Note 6 - Fair Value of Financial Instruments (Details) - Fair Value and Carrying Amount of Long-term Debt (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Note 6 - Fair Value of Financial Instruments (Details) - Fair Value and Carrying Amount of Long-term Debt [Line Items]
Loan from institutional investors	$ 23.3	$ 36.7
Olkaria III - DEG [Member]
Note 6 - Fair Value of Financial Instruments (Details) - Fair Value and Carrying Amount of Long-term Debt [Line Items]
Loan	40.3	48.8
Loan from institutional investors	40.3	48.8
Olkaria III - OPIC [Member]
Note 6 - Fair Value of Financial Instruments (Details) - Fair Value and Carrying Amount of Long-term Debt [Line Items]
Loan	279.6	220.0
Loan from institutional investors	279.6	220.0
Amatitlan Member
Note 6 - Fair Value of Financial Instruments (Details) - Fair Value and Carrying Amount of Long-term Debt [Line Items]
Loan	34.8	38.9
Loan from institutional investors	34.8	38.9
Ormat Funding Corp [Member]
Note 6 - Fair Value of Financial Instruments (Details) - Fair Value and Carrying Amount of Long-term Debt [Line Items]
Senior Secured Notes	83.5	105.0
Loan from institutional investors	83.5	105.0
Orcal Geothermal Inc [Member]
Note 6 - Fair Value of Financial Instruments (Details) - Fair Value and Carrying Amount of Long-term Debt [Line Items]
Senior Secured Notes	65.8	77.3
Loan from institutional investors	65.8	77.3
OFC Two Senior Secured Notes [Member]
Note 6 - Fair Value of Financial Instruments (Details) - Fair Value and Carrying Amount of Long-term Debt [Line Items]
Senior Secured Notes	119.0	131.2
Loan from institutional investors	119.0	131.2
Senior Unsecured Bonds Member
Note 6 - Fair Value of Financial Instruments (Details) - Fair Value and Carrying Amount of Long-term Debt [Line Items]
Senior Unsecured Bonds	270.6	273.2
Loan from institutional investors	270.6	273.2
Institutional Investors [Member]
Note 6 - Fair Value of Financial Instruments (Details) - Fair Value and Carrying Amount of Long-term Debt [Line Items]
Loan from institutional investors	20.1	27.7
Reported Value Measurement [Member] | Olkaria III - DEG [Member]
Note 6 - Fair Value of Financial Instruments (Details) - Fair Value and Carrying Amount of Long-term Debt [Line Items]
Loan	39.5	47.4
Reported Value Measurement [Member] | Olkaria III - OPIC [Member]
Note 6 - Fair Value of Financial Instruments (Details) - Fair Value and Carrying Amount of Long-term Debt [Line Items]
Loan	299.9	220.0
Reported Value Measurement [Member] | Amatitlan Member
Note 6 - Fair Value of Financial Instruments (Details) - Fair Value and Carrying Amount of Long-term Debt [Line Items]
Loan	31.5	34.3
Reported Value Measurement [Member] | Ormat Funding Corp [Member]
Note 6 - Fair Value of Financial Instruments (Details) - Fair Value and Carrying Amount of Long-term Debt [Line Items]
Senior Secured Notes	90.8	114.1
Reported Value Measurement [Member] | Orcal Geothermal Inc [Member]
Note 6 - Fair Value of Financial Instruments (Details) - Fair Value and Carrying Amount of Long-term Debt [Line Items]
Senior Secured Notes	66.2	76.5
Reported Value Measurement [Member] | OFC Two Senior Secured Notes [Member]
Note 6 - Fair Value of Financial Instruments (Details) - Fair Value and Carrying Amount of Long-term Debt [Line Items]
Senior Secured Notes	144.4	150.5
Reported Value Measurement [Member] | Senior Unsecured Bonds Member
Note 6 - Fair Value of Financial Instruments (Details) - Fair Value and Carrying Amount of Long-term Debt [Line Items]
Senior Unsecured Bonds	250.6	250.9
Reported Value Measurement [Member] | Institutional Investors [Member]
Note 6 - Fair Value of Financial Instruments (Details) - Fair Value and Carrying Amount of Long-term Debt [Line Items]
Loan from institutional investors	$ 19.5	$ 27.0