Note 5 - Fair Value of Financial Instruments (Tables)

6 Months Ended

Jun. 30, 2018

Notes Tables

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

				June 30, 2018
				Fair Value
	Carrying Value at June 30, 2018			Total			Level 1		Level 2			Level 3
	(Dollars in thousands)
Assets:
Current assets:
Cash equivalents (including restricted cash accounts)	$	19,069		$	19,069		$	19,069	$	—		$	—
Derivatives:
Contingent receivable (1)		106			106			—		—			106
Liabilities:
Current liabilities:
Derivatives:
Contingent payables (1)		(13,808	)		(13,808	)		—		—			(13,808	)
Currency forward contracts (2)		(507	)		(507	)		—		(507	)		—
	$	4,860		$	4,860		$	19,069	$	(507	)	$	(13,702	)

				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 hedging instruments	Location of recognized gain (loss)	Three Months Ended June 30,						Six Months Ended June 30,
		2018			2017			2018			2017
Put options on natural gas price	Derivatives and foreign transaction gains (losses)		—			(48	)		—			(241	)
Contingent considerations	Derivative and foreign transaction gains (losses)		—			(45	)		—			(95	)
Currency forward contracts	Derivative and foreign and transaction gains (losses)		(911	)		1,457			(1,457	)		3,719
		$	(911	)	$	1,364		$	(1,457	)	$	3,383

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

	Fair Value				Carrying Amount
	June 30, 2018		December 31, 2017		June 30, 2018		December 31, 2017
	(Dollars in millions)				(Dollars in millions)
Olkaria III Loan - OPIC		219.6		234.6		219.6		228.6
Olkaria IV Loan - DEG 2		49.5		50.7		50.0		50.0
Amatitlan Loan		31.7		32.8		31.5		33.3
Senior Secured Notes:
OrCal Geothermal Inc. ("OrCal")		28.7		34.2		27.3		32.1
OFC 2 LLC ("OFC 2")		219.2		234.6		224.2		232.5
Don A. Campbell 1 ("DAC 1")		79.9		85.5		85.3		88.3
USG Prudential - NV		29.7		—		28.3		—
USG Prudential - ID		18.6		—		18.9		—
USG DOE		49.0		—		53.0		—
Senior Unsecured Bonds		198.1		200.3		204.3		204.3
Senior Unsecured Loan		101.3		—		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		—		—		219.6		219.6
Olkaria IV - DEG 2		—		—		49.5		49.5
Amatitlan Loan		—		31.7		—		31.7
Senior Secured Notes:
OrCal Senior Secured Notes		—		—		28.7		28.7
OFC 2 Senior Secured Notes		—		—		219.2		219.2
DAC 1 Senior Secured Notes		—		—		79.9		79.9
USG Prudential - NV		—		—		29.7		29.7
USG Prudential - ID		—		—		18.6		18.6
USG DOE		—		—		49.0		49.0
Senior Unsecured Bonds		—		—		198.1		198.1
Senior Unsecured Loan		—		—		101.3		101.3
Other long-term debt		—		—		5.4		5.4
Revolving lines of credit		—		158.6		—		158.6
Deposits	19.3			—		—		19.3

	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