Note 6 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Note 6 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments [Line Items]
Other long-term debt	$ 23.3	$ 36.7
Revolving lines of credit	112.0	73.6
Deposits	21.3	21.7
Olkaria III - DEG [Member] | Fair Value, Inputs, Level 3 [Member]
Note 6 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments [Line Items]
Other long-term debt	40.3	48.8
Olkaria III - DEG [Member]
Note 6 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments [Line Items]
Other long-term debt	40.3	48.8
Olkaria III - OPIC [Member] | Fair Value, Inputs, Level 3 [Member]
Note 6 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments [Line Items]
Other long-term debt	279.6	220.0
Olkaria III - OPIC [Member]
Note 6 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments [Line Items]
Other long-term debt	279.6	220.0
Amatitlan Member | Fair Value, Inputs, Level 3 [Member]
Note 6 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments [Line Items]
Other long-term debt	34.8	38.9
Amatitlan Member
Note 6 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments [Line Items]
Other long-term debt	34.8	38.9
Ormat Funding Corp [Member] | Fair Value, Inputs, Level 2 [Member]
Note 6 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments [Line Items]
Other long-term debt	83.5	105.0
Ormat Funding Corp [Member]
Note 6 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments [Line Items]
Other long-term debt	83.5	105.0
Orcal Geothermal Inc [Member] | Fair Value, Inputs, Level 3 [Member]
Note 6 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments [Line Items]
Other long-term debt	65.8	77.3
Orcal Geothermal Inc [Member]
Note 6 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments [Line Items]
Other long-term debt	65.8	77.3
OFC Two Senior Secured Notes [Member] | Fair Value, Inputs, Level 3 [Member]
Note 6 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments [Line Items]
Other long-term debt	119.0	131.2
OFC Two Senior Secured Notes [Member]
Note 6 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments [Line Items]
Other long-term debt	119.0	131.2
Senior Unsecured Bonds Member | Fair Value, Inputs, Level 3 [Member]
Note 6 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments [Line Items]
Other long-term debt	270.6	273.2
Senior Unsecured Bonds Member
Note 6 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments [Line Items]
Other long-term debt	270.6	273.2
Institutional Investors [Member] | Fair Value, Inputs, Level 3 [Member]
Note 6 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments [Line Items]
Other long-term debt	20.1	27.7
Institutional Investors [Member]
Note 6 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments [Line Items]
Other long-term debt	20.1	27.7
Fair Value, Inputs, Level 1 [Member]
Note 6 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments [Line Items]
Deposits	21.3	21.7
Fair Value, Inputs, Level 2 [Member]
Note 6 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments [Line Items]
Other long-term debt	23.3	36.7
Revolving lines of credit	$ 112.0	$ 73.6