Inventory Disclosure [Text Block]

NOTE

3

— INVENTORIES

Inventories consist of the following:

	September 30,		December 31,
	2017		2016
	(Dollars in thousands)
Raw materials and purchased parts for assembly	$	9,461	$	5,429
Self-manufactured assembly parts and finished products		9,224		6,571
Total	$	18,685	$	12,000

Note 4 - Unconsolidated Investments

9 Months Ended

Sep. 30, 2017

Equity Method Investments and Joint Ventures Disclosure [Text Block]

NOTE

4

— UNCONSOLIDATED INVESTMENTS

Unconsolidated investments consist of the following:

	September 30,		December 31,
	2017		2016
	(Dollars in thousands)
Sarulla	$	25,367	$	(11,081	)

The Sarulla Project

The Company holds a

12.75%

equity interest in a consortium which is in the process of developing the Sarulla geothermal power project in Indonesia with an expected generating capacity of approximately

330

MW. The Sarulla project is located in Tapanuli Utara, North Sumatra, Indonesia and is owned and operated by the consortium members under the framework of a joint operating contract and energy sales contract that were both signed on

April 4, 2013.

Under the joint operating contract, PT Pertamina Geothermal Energy, the concession holder for the project, has provided the consortium with the right to use the geothermal field, and under the energy sales contract, PT PLN, the state electric utility, is the off-taker at Sarulla for a period of

30

years. In addition to its equity interest in the consortium, the Company designed the Sarulla power plant and supplies its Ormat energy converters to the power plant pursuant to a supply agreement that was signed in

October 2013,

as further described below.

The project is being constructed in

three

phases of approximately

110

MW each, utilizing both steam and brine extracted from the geothermal field to increase the power plant

’s efficiency. The

first

phase of the power plant commenced commercial operation on

March 17, 2017

and is performing well, demonstrating its ability to produce geothermal power in excess of its design capacity. The

second

phase of the power plant commenced commercial operation on

October 2, 2017.

Construction work on the

third

phase of the power plant is progressing and on schedule although the gathering piping system

may

face some delays. The Company has achieved all of its contractual milestones under the Supply Agreement. Drilling for the

third

phase of the power plant is ongoing and the project has achieved to date, based on preliminary estimates,

100%

of the required injection capacity and approximately

85%

of the required production capacity.

On

May 16, 2014,

the consortium closed

$1.17

billion in financing for the development of the Sarulla project with a consortium of lenders comprised of Japan Bank for International Cooperation (“JBIC”), the Asian Development Bank and

six

commercial banks and obtained construction and term loans on a limited recourse basis backed by a political risk guarantee from JBIC. Of the

$1.17

billion,

$0.1

billion (which was drawn down by the Sarulla project company on

May 23, 2014)

bears interest at a fixed rate and

$1.07

billion bears interest at a rate linked to LIBOR. The project has missed several milestones under the financing documents, but, in each case, has either already received, or expects to receive in the near future, waivers from the lenders. The project experienced delays in field development and cost overruns resulting from delays and excess drilling costs. Due to the cost overruns in drilling, the lenders

may

request that the project sponsors contribute additional equity to the project.

The Sarulla consortium entered into interest rate swap agreements with various international banks, effective as of

June 4, 2014,

in order to fix the interest rate linked to LIBOR on up to

$0.96

billion of the

$1.07

billion portion of the financing arrangement subject to such interest rate at

3.4565%.

The Sarulla project company accounted for the interest rate swap as a cash flow hedge upon which changes in the fair value of the hedging instrument, relative to the effective portion, are recorded in other comprehensive income. During the

three

and

nine

months ended

September 30, 2017,

the Sarulla project company recorded gains of

$4.8

million and

$2.1

million, respectively, net of deferred tax, of which the Company

’s share was

$0.6

million and

$0.3

million, respectively. The Company’s share of such gains were recorded in other comprehensive income. During the

three

and

nine

months ended

September 30, 2016,

the Sarulla project company recorded a gain of

$10.5

million and a loss of

$30.0

million, respectively, net of deferred tax, of which the Company’s share was

$1.3

million and

$3.8

million, respectively. The Company’s share of such losses were recorded in other comprehensive income. The related accumulated loss recorded by the Company in other comprehensive income (loss) as of

September 30, 2017

is

$5.6

million.

The Company had added the

$255.6

million supply agreement to its Product segment backlog in

2014.

The Company started to recognize revenue from the project during the

third

quarter of

2014

and will complete revenue recognition over the course of the next year. The Company has eliminated the related intercompany profit of

$14.1

million against equity in loss of investees.

During the

three

and

nine

months ended

September 30, 2017,

the Company made additional equity investments in the Sarulla project of approximately

$10.5

million and

$37.9

million, respectively, for a total of

$49.8

million since inception.

Note 5 - Fair Value of Financial Instruments

9 Months Ended

Sep. 30, 2017

Fair Value Disclosures [Text Block]

NOTE

5

— FAIR VALUE OF FINANCIAL INSTRUMENTS

The fair value measurement guidance clarifies that fair value is an exit price, representing the amount that would be received upon selling an asset or paid upon transferring a liability in an orderly transaction between market participants. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. The guidance establishes a fair value hierarchy that prioritizes the inputs to valuation techniques used to measure fair value. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (Level

1

measurements) and the lowest priority to unobservable inputs (Level

3

measurements). The

three

levels of the fair value hierarchy under the fair value measurement guidance are described below

:

Level

1

— Unadjusted quoted prices in active markets that are accessible at the measurement date for identical assets or liabilities;

Level

2

— Quoted prices in markets that are

not

active, or inputs that are observable, either directly or indirectly, for substantially the full term of the asset or liability

Level

3

— Prices or valuation techniques that require inputs that are both significant to the fair value measurement and unobservable (supported by little or

no

market activity).

The following table sets forth certain fair value information at

September 30, 2017

and

December 31, 2016

for financial assets and liabilities measured at fair value by level within the fair value hierarchy, as well as cost or amortized cost. As required by the fair value measurement guidance, assets and liabilities are classified in their entirety based on the lowest level of inputs that is significant to the fair value measurement.

				September 30, 2017
				Fair Value
	Carrying Value at September 30, 2017			Total			Level 1		Level 2			Level 3
	(Dollars in thousands)
Assets:
Current assets:
Cash equivalents (including restricted cash accounts)	$	13,497		$	13,497		$	13,497	$	—		$	—
Derivatives:
Put options on gas price (3)		61			61			—		61			—
Contingent receivable (1)		1,125			1,125			—		—			1,125
Currency forward contracts (2)		486			486			—		486			—
Liabilities:
Current and long-term liabilities:
Derivatives:
Contingent payables (1)	$	(25,913	)	$	(25,913	)	$	—	$	—		$	(25,913	)
Warrants (1)		(3,889	)		(3,889	)							(3,889	)
Currency forward contracts (2)		(203	)		(203	)		—		(203	)		—
	$	(14,836	)	$	(14,836	)	$	13,497	$	344		$	(28,677	)

				December 31, 2016
				Fair Value
	Carrying Value at December 31, 2016			Total			Level 1		Level 2			Level 3
	(Dollars in thousands)
Assets
Current assets:
Cash equivalents (including restricted cash accounts)	$	14,922		$	14,922		$	14,922	$	—		$	—
Derivatives:
Contingent receivable (1)		1,443			1,443			—		—			1,443
Liabilities:
Current and long-term liabilities:
Derivatives:
Contingent payables (1)	$	(11,581	)	$	(11,581	)	$	—	$	—		$	(11,581	)
Warrants (1)		(3,429	)		(3,429	)		—		—			(3,429	)
Currency forward contracts (2)		(481	)		(481	)		—		(481	)		—
	$	874		$	874		$	14,922	$	(481	)	$	(13,567	)

(

1

)

These amounts relate to contingent receivables and payables relating to the Viridity acquisition and Guadeloupe power plant purchase transaction, valued primarily based on unobservable inputs and are included within Prepaid expenses and other, Accounts payable and accrued expenses and Other long-term liabilities on

September 30, 2017

and within Prepaid expenses and other and Other long-term liabilities on

December 31, 2016

in the consolidated balance sheets with the corresponding gain or loss being recognized within Derivatives and foreign currency transaction gains (losses) in the consolidated statement of operations and comprehensive income.

