OPC TRANSACTION - Additional Information (Detail) (Ormat Nevada, OPC LLC, USD $) In Millions, unless otherwise specified	1 Months Ended			12 Months Ended
	Feb. 03, 2011	Oct. 30, 2009	Jun. 30, 2007 Entity	Dec. 31, 2009	Dec. 31, 2008	Dec. 31, 2007	Dec. 31, 2010
Ormat Nevada, OPC LLC
Schedule of Investments [Line Items]
Number of geothermal power plants			4
Amount paid by investors at the first closing in 2007 and second closing in 2008					$ 63.0	$ 71.8
Percentage of ownership interests, on the flip date							95.00%
Percentage of ownership interests by minority investor, on the flip date							5.00%
Percentage of ownership interests							75.00%
Percentage of ownership interests by minority investor							25.00%
Payment to acquire membership units		18.5
Pre-tax gain resulted from acquisition of membership units				13.3
Amount reclassified from noncontrolling interest to additional paid-in capital				1.1
Percentage of Ownership Interests Purchased from Lehman-OPC				1.50%
Proceeds from sale of membership units	24.9
Amount reclassified from additional paid-in capital to noncontrolling interest	$ 2.3
Percentage of Ownership Interests sold to JPM Capital Corporation	1.50%