Note 10 - Stock-Based Compensation - Changes in Shares Under Option Plans (Details) - $ / shares	3 Months Ended
Mar. 31, 2016	Mar. 31, 2015
Beginning balance (in shares)	298,740	759,683
Beginning balance (in dollars per share)	$ 9.97	$ 11.36
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	0
Issued (in dollars per share)
Exercised (in shares)	(16,759)	(280,425)
Exercised (in dollars per share)	$ 11.80	$ 12.40
Forfeited (in shares)	(1,100)
Forfeited (in dollars per share)	$ 15.48
Expired (in shares)	(6,037)	(8,007)
Expired (in dollars per share)	$ 13.57	$ 16.90
Ending balance (in shares)	274,844	471,251
Ending balance (in dollars per share)	$ 9.76	$ 10.65

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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(4)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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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.

+ References

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-Publisher FASB
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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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