Note 12 - Long-term Debt and Credit Agreements (Details Textual)								1 Months Ended													3 Months Ended				12 Months Ended
	Dec. 21, 2016 USD ($)	Nov. 29, 2016 USD ($)	Sep. 14, 2016 USD ($)	Jul. 31, 2015 USD ($) MWh	Feb. 28, 2013 USD ($)	Nov. 30, 2012 USD ($)	Jul. 01, 2009 USD ($)	Aug. 18, 2014 USD ($)	Jun. 20, 2014 USD ($)	Nov. 30, 2013 USD ($)	May 31, 2013 USD ($)	Oct. 31, 2012 USD ($)	Feb. 29, 2012 USD ($)	Oct. 31, 2011 USD ($)	Nov. 30, 2010 USD ($)	Jul. 31, 2009 USD ($)	Mar. 31, 2009 USD ($)	Mar. 30, 2009 USD ($)	Dec. 31, 2005 USD ($)	Feb. 29, 2004 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2014 USD ($)	Mar. 31, 2013 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Oct. 20, 2016 USD ($)	Jun. 30, 2016	Oct. 31, 2015 USD ($)	Aug. 29, 2014 USD ($)	Jan. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Aug. 23, 2012 USD ($)	Feb. 28, 2012 USD ($)	Sep. 30, 2011 USD ($)	Feb. 28, 2011 USD ($)	Aug. 31, 2010 USD ($)
Letters of Credit Outstanding, Amount																									$ 341,600,000
Repayments of Long-term Debt																									62,052,000	$ 71,701,000	$ 111,180,000
Payments for Derivative Instrument, Financing Activities																											1,505,000
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax																									87,000	91,000	(902,000)
Proceeds from Issuance of Unsecured Debt																									$ 203,483,000
Debt To Earnings Before Interest Tax Depreciation And Amortization Ratio																									2.32
Stockholders' Equity Attributable to Parent																									$ 1,078,425,000	990,001,000
Percentage Of Company Assets																									47.53%
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest																									$ 1,170,007,000	1,083,874,000	786,746,000						$ 745,111,000
Payments of Dividends																									25,700,000
Interest Rate Cap [Member]
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
Covenant Requirement Minimum [Member]
Amount Available For Dividend Distribution Percent Of Cumulative Net Income																									0.35
Stockholders' Equity Attributable to Parent																									$ 600,000,000
Percentage Of Company Assets																									25.00%
London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument, Basis Spread on Variable Rate																										1.00%
Maximum [Member] | Covenant Requirement Minimum [Member]
Debt To Earnings Before Interest Tax Depreciation And Amortization Ratio																									6
Loan Agreement with Banco Industrial S.A. and Westrust Bank (International) Limited [Member]
Debt Instrument, Term				12 years
Debt Instrument, Face Amount				$ 42,000,000
Power Utilization | MWh				20
Debt Instrument, Payment Frequency				12 years
Long-term Debt, Gross																									$ 36,800,000
Loan Agreement with Banco Industrial S.A. and Westrust Bank (International) Limited [Member] | Historical [Member]
Debt Services, Coverage Ratio																									1.87
Loan Agreement with Banco Industrial S.A. and Westrust Bank (International) Limited [Member] | Projected [Member]
Debt Services, Coverage Ratio																									1.92
Loan Agreement with Banco Industrial S.A. and Westrust Bank (International) Limited [Member] | Covenant Requirement Minimum [Member]
Debt Services, Coverage Ratio				1.15
Loan Agreement with Banco Industrial S.A. and Westrust Bank (International) Limited [Member] | Covenant Required to not Limit Dividends [Member]
Debt Services, Coverage Ratio				1.25
Loan Agreement with Banco Industrial S.A. and Westrust Bank (International) Limited [Member] | London Interbank Offered Rate (LIBOR) [Member] | Guaranteed [Member]
Debt Instrument, Basis Spread on Variable Rate				4.35%
Loan Agreement with Banco Industrial S.A. and Westrust Bank (International) Limited [Member] | London Interbank Offered Rate (LIBOR) [Member] | Not Guaranteed [Member]
Debt Instrument, Basis Spread on Variable Rate				4.75%
