Note 1 - General and Basis of Presentation (Details) - USD ($)					1 Months Ended	3 Months Ended			6 Months Ended		12 Months Ended
	Apr. 30, 2015	Feb. 15, 2015	Jun. 20, 2014	Mar. 26, 2014	Jun. 30, 2015	Jun. 30, 2015	Jun. 30, 2014	Mar. 31, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014	Feb. 14, 2015	Feb. 11, 2015	Dec. 31, 2013
Note 1 - General and Basis of Presentation (Details) [Line Items]
Repayments of Secured Debt									$ 30,638,000	$ 12,860,000
Proceeds from Sales of Business, Affiliate and Productive Assets										35,250,000
Noncontrolling Interest, Increase from Subsidiary Equity Issuance										257,000
									$ 156,761,000
Percentage of Public Float Before Transition to Noncontrolled Public Company													40.00%
Percentage of Public Float After Transition to Noncontrolled Public Company		76.00%
Share Exchange Shares Granted Per Share (in Shares)		0.2592
Common Stock, Shares, Issued (in Shares)		3,000,000			49,002,583	49,002,583			49,002,583		45,537,162
Common Stock, Shares, Outstanding (in Shares)		48,500,000			49,002,583	49,002,583			49,002,583		45,537,162	45,500,000
Sale of Stock, Consideration Received on Transaction		$ 15,400,000
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax						$ 8,000	$ 36,000		$ 15,000	72,000
Interest Expense						18,859,000	22,072,000		36,687,000	42,590,000
Income Tax Expense (Benefit)						6,056,000	4,967,000		11,515,000	11,287,000
Exploration Abandonment and Impairment Expense							8,107,000		174,000	8,107,000
Cash, Cash Equivalents, and Short-term Investments					$ 137,665,000	137,665,000	80,120,000		137,665,000	80,120,000	$ 40,230,000			$ 57,354,000
Accounts Receivable, Net, Current					58,089,000	58,089,000			58,089,000		48,609,000
Provision for Doubtful Accounts									0
UNITED STATES
Note 1 - General and Basis of Presentation (Details) [Line Items]
Cash, Cash Equivalents, and Short-term Investments					49,931,000	49,931,000			49,931,000		23,488,000
Foreign Countries [Member]
Note 1 - General and Basis of Presentation (Details) [Line Items]
Cash, Cash Equivalents, and Short-term Investments					22,796,000	22,796,000			22,796,000		24,304,000
Accounts Receivable, Net, Current					33,024,000	33,024,000			33,024,000		$ 21,935,000
Additional Paid-in Capital [Member]
Note 1 - General and Basis of Presentation (Details) [Line Items]
									71,291,000
Noncontrolling Interest [Member]
Note 1 - General and Basis of Presentation (Details) [Line Items]
Noncontrolling Interest, Increase from Subsidiary Equity Issuance										257,000
									85,470,000
Maximum [Member]
Note 1 - General and Basis of Presentation (Details) [Line Items]
Cash, FDIC Insured Amount														$ 250,000
Reclassification out of Accumulated Other Comprehensive Income [Member]
Note 1 - General and Basis of Presentation (Details) [Line Items]
Interest Expense						14,000	58,000		25,000	116,000
Income Tax Expense (Benefit)						$ 5,000	$ 22,000		$ 10,000	$ 44,000
Northleaf Geothermal Holdings (Northleaf) [Member]
Note 1 - General and Basis of Presentation (Details) [Line Items]
Equity Method Investment, Ownership Percentage	36.75%
Number of Power Plants Acquired	9
Recovered Energy Generation Assets	3
Business Combination, Consideration Transferred	$ 162,300,000
Proceeds from Sales of Business, Affiliate and Productive Assets	156,800,000
Business Acquisition, Transaction Costs	5,500,000
Business Combination, Bargain Purchase, Gain Recognized, Amount	102,100,000
Northleaf Geothermal Holdings (Northleaf) [Member] | Additional Paid-in Capital [Member]
Note 1 - General and Basis of Presentation (Details) [Line Items]
Noncontrolling Interest, Increase from Subsidiary Equity Issuance	71,300,000
Northleaf Geothermal Holdings (Northleaf) [Member] | Noncontrolling Interest [Member]
Note 1 - General and Basis of Presentation (Details) [Line Items]
	$ 85,500,000
Primary Customers [Member] | Accounts Receivable [Member] | Customer Concentration Risk [Member]
Note 1 - General and Basis of Presentation (Details) [Line Items]
Concentration Risk, Percentage									59.50%		69.00%
Hawaii Electric Light Company [Member] | Sales Revenue, Net [Member] | Customer Concentration Risk [Member]
Note 1 - General and Basis of Presentation (Details) [Line Items]
Concentration Risk, Percentage						20.00%	17.40%		21.80%	17.50%
Southern California Edison Company [Member] | Sales Revenue, Net [Member] | Customer Concentration Risk [Member]
Note 1 - General and Basis of Presentation (Details) [Line Items]
Concentration Risk, Percentage						13.50%	10.30%		9.70%	12.70%
Kenya Power And Lighting Co Limited [Member] | Sales Revenue, Net [Member] | Customer Concentration Risk [Member]
Note 1 - General and Basis of Presentation (Details) [Line Items]
Concentration Risk, Percentage						15.40%	16.90%		16.50%	15.60%
Heber Solar Project [Member]
Note 1 - General and Basis of Presentation (Details) [Line Items]
Proceeds from Sales of Business, Affiliate and Productive Assets							$ 20,250,000	$ 15,000,000
Sales Price of Disposition				$ 35,250,000
Gain (Loss) on Sale of Project							$ 7,600,000
Aggregate Shares Issued [Member]
Note 1 - General and Basis of Presentation (Details) [Line Items]
Conversion of Stock, Shares Issued (in Shares)		30,200,000
Shares Issued to Self, Deducted [Member]
Note 1 - General and Basis of Presentation (Details) [Line Items]
Conversion of Stock, Shares Issued (in Shares)		27,200,000
Sale of Stock, Other Assets Received [Member]
Note 1 - General and Basis of Presentation (Details) [Line Items]
Sale of Stock, Consideration Received Per Transaction		$ 600,000
Sale of Stock, Land and Buildings Received [Member]
Note 1 - General and Basis of Presentation (Details) [Line Items]
Sale of Stock, Consideration Received Per Transaction		12,100,000
Sale of Stock, Liabilities Assumed [Member]
Note 1 - General and Basis of Presentation (Details) [Line Items]
Sale of Stock, Consideration Received Per Transaction		$ 500,000
Ormat Funding Corp [Member]
Note 1 - General and Basis of Presentation (Details) [Line Items]
Repayments of Secured Debt					30,600,000
Gains (Losses) on Extinguishment of Debt					$ 1,700,000
Ormat Funding Corp [Member] | Other Nonoperating Income (Expense) [Member]
Note 1 - General and Basis of Presentation (Details) [Line Items]
Amortization of Financing Costs									$ 500,000
OFC Two Senior Secured Notes [Member]
Note 1 - General and Basis of Presentation (Details) [Line Items]
Repayments of Secured Debt			$ 4,300,000