Note 6 - Stock Based Compensation - Summary of Stock Option Activity (Details) - USD ($)	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Outstanding (in shares)	1,129,582	1,166,192
Outstanding (in dollars per share)	$ 5.35	$ 5.93
Outstanding (Year)	2 years 292 days	3 years 292 days	4 years 255 days
Outstanding
Expired (in shares)	(44,294)	(36,610)
Expired (in dollars per share)	$ 12.51	$ 23.88
Cancelled/Forfeited (in shares)	(258,706)
Cancelled/Forfeited (in dollars per share)	$ 4.10
Outstanding (in shares)	826,582	1,129,582	1,166,192
Outstanding (in dollars per share)	$ 5.35	$ 5.35	$ 5.93
Exercisable at December 31, 2017 (in shares)	826,582
Exercisable at December 31, 2017 (in dollars per share)	$ 5.35
Exercisable at December 31, 2017 (Year)	2 years 292 days
Exercisable at December 31, 2017

The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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)(iii)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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

+ References

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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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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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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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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable.

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Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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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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