(

2

)

These amounts relate to currency forward contracts valued primarily based on observable inputs, including forward and spot prices for currencies, net of contracted rates and then multiplied by notional amounts, and are included within Prepaid expenses and other and Accounts payable and accrued expenses on

September 30, 2017

and

December 31, 2016,

in the consolidated balance sheet with the corresponding gain or loss being recognized within Derivatives and foreign currency transaction gains (losses) in the consolidated statement of operations and comprehensive income.

(

3

)

These amounts relate to natural gas put options, valued primarily based on observable inputs, including spot prices on related commodity indices, and are included within Prepaid expenses and other on

September 30, 2017

in the consolidated balance sheets with the corresponding gain or loss being recognized within Derivatives and foreign currency transaction gains (losses) in the consolidated statement of operations and comprehensive income.

The amounts set forth in the tables above include investments in debt instruments and money mark

et funds (which are included in cash equivalents). Those securities and deposits are classified within Level

1

of the fair value hierarchy because they are valued using quoted market prices in an active market.

The following table presents the amounts of gain (loss) recognized in the consolidated statements of operations and comprehensive income on derivative instruments

not

designated as hedges:

		Amount of recognized gain (loss)
Derivatives not designated	Location of recognized	Three Months Ended September 30,					Nine Months Ended September 30,
as hedging instruments	gain (loss)	2017			2016		2017			2016

Put options on natural gas price	Derivatives and foreign currency transaction gains (losses)	$	(121	)	$	—	$	(362	)	$	—
Call options on natural gas price	Derivatives and foreign currency transaction gains (losses)		—			32		—			(1,114	)
Call and put options on oil price	Derivatives and foreign currency transaction gains (losses)		—			230		—			(1,312	)
Contingent considerations	Derivative and foreign currency transaction gains (losses)		(19	)		—		(114	)		—
Currency forward contracts	Derivative and foreign currency and transaction gains (losses)		(887	)		689		2,832			1,154
		$	(1,027	)	$	951	$	2,356		$	(1,272	)

In

January 2017,

the Company entered into Henry Hub Natural Gas Future contracts under which it has bought a number of put options covering a notional quantity of approximately

4.1

million British Thermal Units (“MMBtu”) with exercise prices of

$3

and expiration dates ranging from

January 26, 2017

until

November 27, 2017

in order to reduce its exposure to fluctuations in natural gas prices under its PPAs with Southern California Edison. The Company paid an aggregate amount of approximately

$0.7

million for these put options. The put option contracts have monthly expiration dates at which the options can be called and the transaction would be settled on a net cash basis.

On

February 2, 2016,

the Company entered into Henry Hub Natural Gas Future contracts under which it had written a number of call options covering a notional quantity of approximately

4.1

MMBtu with exercise prices of

$2

and expiration dates ranging from

February 24, 2016

until

December 27, 2016

in order to reduce its exposure to fluctuations in natural gas prices under its PPAs with Southern California Edison. The Company received an aggregate premium of approximately

$1.9

million from these call options. The call option contracts had monthly expiration dates on which the options could have been called and the Company would have had to settle its liability on a cash basis.

On

February 24, 2016,

the Company entered into Brent Oil Future contracts under which it had written a number of call options covering a notional quantity of approximately

185,000

barrels (“BBL”) of Brent with exercise prices of

$32.80

to

$35.50

and expiration dates ranging from

March 24, 2016

until

December 22, 2016

in order to reduce its exposure to fluctuations in Brent prices under its PPA with HELCO. The Company received an aggregate premium of approximately

$1.1

million from these call options. The call option contracts had monthly expiration dates on which the options could have been be called and the Company would have had to settle its liability on a cash basis. Moreover, during

March 2016,

the Company rolled

2

existing call options covering a total notional quantity of

31,800

BBL of Brent in order to limit its exposure to

$41

to

$42.50

instead of

$32.80

to

$33.50.

In addition, the Company entered into short risk reversal transactions (sell call and buy put options) by rolling existing call options covering notional quantities of

16,500

BBL and

17,000

BBL in order to limit its exposure from the outstanding call options originally entered into in

February 2016

to between

$28.50

and

$37.50

and

$28

and

$38.50,

respectively.

The foregoing future and forward transactions were

not

designated as hedge transactions and are marked to market with the corresponding gains or losses recognized within “Derivatives and f

oreign currency transaction gains (losses)”.

There were

no

transfers of assets or liabilities between Level

1,

Level

2

and Level

3

during the

nine

months ended

September 30, 2017.

The fair value of the Company

’s long-term debt approximates its carrying amount, except for the following:

	Fair Value				Carrying Amount
	September 30, 2017		December 31, 2016		September 30, 2017		December 31, 2016
	(Dollars in millions)				(Dollars in millions)
Olkaria III Loan - DEG	$	—	$	16.3	$	—	$	15.8
Olkaria III Loan - OPIC		242.9		253.4		233.1		246.6
Olkaria IV Loan - DEG 2		52.4		50.9		50.0		50.0
Amatitlan Loan		34.2		37.3		34.1		36.8
Senior Secured Notes:
Ormat Funding Corp. ("OFC")		—		17.0		—		17.0
OrCal Geothermal Inc. ("OrCal")		34.1		37.4		32.1		35.2
OFC 2 LLC ("OFC 2")		242.5		249.0		236.6		247.2
Don A. Campbell 1 ("DAC1")		88.2		88.9		89.6		92.4
Senior Unsecured Bonds		201.4		200.1		204.3		204.3
Other long-term debt		7.3		10.4		8.0		11.2

The fair value of the OFC Senior Secured Notes is determined using observable market prices as these securities are traded. The fair value of all the other long-term debt is determined by a valuation model, which is based on a conventional discounted cash flow methodology and utilizes assumptions of current borrowing rates

.

The fair value of revolving lines of credit is determined using a comparison of market-based price sources that are reflective of similar credit ratings to those of the Company.

The carrying value of other financial instruments, such as revolving lines of credit, deposits, and other long-term debt approximates fair value.

