Long-Term Debt (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Debt Instrument [Line Items]
Limited and Non Recourse Debt	$ 476,753	$ 361,024
Less current portion	(35,011)	(36,010)
Non current portion	441,742	325,014
Full recourse agreements	548,257	428,645
Less current portion	(20,543)	(13,010)
Non current portion	527,714	415,635
Senior loans (Zunil power plant)
Debt Instrument [Line Items]
Non-recourse agreement		1,713
Loan agreement (Olkaria III power plant)
Debt Instrument [Line Items]
Non-recourse agreement	77,368	88,420
Loan agreement ( Amatitlan power plant)
Debt Instrument [Line Items]
Non-recourse agreement	36,764	39,019
Ormat Funding Corp. ("OFC")
Debt Instrument [Line Items]
Senior Secured Notes (non-recourse)	125,022	136,312
OrCal Geothermal Inc. ("OrCal")
Debt Instrument [Line Items]
Senior Secured Notes (non-recourse)	85,860	95,560
OFC 2 Senior Secured Notes
Debt Instrument [Line Items]
Senior Secured Notes (non-recourse)	151,739
Senior Unsecured Bonds
Debt Instrument [Line Items]
Full recourse agreements	250,042	142,003
Institutional Investors
Debt Instrument [Line Items]
Full recourse agreements	54,166	57,176
Commercial bank
Debt Instrument [Line Items]
Full recourse agreements	30,000	40,000
Revolving Credit Facility
Debt Instrument [Line Items]
Full recourse agreements	$ 214,049	$ 189,466