INCOME TAXES - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Dec. 31, 2010
Reconciliation of Statutory Federal Tax Rate [Line Items]
Effective tax rate	39.70%	26.90%	711.80%	18.00%
Federal statutory rate	35.00%	35.00%	35.00%	35.00%
Deferred tax assets					$ 18.1
Maximum | ISRAEL | Ormat Systems Ltd | First benefited investment
Reconciliation of Statutory Federal Tax Rate [Line Items]
Income Tax Rate			25.00%
Maximum | ISRAEL | Ormat Systems Ltd | Second benefited investment
Reconciliation of Statutory Federal Tax Rate [Line Items]
Income Tax Rate			25.00%
ISRAEL | Ormat Systems Ltd
Reconciliation of Statutory Federal Tax Rate [Line Items]
Effective Income Tax Rate, Year One and Year two			15.00%
Effective Income Tax Rate, Year Three and Year Four			12.50%
Effective Income Tax Rate, Year Five and Thereafter			12.00%
Reduction in deferred taxes due to change in tax law			$ 0.5
ISRAEL | Ormat Systems Ltd | First benefited investment
Reconciliation of Statutory Federal Tax Rate [Line Items]
Income tax exemption period	2 years		2 years
Additional reduced income tax period	5 years		5 years
ISRAEL | Ormat Systems Ltd | Second benefited investment
Reconciliation of Statutory Federal Tax Rate [Line Items]
Income tax exemption period	2 years		2 years
Additional reduced income tax period	5 years		5 years