Note 18 - Income Taxes (Details Textual) - USD ($) $ in Thousands				1 Months Ended					12 Months Ended
		Apr. 24, 2018	Sep. 11, 2015	Dec. 31, 2019	Jul. 31, 2019	Mar. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2014	Dec. 31, 2016
Deferred Tax Assets, Tax Credit Carryforwards, General Business				$ 100,524			$ 90,913					$ 100,524	$ 90,913
Deferred Tax Assets, Tax Credit Carryforwards, Foreign				92,497			58,072					92,497	58,072
Deferred Tax Assets, Investments				813			813					813	813
Deferred Tax Assets, Valuation Allowance, Total				17,412			22,441	$ 77,571				17,412	$ 22,441	$ 77,571		$ 116,234
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount												$ (5,000)
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent												21.00%	21.00%	35.00%
Uncertain Tax Benefit, Reudction to Deferred Tax Asset	[1]			95			95	95				$ 95	$ 95	$ 95
Deferred Tax Liabilities, Gross, Total				97,126			61,323	61,961				97,126	61,323	61,961
Foreign Earnings Repatriated								300,000						396,000
Distribution of Earnings in Foreign Subsidiaries							96,000
Unrecognized Tax Benefits that Would Impact Effective Tax Rate				14,600			11,800					$ 14,600	11,800
Depreciation Bonus Permitted Write Off Equipment Cost Percentage												100.00%
Placed in Service After December 31, 2022 and Before January 1, 2024 [Member]
Depreciation Bonus Permitted Write Off Equipment Cost Percentage												80.00%
Placed in Service After December 31, 2023 and Before January 1, 2025 [Member]
Depreciation Bonus Permitted Write Off Equipment Cost Percentage												60.00%
Placed in Service After December 31, 2024 and Before January 1, 2026 [Member]
Depreciation Bonus Permitted Write Off Equipment Cost Percentage												40.00%
Placed in Service After December 31, 2025 and Before January 1, 2027 [Member]
Depreciation Bonus Permitted Write Off Equipment Cost Percentage												20.00%
Accounting Standards Update 2013-11 [Member]
Uncertain Tax Benefit, Reudction to Deferred Tax Asset								$ 100						$ 100
U.S. Geothermal [Member]
Business Acquisition, Percentage of Voting Interests Acquired		100.00%
Business Combination, Consideration Transferred, Total		$ 110,000
Business Combination Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Assets (Liabilities), Net		1,700
Business Combination Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Assets		1,700
Deferred Taxes, Business Combination, Valuation Allowance, Available to Reduce Deferred Tax Asset		2,100
General Business Tax Credit Carryforward [Member]
Deferred Tax Assets, Tax Credit Carryforwards, General Business				100,500								$ 100,500
Tax Credit Carryforward Expiration Period												20 years
Minimum [Member] | General Business Tax Credit Carryforward [Member]
Tax Credit Carryforward Expiration Year												2022
Maximum [Member] | General Business Tax Credit Carryforward [Member]
Tax Credit Carryforward Expiration Year												2039
Domestic Tax Authority [Member]
Operating Loss Carryforwards, Total				132,700								$ 132,700
Operating Loss Carryforwards Expiring Amount				127,900								127,900
Operating Loss Carryforwards Available For Indefinite Period				4,800								$ 4,800
Open Tax Year												2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019
Domestic Tax Authority [Member] | U.S. Geothermal [Member]
Business Combination Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Assets		115,200
Domestic Tax Authority [Member] | Minimum [Member]
Tax Credit Carryforward Expiration Year												2032
Domestic Tax Authority [Member] | Maximum [Member]
Tax Credit Carryforward Expiration Year												2037
Foreign Tax Authority [Member]
Tax Credit Carryforward Expiration Year												2022
Tax Credit Carryforward Expiration Period												10 years
Deferred Tax Assets, Tax Credit Carryforwards, Foreign				92,500								$ 92,500
Foreign Tax Authority [Member] | Israel Tax Authority [Member]
Foreign Income Tax Expense (Benefit), Continuing Operations, Total												$ 13,900	14,400
Deferred Tax Liabilities, Gross, Total							$ 0						$ 0
National Corporate Tax Rate												23.00%	23.00%	24.00%
Foreign Tax Authority [Member] | Israel Tax Authority [Member] | Ormat Systems Ltd [Member]
Effective Income Tax Rate, Year Four and Thereafter															16.00%
Tax Rate on Exempt Income, in Event of Distribution												25.00%
Deferred Tax Liability, Rate, Respect of Tax Exempt Income												25.00%
Foreign Tax Authority [Member] | Tax Authority of Guatemala in Guatemala [Member]
National Corporate Tax Rate												25.00%
Tax Exemption Period												10 years
Effective Income Tax Rate												7.00%
Foreign Tax Authority [Member] | Kenya Revenue Authority [Member]
National Corporate Tax Rate												37.50%
Investment Deduction Percentage			150.00%
Income Tax Examination, Liability (Refund) Adjustment from Settlement with Taxing Authority				0								$ 0
Foreign Tax Authority [Member] | Kenya Revenue Authority [Member] | Tax Years 2014-2017 [Member]
Income Tax Examination, Settlement Demanded Including Accrued Interest and Penalties						$ 5,600
Income Tax Examination, Interest Accrued and Waiver Requested					$ 4,400
Foreign Tax Authority [Member] | Kenya Revenue Authority [Member] | Tax Years 2013-2017 [Member]
Income Tax Examination, Settlement Demanded Including Accrued Interest and Penalties				17,000	$ 205,000
Foreign Tax Authority [Member] | Ministry of the Economy, Finance and Industry, France [Member]
National Corporate Tax Rate														34.43%
Corporate Income Tax Rate, Taxable Income Exceeding Euro 0.5 Million												31.00%	33.30%
Foreign Tax Authority [Member] | Ministry of the Economy, Finance and Industry, France [Member] | Forecast [Member]
National Corporate Tax Rate									25.00%	26.50%	28.00%
Foreign Tax Authority [Member] | Sistema de Administración de Rentas [Member]
Income Taxes Exempt Period												10 years
Foreign Tax Authority [Member] | Minimum [Member] | Kenya Revenue Authority [Member]
Tax Losses Carryforward Period												5 years
Foreign Tax Authority [Member] | Maximum [Member] | Kenya Revenue Authority [Member]
Tax Losses Carryforward Period												10 years
State and Local Jurisdiction [Member]
Operating Loss Carryforwards, Total				277,900								$ 277,900
Operating Loss Carryforwards Expiring Amount				275,500								275,500
Operating Loss Carryforwards Available For Indefinite Period				2,400								2,400
Deferred Tax Assets, Investments				$ 800								$ 800
Open Tax Year												2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019
State and Local Jurisdiction [Member] | U.S. Geothermal [Member]
Business Combination Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Assets		$ 49,900
State and Local Jurisdiction [Member] | Minimum [Member]
Tax Credit Carryforward Expiration Year												2025
State and Local Jurisdiction [Member] | Maximum [Member]
Tax Credit Carryforward Expiration Year												2039

[1] The non-current deferred tax asset has been reduced by the uncertain tax benefit of $0.1 million in accordance with ASU 2013-11, Income Taxes.