Note 6 - Income Taxes (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Deferred Tax Assets, Valuation Allowance, Total	$ 64,102	$ 62,431
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount	1,700	29,000
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense, Total	0	$ 0
Domestic Tax Authority [Member]
Operating Loss Carryforwards, Total	260,000
State and Local Jurisdiction [Member]
Operating Loss Carryforwards, Total	$ 186,000