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Note 6 - Stock Compensation Plan - BSM Option Valuation Model Assumptions (Details) - Employee Stock Option [Member] - $ / shares
9 Months Ended
Sep. 30, 2016
Sep. 30, 2015
Minimum [Member]    
Risk-free interest rate 0.52% 1.34%
Volatility 66.20% 58.90%
Maximum [Member]    
Risk-free interest rate 1.38% 1.94%
Volatility 75.40% 67.80%
Weighted-average volatility 73.90% 60.10%
Dividend yield 0.00% 0.00%
Contractual term (in years) 1 year 292 days 6 years
Weighted-average grant date fair value per share (in dollars per share) $ 0.17 $ 0.91