Note 6 - Warrants (Details Textual)									1 Months Ended	3 Months Ended		4 Months Ended	12 Months Ended
	Sep. 16, 2019 USD ($) $ / shares shares	Jun. 24, 2019 USD ($) shares	Jun. 07, 2019 USD ($) $ / shares shares	Oct. 16, 2018 USD ($) $ / shares shares	Sep. 19, 2018 USD ($) $ / shares shares	Mar. 08, 2018 USD ($) $ / shares shares	Feb. 12, 2018 $ / shares shares	Dec. 29, 2017 USD ($) $ / shares shares	May 31, 2018 USD ($) $ / shares shares	Sep. 30, 2019 USD ($) $ / shares shares	Mar. 31, 2018 USD ($) shares	Sep. 30, 2019 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares	Aug. 31, 2019 $ / shares shares	Aug. 20, 2019 USD ($)	Aug. 15, 2019 $ / shares shares	Aug. 09, 2019 USD ($) $ / shares shares	Mar. 31, 2019 USD ($) $ / shares shares	Mar. 05, 2019 $ / shares shares	Mar. 04, 2019 $ / shares shares	Jan. 31, 2019 USD ($) $ / shares shares	Sep. 30, 2018 $ / shares	Sep. 12, 2018 $ / shares shares	Feb. 08, 2018 $ / shares	Dec. 31, 2017 USD ($) $ / shares shares
Share Price | $ / shares													$ 0.22												$ 0.3147
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ / shares									$ 0.30
Class of Warrant or Right, Number of Securities Called by Warrants or Rights | shares									4,326,358
Deemed Dividends		$ 355,000											$ 809,000	$ 297,000
Proceeds from Adjustment of Warrant									$ 149,000					149,000
Fair Value Adjustment of Warrants									$ 149,000
Interest Expense, Total													$ 3,996,000	$ 3,494,000
Class of Warrant or Right, Issued During Period | shares													24,490,687	7,451,013
Stock Issued During Period, Shares, Exercise of Warrants | shares													7,544,456
Proceeds from Warrant Exercises													$ 560,000
Nine Months OID Notes In Connection With Warrant [Member]
Debt Instrument, Convertible, Conversion Price | $ / shares			$ 0.17																$ 0.25
Vista Warrant [Member]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights | shares		2,877,790
Class of Warrant or Right, Increase Shares Available for Purchase | shares		2,520,780
Convertible Twelve Months OID Notes [Member]
Debt Instrument, Face Amount										$ 2,794,000		$ 2,794,000
Debt Instrument, Term												1 year
Debt Instrument, Unamortized Discount, Total										559,000		$ 559,000
Proceeds from Convertible Debt												2,235,000
Convertible Twelve Months OID Notes [Member] | Convertible Notes Payable [Member]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights | shares																	2,095,588
Debt Instrument, Face Amount										$ 381,000		$ 381,000				$ 330,882
Debt Instrument, Term										1 year
Original Issue Discount, Percentage										25.00%		25.00%
Debt Instrument, Unamortized Discount, Total										$ 76,000		$ 76,000
Convertible Notes Maturing June 15, 2021 [Member] | Convertible Notes Payable [Member]
Debt Instrument, Face Amount	$ 100,000
Debt Instrument, Term	1 year
Original Issue Discount, Percentage	25.00%
Warrant In Connection With Convertible Note [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ / shares																	$ 0.25	$ 0.30
Class of Warrant or Right, Number of Securities Called by Warrants or Rights | shares																		1,200,000
Warrants and Rights Outstanding, Term																	5 years	5 years
Warrants and Rights Outstanding																		$ 198,000
Warrants Issued in Conversion of Secured Line of Credit to Twelve Month OID Notes [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ / shares										$ 0.25		$ 0.25			$ 0.17
Class of Warrant or Right, Number of Securities Called by Warrants or Rights | shares										1,130,515		1,130,515			1,130,515
Warrants and Rights Outstanding, Term										5 years		5 years
Warrants Issued in Connection with Conversion of Notes Due June 15, 2021 [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ / shares	$ 0.25									$ 0.17		$ 0.17
Class of Warrant or Right, Number of Securities Called by Warrants or Rights | shares										551,471		551,471
Warrants and Rights Outstanding, Term	5 years
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right | shares	551,471
Warrants Issued Concurrently with the Nine-month Note Payable [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ / shares																			$ 0.25
Class of Warrant or Right, Number of Securities Called by Warrants or Rights | shares																			637,500
Warrants and Rights Outstanding, Term																			5 years
Discount On Convertible Note Payable																			$ 89,000
Nine Months OID Notes In Connection With Warrant [Member]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights | shares			937,500
Class of Warrant or Right, Number of Securities Called by Warrants or Rights, Increased			$ 300,000
Deemed Dividends			$ 84,000
Twelve Months OID Notes In Connection With Warrant [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ / shares										$ 0.25		$ 0.25
Class of Warrant or Right, Number of Securities Called by Warrants or Rights | shares										12,325,370		12,325,370
Warrants and Rights Outstanding, Term										5 years		5 years
Stock Purchase Warrant, Percentage of Principal										75.00%		75.00%
Class of Warrant or Right, Percentage of Principal Value of Note Calculation, Investment										$ 300,000		$ 300,000
Class of Warrant or Right, Percentage of Principal Value of Note Calculation, Numerator Value of Calculation										$ 375,000		$ 375,000
Class of Warrant or Right, Percentage of Principal Value of Note Calculation, Denominator Value of Calculation | shares										1,654,412		1,654,412
