Note 9 - Financial Instruments	12 Months Ended
Dec. 31, 2021
Notes to Financial Statements
Financial Instruments Disclosure [Text Block]	9. Financial Instruments 2016 Warrant On September 2, 2016, in connection with the entry into the Loan Agreement (see Note 7 for additional information), the Company issued a warrant (the “Warrant”) to the Lender to purchase a number of shares of the Company’s common stock equal to $4.0 million divided by the lower of (i) $2.29 per share and (ii) the subscription price paid in connection with the Rights Offering completed on November 16, 2016. The subscription price paid was $1.50 in connection with the Rights Offering; accordingly, the exercise price of the Warrant was set at $1.50 per share, and there were 2.7 million shares underlying the Warrant. During the year ended December 31, 2021, no shares on the warrant were exercised. During the year ended December 31, 2020, 0.5 million shares on the warrant were exercised. Subsequent to partial exercises of the Warrant, there are approximately 1.0 million shares underlying the Warrant as of December 31, 2021. The Warrant provides for weighted average anti-dilution protection and is exercisable in whole or in part for ten (10) years from the date of issuance. The Company accounted for the Warrant in accordance with the authoritative guidance which requires that free-standing derivative financial instruments with certain anti-dilution and cash settlement features be classified as assets or liabilities at the time of the transaction, and recorded at their fair value. Any changes in the fair value of the derivative instruments are reported in earnings or loss as long as the derivative contracts are classified as assets or liabilities. Accordingly, the Company classified the Warrant as a liability and reports its change in fair value in the consolidated statement of operations. On September 2, 2016, the issuance date of the Warrant, the fair value of the liability-classified Warrant was $5.8 million. The Company applied a Monte Carlo Simulation-model to calculate the fair value of the Warrant and compared the Monte Carlo simulation model calculation to a Black-Scholes model calculation as of December 31, 2016. These models generated substantially equivalent fair values for the Warrant. As such, the Company utilized a Black-Scholes model at December 31, 2021 and 2020 to determine the fair value of the Warrant. As of December 31, 2021, the fair value of the Warrant was $6.5 million. A Black Scholes model was applied to calculate the fair value of the Warrant using the following assumptions: risk free interest rate of 1.21%; no dividend yield; an expected life of 4.7 years; and a volatility factor of 55%. As of December 31, 2020, the fair value of the Warrant was $6.6 million. A Black Scholes model was applied to calculate the fair value of the Warrant using the following assumptions: risk free interest rate of 0.46%; no dividend yield; an expected life of 5.7 years; and a volatility factor of 80%. At December 31, 2021, pursuant to the Warrant agreement, there were no conditions under which current assets would have been required to satisfy the Warrant obligation.

Note 9 - Financial Instruments

12 Months Ended

Dec. 31, 2021

Financial Instruments Disclosure [Text Block]

9. Financial Instruments

2016 Warrant

On September 2, 2016, in connection with the entry into the Loan Agreement (see Note 7 for additional information), the Company issued a warrant (the “Warrant”) to the Lender to purchase a number of shares of the Company’s common stock equal to $4.0 million divided by the lower of (i) $2.29 per share and (ii) the subscription price paid in connection with the Rights Offering completed on November 16, 2016. The subscription price paid was $1.50 in connection with the Rights Offering; accordingly, the exercise price of the Warrant was set at $1.50 per share, and there were 2.7 million shares underlying the Warrant. During the year ended December 31, 2021, no shares on the warrant were exercised. During the year ended December 31, 2020, 0.5 million shares on the warrant were exercised. Subsequent to partial exercises of the Warrant, there are approximately 1.0 million shares underlying the Warrant as of December 31, 2021. The Warrant provides for weighted average anti-dilution protection and is exercisable in whole or in part for ten (10) years from the date of issuance.

The Company accounted for the Warrant in accordance with the authoritative guidance which requires that free-standing derivative financial instruments with certain anti-dilution and cash settlement features be classified as assets or liabilities at the time of the transaction, and recorded at their fair value. Any changes in the fair value of the derivative instruments are reported in earnings or loss as long as the derivative contracts are classified as assets or liabilities. Accordingly, the Company classified the Warrant as a liability and reports its change in fair value in the consolidated statement of operations.

On September 2, 2016, the issuance date of the Warrant, the fair value of the liability-classified Warrant was $5.8 million. The Company applied a Monte Carlo Simulation-model to calculate the fair value of the Warrant and compared the Monte Carlo simulation model calculation to a Black-Scholes model calculation as of December 31, 2016. These models generated substantially equivalent fair values for the Warrant. As such, the Company utilized a Black-Scholes model at December 31, 2021 and 2020 to determine the fair value of the Warrant.

As of December 31, 2021, the fair value of the Warrant was $6.5 million. A Black Scholes model was applied to calculate the fair value of the Warrant using the following assumptions: risk free interest rate of 1.21%; no dividend yield; an expected life of 4.7 years; and a volatility factor of 55%.

As of December 31, 2020, the fair value of the Warrant was $6.6 million. A Black Scholes model was applied to calculate the fair value of the Warrant using the following assumptions: risk free interest rate of 0.46%; no dividend yield; an expected life of 5.7 years; and a volatility factor of 80%.

At December 31, 2021, pursuant to the Warrant agreement, there were no conditions under which current assets would have been required to satisfy the Warrant obligation.