Note 12 - Equity Offerings - Summary of Sales Under Offering (Details) $ / shares in Units, $ in Thousands	6 Months Ended
	Jun. 30, 2022 USD ($) $ / shares shares
Total shares of common stock sold (in shares) | shares	19,451,848
Average price per share (in dollars per share) | $ / shares	$ 1.50
Gross proceeds	$ 29,252
Commission earned by Sales Agents	877
Net proceeds	$ 28,375
The 2021 ATM Offering [Member]
Total shares of common stock sold (in shares) | shares	331,811
Average price per share (in dollars per share) | $ / shares	$ 3.47
Gross proceeds	$ 1,152
Commission earned by Sales Agents	34
Net proceeds	$ 1,118
The 2020 ATM Offering [Member]
Total shares of common stock sold (in shares) | shares	19,120,037
Average price per share (in dollars per share) | $ / shares	$ 1.47
Gross proceeds	$ 28,100
Commission earned by Sales Agents	843
Net proceeds	$ 27,257