Note 7 - Income Taxes (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount		$ (21,189,000)	$ 7,121,000
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent		34.00%	34.00%	34.00%
Increase (Decrease) in Deferred Tax Assets, Change in Enacted Rate		$ (30,675,000)
Unrecognized Tax Benefits		2,800,000
Unrecognized Tax Benefits that Would Impact Effective Tax Rate		0
Deferred Tax Assets, Net		0
Domestic Tax Authority [Member] | Internal Revenue Service (IRS) [Member]
Operating Loss Carryforwards		$ 286,300,000
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] | California Franchise Tax Board [Member]
Operating Loss Carryforwards		$ 166,300,000
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
Scenario, Forecast [Member]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%