Discount on Notes Payable										$ 2,240,000		$ 2,240,000
Triton Warrant [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ / shares				$ 0.25
Class of Warrant or Right, Number of Securities Called by Warrants or Rights | shares				1,000,000
Debt Instrument, Face Amount				$ 300,000
Discount On Convertible Note Payable				225,000
Bridge Loan				$ 225,000
Class Of Warrant Or Right, Call Feature, Stock Price Trigger | $ / shares				$ 0.50
Class Of Warrant Or Right, Threshold Consecutive Trading Days				10
Class of Warrant or Right, Call Feature, Exercise Period				30 days
Stock Purchase Warrant [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ / shares					$ 0.25
Class of Warrant or Right, Number of Securities Called by Warrants or Rights | shares					1,387,500
Discount On Convertible Note Payable					$ 217,000
Class Of Warrant Or Right, Call Feature, Stock Price Trigger | $ / shares					$ 2.50
Class Of Warrant Or Right, Threshold Consecutive Trading Days					10
Class of Warrant or Right, Call Feature, Exercise Period					30 days
Extension of Convertible Note Maturity Date, Vista Capital [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ / shares																								$ 0.25
Class of Warrant or Right, Number of Securities Called by Warrants or Rights | shares																								1,812,000
Extinguishment of Debt, Gain (Loss), Net of Tax, Total														$ (488,000)
Warrants Issued Concurrently with Note Payable [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ / shares						$ 0.35
Class of Warrant or Right, Number of Securities Called by Warrants or Rights | shares						150,000
Notes Payable, Total						$ 50,000
Warrants Vested Monthly Contingent That Outstanding Note Payable is Present | shares						6,250
Warrants Vested, Cumulative Total of Warrants Vested | shares														56,250
Minimum Number of Warrants Vested For the Life of the Outstanding Note Payable, Fair Value Amount														$ 7,000
Warrants Issued Concurrently to the Spring 2018 Unit Offering [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ / shares														$ 0.48									$ 0.40
Class of Warrant or Right, Number of Securities Called by Warrants or Rights | shares													400,000	333,333
Debt Instrument, Convertible, Conversion Price | $ / shares																							$ 0.25
Discount on Notes Payable														$ 49,000
Interest Expense, Total														$ 17,000
Class of Warrant or Right, Exercise Period Condition, Number of Trading Days Common Stock Closes at or above 2 Times the Exercise Price														30 years
Warrant Subject to Call provision, Threshold Consecutive Trading Days														10 years
Warrants Issued Concurrently with Line of Credit [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ / shares														$ 0.35
Class of Warrant or Right, Number of Securities Called by Warrants or Rights | shares														430,000
Discount On Convertible Note Payable														$ 98,000
Class of Warrant or Right, Exercise Period Condition, Number of Trading Days Common Stock Closes at or above 2 Times the Exercise Price														30 days
Warrant Subject to Call provision, Threshold Consecutive Trading Days														10 days
Warrants Issued Concurrently with Line of Credit, Exercise Price One [Member]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights | shares														390,000
Warrants Issued Concurrently with Line of Credit, Exercise Price Two [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ / shares														$ 0.25
Class of Warrant or Right, Number of Securities Called by Warrants or Rights | shares														40,000
Warrants Issued Concurrently to the Summer 2017 Unit Offering 3 [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ / shares							$ 0.30																			$ 0.65
Class of Warrant or Right, Number of Securities Called by Warrants or Rights | shares								1,329,189																		1,246,906
Discount On Convertible Note Payable											$ 103,000															$ 524,000
Debt Instrument, Convertible, Conversion Price | $ / shares								$ 0.394
Class of Warrant or Right, Additional Securities Called by Warrants | shares								82,283
Debt Instrument, Unamortized Discount, Total								$ 32,000
Class of Warrant or Right, Issued During Period | shares							416,478				266,667
Proceeds from Convertible Debt											$ 80,000
Warrants Issued Concurrently With One Year Convertible Note [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ / shares													$ 0.12	$ 0.25
Deemed Dividends													$ 342,000	$ 297,000
Class of Warrant or Right, Issued During Period | shares														1,200,000
Class of Warrant or Right, Increase Shares Available for Purchase | shares													2,595,406
Vernal Bay Investments, LLC [Member] | Warrants Issued as Part of Debt Extension [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ / shares																				$ 0.20	$ 0.25
Class of Warrant or Right, Number of Securities Called by Warrants or Rights | shares																				2,484,375	1,987,500
Lincoln Park Capital Fund, LLC [Member] | Warrants Issued as Consent for Variable Rate Date [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ / shares																						$ 0.25
Class of Warrant or Right, Number of Securities Called by Warrants or Rights | shares																						300,000
Warrants and Rights Outstanding, Term																						5 years
Discount On Convertible Note Payable																						$ 54,000