Note 10 - Long-term Debt and Credit Agreements (Details) (USD $)	3 Months Ended								12 Months Ended			1 Months Ended								0 Months Ended	1 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Nov. 30, 2012	Feb. 28, 2013	Nov. 30, 2013	Jun. 20, 2014	Oct. 31, 2011	Jul. 31, 2009	Nov. 30, 2010	May 31, 2009 MW	Jul. 10, 2009	Oct. 31, 2012	Mar. 30, 2009	Mar. 31, 2009	Feb. 29, 2004	Dec. 31, 2005	Nov. 30, 2009	May 31, 2013	Aug. 18, 2014	Sep. 30, 2014	Dec. 31, 2011	Jul. 31, 2013	Aug. 23, 2012	Jan. 31, 2014	Aug. 29, 2014	Sep. 30, 2011	Feb. 28, 2011	Aug. 30, 2010
Note 10 - Long-term Debt and Credit Agreements (Details) [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	7.00%				7.00%				7.00%	7.00%
Letters of Credit Outstanding, Amount	$ 353,100,000								$ 353,100,000
Interest Expense	19,570,000	22,494,000	22,072,000	20,518,000	21,950,000	18,459,000	17,504,000	15,863,000	84,654,000	73,776,000	64,069,000
Repayments of Long-term Debt									111,180,000	68,370,000	74,502,000
Payments for Derivative Instrument, Financing Activities									1,505,000
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax									(902,000)
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Tax									554,000
Line of Credit, Current	20,300,000								20,300,000
Stockholders' Equity Attributable to Parent	774,923,000				732,740,000				774,923,000	732,740,000	695,607,000																			906,644,000
Percentage of Company Assets									37.10%
Debt to Earnings before Interest Tax Depreciation and Amortization Ratio									3.70
Payments of Dividends										3,600,000
Tranche One Member | Loan Agreement with OPIC [Member]
Note 10 - Long-term Debt and Credit Agreements (Details) [Line Items]
Debt Instrument, Face Amount												85,000,000
Debt Instrument, Interest Rate, Stated Percentage	6.31%								6.31%
Long-term Debt, Gross																															75,500,000
Tranche One Member | Olkaria III - DEG [Member]
Note 10 - Long-term Debt and Credit Agreements (Details) [Line Items]
Prepayment Deposit on Debt												20,500,000
Prepayment Penalty Charges												1,500,000
Tranche Two [Member] | Loan Agreement with OPIC [Member]
Note 10 - Long-term Debt and Credit Agreements (Details) [Line Items]
Debt Instrument, Face Amount												180,000,000
Debt Instrument, Interest Rate, Stated Percentage	6.31%								6.31%
Proceeds from Issuance of Debt												135,000,000	45,000,000
Long-term Debt, Gross																															164,100,000
Tranche Three [Member] | Loan Agreement with OPIC [Member]
Note 10 - Long-term Debt and Credit Agreements (Details) [Line Items]
Debt Instrument, Face Amount													45,000,000
Debt Instrument, Interest Rate, Stated Percentage	6.12%								6.12%
Proceeds from Issuance of Debt														45,000,000
Long-term Debt, Gross	43,000,000								43,000,000
Historical [Member] | Loan Agreement with OPIC [Member] | Minimum [Member]
Note 10 - Long-term Debt and Credit Agreements (Details) [Line Items]
Debt Services Coverage Ratio	1.4								1.4
Historical [Member] | Loan Agreement with OPIC [Member]
Note 10 - Long-term Debt and Credit Agreements (Details) [Line Items]
Debt Services Coverage Ratio	2.05								2.05
Historical [Member] | OrCal Senior Secured Notes [Member]
Note 10 - Long-term Debt and Credit Agreements (Details) [Line Items]
Debt Services Coverage Ratio	1.28								1.28
Historical [Member] | OFC Two Senior Secured Notes [Member] | Minimum [Member]
Note 10 - Long-term Debt and Credit Agreements (Details) [Line Items]
Debt Services Coverage Ratio	1.2								1.2
Historical [Member] | OFC Two Senior Secured Notes [Member]
Note 10 - Long-term Debt and Credit Agreements (Details) [Line Items]
Debt Services Coverage Ratio	1.62								1.62
Projected [Member] | Loan Agreement with OPIC [Member]
Note 10 - Long-term Debt and Credit Agreements (Details) [Line Items]
Debt Services Coverage Ratio	1.94								1.94
Projected [Member] | OrCal Senior Secured Notes [Member]
Note 10 - Long-term Debt and Credit Agreements (Details) [Line Items]
Debt Services Coverage Ratio	1.29								1.29
Projected [Member] | OFC Two Senior Secured Notes [Member] | Minimum [Member]
