Note 8 - Capital Stock - Issuance of Common Stock (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended					12 Months Ended		15 Months Ended
		Mar. 31, 2024		Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2023		Dec. 31, 2023
Issuance of common stock pursuant to public offerings, net (in shares)	[1]	1,490,075					15,880,039
Issuance of common stock pursuant to public offerings, net		$ 13,109	[2]			$ 31,657	$ 159,438	[2]
At the Market Offering Program [Member]
Price per share (in dollars per share)	[1],[3],[4]	$ 8.8		$ 9.54	$ 9.95	$ 11.77	$ 0		$ 0
Issuance of common stock pursuant to public offerings, net (in shares)	[1],[3]	1,490,075		8,432,086	4,757,953	2,690,000			0
Issuance of common stock pursuant to public offerings, net	[1],[2]	$ 13,109		$ 80,426	$ 47,355	$ 31,657			$ 0

[1] 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.

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

[3] 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.

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