Note 8 - Capital Stock - Issuance of Common Stock (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2023		Dec. 31, 2022		Dec. 31, 2021
Price per share (in dollars per share)	[1]					$ 10.45						$ 10.45
Issuance of common stock pursuant to public offerings, net (in shares)	[1]					3,885,048				15,880,039		3,885,048
Issuance of common stock pursuant to public offerings, net						$ 40,580				$ 159,438	[2]	$ 40,580	[2]	$ 514,059
At the Market Offering Program [Member]
Price per share (in dollars per share)	[1],[3]	$ 0	$ 9.54	$ 9.95	$ 11.77		$ 0	$ 0	$ 0	$ 0
Issuance of common stock pursuant to public offerings, net (in shares)	[1]	0	8,432,086	4,757,953	2,690,000		0	0	0
Issuance of common stock pursuant to public offerings, net	[1],[2]	$ 0	$ 80,426	$ 47,355	$ 31,657		$ 0	$ 0	$ 0

[1] As of December 31, 2023, the Company had 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.

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

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