Note 6 - Stockholders' Equity - Warrant Activity (Details) - $ / shares	9 Months Ended	12 Months Ended
Sep. 30, 2019	Dec. 31, 2018
Forfeited/cancelled, options (in shares)	(637,500)
Forfeited/cancelled, weighted average price per share (in dollars per share)	$ 1
Vested and expected to vest, options (in shares)	6,595,000
Vested and expected to vest, weighted average price per share (in dollars per share)	$ 0.34
Vested and expected to vest, weighted average remaining contractual term (Year)	2 years 219 days
Exercisable balance, options (in shares)	6,595,000
Exercisable balance, weighted average price per share (in dollars per share)	$ 0.34
Exercisable balance, weighted average remaining contractual term (Year)	2 years 219 days
Warrant [Member]
Warrants outstanding at end of period, weighted average remaining contractual term (Year)	3 years 138 days	4 years 58 days
Warrants granted (in shares)	1,000,000
Warrants granted, weighted average price per share (in dollars per share)	$ 0.13
Forfeited/cancelled, options (in shares)	(17,918,333)
Forfeited/cancelled, weighted average price per share (in dollars per share)	$ 0.50
Warrants outstanding at end of period (in shares)	8,127,184	25,045,517
Warrants outstanding at end of period, weighted average price per share (in dollars per share)	$ 0.56	$ 0.53
Vested and expected to vest, options (in shares)	8,127,184
Vested and expected to vest, weighted average price per share (in dollars per share)	$ 0.56
Vested and expected to vest, weighted average remaining contractual term (Year)	3 years 138 days
Exercisable balance, options (in shares)	8,127,184
Exercisable balance, weighted average price per share (in dollars per share)	$ 0.56
Exercisable balance, weighted average remaining contractual term (Year)	3 years 138 days

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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Per share or unit weighted-average fair value of nonvested award under share-based payment arrangement. Excludes share and unit options.

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Weighted average remaining contractual term for equity-based awards excluding options, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Number of equity instruments other than options outstanding, including both vested and non-vested instruments.

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-Publisher FASB
-Name Accounting Standards Codification
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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.

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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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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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Number of fully vested and expected to vest options outstanding that can be converted into shares under option plan. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Weighted-average exercise price, at which grantee can acquire shares reserved for issuance, for fully vested and expected to vest options outstanding. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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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 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 fully vested and expected to vest options outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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