Note 7 - Income Taxes (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount	$ 5,563,000	$ (21,189,000)
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%	34.00%
Unrecognized Tax Benefits, Ending Balance	$ 1,800,000
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	0
Deferred Tax Assets, Net, Total	0
Domestic Tax Authority [Member] | Internal Revenue Service (IRS) [Member]
Operating Loss Carryforwards, Total	$ 308,800,000
Open Tax Year	2015 2016 2017 2018
Open Tax Period	3 years
State and Local Jurisdiction [Member] | California Franchise Tax Board [Member]
Operating Loss Carryforwards, Total	$ 188,800,000
Open Tax Year	2014 2015 2016 2017 2018
Open Tax Period	4 years