Business Combinations Policy [Policy Text Block]

Business combination - Enel purchase transaction

On January 4, 2024, the Company closed a purchase transaction with Enel Green Power North America ("EGPNA"), a subsidiary of Enel SpA (ENEL.MI) to acquire a portfolio of assets which includes two contracted geothermal power plants, one triple hybrid power plant which consists of geothermal, solar PV and solar thermal units, two stand alone solar power plants, and two greenfield development assets, for a total cash consideration of $274.6 million (including customary post-closing working capital adjustment to the purchase price, based on the levels of net working capital of the acquired companies) for 100% of the equity interests in the entities holding those assets.

The geothermal power plants include the Cove Fort power plant located in Beaver County, Utah, which sells electricity under a long-term power purchase agreement with Salt River Project and the Salt Wells power plant located in Churchill County, Nevada, which sells electricity under a long-term power purchase agreement ("PPA") with NV Energy. The Stillwater triple hybrid geothermal, solar PV and solar thermal power plant is located in Churchill County, Nevada, and sells electricity to NV Energy under a power purchase agreement. The Solar assets of Stillwater Solar PV II in Churchill County, Nevada, and Woods Hill in Windham County, Connecticut, sell their electricity under power purchase agreements, respectively.

As a result of the acquisition, the Company expanded its overall generation capacity and expects to improve the profitability of the purchased assets through cost reduction, synergies and development of the greenfield assets. The Company accounted for the transaction in accordance with Accounting Standard Codification ("ASC") 805, Business Combinations, and following the transaction, the Company consolidates the power plants and all other assets included in the transaction in accordance with ASC 810, Consolidation.

In the first quarter of 2024, and during annual 2023, the Company incurred $1.3 million and $1.1 million of acquisition-related costs, respectively. Such costs are included under "General and administrative expenses" in the consolidated statements of operations and comprehensive income for the respective periods. Accounting guidance provides that the allocation of the purchase price may be adjusted for up to one year from the date of the acquisition to the extent that additional information is obtained about the facts and circumstances that existed as of the acquisition date. The primary area of the purchase price allocation that is not yet finalized is related to intangible assets, property, plant and equipment, and certain tax matters and the related impact on goodwill.

The following table summarizes the purchase price allocation to the fair value of the assets acquired and liabilities assumed (in millions):

Trade receivables and others ⁽¹⁾	$	4.4
Deferred income taxes		3.1
Property, plant and equipment and construction-in-process ⁽²⁾		197.7
Operating lease right of use		1.2
Other long-term assets		0.2
Intangible assets ⁽³⁾		23.6
Goodwill ⁽⁴⁾		60.7
Total assets acquired	$	290.9

Accounts payable, accrued expenses and others	$	1.5
Other current liabilities		1.8
Operating lease liabilities		1.2
Other long-term liabilities		5.0
Asset retirement obligation		6.8
Total liabilities assumed	$	16.3

Total assets acquired, and liabilities assumed, net	$	274.6

⁽¹⁾ The gross amount of trade receivables was fully collected subsequent to acquisition date.

⁽²⁾ The fair value of Property, Plant and equipment was estimated by applying the income approach and utilizing the discounted cash flow method. This methodology assesses the value of tangible assets by computing the anticipated cash flows expected to be generated by the respective assets.

⁽³⁾ Intangible assets are related to the long-term electricity PPAs described above and are amortized over the term of those PPAs. The fair value of the intangible assets was estimated by applying the income approach and utilizing the With and Without method.

⁽⁴⁾ Goodwill is primarily related to the expected synergies, potential cost savings in operations as a result of the purchase transaction as well as potential future development of the greenfield assets. The goodwill is allocated to the Electricity segment and is deductible for tax purposes.

For the period from acquisition date to March 31, 2024, the acquired portfolio of assets contributed $9.4 million to the Company's Electricity revenues, and $3.3 million to the Company's earnings, which were included in the Company’s condensed consolidated statements of operations and comprehensive income for the three months ended March 31, 2024.

The following unaudited pro forma summary presents condensed consolidated information of the Company as if the business combination had occurred on January 1, 2023. The pro forma results below include the impact of certain adjustments related to the depreciation of property plant and equipment, amortization of intangible assets, transaction-related costs, and the related income tax effects. This pro forma presentation does not include any impact from transaction synergies or any other material, nonrecurring adjustments directly attributable to the business combination.

	Pro forma for the Three Months Ended March 31,
	2024		2023
	(Dollars in millions)
Electricity revenues	$	191.3	$	179.8
Total revenues	$	224.2	$	194.7
Net income attributable to the Company's stockholders	$	39.9	$	27.7

Catastrophe [Policy Text Block]

War in Israel

On October 7, 2023, Hamas terrorists and members of other terrorist organizations infiltrated Israel’s southern border from the Gaza Strip and conducted a series of attacks on civilian and military targets, including widespread killings and kidnappings. They also launched extensive rocket attacks on the Israeli civilian population. Shortly following the attack, Israel declared war against Hamas. The majority of the Company's senior management and its main Product segment production and manufacturing facilities are located in Israel approximately 26 miles from the border with the Gaza Strip. More recently, the Houthi movement, which controls parts of Yemen, launched a number of attacks on marine vessels in the Red Sea. The Red Sea is an important maritime route for international trade. These disruptions have resulted, and may continue to result in, delayed deliveries of several key components used in the manufacturing of the Company's products and could impact its ability to timely deliver products to its customers under the Product Segment. This has also resulted in an increase in insurance premium costs for shipments into and out of the sea port.

