Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments (USD $) In Millions, unless otherwise specified	Sep. 30, 2013
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments [Line Items]
Other long-term debt	$ 28.3
Revolving lines of credit	123.3
Deposits	21.0
Olkaria III - DEG [Member] \| Fair Value, Inputs, Level 3 [Member]
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments [Line Items]
Loan	44.7
Olkaria III - DEG [Member]
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments [Line Items]
Loan	44.7
Olkaria III - OPIC [Member] \| Fair Value, Inputs, Level 3 [Member]
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments [Line Items]
Loan	241.4
Olkaria III - OPIC [Member]
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments [Line Items]
Loan	241.4
Amatitlan Member \| Fair Value, Inputs, Level 3 [Member]
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments [Line Items]
Loan	35.7
Amatitlan Member
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments [Line Items]
Loan	35.7
Ormat Funding Corp [Member] \| Fair Value, Inputs, Level 2 [Member]
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments [Line Items]
Senior Secured Notes	88.5
Ormat Funding Corp [Member]
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments [Line Items]
Senior Secured Notes	88.5
Orcal Geothermal Inc [Member] \| Fair Value, Inputs, Level 3 [Member]
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments [Line Items]
Senior Secured Notes	74.8
Orcal Geothermal Inc [Member]
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments [Line Items]
Senior Secured Notes	74.8
OFC Two Senior Secured Notes [Member] \| Fair Value, Inputs, Level 3 [Member]
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments [Line Items]
Senior Secured Notes	121.3
OFC Two Senior Secured Notes [Member]
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments [Line Items]
Senior Secured Notes	121.3
Senior Unsecured Bonds Member \| Fair Value, Inputs, Level 3 [Member]
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments [Line Items]
Senior unsecured bonds	265.8
Senior Unsecured Bonds Member
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments [Line Items]
Senior unsecured bonds	265.8
Institutional Investors [Member] \| Fair Value, Inputs, Level 3 [Member]
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments [Line Items]
Loan from institutional investors	22.2
Institutional Investors [Member]
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments [Line Items]
Loan from institutional investors	22.2
Fair Value, Inputs, Level 1 [Member]
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments [Line Items]
Deposits	21.0
Fair Value, Inputs, Level 2 [Member]
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments [Line Items]
Other long-term debt	28.3
Revolving lines of credit	$ 123.3

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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