The

following table presents the fair value of financial instruments as of

September 30,

2017:

	Level 1		Level 2		Level 3		Total
	(Dollars in millions)
Olkaria III - OPIC	$	—	$	—	$	242.9	$	242.9
Olkaria IV - DEG 2		—		—		52.4		52.4
Amatitlan Loan		—		34.2		—		34.2
Senior Secured Notes:
OrCal		—		—		34.1		34.1
OFC 2		—		—		242.5		242.5
Don A. Campbell 1		—		—		88.2		88.2
Senior Unsecured Bonds		—		—		201.4		201.4
Other long-term debt		—		—		7.3		7.3
Revolving lines of credit		—		33.9		—		33.9
Deposits		15.2		—		—		15.2

The following table presents the fair value of financial instruments as of

December

31,

2016:

	Level 1		Level 2		Level 3		Total
	(Dollars in millions)
Olkaria III Loan - DEG	$	—	$	—	$	16.3	$	16.3
Olkaria III Loan - OPIC		—		—		253.4		253.4
Olkaria IV - DEG 2		—		—		50.9		50.9
Amatitlan Loan		—		37.3		—		37.3
Senior Secured Notes:
OFC		—		17.0		—		17.0
OrCal		—		—		37.4		37.4
OFC 2		—		—		249.0		249.0
Don A. Campbell 1		—		—		88.9		88.9
Senior Unsecured Bonds		—		—		200.1		200.1
Other long-term debt		—		3.3		7.1		10.4
Deposits		14.4		—		—		14.4

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Note 6 - Stock-based Compensation	9 Months Ended
Note 6 - Stock-based Compensation	Sep. 30, 2017
Notes to Financial Statements
Disclosure of Compensation Related Costs, Share-based Payments [Text Block]	NOTE 6 — STOCK-BASED COMPENSATION The 2004 Incentive Compensation Plan In 2004, the Board adopted the 2004 Incentive Compensation Plan ( “2004 Incentive Plan”), which provided for the grant of the following types of awards: incentive stock options, non-qualified stock options, restricted stock, stock appreciation rights (“SARs”), stock units, performance awards, phantom stock, incentive bonuses, and other possible related dividend equivalents to employees of the Company, directors and independent contractors. Under the 2004 Incentive Plan, a total of 3,750,000 shares of the Company’s common stock were reserved for issuance, all of which could be issued as options or as other forms of awards. Options and SARs granted to employees under the 2004 Incentive Plan cliff vest and are exercisable from the grant date as follows: 25% after 24 months, 25% after 36 months, and the remaining 50% after 48 months. Options granted to non-employee directors under the 2004 Incentive Plan cliff vest and are exercisable one year after the grant date. Vested stock-based awards may be exercised for up to ten years from the grant date. The shares of common stock issued in respect of awards under the 2004 Incentive Plan are issued from the Company’s authorized share capital upon exercise of options or SARs. The 2004 Incentive Plan expired in May 2012 upon adoption of the 2012 Incentive Compensation Plan ( “2012 Incentive Plan”), except as to stock-based awards outstanding under the 2004 Incentive Plan on that date. The 2012 Incentive Compensation Plan In May 2012, the Company ’s shareholders adopted the 2012 Incentive Plan, which provides for the grant of the following types of awards: incentive stock options, non-qualified stock options, restricted stock, SARs, stock units, performance awards, phantom stock, incentive bonuses, and other possible related dividend equivalents to employees of the Company, directors and independent contractors. Under the 2012 Incentive Plan, a total of 4,000,000 shares of the Company’s common stock have been reserved for issuance, all of which could be issued as options or as other forms of awards. Options and SARs granted to employees under the 2012 Incentive Plan typically vest and become exercisable as follows: 25% vest 24 months after the grant date, an additional 25% vest 36 months after the grant date, and the remaining 50% vest 48 months after the grant date. Options granted to non-employee directors under the 2012 Incentive Plan will vest and become exercisable one year after the grant date. The term of stock-based awards typically ranges from six to ten years from the grant date. The shares of common stock issued in respect of awards under the 2012 Incentive Plan are issued from the Company’s authorized share capital upon exercise of options or SARs. The 2012 Incentive Plan empowers the Board, in its discretion, to amend the 2012 Incentive Plan in certain respects. Consistent with this authority, in February 2014 the Board adopted and approved certain amendments to the 2012 Incentive Plan. The key amendments are as follows: ● Increase of per grant limit: Section 15 (a) of the 2012 Incentive Plan was amended to allow the grant of up to 400,000 shares of the Company ’s common stock with respect to the initial grant of an equity award to newly hired executive officers in any calendar year; and ● Acceleration of vesting: Section 15 (l) of the 2012 Incentive Plan was amended to clarify the Company’s ability to provide in the applicable award agreement that part and/or all of the award will be accelerated upon the occurrence of certain predetermined events and/or conditions, such as a change in control (as defined in the 2012 Incentive Plan, as amended).

Note 7 - Interest Expense, Net

9 Months Ended

Sep. 30, 2017

Interest Expense Disclosure [Text Block]

NOTE

7

— INTEREST EXPENSE, NET

The components of interest expense are as follows:

	Three Months Ended September 30,						Nine Months Ended September 30,
	2017			2016			2017			2016

Interest related to sale of tax benefits	$	1,607		$	2,565		$	5,468		$	6,269
Interest expense		13,299			15,726			41,620			47,214
Less — amount capitalized		(3,214	)		(1,154	)		(5,933	)		(1,922	)
	$	11,692		$	17,137		$	41,155		$	51,561

Note 8 - Earnings Per Share

9 Months Ended

Sep. 30, 2017

Earnings Per Share [Text Block]

NOTE

8

— EARNINGS PER SHARE

Basic earnings per share attributable to the Company

’s stockholders is computed by dividing net income or loss attributable to the Company’s stockholders by the weighted average number of shares of common stock outstanding for the period. The Company does

not

have any equity instruments that are dilutive, except for employee stock-based awards.

The table below shows the reconciliation of the number of shares used in the computation of basic and diluted earnings per share:

	Three Months Ended September 30,				Nine Months Ended September 30,
	2017		2016		2017		2016

Weighted average number of shares used in computation of basic earnings per share		50,367		49,599		49,942		49,410
Add:
Additional shares from the assumed exercise of employee stock options		500		690		727		687

Weighted average number of shares used in computation of diluted earnings per share		50,867		50,289		50,669		50,097

The number of stock-based awards that could potentially dilute future earnings per share and that were

not

included in the computation of diluted

earnings per share because to do so would have been anti-dilutive was

8,851

and

225,191

for the

three

months ended

September 30, 2017

and

2016,

respectively, and

6,494

and

116,641

for the

nine

months ended

September 30, 2017

and

2016,

respectively.

Note 9 - Business Segments

9 Months Ended

Sep. 30, 2017

Segment Reporting Disclosure [Text Block]

NOTE

9

— BUSINESS SEGMENTS

The Company has

two

reporting segments: the Electricity segment and the Product segment. These segments are managed and reported separately as each offers different products and serves different markets. The Electricity segment is engaged in the sale of electricity from the Company

’s power plants pursuant to PPAs. The Product segment is engaged in the manufacture, including design and development, of turbines and power units for the supply of electrical energy and in the associated construction of power plants utilizing the power units manufactured by the Company to supply energy from geothermal fields and other alternative energy sources

.

Transfer prices between the operating segments are determined based on current market values or cost plus markup of the seller

’s business segment.

