Note 15 - Warrant Liabilities - Warrant Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended			12 Months Ended
	Jun. 30, 2022	Jun. 30, 2021		Jun. 30, 2022	Jun. 30, 2021		Dec. 31, 2021	Dec. 31, 2020		Mar. 31, 2022	Mar. 31, 2021		Feb. 18, 2021
Proceeds allocated to warrant liabilities	$ 257	$ 6,597		$ 257	$ 6,597			$ 1,505		$ 1,244	$ 10,919		$ 11,921
Change in fair value of warrants	(987)	(4,322)		(1,782)	(6,829)		$ 2,039
Investor Warrants Issued in Connection with 2021 Financing [Member]
Proceeds allocated to warrant liabilities	167	3,257		167	3,257		964			626	5,942	[1]	10,476
Change in fair value of warrants	(459)	(2,685)		(797)	(7,219)		964
Placement Agent Warrants Issued in Connection with 2021 Financing [Member]
Proceeds allocated to warrant liabilities	22	431	[1]	22	431	[1]	132			84	817	[1]	$ 1,445	[1]
Change in fair value of warrants	(62)	(386)		(110)	(1,014)		132
Investor Warrants Issued in Connection with 2020 Financing [Member]
Proceeds allocated to warrant liabilities	57	2,420		57	2,420		795	1,279		449	3,370
Change in fair value of warrants	(392)	(950)		(738)	1,141		795
Placement Agent Warrants Issued in Connection with 2020 Financing [Member]
Proceeds allocated to warrant liabilities	11	423		11	423		148	224		$ 85	590
Change in fair value of warrants	$ (74)	(167)		$ (137)	199		$ 148	224
Placement Agent Warrants Issued in Connection with 2018 Financing [Member]
Proceeds allocated to warrant liabilities		66			66			$ 2	[2]		$ 200	[2]
Change in fair value of warrants		$ (134)			$ 64

[1] Closing date of the 2021 Financing.

[2] The investor warrants issued in the 2018 Financing expired in July 2020. The placement agent warrants issued in the 2018 Financing were cashless exercised in July 2021.