Note 9 - Stockholders' Equity - Summary of Outstanding Options (Details) - USD ($)	3 Months Ended
Mar. 31, 2022	Dec. 31, 2021
Quantity, outstanding (in shares)	42,655	45,468
Quantity, vested (in shares)	42,655
Weighted-average exercise price, outstanding (in dollars per share)	$ 10.81	$ 14.28
Weighted-average exercise price, vested (in dollars per share)	$ 10.81
Weighted average remaining contractual term, outstanding (Year)	2 years 6 months
Weighted average remaining contractual term , vested (Year)	2 years 6 months
Intrinsic value, outstanding	$ 0
Intrinsic value, vested	$ 0

Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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Number of options outstanding, including both vested and non-vested options.

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Amount by which current fair value of underlying stock exceeds exercise price of fully vested and expected to vest options outstanding. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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