Summarized financial information concerning the Company

’s reportable segments is shown in the following tables:

	Electricity		Product		Consolidated
	(Dollars in thousands)
Three Months Ended September 30, 2017:
Net revenue from external customers	$	112,273	$	44,912	$	157,185
Intersegment revenue		—		28,248		28,248
Operating income		36,205		7,765		43,970
Segment assets at period end (1)		2,371,855		131,883		2,503,738

Three Months Ended September 30, 2016:
Net revenue from external customers	$	109,795	$	74,822		184,617
Intersegment revenue		—		14,835		14,835
Operating income		23,903		24,320		48,223
Segment assets at period end		2,137,845		141,426		2,279,271

Nine Months Ended September 30, 2017:
Net revenues from external customers	$	339,826	$	186,621		526,447
Intersegment revenues		—		61,026		61,026
Operating income		113,220		43,398		156,618
Segment assets at period end (1)		2,371,855		131,883		2,503,738

Nine Months Ended September 30, 2016:
Net revenues from external customers	$	321,664	$	174,408		496,072
Intersegment revenues		—		36,042		36,042
Operating income		91,502		59,151		150,653
Segment assets at period end		2,137,845		141,426		2,279,271

(

1

)

Electricity segment assets include goodwill in the amount of

$20.7

million

.

Reconciling information between reportable segments and the Company

’s consolidated totals is shown in the following table:

	Three Months Ended September 30,						Nine Months Ended September 30,
	2017			2016			2017			2016
Revenue:
Total segment revenue	$	157,185		$	184,617		$	526,447		$	496,072
Intersegment revenue		28,248			14,835			61,026			36,042
Elimination of intersegment revenue		(28,248	)		(14,835	)		(61,026	)		(36,042	)
Total consolidated revenue	$	157,185		$	184,617		$	526,447		$	496,072

Operating income:
Operating income	$	43,970		$	48,223		$	156,618		$	150,653
Interest income		255			266			861			831
Interest expense, net		(11,692	)		(17,137	)		(41,155	)		(51,561	)
Derivatives and foreign currency transaction gains (losses)		(1,001	)		(222	)		2,040			(2,592	)
Income attributable to sale of tax benefits		3,506			3,463			14,019			12,380
Other non-operating expense, net		(1,592	)		(5,546	)		(1,678	)		(5,306	)
Total consolidated income before income taxes and equity in losses of investees	$	33,446		$	29,047		$	130,705		$	104,405

Note 10 - Commitments and Contingencies

9 Months Ended

Sep. 30, 2017

Commitments and Contingencies Disclosure [Text Block]

NOTE

10

— COMMITMENTS AND CONTINGENCIES

●

Jon Olson and Hilary Wilt, together with Puna Pono Alliance filed a complaint on

February 17, 2015

in the Third Circuit Court for the State of Hawaii, requesting declaratory and injunctive relief requiring that Puna Geothermal Venture comply with an ordinance that the plaintiffs allege will prohibit PGV from engaging in night drilling operations at its KS-

16

well site. On

May 17, 2015,

the original complaint was amended to add the County of Hawaii and the State of Hawaii Department of Land and Natural Resources as defendants to the case. On

October 10, 2016,

the court issued its decision in response to each of the plaintiffs

’ and defendants’ motions for summary judgment, denying plaintiffs’ motion and granting defendant PGV's and the County of Hawaii’s cross motions for summary judgment, effectively rendering the plaintiffs’ action moot. On

January 23, 2017,

the plaintiffs filed a motion requesting that the Intermediate Court of Appeals address appellate jurisdiction, which was denied by the court on

April 20, 2017

as premature. The Company believes that it has valid defenses under law, and intends to defend itself vigorously.

●

On

July 8, 2014,

Global Community Monitor, LiUNA, and

two

residents of Bishop, California filed a complaint in the U.S. District Court for the Eastern District of California, alleging that Mammoth Pacific, L.P., the Company and Ormat Nevada are operating

three

geothermal generating plants in Mammoth Lakes, California (MP-

1,

MP-II and PLES-I) in violation of the federal Clean Air Act and Great Basin Unified Air Pollution Control District rules. On

June 26, 2015,

in response to a motion by the defendants, the court dismissed all but

one

of the plaintiffs

’ causes of action. On

January 6, 2017,

the court issued its order regarding several pending motions, including plaintiffs’ motion for partial summary judgment, defendants' motion for summary judgment, defendants' motion to exclude and defendants' motion for leave to file a sur-reply. The impact of the court’s

January 6, 2017

order is to deny the plaintiffs’ sole remaining cause of action.

No

appeal by the plaintiffs is expected and the company considers this case to be effectively closed.

●

On

March 29, 2016,

a former local sales representative in Chile, Aquavant, S.A., filed a claim against Ormat

’s subsidiaries in the

27

th

Civil Court of Santiago, Chile on the basis of unjust enrichment. The claim requests that the court order Ormat to pay Aquavant

$4.8

million in connection with its activities in Chile, including the EPC contract for the Cerro Pabellon project and various geothermal concessions, plus

3.75%

of Ormat geothermal products sales in Chile over the next

10

years. Pursuant to various motions submitted by the defendants and the plaintiffs to various courts, including the Court of Appeals, the

11th

Civil Court of Santiago, rather than the

27th

Civil Court, was found to be the competent court. Plaintiffs appealed to the

11th

Civil Court to accept the case as it stood for continued review although

not

submitted to that court originally, but the court denied the plaintiffs’ request. The Company believes that it has valid defenses under law, and intends to defend itself vigorously.

●

On

August 5, 2016,

George Douvris, Stephanie Douvris, Michael Hale, Cheryl Cacocci, Hillary E. Wilt and Christina Bryan, acting for themselves and on behalf of all other similarly situated residents of the lower Puna District, filed a complaint in the Third Circuit Court for the State of Hawaii seeking certification of a class action for preliminary and permanent injunctive relief, consequential and punitive damages, attorney

’s fees and statutory interest against PGV and other presently unknown defendants. On

December 12, 2016,

the federal district court granted plaintiffs’ motion for joinder of HELCO as a co-defendant, and the case, which had previously been removed to the U.S. District Court for the District of Hawaii, was remanded back to the Third Circuit Court. The amended complaint alleged that injuries and other damages in an undisclosed amount were caused to the plaintiffs as a result of an alleged toxic release by PGV in the wake of Hurricane Iselle in

August 2014.

On

June 14, 2017,

the Third Circuit Court denied HELCO’s motion to dismiss the complaint against HELCO. Discovery is underway. The Company believes that it has valid defenses under law, and intends to defend itself vigorously.

●

On

June 20, 2016,

Nadia Garcia, individually and as successor in interest to Thomas Garcia Valenzuela, and as guardian ad litem to Emerie Garcia, Khamilla Garcia and Reyene Adam, filed a complaint against Ormat Technologies, Ormat Nevada and Ormesa LLC in the Superior Court of Imperial County seeking unspecified monetary damages. The complaint alleges that the Ormat defendants caused the wrongful death, personal injury and other harm to Thomas Garcia when he was employed by Martin Hydroblasting Services, Inc. and suffered injuries leading to his death while performing work at the Ormesa plant site on or around

March 31, 2016.

The plaintiffs and the deceased's employer

’s insurer reached an out of court settlement that was approved by the US District Court, Southern District of California, and executed

May 25, 2017.

The case has been dismissed, without liability to the Company.

I

n addition, from time to time, the Company is named as a party to various other lawsuits, claims and other legal and regulatory proceedings that arise in the ordinary course of our business. These actions typically seek, among other things, compensation for alleged personal injury, breach of contract, property damage, punitive damages, civil penalties or other losses, or injunctive or declaratory relief. With respect to such lawsuits, claims and proceedings, the Company accrues reserves when a loss is probable and the amount of such loss can be reasonably estimated. It is the opinion of the Company’s management that the outcome of these proceedings, individually and collectively, will

not

be material to the Company’s consolidated financial statements as a whole.

