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, 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	$ 15.0	$ 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	36.6	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	36.6	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	276.8	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	276.8	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	287.1	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		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		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		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	78.0	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	78.0	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	64.3	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	64.3	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	233.9	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	233.9	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	274.5	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	264.9	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	264.9	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	14.2	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	14.2	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	$ 13.9	$ 19.5