Loan Agreement with Banco Industrial S.A. and Westrust Bank (International) Limited [Member] | Minimum [Member] | London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument, Basis Spread on Variable Rate				1.25%
Loan Agreement with OPIC [Member]
Debt Instrument, Face Amount																																		$ 310,000,000
Debt Services, Coverage Ratio																									1.7
Long-term Debt, Gross																									$ 246,600,000
Restricted Cash and Cash Equivalents, Current																									4,300,000	$ 7,200,000
Letters of Credit Outstanding, Amount																									$ 17,300,000
Loan Agreement with OPIC [Member] | In The First Two Years After The Plant2 Commercial Operation Date [Member]
Debt Instrument, Prepayment Premium Percentage																									2.00%
Loan Agreement with OPIC [Member] | Third Year After the Plant 2 Commercial Operation Date [Member]
Debt Instrument, Prepayment Premium Percentage																									1.00%
Loan Agreement with OPIC [Member] | Historical [Member]
Debt Services, Coverage Ratio																									2.69
Loan Agreement with OPIC [Member] | Projected [Member]
Debt Services, Coverage Ratio																									2.96
Loan Agreement with OPIC [Member] | Tranche One [Member]
Debt Instrument, Face Amount						$ 85,000,000
Long-term Debt, Gross																									$ 66,000,000
Debt Instrument, Interest Rate, Stated Percentage																									6.31%
Loan Agreement with OPIC [Member] | Tranche Two [Member]
Debt Instrument, Face Amount						180,000,000
Long-term Debt, Gross						135,000,000																			$ 142,900,000
Proceeds from Issuance of Debt					$ 45,000,000
Debt Instrument, Interest Rate, Stated Percentage																									2.00%
Loan Agreement with OPIC [Member] | Tranche Three [Member]
Debt Instrument, Face Amount						45,000,000
Long-term Debt, Gross																									$ 37,600,000
Proceeds from Issuance of Debt										$ 45,000,000
Debt Instrument, Interest Rate, Stated Percentage																									6.12%
Loan Agreement with OPIC [Member] | Threshold For Loan Default [Member]
Debt Services, Coverage Ratio																											1.1
Loan Agreement with OPIC [Member] | Minimum [Member] | Historical [Member]
Debt Services, Coverage Ratio																											1.4
Olkaria III DEG [Member]
Debt Instrument, Face Amount												$ 20,500,000					$ 77,000,000	$ 105,000,000
Debt Instrument, Basis Spread on Variable Rate																	4.00%
Long-term Debt, Gross																									$ 15,800,000
Proceeds from Issuance of Debt							$ 15,000,000											$ 90,000,000
Debt Instrument, Interest Rate, Stated Percentage																	6.90%
Olkaria III DEG [Member] | Tranche One [Member]
Prepayment Deposit On Debt						20,500,000
Prepayment Penalty Charges						$ 1,500,000
Olkaria III DEG [Member] | Subject to Fixed Interest Rate [Member] | Loans Payable [Member]
Secured Debt																									10,800,000
Olkaria III DEG [Member] | London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument, Basis Spread on Variable Rate												1.25%
Ormat Funding Corp [Member]
Debt Instrument, Face Amount																				$ 190,000,000
Proceeds from Issuance of Debt																				$ 179,700,000
Debt Instrument, Interest Rate, Stated Percentage																				8.25%
Restricted Cash and Cash Equivalents, Current																									2,100,000	1,400,000
Letters of Credit Outstanding, Amount																									$ 11,500,000	11,600,000
Debt Instrument, Issuance Costs																				$ 10,300,000
Ormat Funding Corp [Member] | Senior Notes [Member]
Debt Instrument, Repurchase Amount					$ 12,800,000																$ 6,800,000	$ 30,600,000										$ 13,200,000
Gain (Loss) on Extinguishment of Debt																					$ (600,000)	$ (1,700,000)	$ 300,000	$ 800,000
Ormat Funding Corp [Member] | Historical [Member]
Debt Services, Coverage Ratio																									1.25
Ormat Funding Corp [Member] | Projected [Member]
Debt Services, Coverage Ratio																									1.38
Ormat Funding Corp [Member] | Minimum [Member]
Debt Services, Coverage Ratio																				1.25