Note 10 - Long-term Debt and Credit Agreements (Details) [Line Items]
Debt Services Coverage Ratio	1.5								1.5
Projected [Member] | OFC Two Senior Secured Notes [Member]
Note 10 - Long-term Debt and Credit Agreements (Details) [Line Items]
Debt Services Coverage Ratio	2.24								2.24
Phase I Series A Senior Notes [Member] | OFC Two Senior Secured Notes [Member]
Note 10 - Long-term Debt and Credit Agreements (Details) [Line Items]
Debt Instrument, Face Amount																151,700,000
Debt Instrument, Interest Rate, Stated Percentage																4.687%
Proceeds from Issuance of Debt																141,100,000
Repayments of Long-term Debt															4,300,000
Other Reserves	28,000,000								28,000,000
Other Reserves, Net	38,700,000								38,700,000
McGinness Hills Phase II [Member] | OFC Two Senior Secured Notes [Member]
Note 10 - Long-term Debt and Credit Agreements (Details) [Line Items]
Letters of Credit Outstanding, Amount	53,400,000								53,400,000
First Loan [Member] | Institutional Investors [Member]
Note 10 - Long-term Debt and Credit Agreements (Details) [Line Items]
Debt Instrument, Face Amount																	20,000,000
Debt Instrument, Interest Rate, Stated Percentage																	6.50%
Debt Instrument, Term																	6 years
Second Loan [Member] | Institutional Investors [Member]
Note 10 - Long-term Debt and Credit Agreements (Details) [Line Items]
Debt Instrument, Face Amount																	20,000,000
Debt Instrument, Term																	8 years
Debt Instrument, Basis Spread on Variable Rate																	5.00%
Third Loan [Member] | Institutional Investors [Member]
Note 10 - Long-term Debt and Credit Agreements (Details) [Line Items]
Debt Instrument, Face Amount																		20,000,000
Debt Instrument, Interest Rate, Stated Percentage																		5.75%
Debt Instrument, Term																		6 years
Threshold for Loan Default [Member] | Loan Agreement with OPIC [Member]
Note 10 - Long-term Debt and Credit Agreements (Details) [Line Items]
Debt Services Coverage Ratio	1.1								1.1
Debt Service Reserve Backing [Member] | OrCal Senior Secured Notes [Member]
Note 10 - Long-term Debt and Credit Agreements (Details) [Line Items]
Letters of Credit Outstanding, Amount	10,100,000				10,200,000				10,100,000	10,200,000
In Addition To [Member] | OFC Two Senior Secured Notes [Member]
Note 10 - Long-term Debt and Credit Agreements (Details) [Line Items]
Letters of Credit Outstanding, Amount	17,100,000								17,100,000
Subject to Fixed Interest Rate [Member] | Loans Payable [Member] | Olkaria III - DEG [Member]
Note 10 - Long-term Debt and Credit Agreements (Details) [Line Items]
Secured Debt	21,700,000								21,700,000
Extensions of Credit in the Form of Loans and or Letters of Credit [Member] | Revolving Credit Lines With Commerical Banks [Member]
Note 10 - Long-term Debt and Credit Agreements (Details) [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	247,000,000								247,000,000
Issuance of Letters of Credit [Member] | Revolving Credit Lines With Commerical Banks [Member]
Note 10 - Long-term Debt and Credit Agreements (Details) [Line Items]
Letters of Credit Outstanding, Amount	308,200,000								308,200,000
Covenant Requirement Minimum [Member] | Maximum [Member]
Note 10 - Long-term Debt and Credit Agreements (Details) [Line Items]
Debt to Earnings before Interest Tax Depreciation and Amortization Ratio									7
Covenant Requirement Minimum [Member]
Note 10 - Long-term Debt and Credit Agreements (Details) [Line Items]
Stockholders' Equity Attributable to Parent	600,000,000								600,000,000
Percentage of Company Assets									30.00%
Amount Available for Dividend Distribution Percent of Cumulative Net Income									0.35
Senior Notes [Member] | Ormat Funding Corp Senior Secured Notes [Member]
Note 10 - Long-term Debt and Credit Agreements (Details) [Line Items]
Secured Debt	67,200,000				90,800,000				67,200,000	90,800,000
Senior Notes [Member] | OFC Two Senior Secured Notes [Member]
Note 10 - Long-term Debt and Credit Agreements (Details) [Line Items]
Secured Debt	272,500,000				144,400,000				272,500,000	144,400,000
Loans Payable [Member] | Olkaria III - DEG [Member]