As of the date of these condensed consolidated financial statements, none of the Company's facilities or infrastructure have been damaged nor have its supply chains been significantly impacted since the war broke out. However, a prolonged war could result in further military reserve duty call-ups as well as irregularities to the Company's supply chain and to its ability to ship its products from Israel, which could disrupt the operations of the Company's Product segment and potentially delay some of its growth plans in the Electricity segment. Management continuously monitors the effect of the war on the Company's financial position and results of operations.

Oil and Gas, Capitalized Exploratory Well Cost [Policy Text Block]

Write-offs of unsuccessful exploration activities

There were no write-offs of unsuccessful exploration activities during the three months ended March 31, 2024 and 2023.

Concentration Risk, Credit Risk, Policy [Policy Text Block]

Concentration of credit risk

Financial instruments that potentially subject the Company to a concentration of credit risk consist principally of cash investments and accounts receivable.

The Company places its cash investments with high credit quality financial institutions located in the United States (“U.S.”) and in foreign countries. At March 31, 2024 and December 31, 2023, the Company had deposits totaling $68.2 million and $43.2 million, respectively, in ten U.S. financial institutions that were federally insured up to $250,000 per account. At March 31, 2024 and December 31, 2023, the Company’s deposits in foreign countries amounted to approximately $55.9 million and $57.5 million, respectively.

At March 31, 2024 and December 31, 2023, accounts receivable related to operations in foreign countries amounted to approximately $98.1 million and $152.2 million, respectively. At March 31, 2024 and December 31, 2023, accounts receivable from the Company’s primary customers, which each accounted for revenues in excess of 10% of total consolidated revenues for the related period, amounted to approximately 61% and 57% of the Company’s trade receivables, respectively. The aggregate amount of notes receivable exceeding 10% of total receivables as of March 31, 2024 and December 31, 2023 is $85.3 million and $161.0 million, respectively.

The Company's revenues from its primary customers as a percentage of total revenues are as follows:

	Three Months Ended March 31,
	2024			2023
Southern California Public Power Authority (“SCPPA”)		24.7	%		26.7	%
Sierra Pacific Power Company and Nevada Power Company		16.8			18.9
Kenya Power and Lighting Co. Ltd. ("KPLC")		12.2			14.5

The Company has historically been able to collect on substantially all of its receivable balances. As of March 31, 2024, the amount overdue from KPLC in Kenya was $40.0 million of which $12.4 million was paid in April 2024. The Company believes it will be able to collect all past due amounts in Kenya. This belief is supported by the fact that in addition to KPLC's obligations under its power purchase agreement, the Company holds a support letter from the Government of Kenya that covers certain cases of KPLC non-payment (such as non-payments that are caused by government actions and/or political events).

In Honduras, as of March 31, 2024, the total amount overdue from Empresa Nacional de Energía Eléctrica ("ENEE") was $16.9 million of which none was paid to date. In addition, due to the financial situation in Honduras, the Company may experience further delays in collection. The Company believes it will be able to collect all past due amounts in Honduras.

Revenue [Policy Text Block]

Revenues from contracts with customers

Contract assets related to our Product segment reflect revenue recognized and performance obligations satisfied in advance of customer billing. Contract liabilities related to the Company's Product segment reflect payments received in advance of the satisfaction of performance under the contract. The Company receives payments from customers based on the terms established in the contracts. Total contract assets and contract liabilities as of March 31, 2024 and December 31, 2023 are as follows:

	March 31,			December 31,
	2024			2023
	(Dollars in thousands)
Contract assets (*)	$	23,616		$	18,367
Contract liabilities (*)	$	(21,376	)	$	(18,669	)

(*) Contract assets and contract liabilities are presented as "Costs and estimated earnings in excess of billings on uncompleted contracts" and "Billings in excess of costs and estimated earnings on uncompleted contracts", respectively, on the condensed consolidated balance sheets. The contract liabilities balance at the beginning of the year was not yet fully recognized as product revenues during the three months ended March 31, 2024 as a result of performance obligations having not been fully satisfied yet.

On March 31, 2024, the Company had approximately $128.7 million of remaining performance obligations not yet satisfied or partly satisfied related to our Product segment. The Company expects to recognize approximately 100% of this amount as Product revenues during the next 24 months.

Disaggregated revenues from contracts with customers for the three months ended March 31, 2024 and 2023 are disclosed under Note 8 - Business Segments, to the condensed consolidated financial statements.

Derivatives, Policy [Policy Text Block]

Derivative instruments

Derivative instruments (including certain derivative instruments embedded in other contracts) are measured at their fair value and recorded as either assets or liabilities unless exempted from derivative treatment as a normal purchase and sale. Changes in the fair value of derivatives not designated as hedging instruments are recognized in earnings. Changes in the fair value of derivatives designated as cash flow hedging instruments are initially recorded in "Other comprehensive income (loss)" and a corresponding amount is reclassified out of "Accumulated other comprehensive income (loss)" to earnings to offset the remeasurement of the underlying hedge transaction which also impacts the same line item in the condensed consolidated statements of operations and comprehensive income.

The Company maintains a risk management strategy that may incorporate the use of swap contracts, put options, forward exchange contracts, interest rate swaps, and cross-currency swaps to minimize significant fluctuation in cash flows and/or earnings that are caused by oil and natural gas prices, exchange rate or interest rate volatility.