Note 17 - Equity Offerings - Summary of Sales Under Offering (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Apr. 28, 2017
Average price per share (in dollars per share)				$ 1.00
Net proceeds	$ 0	$ 13,478	$ 0
The 2019, 2020, and 2021 ATM Offerings [Member]
Total shares of common stock sold (in shares)	20,237,045	23,008,639	1,374,685
Average price per share (in dollars per share)	$ 1.53	$ 0.90	$ 5.23
Gross proceeds	$ 30,943	$ 20,822	$ 7,193
Commissions	928	625	212
Net proceeds	$ 30,015	$ 20,197	$ 6,981