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, 2013	Dec. 31, 2012
Olkaria III [Member]
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Long-term Debt Approximates Its Carrying Amount, Exceptions [Line Items]
Loan	$ 44.6
Amatitlan Member
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Long-term Debt Approximates Its Carrying Amount, Exceptions [Line Items]
Loan	36.9
Ormat Funding Corp [Member]
Senior secured notes:
Senior Secured Notes	93.2
Orcal Geothermal Inc [Member]
Senior secured notes:
Senior Secured Notes	79.6
OFC Two Senior Secured Notes [Member]
Senior secured notes:
Senior Secured Notes	128.7
Senior Unsecured Bonds Member
Senior secured notes:
Senior unsecured bonds	273.1
Institutional Investors [Member]
Senior secured notes:
Loans from institutional investors	24.0
Estimate of Fair Value Measurement [Member] | Olkaria III [Member]
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Long-term Debt Approximates Its Carrying Amount, Exceptions [Line Items]
Loan	44.6	48.8
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	36.9	38.9
Estimate of Fair Value Measurement [Member] | Ormat Funding Corp [Member]
Senior secured notes:
Senior Secured Notes	93.2	105.0
Estimate of Fair Value Measurement [Member] | Orcal Geothermal Inc [Member]
Senior secured notes:
Senior Secured Notes	79.6	77.3
Estimate of Fair Value Measurement [Member] | OFC Two Senior Secured Notes [Member]
Senior secured notes:
Senior Secured Notes	128.7	131.2
Estimate of Fair Value Measurement [Member] | Senior Unsecured Bonds Member
Senior secured notes:
Senior unsecured bonds	273.1	273.2
Estimate of Fair Value Measurement [Member] | Institutional Investors [Member]
Senior secured notes:
Loans from institutional investors	24.0	27.7
Reported Value Measurement [Member] | Olkaria III [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] | Amatitlan Member
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Long-term Debt Approximates Its Carrying Amount, Exceptions [Line Items]
Loan	32.9	34.3
Reported Value Measurement [Member] | Ormat Funding Corp [Member]
Senior secured notes:
Senior Secured Notes	101.3	114.1
Reported Value Measurement [Member] | Orcal Geothermal Inc [Member]
Senior secured notes:
Senior Secured Notes	76.5	76.5
Reported Value Measurement [Member] | OFC Two Senior Secured Notes [Member]
Senior secured notes:
Senior Secured Notes	149.7	150.5
Reported Value Measurement [Member] | Senior Unsecured Bonds Member
Senior secured notes:
Senior unsecured bonds	250.8	250.9
Reported Value Measurement [Member] | Institutional Investors [Member]
Senior secured notes:
Loans from institutional investors	$ 23.3	$ 27.0