Note 11 - Income Taxes	9 Months Ended
Note 11 - Income Taxes	Sep. 30, 2017
Notes to Financial Statements
Income Tax Disclosure [Text Block]	NOTE 11 — INCOME TAXES As further described in Note 1 and in connection with the closing of the SCPPA PPA portfolio agreement, during the second quarter of 2017 the Company changed its assertion related to permanent reinvestment of foreign unremitted earnings in Ormat Systems, its Israeli fully owned subsidiary. Accordingly, a deferred tax liability in the amount of $111.0 million was recorded which represents the estimated tax impact of future repatriation of the unremitted foreign earning in Ormat Systems at the statutory U.S. tax rate of 35%. Additionally, the Company accrued $53.9 million for the estimated Israeli withholding taxes expected when Ormat Systems remits its earnings to the U.S. The Company also recorded a deferred tax asset in the amount of $111.1 million for foreign tax credits related to taxes already paid by Ormat Systems on such earnings in Israel. Realization of the deferred tax assets and tax credits is dependent on generating sufficient taxable income in appropriate jurisdictions prior to expiration of the NOL carryforwards and tax credits. In prior periods and through March 31, 2017 the Company had maintained a valuation allowance against its net deferred tax asset balance in the US. As of March 31, 2017 such valuation allowance was $109.6 million. Based upon new available evidence of the Company’s ability to generate additional taxable income in the U.S. due to the closing of the SCPPA PPA portfolio and the Company’s permanent reinvestment of unremitted earnings assertion change with respect to Ormat Systems Ltd., $61.5 million of valuation allowance was released against the U.S. deferred tax assets, as it is more likely than not that the deferred tax assets will be utilized. However, the Company is maintaining a valuation allowance of $47.0 million against a portion of the U.S. foreign tax credits that are expected to expire before they can be utilized in future periods. Additionally, the Company recorded a specific valuation allowance of $1.1 million attributable to current year projected activity as this will need to be held back and recognized throughout the year as current year income is earned for a total valuation allowance of $48.1 million as of September 30, 2017. This valuation allowance is based upon management’s estimates of future taxable income. Although the degree of variability inherent in the estimates of future taxable income is significant and subject to change in the near term, management believes that the estimate is adequate. However, the amount of deferred tax asset considered realizable could change in the near term if estimates which require significant judgment of future taxable income during the carryforward period are increased or decreased. Accordingly, the estimated valuation allowance is continually reviewed and as adjustments to the valuation allowance become necessary, such adjustments will be reflected in current earnings. The Company ’s effective tax rate for the three months ended September 30, 2017 and 2016 was 32.9% and 41.3%, respectively, and 21.6% and 28.1% for the nine months ended September 30, 2017 and 2016, respectively. The effective rate differs from the federal statutory rate of 35% for the nine months ended September 30, 2017 due to: (i) a partial valuation allowance release against the Company’s U.S. deferred tax assets as described above in respect of net operating loss (“NOL”) carryforwards (see below) offset by withholding taxes related to the assertion change on the Company’s permanent reinvestment of foreign unremitted earnings in Ormat Systems also as described above, (ii) lower tax rate in Israel of 16%, partially offset by a tax rate in Kenya of 37.5%; and (iii) a tax credit and tax exemption related to the Company’s subsidiaries in Guatemala and Honduras. The effect of the tax credit and tax exemption for the three months ended September 30, 2017 and 2016 was $0.6 million in both periods and for the nine months ended September 30, 2017 and 2016 was $2.3 million and $2.4 million, respectively. As described above, t he Company is currently in a net deferred tax asset position with a partial valuation allowance against the Company’s foreign tax credits that are expected to expire before they can be utilized in future periods. As of December 31, 2016, the Company had U.S. Federal NOL carryforwards of approximately $299.6 million, which expire between 2029 and 2036, and state NOL carryforwards of approximately $244.7 million, which expire between 2018 and 2036 which are available to reduce future taxable income. The Company's investment tax credits (“ITCs”) in the amount of $0.7 million at December 31, 2016 are available for a 20 -year period and expire between 2022 and 2024. The Company's production tax credits (“PTCs”) in the amount of $82.5 million at December 31, 2016 are available for a 20 -year period and expire between 2026 and 2036. The Company also has offsetting deferred tax liabilities in the U.S. The total amount of undistributed earnings of foreign subsidiaries related to Ormat Systems for income tax purposes was approximately $367 million at December 31, 2016. Although the Company plans to repatriate undistributed earnings related to Ormat Systems to support expected capital expenditure requirements in the U.S., based upon its plans to increase its operations outside of the U.S., it is the Company ’s intention to reinvest undistributed earnings of its other foreign subsidiaries and thereby indefinitely postpone their remittance, given that the Company requires existing and future cash to fund the anticipated investment and development activities as well as debt service requirements in those jurisdictions. In addition, the Company believes that existing and anticipated cash flows as well as borrowing capacity in the U.S. and cash to be remitted to the U.S. from Ormat Systems will be sufficient to meet its needs in the U.S. Accordingly, no provision has been made for foreign withholding taxes or U.S. income taxes with respect to its foreign subsidiaries, other than Ormat Systems, which may become payable if undistributed earnings of foreign subsidiaries were paid as dividends to the Company. The additional taxes on that portion of undistributed earnings in those other jurisdictions which is available for dividends are not practicably determinable. If plans change the Company may be required to accrue and pay U.S. taxes to repatriate these funds. The Company is subject to income taxes in the U.S. (federal and state) and numerous foreign jurisdictions. Significant judgment is required in evaluating tax positions and determining the position for income taxes. Reserves are established to tax-related uncertainties based on estimates of whether, and the extent to which additional taxes will be due. As of September 30, 2017, the Company is unaware of any potentially significant uncertain tax positions for which a reserve has not been established. As previously reported by the Company, the Kenya Revenue Authority (“KRA”) conducted an audit related to the Company ’s operations in Kenya for fiscal years 2012 and 2013. On June 20, 2017, the Company has signed a Settlement Agreement with the KRA under which it paid approximately $2.6 million in principal for full settlement of all claims raised by the KRA during the audit. The principal amount that was paid in June 2017 was recorded as an addition to the cost of the power plants and is qualified for investment deduction at 150% under the terms of the settlement agreement. Additionally, as per the Settlement Agreement, the Company submitted a request for waiver on the applied interest in the amount of approximately $1.2 million, for which the Company recorded a provision to cover such a potential exposure.

Note 12 - Subsequent Events	9 Months Ended
Note 12 - Subsequent Events	Sep. 30, 2017
Notes to Financial Statements
Subsequent Events [Text Block]	NOTE 12 — SUBSEQUENT EVENTS Cash dividend On November 7, 2017, the Board declared, approved and authorized payment of a quarterly dividend of $4.0 million ( $0.08 per share) to all holders of the Company ’s issued and outstanding shares of common stock on November 21, 2017, payable on December 5, 2017. OPC buyout On May 31, 2017, the Company ’s partners JPM and Morgan Stanley achieved their target after-tax yield on its investment in OPC, LLC (“OPC”) and on October 31, 2017, Ormat Nevada purchased all of the Class B membership units in OPC from JPM and Morgan Stanley for $1.9 million. As a result, Ormat Nevada is now the sole owner of all of the economic and voting interests in OPC and continues to consolidate OPC in its financial statements.

