Note 2 - Business Acquisitions and Others (Details Textual) $ in Thousands				12 Months Ended
		Apr. 24, 2018 USD ($) MWh	Mar. 15, 2017 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Goodwill, Ending Balance				$ 19,950	$ 21,037	$ 6,650
U.S. Geothermal [Member]
Payments to Acquire Businesses, Gross		$ 110,000
Current Power Generation | MWh		38
Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual				21,400
Business Acquisition, Pro Forma Operating Income (Loss) since Acquisition Date, Actual				$ 2,500
Business Combination, Consideration Transferred, Total		$ 110,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill, Total	[1]	127,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Working Capital		(8,200)
Goodwill, Ending Balance	[2]	12,700
U.S. Geothermal [Member] | Neal Hot Springs [Member]
Business Combination, Acquisition of Less than 100 Percent, Noncontrolling Interest, Fair Value		$ 34,900
Business Combination, Acquisition of Less than 100 Percent, Noncontrolling Interest, Percent		40.00%
U.S. Geothermal [Member] | Neal Hot Springs [Member] | Measurement Input, Expected Term [Member]
Noncontrolling Interest, Measurement Input		20
U.S. Geothermal [Member] | Neal Hot Springs [Member] | Measurement Input, Discount Rate [Member]
Noncontrolling Interest, Measurement Input		0.09
U.S. Geothermal [Member] | Long-term Electricity Power Purchase Agreements [Member]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life		19 years
U.S. Geothermal [Member] | Ormat Nevada Inc. [Member]
Payments to Acquire Businesses, Gross		$ 106,000
U.S. Geothermal [Member] | Heit vs Ormat Technologies, Inc. [Member]
Payments to Acquire Businesses, Gross		$ 4,000
Viridity Energy, Inc. [Member]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life			19 years	19 years
Business Combination, Consideration Transferred, Total			$ 35,300
Business Combination, Contingent Consideration, Liability, Total			12,400	$ 10,300
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill, Total			34,700
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Working Capital			400
Goodwill, Ending Balance			13,500
Viridity Energy, Inc. [Member] | General and Administrative Expense [Member]
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability			$ (600)

[1] Intangible assets are primarily related to long-term electricity power purchase agreements and depreciated over an average of 19 years.

[2] Goodwill is primarily related to the expected synergies in operations as a result of the purchase transaction. The goodwill is allocated to the Electricity segment and not deductible for tax purposes.