Note 5 - Fair Value of Financial Instruments - Fair Value of Financial Instruments (Details) - USD ($) $ in Millions | Jun. 30, 2017 | Dec. 31, 2016 |
Deposits | $ 15.9 | $ 14.4 |
Revolving lines of credit | 30 | |
Fair Value, Inputs, Level 1 [Member] | | |
Deposits | 15.9 | 14.4 |
Revolving lines of credit | | |
Fair Value, Inputs, Level 2 [Member] | | |
Deposits | | |
Revolving lines of credit | 30 | |
Fair Value, Inputs, Level 3 [Member] | | |
Deposits | | |
Revolving lines of credit | | |
Olkaria III DEG [Member] | | |
Fair value levels-secured, unsecured and long term debt | 12.5 | 16.3 |
Olkaria III DEG [Member] | Fair Value, Inputs, Level 1 [Member] | | |
Fair value levels-secured, unsecured and long term debt | | |
Olkaria III DEG [Member] | Fair Value, Inputs, Level 2 [Member] | | |
Fair value levels-secured, unsecured and long term debt | | |
Olkaria III DEG [Member] | Fair Value, Inputs, Level 3 [Member] | | |
Fair value levels-secured, unsecured and long term debt | 12.5 | 16.3 |
Olkaria III OPIC [Member] | | |
Fair value levels-secured, unsecured and long term debt | 247.8 | 253.4 |
Olkaria III OPIC [Member] | Fair Value, Inputs, Level 1 [Member] | | |
Fair value levels-secured, unsecured and long term debt | | |
Olkaria III OPIC [Member] | Fair Value, Inputs, Level 2 [Member] | | |
Fair value levels-secured, unsecured and long term debt | | |
Olkaria III OPIC [Member] | Fair Value, Inputs, Level 3 [Member] | | |
Fair value levels-secured, unsecured and long term debt | 247.8 | 253.4 |
Olkaria IV Loan - DEG 2 [Member] | | |
Fair value levels-secured, unsecured and long term debt | 51.7 | 50.9 |
Olkaria IV Loan - DEG 2 [Member] | Fair Value, Inputs, Level 1 [Member] | | |
Fair value levels-secured, unsecured and long term debt | | |
Olkaria IV Loan - DEG 2 [Member] | Fair Value, Inputs, Level 2 [Member] | | |
Fair value levels-secured, unsecured and long term debt | | |
Olkaria IV Loan - DEG 2 [Member] | Fair Value, Inputs, Level 3 [Member] | | |
Fair value levels-secured, unsecured and long term debt | 51.7 | 50.9 |
Amatitlan Loan [Member] | | |
Fair value levels-secured, unsecured and long term debt | 35.1 | 37.3 |
Amatitlan Loan [Member] | Fair Value, Inputs, Level 1 [Member] | | |
Fair value levels-secured, unsecured and long term debt | | |
Amatitlan Loan [Member] | Fair Value, Inputs, Level 2 [Member] | | |
Fair value levels-secured, unsecured and long term debt | 35.1 | 37.3 |
Amatitlan Loan [Member] | Fair Value, Inputs, Level 3 [Member] | | |
Fair value levels-secured, unsecured and long term debt | | |
Ormat Funding Corp [Member] | | |
Fair value levels-secured, unsecured and long term debt | 14.3 | 17 |
Ormat Funding Corp [Member] | Fair Value, Inputs, Level 1 [Member] | | |
Fair value levels-secured, unsecured and long term debt | | |
Ormat Funding Corp [Member] | Fair Value, Inputs, Level 2 [Member] | | |
Fair value levels-secured, unsecured and long term debt | 14.3 | 17 |
Ormat Funding Corp [Member] | Fair Value, Inputs, Level 3 [Member] | | |
Fair value levels-secured, unsecured and long term debt | | |
Orcal Geothermal Inc [Member] | | |
Fair value levels-secured, unsecured and long term debt | 33.8 | 37.4 |
Orcal Geothermal Inc [Member] | Fair Value, Inputs, Level 1 [Member] | | |
Fair value levels-secured, unsecured and long term debt | | |
Orcal Geothermal Inc [Member] | Fair Value, Inputs, Level 2 [Member] | | |
Fair value levels-secured, unsecured and long term debt | | |
Orcal Geothermal Inc [Member] | Fair Value, Inputs, Level 3 [Member] | | |
Fair value levels-secured, unsecured and long term debt | 33.8 | 37.4 |
OFC Two Senior Secured Notes [Member] | | |
Fair value levels-secured, unsecured and long term debt | 245.1 | 249 |
OFC Two Senior Secured Notes [Member] | Fair Value, Inputs, Level 1 [Member] | | |
Fair value levels-secured, unsecured and long term debt | | |
OFC Two Senior Secured Notes [Member] | Fair Value, Inputs, Level 2 [Member] | | |
Fair value levels-secured, unsecured and long term debt | | |
OFC Two Senior Secured Notes [Member] | Fair Value, Inputs, Level 3 [Member] | | |
Fair value levels-secured, unsecured and long term debt | 245.1 | 249 |
Don A. Campbell 1 ("DAC1") [Member] | | |
Fair value levels-secured, unsecured and long term debt | 88.7 | 88.9 |
Don A. Campbell 1 ("DAC1") [Member] | Fair Value, Inputs, Level 1 [Member] | | |
Fair value levels-secured, unsecured and long term debt | | |
Don A. Campbell 1 ("DAC1") [Member] | Fair Value, Inputs, Level 2 [Member] | | |
Fair value levels-secured, unsecured and long term debt | | |
Don A. Campbell 1 ("DAC1") [Member] | Fair Value, Inputs, Level 3 [Member] | | |
Fair value levels-secured, unsecured and long term debt | 88.7 | 88.9 |
Senior Unsecured Bonds [Member] | | |
Fair value levels-secured, unsecured and long term debt | 203.3 | 200.1 |
Senior Unsecured Bonds [Member] | Fair Value, Inputs, Level 1 [Member] | | |
Fair value levels-secured, unsecured and long term debt | | |
Senior Unsecured Bonds [Member] | Fair Value, Inputs, Level 2 [Member] | | |
Fair value levels-secured, unsecured and long term debt | | |
Senior Unsecured Bonds [Member] | Fair Value, Inputs, Level 3 [Member] | | |
Fair value levels-secured, unsecured and long term debt | 203.3 | 200.1 |
Other Long-term Debt [Member] | | |
Fair value levels-secured, unsecured and long term debt | 8.9 | 10.4 |
Other Long-term Debt [Member] | Fair Value, Inputs, Level 1 [Member] | | |
Fair value levels-secured, unsecured and long term debt | | |
Other Long-term Debt [Member] | Fair Value, Inputs, Level 2 [Member] | | |
Fair value levels-secured, unsecured and long term debt | 1.7 | 3.3 |
Other Long-term Debt [Member] | Fair Value, Inputs, Level 3 [Member] | | |
Fair value levels-secured, unsecured and long term debt | $ 7.2 | $ 7.1 |