Note 4 - Income Taxes (Details Textual) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%	35.00%
Unrecognized Tax Benefits, Ending Balance	$ 1,800
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	$ 297,000
Open Tax Period	3 years
Domestic Tax Authority [Member] | Internal Revenue Service (IRS) [Member] | Earliest Tax Year [Member]
Open Tax Year	2014
Domestic Tax Authority [Member] | Internal Revenue Service (IRS) [Member] | Latest Tax Year [Member]
Open Tax Year	2017
State and Local Jurisdiction [Member] | Internal Revenue Service (IRS) [Member]
Operating Loss Carryforwards, Total	$ 177,000
State and Local Jurisdiction [Member] | California Franchise Tax Board [Member]
Open Tax Period	4 years
State and Local Jurisdiction [Member] | California Franchise Tax Board [Member] | Earliest Tax Year [Member]
Open Tax Year	2013
State and Local Jurisdiction [Member] | California Franchise Tax Board [Member] | Latest Tax Year [Member]
Open Tax Year	2017