Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Long-term Debt Approximates Its Carrying Amount, Exceptions (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Olkaria III - DEG [Member]
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Long-term Debt Approximates Its Carrying Amount, Exceptions [Line Items]
Loan	$ 44.7
Olkaria III - OPIC [Member]
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Long-term Debt Approximates Its Carrying Amount, Exceptions [Line Items]
Loan	241.4
Amatitlan Member
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Long-term Debt Approximates Its Carrying Amount, Exceptions [Line Items]
Loan	35.7
Ormat Funding Corp [Member]
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Long-term Debt Approximates Its Carrying Amount, Exceptions [Line Items]
Senior Secured Notes	88.5
Orcal Geothermal Inc [Member]
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Long-term Debt Approximates Its Carrying Amount, Exceptions [Line Items]
Senior Secured Notes	74.8
OFC Two Senior Secured Notes [Member]
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Long-term Debt Approximates Its Carrying Amount, Exceptions [Line Items]
Senior Secured Notes	121.3
Senior Unsecured Bonds Member
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Long-term Debt Approximates Its Carrying Amount, Exceptions [Line Items]
Senior unsecured bonds	265.8
Institutional Investors [Member]
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Long-term Debt Approximates Its Carrying Amount, Exceptions [Line Items]
Loans from institutional investors	22.2
Estimate of Fair Value Measurement [Member] | Olkaria III - DEG [Member]
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Long-term Debt Approximates Its Carrying Amount, Exceptions [Line Items]
Loan	44.7	48.8
Estimate of Fair Value Measurement [Member] | Olkaria III - OPIC [Member]
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Long-term Debt Approximates Its Carrying Amount, Exceptions [Line Items]
Loan	241.4	220.0
Estimate of Fair Value Measurement [Member] | Amatitlan Member
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Long-term Debt Approximates Its Carrying Amount, Exceptions [Line Items]
Loan	35.7	38.9
Estimate of Fair Value Measurement [Member] | Ormat Funding Corp [Member]
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Long-term Debt Approximates Its Carrying Amount, Exceptions [Line Items]
Senior Secured Notes	88.5	105.0
Estimate of Fair Value Measurement [Member] | Orcal Geothermal Inc [Member]
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Long-term Debt Approximates Its Carrying Amount, Exceptions [Line Items]
Senior Secured Notes	74.8	77.3
Estimate of Fair Value Measurement [Member] | OFC Two Senior Secured Notes [Member]
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Long-term Debt Approximates Its Carrying Amount, Exceptions [Line Items]
Senior Secured Notes	121.3	131.2
Estimate of Fair Value Measurement [Member] | Senior Unsecured Bonds Member
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Long-term Debt Approximates Its Carrying Amount, Exceptions [Line Items]
Senior unsecured bonds	265.8	273.2
Estimate of Fair Value Measurement [Member] | Institutional Investors [Member]
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Long-term Debt Approximates Its Carrying Amount, Exceptions [Line Items]
Loans from institutional investors	22.2	27.7
Reported Value Measurement [Member] | Olkaria III - DEG [Member]
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Long-term Debt Approximates Its Carrying Amount, Exceptions [Line Items]
Loan	43.4	47.4
Reported Value Measurement [Member] | Olkaria III - OPIC [Member]
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Long-term Debt Approximates Its Carrying Amount, Exceptions [Line Items]
Loan	258.8	220.0
Reported Value Measurement [Member] | Amatitlan Member
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Long-term Debt Approximates Its Carrying Amount, Exceptions [Line Items]
Loan	32.2	34.3
Reported Value Measurement [Member] | Ormat Funding Corp [Member]
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Long-term Debt Approximates Its Carrying Amount, Exceptions [Line Items]
Senior Secured Notes	96.2	114.1
Reported Value Measurement [Member] | Orcal Geothermal Inc [Member]
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Long-term Debt Approximates Its Carrying Amount, Exceptions [Line Items]
Senior Secured Notes	74.0	76.5
Reported Value Measurement [Member] | OFC Two Senior Secured Notes [Member]
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Long-term Debt Approximates Its Carrying Amount, Exceptions [Line Items]
Senior Secured Notes	146.6	150.5
Reported Value Measurement [Member] | Senior Unsecured Bonds Member
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Long-term Debt Approximates Its Carrying Amount, Exceptions [Line Items]
Senior unsecured bonds	250.7	250.9
Reported Value Measurement [Member] | Institutional Investors [Member]
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Long-term Debt Approximates Its Carrying Amount, Exceptions [Line Items]
Loans from institutional investors	$ 21.5	$ 27.0