Note 7 - Fair Value of Financial Instruments (Tables)

12 Months Ended

Dec. 31, 2018

Notes Tables

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

				December 31, 2018
				Fair Value
	Carrying Value at December 31, 2018			Total			Level 1		Level 2			Level 3
	(Dollars in thousands)
Assets:
Current assets:
Cash equivalents (including restricted cash accounts)	$	18,787		$	18,787		$	18,787	$	—		$	—
Derivatives:
Contingent receivable (1)		104			104			—		—			104
Liabilities:
Current liabilities:
Derivatives:
Contingent payables (1)		(3,424	)		(3,424	)		—		—			(3,424	)
Currency forward contracts (2)		(1,040	)		(1,040	)		—		(1,040	)		—
	$	14,427		$	14,427		$	18,787	$	(1,040	)	$	(3,320	)

				December 31, 2017
				Fair Value
	Carrying Value at December 31, 2017			Total			Level 1		Level 2		Level 3
	(Dollars in thousands)
Assets
Current assets:
Cash equivalents (including restricted cash accounts)	$	18,359		$	18,359		$	18,359	$	—	$	—
Derivatives:
Contingent receivable (1)		108			108			—		—		108
Currency forward contracts (2)		992			992			—		992		—
Liabilities:
Current liabilities:
Derivatives:
Contingent payables (1)		(13,904	)		(13,904	)		—		—		(13,904	)
Warrants (1)		(3,967	)		(3,967	)		—		—		(3,967	)
	$	1,588		$	1,588		$	18,359	$	992	$	(17,763	)

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

Derivatives not designated as hedging instruments	Location of recognized gain (loss)	Amount of recognized gain (loss)
		2018			2017			2016
		(Dollars in thousands)
Put options on natural gas price	Derivative and foreign currency transaction gains (losses)	$	—		$	(350	)	$	—
Call options on natural gas price	Derivative and foreign currency transaction gains (losses)		—			—			(1,340	)
Call and put options on oil price	Derivative and foreign currency transaction gains (losses)		—			—			(1,313	)
Contingent considerations	Derivative and foreign currency transaction gains (losses)		170			(129	)		(1,527	)
Contingent considerations	General and administrative expenses		10,322			2,048			—
Currency forward contracts	Derivative and foreign currency transaction gains (losses)		(3,081	)		3,699			238
		$	7,411		$	5,268		$	(3,942	)

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

	Fair Value				Carrying Amount
	2018		2017		2018		2017
	(Dollars in millions)				(Dollars in millions)
Olkaria III Loan - OPIC		211.8		234.6		210.6		228.6
Olkaria IV Loan - DEG 2		47.2		50.7		47.5		50.0
Platanares Loan - OPIC		119.1		—		112.7		—
Amatitlan Loan		29.9		32.8		29.8		33.3
Senior Secured Notes:
OrCal Geothermal Inc. ("OrCal")	19.0			34.2		18.7		32.1
OFC 2 LLC ("OFC 2")		214.5		234.6		217.8		232.5
Don A. Campbell 1 ("DAC 1")		78.8		85.5		83.3		88.3
USG Prudential - NV		29.4		—		27.8		—
USG Prudential - ID		18.6		—		18.9		—
USG DOE		48.3		—		51.4		—
Senior Unsecured Bonds		199.4		200.3		204.3		204.3
Senior Unsecured Loan		102.2		—		100.0		—
Other long-term debt		5.4		7.0		6.2		7.9

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

	Level 1		Level 2		Level 3		Total
	(Dollars in millions)
Olkaria III - OPIC		—		—		211.8		211.8
Olkaria IV - DEG 2		—		—		47.2		47.2
Platanares Loan - OPIC		—		—		119.1		119.1
Amatitlan Loan		—		29.9		—		29.9
Senior Secured Notes:
OrCal Senior Secured Notes		—		—		19.0		19.0
OFC 2 Senior Secured Notes		—		—		214.5		214.5
DAC 1 Senior Secured Notes		—		—		78.8		78.8
USG Prudential - NV		—		—		29.4		29.4
USG Prudential - ID		—		—		18.6		18.6
USG DOE		—		—		48.3		48.3
Senior Unsecured Bonds		—		—		199.4		199.4
Senior Unsecured Loan		—		—		102.2		102.2
Other long-term debt		—		—		5.4		5.4
Revolving lines of credit		—		159.0		—		159.0
Deposits		12.0		—		—		12.0

	Level 1		Level 2		Level 3		Total
	(Dollars in millions)
Olkaria III Loan - OPIC	$	—	$	—	$	234.6	$	234.6
Olkaria IV - DEG 2						50.7		50.7
Amatitlan Loan		—		32.8		—		32.8
Senior Secured Notes:
OrCal Senior Secured Notes		—		—		34.2		34.2
OFC 2 Senior Secured Notes		—		—		234.6		234.6
DAC 1 Senior Secured Notes		—		—		85.5		85.5
Senior Unsecured Bonds		—		—		200.3		200.3
Other long-term debt		—		—		7.0		7.0
Revolving lines of credit		—		51.5		—		51.5
Deposits		15.6		—		—		15.6