Note 5 - Fair Value of Financial Instruments (Tables)

9 Months Ended

Sep. 30, 2018

Notes Tables

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

				September 30, 2018
				Fair Value
	Carrying Value at September 30, 2018			Total			Level 1		Level 2			Level 3
	(Dollars in thousands)
Assets:
Current assets:
Cash equivalents (including restricted cash accounts)	$	15,941		$	15,941		$	15,941	$	—		$	—
Derivatives:
Contingent receivable (1)		105			105			—		—			105
Liabilities:
Current liabilities:
Derivatives:
Contingent payables (1)		(13,798	)		(13,798	)		—		—			(13,798	)
Currency forward contracts (2)		(210	)		(210	)		—		(210	)		—
	$	2,038		$	2,038		$	15,941	$	(210	)	$	(13,693	)

				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]

		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)	2018			2017			2018			2017
Put options on natural gas price	Derivatives and foreign currency transaction gains (losses)		—			(121	)		—			(362	)
Contingent considerations	Derivative and foreign currency transaction gains (losses)		—			(19	)		—			(114	)
Currency forward contracts	Derivative and foreign currency and transaction gains (losses)		(198	)		(887	)		(1,655	)		2,832
		$	(198	)	$	(1,027	)	$	(1,655	)	$	2,356

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

	Fair Value				Carrying Amount
	September 30, 2018		December 31, 2017		September 30, 2018		December 31, 2017
	(Dollars in millions)				(Dollars in millions)
Olkaria III Loan - OPIC		214.2		234.6		215.1		228.6
Olkaria IV Loan - DEG 2		50.1		50.7		50.0		50.0
Amatitlan Loan		30.8		32.8		30.6		33.3
Senior Secured Notes:
OrCal Geothermal Inc. ("OrCal")		24.7		34.2		24.0		32.1
OFC 2 LLC ("OFC 2")		215.9		234.6		221.8		232.5
Don A. Campbell 1 ("DAC 1")		79.0		85.5		84.7		88.3
USG Prudential - NV		29.4		—		28.2		—
USG Prudential - ID		18.7		—		18.9		—
USG DOE		47.2		—		51.4		—
Senior Unsecured Bonds		195.7		200.3		204.3		204.3
Senior Unsecured Loan		99.7		—		100.0		—
Other long-term debt		5.4		7.0		6.4		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		—		—		214.2		214.2
Olkaria IV - DEG 2		—		—		50.1		50.1
Amatitlan Loan		—		30.8		—		30.8
Senior Secured Notes:
OrCal Senior Secured Notes		—		—		24.7		24.7
OFC 2 Senior Secured Notes		—		—		215.9		215.9
DAC 1 Senior Secured Notes		—		—		79.0		79.0
USG Prudential - NV		—		—		29.4		29.4
USG Prudential - ID		—		—		18.7		18.7
USG DOE		—		—		47.2		47.2
Senior Unsecured Bonds		—		—		195.7		195.7
Senior Unsecured Loan		—		—		99.7		99.7
Other long-term debt		—		—		5.4		5.4
Revolving lines of credit		—		209.5		—		209.5
Deposits		14.2		—		—		14.2

	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:
OFC 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