Note 8 - Capital Stock - Issuance of Common Stock (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended							9 Months Ended		12 Months Ended
		Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2023		Dec. 31, 2022
Issuance of common stock pursuant to public offerings, net (in shares)									15,880,039		3,885,048
Issuance of common stock pursuant to public offerings, net		$ 80,426	$ 47,355	$ 31,657					$ 159,438	[1]	$ 40,580	[1]
At the Market Offering Program [Member]
Price per share (in dollars per share)	[2],[3]	$ 9.54	$ 9.95	$ 11.77	$ 10.45	$ 0	$ 0	$ 0	$ 9.54		$ 10.45
Issuance of common stock pursuant to public offerings, net (in shares)	[2]	8,432,086	4,757,953	2,690,000	3,885,048	0	0	0
Issuance of common stock pursuant to public offerings, net	[1],[2]	$ 80,426	$ 47,355	$ 31,657	$ 40,580	$ 0	$ 0	$ 0

[1] Net proceeds are net of the underwriters' discount, if applicable, and other offering costs.

[2] The Company has entered into eleven equity distribution agreements, ten of which have either been terminated because all shares were sold or were replaced with a subsequent agreement.

[3] Weighted average price received per share is after deducting the underwriters’ discount, if applicable, and other offering costs.