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	Mar. 31, 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	$ 21.7	$ 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	40.7	40.3
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	280.6	279.6
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	33.7	34.8
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	74.9	83.5
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]
Loans from institutional investors	67.1	65.8
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]
Loans from institutional investors	119.1	119.0
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	265.9	270.6
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	18.2	20.1
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	40.7	40.3
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	280.6	279.6
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	33.7	34.8
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	74.9	83.5
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	67.1	65.8
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	119.1	119.0
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	265.9	270.6
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	18.2	20.1
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	39.5	39.5
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	296.1	299.9
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	30.8	31.5
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	77.6	90.8
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	66.2	66.2
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	141.9	144.4
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	250.5	250.6
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	$ 17.7	$ 19.5