Note 6 - Share-based Compensation - Summary of Option Transactions (Details) - $ / shares	3 Months Ended
Mar. 31, 2017	Mar. 31, 2016
Outstanding Options (in shares)	825,251
Outstanding Options (in dollars per share)	$ 10.46
Granted options (in shares)	90,012	109,332
Granted options (in dollars per share)	$ 16.97
Exercised options (in shares)	(56,124)
Exercised options (in dollars per share)	$ 7.22
Lapsed options (in shares)
Lapsed options (in dollars per share)
Cancelled options (in shares)
Cancelled options (in dollars per share)
Outstanding Options (in shares)	859,139
Outstanding Options (in dollars per share)	$ 11.35

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 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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