Ormat Funding Corp [Member] | Minimum [Member] | Senior Notes [Member]
Debt Instrument, Redemption Price, Percentage																									100.00%
Ormat Funding Corp [Member] | Maximum [Member] | Senior Notes [Member]
Debt Instrument, Redemption Price, Percentage																									101.00%
Ormat Funding Corp Senior Secured Notes [Member] | Senior Notes [Member]
Secured Debt																									$ 17,000,000	30,000,000
OrCal Senior Secured Notes [Member]
Debt Instrument, Face Amount																			$ 165,000,000
Proceeds from Issuance of Debt																			$ 161,100,000
Debt Instrument, Interest Rate, Stated Percentage																			6.21%
Restricted Cash and Cash Equivalents, Current																									1,900,000	1,600,000
Letters of Credit Outstanding, Amount																									$ 35,200,000	43,300,000
Debt Instrument, Issuance Costs																			$ 3,900,000
Debt Instrument, Redemption Price, Percentage																									100.00%
OrCal Senior Secured Notes [Member] | Historical [Member]
Debt Services, Coverage Ratio																									1.77
OrCal Senior Secured Notes [Member] | Projected [Member]
Debt Services, Coverage Ratio																									2.57
OrCal Senior Secured Notes [Member] | Debt Service Reserve Backing [Member]
Letters of Credit Outstanding, Amount																									$ 4,600,000	5,500,000
OrCal Senior Secured Notes [Member] | Minimum [Member]
Debt Services, Coverage Ratio																			1.25
OFC Two Senior Secured Notes [Member]
Debt Instrument, Face Amount																																				$ 350,000,000
Government Guarantee Percent																									80.00%
Debtor-in-Possession Financing, Letters of Credit Outstanding																									$ 21,000,000
OFC Two Senior Secured Notes [Member] | Wholly Owned Subsidiaries With Project Debt [Member]
Debt Instrument, Face Amount																															$ 140,000,000
Debt Instrument, Interest Rate, Stated Percentage																															4.61%
OFC Two Senior Secured Notes [Member] | Senior Notes [Member]
Secured Debt																									$ 247,200,000	$ 262,000,000
OFC Two Senior Secured Notes [Member] | Historical [Member]
Debt Services, Coverage Ratio																									2.09				2.49
OFC Two Senior Secured Notes [Member] | Projected [Member]
Debt Services, Coverage Ratio																									2.05				1.98
OFC Two Senior Secured Notes [Member] | Phase One Series A Senior Notes [Member]
Debt Instrument, Face Amount														$ 151,700,000
Proceeds from Issuance of Debt														$ 141,100,000
Debt Instrument, Interest Rate, Stated Percentage														4.687%
Repayments of Long-term Debt									$ 4,300,000
Other Reserves																									$ 9,700,000						$ 28,000,000
OFC Two Senior Secured Notes [Member] | McGinness Hills Phase II [Member]
Letters of Credit Outstanding, Amount																									$ 53,400,000
OFC Two Senior Secured Notes [Member] | Minimum [Member] | Historical [Member]
Debt Services, Coverage Ratio																									1.2
OFC Two Senior Secured Notes [Member] | Minimum [Member] | Projected [Member]
Debt Services, Coverage Ratio																									1.5
Don A. Cambell Senior Secured Notes [Member]
Debt Instrument, Face Amount		$ 92,500,000
Debt Services, Coverage Ratio																									1.85
Proceeds from Issuance of Debt		$ 87,100,000
Debt Instrument, Interest Rate, Stated Percentage		4.03%
Secured Debt																									$ 92,400,000
Debt Instrument, Minimum Prepay Amount		$ 2,000,000
Don A. Cambell Senior Secured Notes [Member] | Minimum [Member]
Debt Services, Coverage Ratio		1.2
Senior Unsecured Bonds [Member]
Debt Instrument, Face Amount			$ 204,000,000																																		$ 107,500,000	$ 142,000,000
Debt Instrument, Interest Rate, Stated Percentage																																					6.75%	7.00%
Proceeds from Issuance of Unsecured Debt			250,000,000
Senior Unsecured Bonds [Member] | Series 2 Bonds [Member]
Debt Instrument, Face Amount			67,000,000
