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Note 14 - Share-based Compensation - Nonemployee Stock Option Valuation Assumptions (Details) - Non-employee Stock Options [Member]
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Risk-free interest rate, minimum 1.60% 1.26%
Risk-free interest rate, maximum 2.42% 2.30%
Volatility, minimum 89.00% 71.00%
Volatility, maximum 91.00% 95.00%
Minimum [Member]    
Expected term (in years) (Year) 9 years 219 days 8 years 182 days
Maximum [Member]    
Expected term (in years) (Year) 9 years 328 days 9 years 255 days