Note 10 - Long-term Debt and Credit Agreements (Details) [Line Items]
Secured Debt	31,600,000								31,600,000
Loan Agreement with TCW [Member]
Note 10 - Long-term Debt and Credit Agreements (Details) [Line Items]
Debt Instrument, Face Amount																			42,000,000
Capacity of Plant (in Megawatts)																			20
Debt Instrument, Interest Rate, Stated Percentage																			9.83%
Loan Agreement with OPIC [Member] | First Two Years After the Plant 2 Commercial Operation Date [Member]
Note 10 - Long-term Debt and Credit Agreements (Details) [Line Items]
Debt Instrument Prepayment Premium Percentage									2.00%
Loan Agreement with OPIC [Member] | Third Year After the Plant 2 Commercial Operation Date [Member]
Note 10 - Long-term Debt and Credit Agreements (Details) [Line Items]
Debt Instrument Prepayment Premium Percentage									1.00%
Loan Agreement with OPIC [Member]
Note 10 - Long-term Debt and Credit Agreements (Details) [Line Items]
Debt Instrument, Face Amount																																310,000,000
Letters of Credit Outstanding, Amount	15,700,000								15,700,000
Long-term Debt, Gross	282,600,000								282,600,000
Debt Services Coverage Ratio	1.7								1.7
Restricted Cash and Cash Equivalents, Current	8,600,000				10,100,000				8,600,000	10,100,000
Olkaria III - DEG [Member]
Note 10 - Long-term Debt and Credit Agreements (Details) [Line Items]
Debt Instrument, Face Amount																					20,500,000	105,000,000	77,000,000
Debt Instrument, Interest Rate, Stated Percentage																							6.90%
Proceeds from Issuance of Debt																				15,000,000		90,000,000
Long-term Debt, Gross	31,600,000								31,600,000
Debt Instrument, Basis Spread on Variable Rate																					1.25%		4.00%
Ormat Funding Corp [Member] | Minimum [Member]
Note 10 - Long-term Debt and Credit Agreements (Details) [Line Items]
Debt Services Coverage Ratio																								1.25
Debt Instrument, Redemption Price, Percentage									100.00%
Ormat Funding Corp [Member] | Maximum [Member]
Note 10 - Long-term Debt and Credit Agreements (Details) [Line Items]
Debt Instrument, Redemption Price, Percentage									101.00%
Ormat Funding Corp [Member]
Note 10 - Long-term Debt and Credit Agreements (Details) [Line Items]
Debt Instrument, Face Amount													12,800,000											190,000,000									13,200,000
Debt Instrument, Interest Rate, Stated Percentage																								8.25%
Letters of Credit Outstanding, Amount	11,100,000				10,600,000				11,100,000	10,600,000
Proceeds from Issuance of Debt																								179,700,000
Restricted Cash and Cash Equivalents, Current	2,000,000				2,900,000				2,000,000	2,900,000
Debt Instrument Issuance Costs																								10,300,000
Gains (Losses) on Extinguishment of Debt				300,000				800,000
OrCal Senior Secured Notes [Member] | Minimum [Member]
Note 10 - Long-term Debt and Credit Agreements (Details) [Line Items]
Debt Services Coverage Ratio																									1.25
OrCal Senior Secured Notes [Member]
Note 10 - Long-term Debt and Credit Agreements (Details) [Line Items]
Debt Instrument, Face Amount																									165,000,000
Debt Instrument, Interest Rate, Stated Percentage																									6.21%
Letters of Credit Outstanding, Amount	55,100,000				66,200,000				55,100,000	66,200,000
Proceeds from Issuance of Debt																									161,100,000
Restricted Cash and Cash Equivalents, Current	800,000				3,000,000				800,000	3,000,000
Debt Instrument Issuance Costs																									3,900,000
Debt Instrument, Redemption Price, Percentage									100.00%
OFC Two Senior Secured Notes [Member] | Subsidiaries [Member]
Note 10 - Long-term Debt and Credit Agreements (Details) [Line Items]
Debt Instrument, Face Amount																																		140,000,000
Debt Instrument, Interest Rate, Stated Percentage																																		4.61%
OFC Two Senior Secured Notes [Member]
Note 10 - Long-term Debt and Credit Agreements (Details) [Line Items]
Debt Instrument, Face Amount																																			350,000,000
Government Guarantee Percent									80.00%
