Note 10 - Income Taxes (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Domestic Tax Authority [Member]
Income Tax Expense (Benefit)	$ 0	$ 0	$ 0
Operating Loss Carryforwards	94,400,000	78,100,000	69,900,000
State and Local Jurisdiction [Member]
Income Tax Expense (Benefit)	0	0	0
Operating Loss Carryforwards	46,400,000	55,100,000	45,400,000
Unrecognized Tax Benefits	0	0	0
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense	0	0	0
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount	9,800,000	3,800,000	7,300,000
Operating Loss Carryforwards Attributable to Excess Stock Option Deductions	400,000
Tax Credit Carryforward, Amount	$ 16,900,000	$ 12,500,000	$ 10,300,000