Note 16 - The Financing and Warrant Liabilities - Warrant Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Mar. 31, 2021	Feb. 18, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Proceeds allocated to warrant liabilities	$ 6,597	$ 39	$ 6,597	$ 39	$ 10,919	$ 11,921	$ 1,505	$ 61	$ 107
Change in fair value of warrants	(4,322)	(22)	(6,829)	(68)
Investor Warrants Issued in Connection with 2021 Financing [Member]
Proceeds allocated to warrant liabilities	3,257		3,257		5,942	10,476
Change in fair value of warrants	(2,685)		(7,219)
Investor Warrants [Member]
Proceeds allocated to warrant liabilities	3,257	13	3,257	13	5,942	10,476		45	71
Change in fair value of warrants		(32)		(58)
Placement Agent Warrants Issued in Connection with 2021 Financing [Member]
Proceeds allocated to warrant liabilities	431		431		817	1,445
Change in fair value of warrants	(386)		(1,014)
Placement Agent Warrants [Member]
Proceeds allocated to warrant liabilities	431	26	431	26	817	$ 1,445		16	36
Change in fair value of warrants		10		(10)
Investor Warrants Issued in Connection with 2020 Financing [Member]
Proceeds allocated to warrant liabilities	2,420		2,420		3,370		1,279
Change in fair value of warrants	(950)		1,141
Placement Agent Warrants Issued in Connection with 2020 Financing [Member]
Proceeds allocated to warrant liabilities	423		423		590		224
Change in fair value of warrants	(167)		199
Placement Agent Warrants Issued in Connection with 2018 Financing [Member]
Proceeds allocated to warrant liabilities	66	$ 26	66	$ 26	$ 200		$ 2	$ 16	$ 36
Change in fair value of warrants	$ (134)		$ 64