Note 6 - Share Based Compensation - Stock Options Outstanding (Details) - USD ($)	3 Months Ended	12 Months Ended
Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Outstanding, number of options (in shares)	4,381,348
Outstanding, weighted average exercise price per share (in dollars per share)	$ 3.85
Outstanding, Weighted Average Remaining Contractual Term (Year)	4 years 3 months 18 days		4 years 3 months 18 days
Outstanding, Aggregate Intrinsic Value	$ 177		$ 1,662
Granted, number of options (in shares)	500,000	765,000
Granted, weighted average exercise price per share (in dollars per share)	$ 2.94	$ 2.60
Exercised, number of options (in shares)	0	(54,705)
Exercised, weighted average exercise price per share (in dollars per share)	$ 0	$ 2.30
Exercised, Aggregate Intrinsic Value	$ 0
Forfeited or expired, number of options (in shares)	(185,826)
Forfeited or expired, weighted average exercise price per share (in dollars per share)	$ 4.58
Outstanding, number of options (in shares)	4,695,522		4,381,348
Outstanding, weighted average exercise price per share (in dollars per share)	$ 3.73		$ 3.85
Vested and expected to vest, number of options (in shares)	4,541,629
Vested and expected to vest, weighted average exercise price per share (in dollars per share)	$ 3.76
Vested and expected to vest,Weighted Average Remaining Contractual Term (Year)	4 years 3 months 18 days
Vested and expected to vest, Aggregate Intrinsic Value	$ 175
Exercisable, number of options (in shares)	3,214,119
Exercisable, weighted average exercise price per share (in dollars per share)	$ 4.15
Exercisable,Weighted Average Remaining Contractual Term (Year)	3 years 7 months 6 days
Exercisable, Aggregate Intrinsic Value	$ 141

The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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Weighted average price of options that were either forfeited or expired.

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The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan.

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Gross number of share options (or share units) granted during the period.

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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 exercisable or convertible options. 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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Number of fully vested and expected to vest exercisable options that may be converted into shares under option plan. 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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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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Number of fully vested and expected to vest options outstanding that can be converted into shares under option plan. 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 exercise price, at which grantee can acquire shares reserved for issuance, for 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 price at which option holders acquired shares when converting their stock options into shares.

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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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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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Number of share options (or share units) exercised during the current period.

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