Note 9 - Incentive Plans - Number of Shares Available for Grant Pursuant to Long-term Incentive Plan (Details) - shares	Mar. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Shares subject to awards issued under plan (in shares)	(13,445,728)	(13,449,061)	(11,517,228)
The 2020 Long-term Incentive Plan [Member]
Approved and authorized shares (in shares)	16,414,015	16,414,015
Shares subject to awards issued under plan (in shares)	(15,756,458)	(15,759,791)
Shares available for future grant (in shares)	657,557	654,224