Note 9 - Fair Value Measurement - Fair Value Assumptions (Details)	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Dividend yield	0.00%	0.00%
Minimum [Member]
Risk free interest rate	1.56%	0.82%
Expected volatility	87.00%	117.30%
Minimum [Member] \| Conversion Feature Liability [Member]
Expected life (Year)	1 year 91 days	1 year 91 days
Minimum [Member] \| Warrant Liability [Member]
Expected life (Year)	91 days	91 days
Maximum [Member]
Risk free interest rate	1.81%	1.45%
Expected volatility	118.40%	143.80%
Maximum [Member] \| Conversion Feature Liability [Member]
Expected life (Year)	3 years 91 days	3 years 91 days
Maximum [Member] \| Warrant Liability [Member]
Expected life (Year)	3 years 91 days	3 years 91 days

Expected dividends to be paid to holders of the underlying shares or financial instruments (expressed as a percentage of the share or instrument's price).

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

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- Definition

Period the instrument, asset or liability is expected to be outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Measure of dispersion, in percentage terms (for instance, the standard deviation or variance), for a given stock price.

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Risk-free interest rate assumption used in valuing an instrument.

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