Note 6 - Share-based Compensation - Stock Option Transactions (Details) - $ / shares	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Outstanding Options (in shares)	676,846
Outstanding options (in dollars per share)	$ 15.70
Granted (in shares)	128,259	87,385
Granted (in dollars per share)	$ 17.77
Exercised (in shares)	(55,344)
Exercised (in dollars per share)	$ 7.41
Lapsed (in shares)
Lapsed (in dollars per share)
Cancelled (in shares)	(17,016)
Cancelled (in dollars per share)	$ 19.62
Outstanding Options (in shares)	732,745
Outstanding Options (in dollars per share)	$ 16.60

Number of options or other stock instruments for which the right to exercise has lapsed under the terms of the plan agreements.

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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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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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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Weighted average price at which grantees could have acquired the underlying shares with respect to stock options of the plan that expired.

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Weighted average price at which grantees could have acquired the underlying shares with respect to stock options that were terminated.

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

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