Significant Accounting Policies (Policies)	9 Months Ended
Significant Accounting Policies (Policies)	Sep. 30, 2017
Accounting Policies [Abstract]
Platanares Geothermal Power Plant, Policy [Policy Text Block]	Platanares geothermal power plant On September 26, 2017, the Company announced that its 35 MW Platanares geothermal project in Honduras commenced commercial operation. The Company constructed the Platanares geothermal project under a Build, Operate, and Transfer (BOT) contract with ELCOSA, a privately owned Honduran energy company. The Company will operate the project for 15 years from commercial operation date (COD). Platanares sells its power under a 30 -year power purchase agreement with the national utility of Honduras, ENEE. A portion of the land on which the project is located at is held by us through a lease from a local municipality. Because the term of the lease exceeds the term in office of the relevant municipal government, it remains subject to an additional approval of the Honduran Congress in order to be fully valid. The Company has commenced the necessary steps to obtain such approval but the current elections in Honduras may result in a delay in obtaining such approval.
OFC Senior Secured Notes Prepayment, Policy [Policy Text Block]	OFC Senior Secured Notes prepayment In September 2017, the Company fully prepaid all of its outstanding OFC Senior Secured Notes for $14.3 million. As a result of the prepayment, the Company recognized a loss of $1.5 million, including amortization of deferred financing costs of $0.2 million, which was included in other non-operating income (expense), net in the consolidated statements of operations and comprehensive income for the three and nine months ended September 30, 2017.
DEG Loan Prepayment, Policy [Policy Text Block]	DEG Loan prepayment In September 2017, the Company fully prepaid its DEG loan for $11.8 million. As a result of the prepayment, the Company recognized a loss of $0.5 million, including amortization of deferred financing costs of $0.4 million, which was included in other non-operating income (expense), net in the consolidated statements of operations and comprehensive income for the three and nine months ended September 30, 2017.
ORIX Transaction, Policy [Policy Text Block]	ORIX transaction On July 26, 2017, we announced that ORIX Corporation (“ORIX”) closed its acquisition of approximately 11 million shares of our common stock, representing an approximately 22% ownership stake in the Company, from FIMI ENRG Limited Partnership, FIMI ENRG, L.P., Bronicki Investments, Ltd. and certain senior members of our management team pursuant to a stock purchase agreement entered into by ORIX and the selling stockholders on May 4, 2017. In connection with the acquisition, on May 4, 2017, we entered into certain related agreements with ORIX, including a Governance Agreement, a Commercial Cooperation Agreement and a Registration Rights Agreement, following the unanimous recommendation of a Special Committee of the board of directors of the Company (the “Board”) that was formed to evaluate and negotiate the stockholder arrangements proposed by ORIX, and following approval by the Board. The closing of the transactions contemplated by the related agreements between ORIX and the Company also occurred on July 26, 2017. Under the Governance Agreement, ORIX has the right to designate three persons to the Board, which was expanded to nine directors, and also propose a fourth person to be mutually agreed by the Company and ORIX to serve as a new independent director on the Board. In addition, for so long as ORIX is entitled to board representation pursuant to the Governance Agreement, ORIX will be subject to certain customary standstill restrictions, including an effective 25% cap on its voting rights. Pursuant to the Registration Rights Agreement, ORIX also has certain customary registration rights with respect to the shares of the Company ’s common stock that it owns. Under the Commercial Cooperation Agreement, the Company has exclusive rights to develop, own, operate and provide equipment for ORIX geothermal energy projects in all markets outside of Japan. In addition, the Company has certain rights to serve as technical partner and co-invest in ORIX geothermal energy projects in Japan. ORIX will also assist the Company in obtaining project financing for its geothermal energy projects from a variety of leading providers of renewable energy debt financing with which ORIX has relationsh ips in Asia and around the world.
ORTP Buyout, Policy [Policy Text Block]	ORTP buyout On March 30, 2017, the Company ’s partner JPM Capital Corporation (“JPM”) achieved its target after-tax yield on its investment in ORTP, LLC (“ORTP”) and on July 10, 2017, Ormat Nevada Inc. (“Ormat Nevada”) purchased all of the Class B membership units in ORTP from JPM for $2.4 million. As a result, Ormat Nevada is now the sole owner of all of the economic and voting interests in ORTP and continues to consolidate ORTP in its financial statements. The purchase of Class B membership units of ORTP was recorded in equity as a reduction to Noncontrolling Interest with the surplus charged to Additional Paid-in Capital.
SCPPA Power Purchase Agreement, policy [Policy Text Block]	SCPPA power purchase agreement During the second quarter of 2017, ONGP LLC (“ONGP”), one of the Company ’s wholly-owned subsidiaries, entered into a power purchase agreement (“PPA”) with Southern California Public Power Authority (“SCPPA”), pursuant to which ONGP will sell, and SCPPA will purchase, geothermal power generated by a portfolio of nine different geothermal power plants owned by the Company and located in the US. The parties’ obligations under the PPA are based on a geothermal power generation capacity of 150 MW, and, pursuant to the PPA, ONGP is required to deliver a minimum of 135 MW and is entitled to deliver a maximum of 185 MW to SCPPA over the next five years. The portfolio PPA is for a term of approximately 26 years, expiring in December 31, 2043 and has a fixed price of $75.50 per MWh.
Assertion of Permanent Reinvestment of Foreign Unremitted Earnings in Subsidiaries, Policy [Policy Text Block]	Assertion of p ermanent reinvestment of foreign unremitted earnings in a subsidiary During the second quarter of 2017, in conjunction with (i) the final approval of the SCPPA PPA which will require the Company to make significant capital expenditures in the United Sates, (ii) the fact that the Company is currently exploring acquisition opportunities in the United States, and (iii) the acquisition of substantially all the assets of Viridity for $35.3 million with two additional earn-out payments that may have to be made in 2018 and 2021, the Company has re-evaluated its position with respect to a portion of the unrepatriated earnings of Ormat Systems Ltd. (“OSL”), its wholly owned Subsidiary in Israel, and after consideration of the aforementioned change in facts, determined that it can no longer maintain the permanent reinvestment position with respect to a portion of OSL ’s unrepatriated earnings which will be repatriated to support the Company’s capital expenditures in the United Sates. Accordingly, and as further described in Note 11, the permanent reinvestment assertion of foreign unremitted earnings of OSL was reassessed and removed and the related deferred tax assets and liabilities as well as the estimated withholding taxes on expected remittance of OSL earnings to the United States were recorded by the Company in the second quarter of 2017.
Business Combinations Policy [Policy Text Block]	Viridity transaction On March 15, 2017, the Company completed the acquisition of substantially all of the business and assets of Viridity Energy, Inc., a privately held Philadelphia-based company formerly engaged in the provision of demand response, energy management and energy storage services. At closing, Viridity Energy Solutions Inc. (“Viridity”), a wholly owned subsidiary of the Company, paid initial consideration of $35.3 million. Additional contingent consideration with an estimated fair value of $ 12.8 million will be payable in two installments upon the achievement of certain performance milestones measured at the end of fiscal years 2017 and 2020. The acquired business and assets are operated by Viridity. Using proprietary software and solutions, Viridity serves primarily retail energy providers, utilities, and large commercial and industrial customers. Viridity ’s offerings enable its customers to optimize and monetize their energy management, demand response and storage facilities potential by interacting on their behalf with regional transmission organizations and independent system operators. The Company accounted for the transaction in accordance with Accounting Standard Codification 805, Business Combinations, and consequently recorded intangible assets of $34.7 million primarily relating to Viridity’s storage and non-storage activities with a weighted-average amortization period of 17 years, approximately $0.4 million of working capital and fixed assets and $13.9 million of goodwill. Following the transaction, the Company consolidated Viridity in accordance with Accounting Standard Codification 810, Consolidation. The acquisition enabled the Company to enter the growing energy storage and demand response markets and expand its market presence. The revenues of Viridity for the period from March 15, 2017 to September 30, 2017 were included in the Company’s consolidated statements of operations and comprehensive income for the three and nine months ended September 30, 2017. Accounting guidance provides that the allocation of the purchase price may be modified for up to one year from the date of the acquisition to the extent that additional information is obtained about the facts and circumstances that existed as of the acquisition date.
