Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments (USD $) In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments [Line Items]
Fair value levels-secured,unsecured and long term debt	$ 15.0	$ 23.3
Revolving credit lines with banks	28.1	112.0
Deposits	21.7	21.3
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]
Fair value levels-secured,unsecured and long term debt	36.6	40.3
Olkaria III - DEG [Member]
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments [Line Items]
Fair value levels-secured,unsecured and long term debt	36.6	40.3
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]
Fair value levels-secured,unsecured and long term debt	276.8	279.6
Olkaria III - OPIC [Member]
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments [Line Items]
Fair value levels-secured,unsecured and long term debt	276.8	279.6
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]
Fair value levels-secured,unsecured and long term debt		83.5
Ormat Funding Corp [Member] | Fair Value, Inputs, Level 3 [Member]
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments [Line Items]
Fair value levels-secured,unsecured and long term debt	78.0
Ormat Funding Corp [Member]
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments [Line Items]
Fair value levels-secured,unsecured and long term debt	78.0	83.5
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]
Fair value levels-secured,unsecured and long term debt	64.3	65.8
Orcal Geothermal Inc [Member]
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments [Line Items]
Fair value levels-secured,unsecured and long term debt	64.3	65.8
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]
Fair value levels-secured,unsecured and long term debt	233.9	119.0
OFC Two Senior Secured Notes [Member]
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments [Line Items]
Fair value levels-secured,unsecured and long term debt	233.9	119.0
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]
Fair value levels-secured,unsecured and long term debt	264.9	270.6
Senior Unsecured Bonds Member
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments [Line Items]
Fair value levels-secured,unsecured and long term debt	264.9	270.6
Institutional Investors [Member] | Fair Value, Inputs, Level 3 [Member]
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments [Line Items]
Fair value levels-secured,unsecured and long term debt	14.2	20.1
Institutional Investors [Member]
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments [Line Items]
Fair value levels-secured,unsecured and long term debt	14.2	20.1
Amatitlan Member | Fair Value, Inputs, Level 3 [Member]
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments [Line Items]
Fair value levels-secured,unsecured and long term debt		34.8
Amatitlan Member
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments [Line Items]
Fair value levels-secured,unsecured and long term debt		34.8
Fair Value, Inputs, Level 1 [Member]
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments [Line Items]
Deposits	21.7	21.3
Fair Value, Inputs, Level 2 [Member]
Note 5 - Fair Value of Financial Instruments (Details) - Fair Value of Financial Instruments [Line Items]
Fair value levels-secured,unsecured and long term debt	15.0	23.3
Revolving credit lines with banks	$ 28.1	$ 112.0