Note 5 - Fair Value of Financial Instruments (Tables)

9 Months Ended

Sep. 30, 2015

Fair Value Disclosures [Abstract]

Fair Value, by Balance Sheet Grouping [Table Text Block]

				September 30, 2015
				Fair Value
	Carrying Value at September 30, 2015			Total			Level 1		Level 2			Level 3
	(Dollars in thousands)
Assets:
Current assets:
Cash equivalents (including restricted cash accounts)	$	44,187		$	44,187		$	44,187	$	—		$	—
Derivatives:
Swap transaction on natural gas price (1)		223			223			—		223			—
Liabilities:
Current liabilities:
Derivatives:
Currency forward contracts (2)		(1,548	)		(1,548	)		—		(1,548	)		—
	$	42,862		$	42,862		$	44,187	$	(1,325	)	$	—

				December 31, 2014
				Fair Value
	Carrying Value at December 31, 2014			Total			Level 1		Level 2			Level 3
	(Dollars in thousands)
Assets
Current assets:
Cash equivalents (including restricted cash accounts)	$	85,076		$	85,076		$	85,076	$	—		$	—
Derivatives:
Swap transaction on natural gas price (1)		4,129			4,129			—		4,129			—
Liabilities:
Current liabilities:
Derivatives:
Currency forward contracts (2)		(2,882	)		(2,882	)		—		(2,882	)		—
	$	86,323		$	86,323		$	85,076	$	1,247		$	—

Derivative Instruments, Gain (Loss) [Table Text Block]

		Amount of recognized gain (loss)
Derivatives not designated as	Location of recognized gain	Three Months Ended September 30,					Nine Months Ended September 30,
hedging instruments	(loss)	2015		2014			2015			2014
Swap transaction on oil price	Electricity revenue		—		1,657			—			1,885
Swap transactions on natural gas price	Electricity revenue		369		2,295			767			(609	)
Currency forward contracts	Foreign currency translation and transaction gains (losses)		869		(2,422	)		(1,349	)		(2,430	)
		$	1,238	$	1,530		$	(582	)	$	(1,154	)

Schedule of Carrying Values and Estimated Fair Values of Debt Instruments [Table Text Block]

	Fair Value				Carrying Amount
	September 30, 2015		December 31, 2014		September 30, 2015		December 31, 2014
	(Dollars in millions)				(Dollars in millions)
Olkaria III Loan - DEG	$	28.5	$	32.2	$	27.6	$	31.6
Olkaria III Loan - OPIC		266.4		279.4		269.1		282.6
Amatitlan Loan		43.2		—		41.1		—
Senior Secured Notes:
Ormat Funding Corp. ("OFC")		36.0		71.4		33.3		67.2
OrCal Geothermal Inc. ("OrCal")		53.3		55.5		51.8		55.1
OFC 2 LLC ("OFC 2")		234.2		238.8		266.0		272.5
Senior Unsecured Bonds		262.0		265.4		250.1		250.4
Loan from institutional investors		6.2		12.2		6.0		11.9

Fair Value, Liabilities Measured on Recurring and Nonrecurring Basis [Table Text Block]

	Level 1		Level 2		Level 3		Total
	(Dollars in millions)
Olkaria III - DEG	$	—	$	—	$	28.5	$	28.5
Olkaria III - OPIC		—		—		266.4		266.4
Amatitlan loan		—		43.2		—		43.2
Senior Secured Notes:
OFC		—		36.0		—		36.0
OrCal		—		—		53.3		53.3
OFC 2		—		—		234.2		234.2
Senior unsecured bonds		—		—		262.0		262.0
Loan from institutional investors		—		—		6.2		6.2
Other long-term debt		—		8.3		—		8.3
Deposits		15.8		—		—		15.8

	Level 1		Level 2		Level 3		Total
	(Dollars in millions)
Olkaria III Loan - DEG	$	—	$	—	$	32.2	$	32.2
Olkaria III Loan - OPIC		—		—		279.4		279.4
Senior Secured Notes:
OFC		—		71.4		—		71.4
OrCal		—		—		55.5		55.5
OFC 2		—		—		238.8		238.8
Senior unsecured bonds		—		—		265.4		265.4
Loan from institutional investors		—		—		12.2		12.2
Other long-term debt		—		10.0		—		10.0
Revolving lines of credit		—		20.3		—		20.3
Deposits		17.3		—		—		17.3