Note 9 - Financial Instruments	12 Months Ended
Dec. 31, 2022
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 per share 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, 2020, 0.5 million shares on the warrant were exercised. Subsequent to partial exercises of the Warrant, there were approximately 1.0 million shares underlying the Warrant as of December 31, 2021. During the year ended December 31, 2022, the remainder of the warrant was fully exercised. During 2022, the Warrant was fully exercised, and therefore there are no remaining underlying shares as of December 31, 2022. For the year ended December 31, 2022, we recorded a gain of approximately $0.4 million, reflecting a decrease in the fair value of the liability-classified warrant primarily due to the decrease in our stock price prior to the exercise of the Warrant. As of December 31, 2021, there were approximately 1.0 million shares underlying the outstanding Warrant and 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%.

Note 9 - Financial Instruments

12 Months Ended

Dec. 31, 2022

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 per share 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, 2020, 0.5 million shares on the warrant were exercised. Subsequent to partial exercises of the Warrant, there were approximately 1.0 million shares underlying the Warrant as of December 31, 2021. During the year ended December 31, 2022, the remainder of the warrant was fully exercised.

During 2022, the Warrant was fully exercised, and therefore there are no remaining underlying shares as of December 31, 2022. For the year ended December 31, 2022, we recorded a gain of approximately $0.4 million, reflecting a decrease in the fair value of the liability-classified warrant primarily due to the decrease in our stock price prior to the exercise of the Warrant.

As of December 31, 2021, there were approximately 1.0 million shares underlying the outstanding Warrant and 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%.