Note 16 - The Financing and Warrant Liabilities - Fair Value of Warrants (Details) $ in Thousands	Dec. 31, 2020 USD ($) yr		Dec. 14, 2020 USD ($) yr		Dec. 31, 2019 USD ($) yr		Dec. 31, 2018 USD ($) yr
Proceeds allocated to warrant liabilities	$ 1,505		$ 2,051		$ 107		$ 606
Investor Warrants [Member]
Proceeds allocated to warrant liabilities	1,279		1,746
Investor Warrants Issued in Connection with 2018 Financing [Member]
Proceeds allocated to warrant liabilities		[1]		[2]	71		503
Placement Agent Warrants Issued in Connection with 2018 Financing [Member]
Proceeds allocated to warrant liabilities	2	[3]			$ 36		$ 103
Placement Agent Warrants [Member]
Proceeds allocated to warrant liabilities	$ 224		$ 305
Measurement Input, Share Price [Member] | Investor Warrants [Member]
Fair value of the warrants	1.35		1.25
Measurement Input, Share Price [Member] | Investor Warrants Issued in Connection with 2018 Financing [Member]
Fair value of the warrants		[1]			1.17		1.34
Measurement Input, Share Price [Member] | Placement Agent Warrants Issued in Connection with 2018 Financing [Member]
Fair value of the warrants	1.35	[3]			1.17		1.34
Measurement Input, Expected Term [Member] | Investor Warrants [Member]
Fair value of the warrants | yr	2.95		3
Measurement Input, Expected Term [Member] | Investor Warrants Issued in Connection with 2018 Financing [Member]
Fair value of the warrants | yr		[1]			0.55		1.55
Measurement Input, Expected Term [Member] | Placement Agent Warrants Issued in Connection with 2018 Financing [Member]
Fair value of the warrants | yr	0.05	[3]			1.05		2.05
Measurement Input, Risk Free Interest Rate [Member] | Investor Warrants [Member]
Fair value of the warrants	0.0017		0.0017
Measurement Input, Risk Free Interest Rate [Member] | Investor Warrants Issued in Connection with 2018 Financing [Member]
Fair value of the warrants		[1]			0.0158		0.025
Measurement Input, Risk Free Interest Rate [Member] | Placement Agent Warrants Issued in Connection with 2018 Financing [Member]
Fair value of the warrants	0.0008	[3]			0.0157		0.025
Measurement Input, Expected Dividend Rate [Member] | Investor Warrants [Member]
Fair value of the warrants
Measurement Input, Expected Dividend Rate [Member] | Investor Warrants Issued in Connection with 2018 Financing [Member]
Fair value of the warrants		[1]
Measurement Input, Expected Dividend Rate [Member] | Placement Agent Warrants Issued in Connection with 2018 Financing [Member]
Fair value of the warrants		[3]
Measurement Input, Price Volatility [Member] | Investor Warrants [Member]
Fair value of the warrants	1.02		1.64
Measurement Input, Price Volatility [Member] | Investor Warrants Issued in Connection with 2018 Financing [Member]
Fair value of the warrants		[1]			0.6		1.99
Measurement Input, Price Volatility [Member] | Placement Agent Warrants Issued in Connection with 2018 Financing [Member]
Fair value of the warrants	0.59	[3]			0.8		1.76
Measurement Input, Exercise Price [Member] | Investor Warrants [Member]
Fair value of the warrants	2.03		2.03
Measurement Input, Exercise Price [Member] | Investor Warrants Issued in Connection with 2018 Financing [Member]
Fair value of the warrants		[1]			1.4927	[4]	6.6
Measurement Input, Exercise Price [Member] | Placement Agent Warrants Issued in Connection with 2018 Financing [Member]
Fair value of the warrants	1.4927	[3],[4]			1.4927	[4]	6.6
Measurement Input, Quoted Price [Member] | Investor Warrants [Member]
Fair value of the warrants	0.74		1.01
Measurement Input, Quoted Price [Member] | Investor Warrants Issued in Connection with 2018 Financing [Member]
Fair value of the warrants		[1]			0.11		0.78
Measurement Input, Quoted Price [Member] | Placement Agent Warrants Issued in Connection with 2018 Financing [Member]
Fair value of the warrants	0.02	[3]			0.28		0.8

[1] The investor warrants issued in the 2018 Financing had expired during the year ended December 31, 2020.

[2] Not applicable.

[3] The placement agent warrants issued in the 2018 Financing with an original termination date on January 18, 2021 was subsequently extended to July 18, 2021 on January 18, 2021.

[4] On September 25, 2019, as a result of the close on the first half of the 2019 Financing, the exercise price of the warrants issued in 2018 Financing that contain the "full ratchet" price protection in the event of subsequent issuances below the applicable exercise price (the "Down round feature") was adjusted to $1.4927.