Note 8 - Property, Plant and Equipment and Construction-in-process (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Depreciation	$ 186,500	$ 163,200	$ 153,000
Depreciation Net Of Amortization Of Cash Grant	6,900	7,500	7,400
Property, Plant and Equipment Including Construction In Progress, Net	3,059,700	2,830,300
Property, Plant and Equipment, Cash Grant, Net	128,000	144,400
Impairment, Long-Lived Asset, Held-for-Use, Total	0	32,648	$ 0
Geotermica Platanares [Member]
Property, Plant and Equipment Including Construction In Progress, Net	$ 81,900	79,500
Power Plant Usage Agreement Term (Year)	15 years
Geothermie Bouillante SA (“GB”) [Member]
Property, Plant and Equipment Including Construction In Progress, Net	$ 101,700	43,500
North Brawley Geothermal Power Plant [Member]
Property, Plant, and Equipment, Fair Value Disclosure		13,600
Impairment, Long-Lived Asset, Held-for-Use, Total		$ 30,500
Weighted Average Cost Of Capital		9.00%
Orzunil I de Electricidad, Limitada [Member]
Property, Plant and Equipment Including Construction In Progress, Net	31,900	$ 27,100
Ortitlan Limitada [Member]
Property, Plant and Equipment Including Construction In Progress, Net	$ 42,800	42,300
Orzunil I de Electricidad, Limitada [Member]
Noncontrolling Interest, Ownership Percentage by Parent	97.00%
Kenya Power and Lighting Co Limited [Member]
Power Purchase Agreements Term (Year)	20 years
EDF [Member] | Geothermie Bouillante SA (“GB”) [Member]
Power Purchase Agreements Term (Year)	15 years
Foreign Countries [Member]
Property, Plant and Equipment Including Construction In Progress, Net	$ 754,200	556,400
KENYA | Power Plants [Member]
Property, Plant and Equipment Including Construction In Progress, Net	$ 377,600	$ 301,500