Note 9 - Property, Plant and Equipment and Construction-in-process (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Depreciation, Total	$ 163,200	$ 153,000	$ 133,500
Depreciation Net Of Amortization Of Cash Grant	7,500	7,400	7,300
Property, Plant and Equipment Including Construction In Progress, Net	2,830,300	2,502,200
Property, Plant and Equipment, Cash Grant, Net	144,400	151,900
Impairment, Long-Lived Asset, Held-for-Use, Total	32,648	0	$ 0
Geotermica Platanares [Member]
Property, Plant and Equipment Including Construction In Progress, Net	$ 79,500	75,400
Power Plant Usage Agreement Term (Year)	15 years
Geothermie Bouillante SA (“GB”) [Member]
Property, Plant and Equipment Including Construction In Progress, Net	$ 43,500	39,400
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	$ 27,100	17,200
Ortitlan Limitada [Member]
Property, Plant and Equipment Including Construction In Progress, Net	$ 42,300	39,800
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	$ 556,400	514,300
KENYA | Power Plants [Member]
Property, Plant and Equipment Including Construction In Progress, Net	$ 301,500	$ 297,400