Note 11 - Long-term Debt and Credit Agreements - Long-term Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Limited Resource	$ 775,547	$ 622,145
	775,547	622,145
Less current portion	(63,180)	(54,720)
Non current portion	712,367	567,425
Recourse Debt	510,832	306,419
Less current portion	(164,000)	(54,587)
Non current portion	346,832	251,832
Other Loans, Limited and Non-recourse [Member]
Non-Recourse Debt	6,241	7,252
Loan Agreement With OPIC the Olkaria III Power Plant [Member]
Non-Recourse Debt	210,641	228,635
Platanares Loan - OPIC [Member]
Non-Recourse Debt	112,652
Loan Agreement with Banco Industrial S.A. and Westrust Bank (International) Limited [Member]
Non-Recourse Debt	29,750	33,251
OrCal Geothermal Inc [Member]
Non-Recourse Debt	18,652	32,142
Don A. Campbell 1 ("DAC1") [Member]
Non-Recourse Debt	83,319	88,339
Ormat Funding Corp [Member]
Limited Resource	217,810	232,526
	217,810	232,526
Other Loans, Limited Resource [Member]
Limited Resource	96,482
	96,482
Senior Unsecured Bonds [Member]
Recourse Debt	204,332	204,332
Migdal Loan [Member]
Recourse Debt	100,000
Olkaria III DEG [Member]
Recourse Debt	47,500	50,000
Loan From Commercial Bank [Member]
Recourse Debt		587
Revolving Credit Lines With Banks [Member]
Recourse Debt	$ 159,000	$ 51,500