Debtor-in-Possession Financing, Letters of Credit Outstanding	17,100,000								17,100,000
Senior Unsecured Bonds Member
Note 10 - Long-term Debt and Credit Agreements (Details) [Line Items]
Debt Instrument, Face Amount																																				108,000,000	142,000,000
Debt Instrument, Interest Rate, Stated Percentage																																				6.75%	7.00%
Commercial Bank [Member]
Note 10 - Long-term Debt and Credit Agreements (Details) [Line Items]
Debt Instrument, Face Amount																										50,000,000
Debt Instrument, Term																										5 years
Debt Instrument, Basis Spread on Variable Rate																										3.25%
Revolving Credit Lines With Commerical Banks [Member]
Note 10 - Long-term Debt and Credit Agreements (Details) [Line Items]
Letters of Credit Outstanding, Amount	357,200,000								357,200,000
Line of Credit Facility, Maximum Borrowing Capacity	555,200,000								555,200,000
Long-term Line of Credit	20,300,000								20,300,000
Line of Credit, Current	20,300,000								20,300,000
Debt Instrument, Interest Rate, Effective Percentage	2.30%								2.30%
Union Bank, N.A. [Member] | Minimum [Member]
Note 10 - Long-term Debt and Credit Agreements (Details) [Line Items]
Debt Services Coverage Ratio	1.35								1.35
Line of Credit Facility, Maximum Borrowing Capacity	39,000,000								39,000,000
Union Bank, N.A. [Member] | Maximum [Member]
Note 10 - Long-term Debt and Credit Agreements (Details) [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	50,000,000								50,000,000
Debt to Earnings before Interest Tax Depreciation and Amortization Ratio									4.5
Amount Available for Dividend Distribution Percent of Cumulative Net Income									2.0
Union Bank, N.A. [Member]
Note 10 - Long-term Debt and Credit Agreements (Details) [Line Items]
Letters of Credit Outstanding, Amount	42,100,000								42,100,000
Debt Services Coverage Ratio	2.45								2.45
Line of Credit Facility, Maximum Borrowing Capacity	50,000,000								50,000,000
Debt to Earnings before Interest Tax Depreciation and Amortization Ratio									3.18
Amount Available for Dividend Distribution Percent of Cumulative Net Income									0.65
HSBC Bank USA, N.A. [Member] | Minimum [Member]
Note 10 - Long-term Debt and Credit Agreements (Details) [Line Items]
Debt Services Coverage Ratio																											1.35
HSBC Bank USA, N.A. [Member] | Maximum [Member]
Note 10 - Long-term Debt and Credit Agreements (Details) [Line Items]
Debt to Earnings before Interest Tax Depreciation and Amortization Ratio																											4.5
Amount Available for Dividend Distribution Percent of Cumulative Net Income																											2.0
HSBC Bank USA, N.A. [Member]
Note 10 - Long-term Debt and Credit Agreements (Details) [Line Items]
Debt Instrument, Face Amount																											25,000,000
Letters of Credit Outstanding, Amount	21,800,000								21,800,000
Debt Services Coverage Ratio					2.45					2.45
Line of Credit Facility, Maximum Borrowing Capacity	25,000,000								25,000,000
Debt to Earnings before Interest Tax Depreciation and Amortization Ratio										3.18
Amount Available for Dividend Distribution Percent of Cumulative Net Income										0.65
Line of Credit Facility, Capacity Available for Specific Purpose Other than for Trade Purchases																											10,000,000
Interest Rate Cap [Member]
Note 10 - Long-term Debt and Credit Agreements (Details) [Line Items]
Payments for Derivative Instrument, Financing Activities																												1,500,000
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax									900,000
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Tax									600,000
Interest Rate Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months, Net	100,000								100,000
Subsidiaries [Member] | EIG Global Fund II, Ltd. [Member]
Note 10 - Long-term Debt and Credit Agreements (Details) [Line Items]
Letters of Credit Outstanding, Amount		30,000,000																											30,000,000
Interest Expense																													1,100,000
Prepayment Premium																													600,000
Write off of Deferred Debt Issuance Cost																													$ 500,000