Note 7 - Income Taxes - Reconciliation of the Income Tax Benefit to the Statutory Federal Income Tax Rate (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Expected federal income tax benefit at 34%	$ (11,477)	$ (8,955)	$ (8,163)
Loss with no tax benefit provided	8,156	6,918	7,389
State income tax	4	4	4
Non-deductible expenses and other	3,321	2,037	774
Income tax expense	$ 4	$ 4	$ 4