Note 19 - Income Taxes (Details Textual) $ in Thousands			3 Months Ended	12 Months Ended
	Dec. 16, 2016 USD ($)	Sep. 11, 2015 USD ($)	Dec. 31, 2016 USD ($) $ / kWh	Dec. 31, 2016 USD ($) $ / kWh shares	Dec. 31, 2015 USD ($) shares	Dec. 31, 2014 USD ($) shares	Dec. 31, 2013 USD ($)	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2004	Nov. 23, 2016
Deferred Tax Assets, Investments			$ 1,341	$ 1,341	$ 1,341
Deferred Tax Assets, Tax Credit Carryforwards, General Business			82,451	82,451	70,792
Deferred Tax Assets, Valuation Allowance			109,611	109,611	70,536	$ 111,280	$ 114,806
Undistributed Earnings of Foreign Subsidiaries			367,000	367,000
Unrecognized Tax Benefits that Would Impact Effective Tax Rate			$ 5,700	5,700	10,400
Unrecognized Tax Benefits, Reduction Resulting from Lapse of Applicable Statute of Limitations				$ 6,400	$ 1,300	600
Investment Tax Credit Per Unit | $ / kWh			2.3	2.3
Production Tax Credit Claim Period				10 years
Depreciation Bonus Period to Write Off The Reminder of Equipment Cost				60 days
Placed into Service after December 31, 2011 and Before January 1, 2017 [Member]
Depreciation Bonus Permitted Write Off Equipment Cost Percentage				50.00%
OrLeaf LLC [Member]
Distributions Received From Subsidiary	$ 43,100
Taxable Gain (Loss) on Distribution from Subsidiary	4,800
OrLeaf LLC [Member] | ORPD LLC [Member]
Distributions Received From Subsidiary	$ 19,000
Northleaf Geothermal Holdings, Northleaf [Member]
Equity Method Investment, Ownership Percentage											36.75%
Taxable Income Recognized				$ 21,400
Investment Tax Credit Carryforward [Member]
Deferred Tax Assets, Investments			$ 1,300	$ 1,300
Tax Credit Carryforward Expiration Period				20 years
General Business Tax Credit Carryforward [Member]
Tax Credit Carryforward Expiration Period					20 years
Minimum [Member] | Investment Tax Credit Carryforward [Member]
Tax Credit Carryforward Expiration Year				2022
Minimum [Member] | General Business Tax Credit Carryforward [Member]
Tax Credit Carryforward Expiration Year					2026
Maximum [Member] | Investment Tax Credit Carryforward [Member]
Tax Credit Carryforward Expiration Year				2024
Maximum [Member] | General Business Tax Credit Carryforward [Member]
Tax Credit Carryforward Expiration Year					2036
Deferred Tax Assets, Tax Credit Carryforwards, General Business			82,500	$ 82,500
Domestic Tax Authority [Member]
Operating Loss Carryforwards			299,600	$ 299,600
Domestic Tax Authority [Member] | Placed in Service before December 2016 [Member]
Effective Income Tax Rate Reconciliation, Tax Credit, Investment, Percent				30.00%
Domestic Tax Authority [Member] | Placed in Service after December 2016 [Member]
Effective Income Tax Rate Reconciliation, Tax Credit, Investment, Percent				10.00%
Domestic Tax Authority [Member] | Minimum [Member]
Tax Credit Carryforward Expiration Year				2029
Domestic Tax Authority [Member] | Maximum [Member]
Tax Credit Carryforward Expiration Year				2036
State and Local Jurisdiction [Member]
Operating Loss Carryforwards			244,700	$ 244,700
State and Local Jurisdiction [Member] | Earliest Tax Year [Member]
Open Tax Year				2002
State and Local Jurisdiction [Member] | Latest Tax Year [Member]
Open Tax Year				2016
State and Local Jurisdiction [Member] | Minimum [Member]
Tax Credit Carryforward Expiration Year				2018
State and Local Jurisdiction [Member] | Maximum [Member]
Tax Credit Carryforward Expiration Year				2036
Internal Revenue Service (IRS) [Member] | Earliest Tax Year [Member]
Open Tax Year				2000
Internal Revenue Service (IRS) [Member] | Latest Tax Year [Member]
Open Tax Year				2016
Foreign Tax Authority [Member] | Tax Authority of Guatemala in Guatemala [Member]
National Corporate Tax Rate				25.00%
Effective Income Tax Rate				0.00%
Tax Exemption Period				10 years
Effective Income Tax Rate Reconciliation, Tax Exempt Income, Amount				$ 3,300	$ 3,600	$ 1,900
Income Tax Benefit From Examination Per Share | shares				0.07	0.08	0.04
Foreign Tax Authority [Member] | Israel Tax Authority [Member]
National Corporate Tax Rate				25.00%	26.50%	26.50%	25.00%	25.00%
Foreign Tax Authority [Member] | Kenya Revenue Authority [Member]
National Corporate Tax Rate				37.50%
Investment Deduction Percentage		150.00%
Income Tax Examination, Estimate of Possible Loss		$ 16,100
Other Tax Expense (Benefit)					$ 49,400
Foreign Tax Authority [Member] | Kenya Revenue Authority [Member] | Reduction of Income Tax Expense and Deferred Liabilities Due to Overstatement of Tax Position [Member]
Current Period Reclassification Adjustment			$ 4,700
Foreign Tax Authority [Member] | Inland Revenue Department, New Zealand [Member]
National Corporate Tax Rate					28.00%	28.00%	28.00%
Foreign Tax Authority [Member] | Ormat Systems Ltd [Member] | Israel Tax Authority [Member]
Effective Income Tax Rate, Year One									15.00%
Effective Income Tax Rate, Year Three							12.50%
Effective Income Tax Rate, Year Four and Thereafter						16.00%
Effective Income Tax Rate, Year Two								15.00%
Foreign Tax Authority [Member] | Ormat Systems Ltd [Member] | Israel Tax Authority [Member] | Investment One [Member]
Income Tax Incentive Period										5 years
Period For Tax Exemption										2 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
Foreign Tax Authority [Member] | Maximum [Member] | Ormat Systems Ltd [Member] | Israel Tax Authority [Member] | Investment One [Member]
Effective Income Tax Rate										25.00%