Note 1 - General and Basis of Presentation (Details Textual)			3 Months Ended				6 Months Ended		12 Months Ended
	Mar. 15, 2017 USD ($)	Dec. 29, 2016 USD ($)	Jun. 30, 2017 USD ($) MWh $ / MWh	Mar. 31, 2017 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Jun. 30, 2017 USD ($) $ / MWh	Jun. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)	Jan. 01, 2016 USD ($)	Dec. 31, 2015 USD ($)
Net Income (Loss) Attributable to Parent, Total			$ 8,640,000		$ 23,724,000		$ 43,834,000	$ 53,425,000
Income Tax Expense (Benefit), Total			32,765,000		8,515,000		43,769,000	17,594,000
Retained Earnings (Accumulated Deficit), Ending Balance			246,760,000		186,753,000		246,760,000	186,753,000	$ 215,352,000		$ 152,326,000
Goodwill, Ending Balance			20,121,000				20,121,000		6,650,000
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax			1,000		2,000		3,000	5,000
Interest Expense, Total			14,540,000		18,401,000		29,463,000	34,424,000
Accumulated Other Comprehensive Income (Loss), Net of Tax, Total			(7,325,000)		(13,308,000)		(7,325,000)	(13,308,000)	(8,175,000)		(8,164,000)
Exploration Abandonment and Impairment Expense			0		863,000		0	1,420,000
Cash, Cash Equivalents, and Short-term Investments, Total			118,390,000		192,556,000		118,390,000	192,556,000	230,214,000		185,919,000
Accounts Receivable, Net, Current, Total			79,587,000				79,587,000		$ 80,807,000
Provision for Doubtful Accounts							0
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest, Total			12,421,000		22,332,000		52,709,000	50,539,000
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest, Total			$ 11,846,000		$ 24,308,000		$ 51,463,000	$ 55,683,000
Accounts Receivable [Member] | Customer Concentration Risk [Member] | Primary Customers [Member]
Concentration Risk, Percentage							55.00%		60.00%
Sales Revenue, Net [Member] | Customer Concentration Risk [Member] | Sierra Pacific Power Company And Nevada Power Company [Member]
Concentration Risk, Percentage			16.70%		19.10%		17.80%	21.10%
Sales Revenue, Net [Member] | Customer Concentration Risk [Member] | Kenya Power and Lighting Co LTD [Member]
Concentration Risk, Percentage			15.40%		17.10%		14.80%	17.20%
Sales Revenue, Net [Member] | Customer Concentration Risk [Member] | Southern California Public Power Authority [Member]
Concentration Risk, Percentage			8.70%		10.40%		8.90%	11.20%
Sales Revenue, Net [Member] | Customer Concentration Risk [Member] | Hyundai (Sarulla Goethermal Power Project) [Member]
Concentration Risk, Percentage			4.90%		8.60%		6.30%	9.00%
UNITED STATES
Cash, Cash Equivalents, and Short-term Investments, Total			$ 31,300,000				$ 31,300,000		$ 72,500,000
Foreign Countries [Member]
Cash, Cash Equivalents, and Short-term Investments, Total			99,900,000				99,900,000		166,200,000
Accounts Receivable, Net, Current, Total			53,500,000				53,500,000		53,300,000
Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax, Total			(600,000)				(600,000)
Reclassification out of Accumulated Other Comprehensive Income [Member]
Income Tax Expense (Benefit), Total			(1,000)		$ (4,000)		(2,000)	$ (5,000)
Interest Expense, Total			$ (3,000)		(6,000)		$ (5,000)	(10,000)
Viridity Energy, Inc. [Member]
Business Combination, Consideration Transferred, Total		$ 35,300,000
Business Combination, Contingent Consideration, Liability, Total	$ 12,800,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill, Total	$ 34,700,000
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	17 years
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Working Capital	$ 400,000
Goodwill, Ending Balance	$ 13,900,000
ONGP, LLC [Member] | Southern California Public Power Authority [Member]
Power Purchase Agreements, Number of Power Plants Portfolio			9				9
Expected Power Generating Capacity | MWh			150
Power Plant Usage Agreement Term			5 years
Power Purchase Agreements Term			26 years
Power Purchase Agreements, Fixed Price Per MWh | $ / MWh			75.5				75.5
Restatement Adjustment [Member]
Net Income (Loss) Attributable to Parent, Total			$ (26,396,000)		(625,000)		$ (26,514,000)	(195,000)
Income Tax Expense (Benefit), Total			26,396,000	$ 100,000	625,000	$ (400,000)	26,514,000	195,000
Retained Earnings (Accumulated Deficit), Ending Balance			(27,806,000)		3,735,000		(27,806,000)	3,735,000	(1,292,000)	$ 3,900,000	3,930,000
Accumulated Other Comprehensive Income (Loss), Net of Tax, Total			(392,000)		(470,000)		(392,000)	(470,000)	(443,000)		$ (497,000)
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest, Total			$ (26,371,000)	(100,000)	(612,000)	400,000	(26,463,000)	(168,000)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest, Total				$ (100,000)	$ (600,000)	$ 400,000	(26,514,000)	$ (195,000)
Minimum [Member] | Ormat Nevada ORTP LLC [Member] | Southern California Public Power Authority [Member]
Expected Power Generating Capacity | MWh			135
Maximum [Member]
Cash, FDIC Insured Amount			$ 250,000				$ 250,000		$ 250,000
Maximum [Member] | Ormat Nevada ORTP LLC [Member] | Southern California Public Power Authority [Member]
Expected Power Generating Capacity | MWh			185
Foreign Tax Authority [Member] | Minimum [Member]
Tax Credit Carryforward Expiration Year							2027