Senior Unsecured Bonds [Member] | Series 3 Bonds [Member]
Debt Instrument, Face Amount			137,000,000
Senior Unsecured Bonds, Series 2 [Member]
Debt Instrument, Face Amount			$ 67,000,000
Debt Instrument, Interest Rate, Stated Percentage			3.70%
Senior Unsecured Bonds, Series 3 [Member]
Debt Instrument, Face Amount			$ 137,000,000
Debt Instrument, Interest Rate, Stated Percentage			4.45%
Institutional Investors [Member] | First Loan [Member]
Debt Instrument, Term																6 years
Debt Instrument, Face Amount																$ 20,000,000
Debt Instrument, Interest Rate, Stated Percentage																6.50%
Institutional Investors [Member] | Second Loan [Member]
Debt Instrument, Term																8 years
Debt Instrument, Face Amount																$ 20,000,000
Debt Instrument, Basis Spread on Variable Rate																5.00%
Long-term Line of Credit																									3,300,000
Institutional Investors [Member] | Third Loans [Member]
Debt Instrument, Term															6 years
Debt Instrument, Face Amount															$ 20,000,000
Debt Instrument, Interest Rate, Stated Percentage															5.75%
Debt Instrument, Repurchase Amount																														$ 6,200,000
DEG 2 Facility Agreement [Member]
Debt Instrument, Interest Rate, Stated Percentage	6.28%
Debt Instrument, Minimum Prepay Amount	$ 5,000,000
Long-term Line of Credit																									50,000,000
Line of Credit Facility, Maximum Borrowing Capacity																												$ 50,000,000
Proceeds from Lines of Credit	$ 50,000,000
Revolving Credit Lines with Commercial Banks [Member]
Long-term Line of Credit																									0
Line of Credit Facility, Maximum Borrowing Capacity																									524,800,000
Revolving Credit Lines with Commercial Banks [Member] | Extensions Of Credit In The Form Of Loans And/Or Letters of Credit [Member]
Line of Credit Facility, Maximum Borrowing Capacity																									215,000,000
Revolving Credit Lines with Commercial Banks [Member] | Issuance Of Letters Of Credit [Member]
Letters of Credit Outstanding, Amount																									$ 309,800,000
Union Bank, N.A. [Member]
Debt Services, Coverage Ratio																									2.54
Letters of Credit Outstanding, Amount																									$ 32,600,000
Line of Credit Facility, Maximum Borrowing Capacity																									$ 60,000,000
Debt To Earnings Before Interest Tax Depreciation And Amortization Ratio																									2.95
Amount Available For Dividend Distribution Percent Of Cumulative Net Income																									0.81
Union Bank, N.A. [Member] | Minimum [Member]
Debt Services, Coverage Ratio													1.35
Line of Credit Facility, Maximum Borrowing Capacity																																			$ 39,000,000
Union Bank, N.A. [Member] | Maximum [Member]
Line of Credit Facility, Maximum Borrowing Capacity													$ 60
Debt To Earnings Before Interest Tax Depreciation And Amortization Ratio													4.5
Amount Available For Dividend Distribution Percent Of Cumulative Net Income													2
HSBC Bank USA, N.A. [Member]
Debt Services, Coverage Ratio																									2.54
Letters of Credit Outstanding, Amount																									$ 23,200,000
Line of Credit Facility, Maximum Borrowing Capacity											$ 35,000,000														$ 35,000,000
Debt To Earnings Before Interest Tax Depreciation And Amortization Ratio																									2.95
Amount Available For Dividend Distribution Percent Of Cumulative Net Income																									0.81
Line of Credit Facility, Borrowing Capacity Increase											10,000,000
Line of Credit Facility, Capacity Available for Specific Purpose Other than for Trade Purchases											$ 10,000,000
HSBC Bank USA, N.A. [Member] | Minimum [Member]
Debt Services, Coverage Ratio											1.35
HSBC Bank USA, N.A. [Member] | Maximum [Member]
Debt To Earnings Before Interest Tax Depreciation And Amortization Ratio											4.5
Amount Available For Dividend Distribution Percent Of Cumulative Net Income											2