Note 5 - Investment in Unconsolidated Companies - Unconsolidated Investments Mainly in Power Plants (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Total investment in unconsolidated companies	$ 125,439	$ 115,693
Sarulla [Member]
Total investment in unconsolidated companies	71,744	74,881
Ijen Geothermal Project Company [Member]
Total investment in unconsolidated companies	51,695	40,812
Other Investment [Member]
Other investment, at cost	$ 2,000	$ 0