, Ending Balance	$ 0