Note 8 - Property, Plant and Equipment and Construction-in-process (Tables)

12 Months Ended

Dec. 31, 2023

Notes Tables

Property, Plant and Equipment [Table Text Block]

	December 31,
	2023			2022
	(Dollars in thousands)
Land owned by the Company where the geothermal resource is located	$	47,612		$	42,335
Leasehold improvements		12,588			13,230
Machinery and equipment		341,931			350,584
Land, buildings and office equipment		127,970			52,222
Vehicles		17,097			14,115
Energy storage equipment		158,604			91,025
Solar facility equipment		59,214			32,003
Geothermal and recovered energy generation power plants, including geothermal wells and exploration and resource development costs:
United States of America, net of cash grants		3,191,505			2,641,280
Foreign countries		868,289			897,657
Asset retirement cost		59,123			48,578
		4,883,933			4,183,029
Less accumulated depreciation		(1,884,984	)		(1,689,572	)
Property, plant and equipment, net	$	2,998,949		$	2,493,457

Construction In Progress [Table Text Block]

	December 31,
	2023		2022
	(Dollars in thousands)
Projects under exploration and development:
Up-front bonus costs	$	5,335	$	5,335
Exploration and development costs		156,438		89,230
Interest capitalized		703		703
		162,476		95,268
Projects under construction:
Up-front bonus costs		11,156		11,156
Drilling and construction costs		618,416		761,129
Interest capitalized		22,919		25,645
		652,491		797,930
Total	$	814,967	$	893,198

Rollforward Of Construction In Process [Table Text Block]

	Projects under exploration and development
	Up-front Bonus Costs			Exploration and Development Costs			Interest Capitalized		Total
	(Dollars in thousands)
Balance at December 31, 2020	$	5,347		$	45,478		$	703	$	51,528
Cost incurred during the year		—			2,680			—		2,680
Transfer of projects under exploration and development to projects under construction		(12	)		(3,494	)		—		(3,506	)
Balance at December 31, 2021		5,335			44,664			703		50,702
Cost incurred during the year		—			44,566			—		44,566
Balance at December 31, 2022		5,335			89,230			703		95,268
Cost incurred during the year		—			70,667			—		70,667
Write off of unsuccessful exploration costs		—			(3,459	)		—		(3,459	)
Balance at December 31, 2023	$	5,335		$	156,438		$	703	$	162,476

	Projects under construction
	Up-front Bonus Costs			Drilling and Construction Costs			Interest Capitalized			Total
	(Dollars in thousands)
Balance at December 31, 2020	$	39,144		$	379,117		$	9,526		$	427,787
Cost incurred during the year		—			403,296			10,546			413,842
Transfer of projects under exploration and development to projects under construction		12			3,494			—			3,506
Transfer of completed projects to property, plant and equipment		—			(174,354	)		—			(174,354	)
Balance at December 31, 2021		39,156			611,553			20,072			670,781
Cost incurred during the year		—			489,953			5,573			495,526
Transfer of completed projects to property, plant and equipment		(28,000	)		(340,377	)		—			(368,377	)
Balance at December 31, 2022		11,156			761,129			25,645			797,930
Cost incurred during the year		—			473,422			15,181			488,603
Cost write off		—			(993	)		—			(993	)
Transfer of completed projects to property, plant and equipment		—			(615,142	)		(17,907	)		(633,049	)
Balance at December 31, 2023	$	11,156		$	618,416		$	22,919		$	652,491

North Brawley Geothermal Power Plant [Member]

Notes Tables

Fair Value Measurement Inputs and Valuation Techniques [Table Text Block]

Significant unobservable inputs:
Average generation capacity (MW)	7
Electricity price escalation (%)	2.2	%
Cost long-term growth rate	2.2
Average realized electricity price ($/MW)	92.2