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	Jun. 30, 2014	Dec. 31, 2013
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	$ 16.7	$ 23.3
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]
Loans from institutional investors	36.2	40.3
Olkaria III - DEG [Member] | Estimate of Fair Value Measurement [Member]
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Long-term Debt Approximates Its Carrying Amount, Exceptions [Line Items]
Loan	36.2	40.3
Olkaria III - DEG [Member] | Reported Value Measurement [Member]
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Long-term Debt Approximates Its Carrying Amount, Exceptions [Line Items]
Loan	35.5	39.5
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]
Loans from institutional investors	279.4	279.6
Olkaria III - OPIC [Member] | Estimate of Fair Value Measurement [Member]
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Long-term Debt Approximates Its Carrying Amount, Exceptions [Line Items]
Loan	279.4	279.6
Olkaria III - OPIC [Member] | Reported Value Measurement [Member]
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Long-term Debt Approximates Its Carrying Amount, Exceptions [Line Items]
Loan	291.6	299.9
Amatitlan 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	32.6	34.8
Amatitlan Member | Estimate of Fair Value Measurement [Member]
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Long-term Debt Approximates Its Carrying Amount, Exceptions [Line Items]
Loan	32.6	34.8
Amatitlan Member | Reported Value Measurement [Member]
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Long-term Debt Approximates Its Carrying Amount, Exceptions [Line Items]
Loan	30.0	31.5
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]
Loans from institutional investors	70.0	83.5
Ormat Funding Corp [Member] | Estimate of Fair Value Measurement [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	70.0	83.5
Ormat Funding Corp [Member] | Reported Value Measurement [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	72.5	90.8
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]
Loans from institutional investors	63.3	65.8
Orcal Geothermal Inc [Member] | Estimate of Fair Value Measurement [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	63.3	65.8
Orcal Geothermal Inc [Member] | Reported Value Measurement [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	63.2	66.2
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]
Loans from institutional investors	115.5	119.0
OFC Two Senior Secured Notes [Member] | Estimate of Fair Value Measurement [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	115.5	119.0
OFC Two Senior Secured Notes [Member] | Reported Value Measurement [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	135.7	144.4
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]
Loans from institutional investors	270.5	270.6
Senior Unsecured Bonds Member | Estimate of Fair Value Measurement [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	270.5	270.6
Senior Unsecured Bonds Member | Reported Value Measurement [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	250.4	250.6
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	16.1	20.1
Institutional Investors [Member] | Estimate of Fair Value Measurement [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	16.1	20.1
Institutional Investors [Member] | Reported Value Measurement [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	$ 15.7	$ 19.5