Note 16 - The Financing and Warrant Liabilities - Fair Value of Warrants (Details) $ in Thousands	Jun. 30, 2021 USD ($) yr	Mar. 31, 2021 USD ($) yr	Feb. 18, 2021 USD ($)	Dec. 31, 2020 USD ($) yr	Jun. 30, 2020 USD ($) yr	Mar. 31, 2020 USD ($) yr		Dec. 31, 2019 USD ($) yr
Proceeds allocated to warrant liabilities	$ 6,597	$ 10,919	$ 11,921	$ 1,505	$ 39	$ 61		$ 107
Investor Warrants [Member]
Proceeds allocated to warrant liabilities	$ 3,257	$ 5,942	$ 10,476		13	45		71
Investor Warrants [Member] | Measurement Input, Share Price [Member]
Fair value of the warrants	2.00	2.64	4.48
Investor Warrants [Member] | Measurement Input, Expected Term [Member]
Fair value of the warrants	3.14	3.38	3.50
Investor Warrants [Member] | Measurement Input, Risk Free Interest Rate [Member]
Fair value of the warrants	0.0048	0.0041	0.0026
Investor Warrants [Member] | Measurement Input, Expected Dividend Rate [Member]
Fair value of the warrants	0	0	0
Investor Warrants [Member] | Measurement Input, Price Volatility [Member]
Fair value of the warrants	1.14	1.68	1.68
Investor Warrants [Member] | Measurement Input, Exercise Price [Member]
Fair value of the warrants	3.59	3.59	3.59
Investor Warrants [Member] | Measurement Input, Quoted Price [Member]
Fair value of the warrants	1.25	2.28	4.02
Placement Agent Warrants [Member]
Proceeds allocated to warrant liabilities	$ 431	$ 817	$ 1,445		26	16		36
Placement Agent Warrants [Member] | Measurement Input, Share Price [Member]
Fair value of the warrants	2.00	2.64	4.48
Placement Agent Warrants [Member] | Measurement Input, Expected Term [Member]
Fair value of the warrants	3.14	3.38	3.50
Placement Agent Warrants [Member] | Measurement Input, Risk Free Interest Rate [Member]
Fair value of the warrants	0.0048	0.0041	0.0026
Placement Agent Warrants [Member] | Measurement Input, Expected Dividend Rate [Member]
Fair value of the warrants	0	0	0
Placement Agent Warrants [Member] | Measurement Input, Price Volatility [Member]
Fair value of the warrants	1.14	1.68	1.68
Placement Agent Warrants [Member] | Measurement Input, Exercise Price [Member]
Fair value of the warrants	4.4875	4.4875	4.4875
Placement Agent Warrants [Member] | Measurement Input, Quoted Price [Member]
Fair value of the warrants	1.18	2.24	3.96
Warrants Issued in Connection with the 2020 Financing [Member] | Measurement Input, Share Price [Member]
Fair value of the warrants	2.00	2.64		1.35
Warrants Issued in Connection with the 2020 Financing [Member] | Measurement Input, Expected Term [Member]
Fair value of the warrants | yr	2.45	2.70		2.95
Warrants Issued in Connection with the 2020 Financing [Member] | Measurement Input, Risk Free Interest Rate [Member]
Fair value of the warrants	0.0034	0.0029		0.0017
Warrants Issued in Connection with the 2020 Financing [Member] | Measurement Input, Expected Dividend Rate [Member]
Fair value of the warrants	0	0		0
Warrants Issued in Connection with the 2020 Financing [Member] | Measurement Input, Price Volatility [Member]
Fair value of the warrants	1.20	1.20		1.02
Warrants Issued in Connection with the 2020 Financing [Member] | Measurement Input, Exercise Price [Member]
Fair value of the warrants	2.03	2.03		2.03
Warrants Issued in Connection with the 2020 Financing [Member] | Measurement Input, Quoted Price [Member]
Fair value of the warrants	1.40	1.95		0.74
Investor Warrants Issued in Connection with 2018 Financing [Member]
Proceeds allocated to warrant liabilities	$ 66	$ 200		$ 2	$ 13	$ 45		$ 71	[1]
Investor Warrants Issued in Connection with 2018 Financing [Member] | Measurement Input, Share Price [Member]
Fair value of the warrants	2.00	2.64		1.35	1.00	0.95		1.17	[1]
Investor Warrants Issued in Connection with 2018 Financing [Member] | Measurement Input, Expected Term [Member]
Fair value of the warrants	0.05	0.30		0.05	0.05	0.30		0.55	[1]
Investor Warrants Issued in Connection with 2018 Financing [Member] | Measurement Input, Risk Free Interest Rate [Member]
Fair value of the warrants	0.0004	0.0003		0.0008	0.0019	0.0010		0.0158	[1]
Investor Warrants Issued in Connection with 2018 Financing [Member] | Measurement Input, Expected Dividend Rate [Member]
Fair value of the warrants	0	0		0	0	0		0	[1]
Investor Warrants Issued in Connection with 2018 Financing [Member] | Measurement Input, Price Volatility [Member]
Fair value of the warrants	0.74	2.06		0.59	1.43	0.99		0.60	[1]
Investor Warrants Issued in Connection with 2018 Financing [Member] | Measurement Input, Exercise Price [Member]
Fair value of the warrants	1.4927	1.4927		1.4927	1.4927	1.4927	[2]	1.4927	[1]
Investor Warrants Issued in Connection with 2018 Financing [Member] | Measurement Input, Quoted Price [Member]
Fair value of the warrants	0.51	1.55		0.02	0.02	0.07		0.11	[1]
Placement Agent Warrants Issued in Connection with 2018 Financing [Member]
Proceeds allocated to warrant liabilities	$ 66	$ 200		$ 2	$ 26	$ 16		$ 36
Placement Agent Warrants Issued in Connection with 2018 Financing [Member] | Measurement Input, Share Price [Member]
Fair value of the warrants					1.00	0.95		1.17
Placement Agent Warrants Issued in Connection with 2018 Financing [Member] | Measurement Input, Expected Term [Member]
Fair value of the warrants | yr					0.55	0.80		1.05
Placement Agent Warrants Issued in Connection with 2018 Financing [Member] | Measurement Input, Risk Free Interest Rate [Member]
Fair value of the warrants					0.0018	0.0013		0.0157
Placement Agent Warrants Issued in Connection with 2018 Financing [Member] | Measurement Input, Expected Dividend Rate [Member]
Fair value of the warrants					0	0		0
Placement Agent Warrants Issued in Connection with 2018 Financing [Member] | Measurement Input, Price Volatility [Member]
Fair value of the warrants					1.12	0.78		0.80
Placement Agent Warrants Issued in Connection with 2018 Financing [Member] | Measurement Input, Exercise Price [Member]
Fair value of the warrants					1.4927	1.4927		1.4927
Placement Agent Warrants Issued in Connection with 2018 Financing [Member] | Measurement Input, Quoted Price [Member]
Fair value of the warrants					0.20	0.12		0.28
Investor Warrants Issued in Connection with 2020 Financing [Member]
Proceeds allocated to warrant liabilities	2,420	3,370		1,279
Placement Agent Warrants Issued in Connection with 2020 Financing [Member]
Proceeds allocated to warrant liabilities	$ 423	$ 590		$ 224

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

[2] 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.