Note 5 - Stock-based Compensation - Summary of Stock Options (Details)	9 Months Ended
Sep. 30, 2019 USD ($) $ / shares shares
Shares outstanding (in shares) \| shares	153,500
Shares outstanding, weighted average exercise price (in dollars per share) \| $ / shares	$ 7.68
Shares outstanding, weighted average remaining contractual life (Year)	4 years 255 days
Shares outstanding, aggregate intrinsic value \| $	$ 5,197,170
Shares vested and exercisable (in shares) \| shares	111,500
Shares vested and exercisable, weighted average exercise price (in dollars per share) \| $ / shares	$ 2.11
Shares vested and exercisable, weighted average remaining contractual life (Year)	3 years
Shares vested and exercisable, aggregate intrinsic value \| $	$ 4,396,270

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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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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