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Note 11 - Stock Incentive Plans - Assumptions Used in the Option Pricing Model (Details) - $ / shares
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Dividend yield 0.00% 0.00% 0.00%
Historical volatility     65.00%
Expected life (years) (Year) 6 years 6 years  
Weighted average grant date fair value (in dollars per share) $ 7.13 $ 11.20 $ 5.80
Minimum [Member]      
Historical volatility 52.00% 51.00%  
Risk-free rate 1.40% 1.50% 1.70%
Expected life (years) (Year)     6 years
Maximum [Member]      
Historical volatility 55.00% 58.00%  
Risk-free rate 1.60% 1.80% 2.10%
Expected life (years) (Year)     6 years 91 days