Comprehensive Income, Policy [Policy Text Block]	Other comprehensive income For the nine months ended September 30, 2017 and 2016, the Company classified $5,000 and $7,000, respectively, related to derivative instruments designated as cash flow hedges, from accumulated other comprehensive income, of which $9,000 and $11,000, respectively, were recorded to reduce interest expense and $4,000 and $4,000, respectively, were recorded against the income tax provision, in the condensed consolidated statements of operations and comprehensive income. For the three months ended September 30, 2017 and 2016, the Company classified $2,000 and $2 ,000, respectively, related to derivative instruments designated as cash flow hedges, from accumulated other comprehensive income, of which $6,000 and $3,000 respectively, was recorded to reduce interest expense and $4,000 and $1,000, respectively, were recorded against the income tax provision, in the condensed consolidated statements of operations and comprehensive income. The accumulated net loss included in Other comprehensive income as of September 30, 2017, is $0.6 million
Exploratory Drilling Costs Capitalization and Impairment, Policy [Policy Text Block]	Write-offs of unsuccessful exploration activities There were no w rite-offs of unsuccessful exploration activities for the three and nine months ended September 30, 2017. Write-offs of unsuccessful exploration activities for the three and nine months ended 2016 were $1.3 million and $2.7 million, respectively. The write-offs of exploration costs in 2016 were related to the Company’s exploration activities in Nevada and Chile, after which the Company determined that the applicable sites would not support commercial operations.
Concentration Risk, Credit Risk, Policy [Policy Text Block]	Concentration of credit risk Financial instruments that potentially subject the Company to a concentration of credit risk consist principally of temporary cash investments and accounts receivable. The Company places its temporary cash investments with high credit quality financial institutions located in the United States and in foreign countries. At September 30, 2017 and December 31, 2016, the Company had deposits totaling $ 23.9 million and $72.5 million, respectively, in seven United States financial institutions that were federally insured up to $250,000 per account. At September 30, 2017 and December 31, 2016, the Company’s deposits in foreign countries amounted to approximately $56.0 million and $166.2 million, respectively. At September 30, 2017 and December 31, 2016, accounts receivable related to operations in foreign countries amounted to approximately $67.5 million and $53.3 million, respectively. At September 30, 2017 and December 31, 2016, accounts receivable from the Company’s primary customers amounted to approximately 48% and 60% of the Company’s accounts receivable, respectively. Sierra Pacific Power Company and Nevada Power Company (subsidiaries of NV Energy, Inc.) accounted for 16.3% and 14.4% of the Company’s total revenues for the three months ended September 30, 2017 and 2016, respectively, and 17.4% and 18.6% for the nine months ended September 30, 2017 and 2016, respectively. Kenya Power and Lighting Co. Ltd. accounted for 17.6% and 15.1% of the Company’s total revenues for the three months ended September 30, 2017 and 2016, respectively, and 15.7% and 16.4% of the Company’s total revenues for the nine months ended September 30, 2017 and 2016, respectively. Southern California Public Power Authority (“SCPPA”) accounted for 9.1% and 7.7% of the Company’s total revenues for the three months ended September 30, 2017 and 2016, respectively, and 8.9% and 9.9% of the Company’s total revenues for the nine months ended September 30, 2017 and 2016, respectively. Hyundai (Sarulla geothermal project) accounted for 0.9% and 24% of the Company’s total revenues for the three months ended September 30, 2017 and 2016, respectively, and 4.7% and 14% for the nine months ended September 30, 2017 and 2016, respectively. The Company has historically been able to collect on all of its receivable balances, and accordingly, no provision for doubtful accounts has been made.
New Accounting Pronouncements, Policy [Policy Text Block]	New accounting pronouncements effective in the nine -month period ended September 30, 2017 Improvement to Employee Share-Based Payment Accounting In March 2016, the Financial Accounting Standards Board “(FASB”) issued Accounting Standard Update (“ASU”) 2016 - 09, Improvement to Employee Share-Based Payment Accounting, an update to the guidance on stock-based compensation. Under the new guidance, all excess tax benefits and tax deficiencies will be recognized in the income statement as they occur. This will replace previous guidance, which required tax benefits that exceed compensation cost (windfalls) to be recognized in equity. It also eliminated the need to maintain a “windfall pool,” and removed the requirement to delay recognizing a windfall until it reduces current taxes payable. The new guidance also changed the cash flow presentation of excess tax benefits, classifying them as operating inflows, consistent with other cash flows related to income taxes. Previously, windfalls were classified as financing activities. This guidance affects the dilutive effects in earnings per share, as there will no longer be excess tax benefits recognized in additional paid in capital. Previously those excess tax benefits were included in assumed proceeds from applying the treasury stock method when computing diluted EPS. Under the amended guidance, companies are able to make an accounting policy election to either ( 1 ) continue to estimate forfeitures or ( 2 ) account for forfeitures as they occur. This updated guidance is effective for annual and interim periods beginning after December 15, 2016. The adoption of this guidance did not have a material impact on the Company’s consolidated financial statements. Interests Held through Related Parties that are under Common Control In October 2016, the FASB issued ASU 2016 - 17, Consolidation (Topic 810 ): Interests held through Related Parties that are under Common Control. The amendments in this update require that if a decision maker is required to evaluate whether it is the primary beneficiary of a VIE, it will need to consider only its proportionate indirect interest in the VIE held through a common control party. The amendments in this update should be applied retrospectively for each period presented and are effective for financial statements issued for fiscal years beginning after December 15, 2016, and interim periods within those fiscal years. The adoption of this guidance did not have a material impact on the Company’s consolidated financial statements. Simplifying the Measurement of Inventory In July 2015, the FASB issued ASU 2015 - 11, Simplifying the Measurement of Inventory, Topic 330. The update contains no amendments to disclosure requirements, but replaces the concept of ‘lower of cost or market’ with that of ‘lower of cost and net realizable value’. The amendments in this update are effective for annual reporting periods beginning after December 15, 2016, including interim periods within those reporting periods. The amendments should be applied prospectively with early adoption permitted. The adoption of this guidance did not have a material impact on the Company’s consolidated financial statements. New accounting pronouncements effective in future periods Derivatives and Hedging In August 2017, the FASB issued ASU 2017 - 12, Targeted Improvements to Accounting for Hedging Activities. The amendments in this Update better align an entity’s risk management activities and financial reporting for hedging relationships through changes to both the designation and measurement guidance for qualifying hedging relationships and the presentation of hedge results. To meet that objective, the amendments expand and refine hedge accounting for both nonfinancial and financial risk components and align the recognition and presentation of the effects of the hedging instrument and the hedged item in the financial statements. The amendments in this Update are effective for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. Early application is permitted in any interim period after issuance of the Update. The Company is currently evaluating the potential impact of the adoption of these amendments on its consolidated financial statements, if any. Intangibles –Goodwill and Other In January 2017, the FASB issued ASU 2017 - 04, Intangibles – Goodwill and Other (Topic 350 ). The amendments in this Update require the entity to perform its annual or interim goodwill impairment test by comparing the fair value of a reporting unit with its carrying amount. An entity should recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit’s fair value, however, the loss recognized should not exceed the total amount of goodwill allocated to that reporting unit. Additionally, an entity should consider the income tax effects from any tax deductible goodwill on the carrying amount of the reporting unit when measuring the goodwill impairment loss, if applicable. This Update, eliminated Step 2 from the goodwill impairment test under the current guidance. Step 2 measures a goodwill impairment loss by comparing the implied fair value of reporting unit’s goodwill with the carrying amount of that goodwill. The amendments in this Update should be applied on a prospective basis. An entity is also required to disclose the nature of and the reason for the change in accounting principal upon transition. That disclosure should be provided in the first annual period and the interim period within the first annual period when the entity initially adopts the amendments in this Update. The amendments in this Update are effective for the annual or any interim goodwill impairment tests in fiscal years beginning after December 15, 2019. Early adoption is permitted for interim or annual impairment tests performed on testing dates after January 1, 2017. The Company is currently evaluating the potential impact of the adoption of these amendments on its consolidated financial statements. Compensation - Stock Compensation In May 2017, the FASB issued ASU 2017 - 09, Compensation—Stock Compensation (Topic 718 ). The amendments in this Update provide guidance about which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting in Topic 718. The amendments in this update require that an entity should account for the effects of a modification unless all of the following are met: ( 1 ) The fair value of the modified award is the same as the fair value of the original award immediately before the original award is modified; ( 2 ) The vesting conditions of the modified award are the same as the vesting conditions of the original award immediately before the original award is modified; ( 3 ) The classification of the modified award as an equity instrument or a liability instrument is the same as the classification of the original award immediately before the original award is modified. The current disclosure requirements in Topic 718 apply regardless of whether an entity is required to apply modification accounting under the amendments in this Update. The amendments in this Update are effective for all entities for annual periods, and interim periods within those annual periods, beginning after December 15, 2017. Early adoption is permitted. The amendments in this Update should be applied prospectively to an award modified on or after the adoption date. The Company is currently evaluating the potential impact of the adoption of these amendments on its consolidated financial statements. Business Combinations In January 2017, the FASB issued ASU 2017 - 01, Business Combinations (Topic 805 ). The update clarifies the definition of a business with the objective of adding guidance to assist entities with evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. The amendments in this update primarily provide a screen to determine when a set of assets and activities is not a business and by that reduces the number of transactions that need to be further evaluated. The amendments in this update should be applied prospectively and are effective for financial statements issued for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years. Early adoption is permitted. The Company is currently evaluating the potential impact of the adoption of these amendments on its consolidated financial statements. Statement of Cash Flow In November 2016, the FASB issued ASU 2016 - 18, Statement of Cash Flows (Topic 230 ) – Restricted Cash. The amendments in this update require that a statement of cash flows explain the changes during the period in total cash, cash equivalents, and the amounts generally described as restricted cash or cash equivalents. Therefore, amounts of restricted cash and restricted cash equivalents should be included with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. The amendments in this update should be applied retrospectively for each period presented and are effective for financial statements issued for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years. Early adoption is permitted. The Company is currently evaluating the potential impact of the adoption of these amendments on its consolidated financial statements. Intra-Entity Transfers of Assets Other than Inventory In October 2016, the FASB issued ASU 2016 - 16, Accounting for Income Taxes: Intra-Entity Asset Transfers of Assets Other than Inventory. The amendments in this update require that the entity would recognize the tax expense from the sale of the asset in the seller ’s tax jurisdiction when the transfer occurs, even though the pre-tax effects of that transaction are eliminated in consolidation. Any deferred tax asset that arises in the buyer’s jurisdiction would also be recognized at the time of the transfer. The new guidance does not apply to intra-entity transfers on inventory. The amendments in this update should be applied for each period presented and are effective for financial statements issued for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years. The modified retrospective approach will be required for transition to the new guidance, with cumulative-effect adjustment recorded in retained earnings as of the beginning of the period of adoption. Early adoption is permitted in the first quarter of 2017. The Company is currently evaluating the potential impact of the adoption of these amendments on its consolidated financial statements. Revenues from Contracts with Customers In May 2014, the FASB issued ASU 2014 - 09, Revenues from Contracts with Customers, Topic 606, which was a joint project of the FASB and the International Accounting Standards Board to clarify the principles for recognizing revenue and to develop a common revenue standard for U.S. GAAP and International Financial Reporting Standards. The update provides that an entity should recognize revenue in connection with the transfer of goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. Specifically, an entity is required to apply each of the following steps: ( 1 ) identify the contract(s) with the customer; ( 2 ) identify the performance obligations in the contracts; ( 3 ) determine the transaction price; ( 4 ) allocate the transaction price to the performance obligation in the contract; and ( 5 ) recognize revenue when (or as) the entity satisfies a performance obligation. ASU 2014 - 09 also prescribes additional financial presentations and disclosures. The amendments in this update are effective for annual reporting periods beginning after December 15, 2017, including interim periods within those reporting periods. Early adoption is permitted no earlier than 2017 for calendar fiscal year entities. The Company expects the adoption of this standard to have an immaterial impact, if any, on its Electricity segment as it accounts for its PPA ’s under ASC 840, Leases, however, the Company is still evaluating the related potential impact on its investment in an unconsolidated company. The Company is still evaluating the potential impact of the adoption of the standard on its Product segment, however, it believes that such impact, if any, will be immaterial. In March 2016, the FASB issued ASU 2016 - 08, Principal versus Agent Considerations. This update does not change the core principles of the guidance and is intended to clarify the implementation guidance on principal versus agent considerations. When another entity is involved in providing goods or services to a customer, an entity is required to determine if the nature of its promise is to provide the specific good or service itself (that is, the entity is a principal) or to arrange for that good or service to be provided by the other party (that is, the entity is an agent). The guidance includes indicators to assist an entity in determining whether it acts as a principal or agent in a specified transaction. The amendments in this update are effective for annual reporting periods beginning after December 15, 2017, including interim periods within those reporting periods. Early adoption is permitted no earlier than 2017 for calendar fiscal year entities. The Company is currently evaluating the potential impact, if any, of the adoption of these amendments on its consolidated financial statements, however, it believes that any such impact, if any, will be immaterial. Leases In February 2016, the FASB issued ASU 2016 - 02, Leases, Topic 842. This update introduces a number of changes and simplifies previous guidance, primarily the recognition of lease assets and lease liabilities by lessees for those leases classified as operating leases. The Update retains the distinction between finance leases and operating leases and the classification criteria between the two types remains substantially similar. Also, lessor accounting remains largely unchanged from previous guidance. However, key aspects of the Update were aligned with the revenue recognition guidance in Topic 606. Additionally, the Update defines a lease as a contract, or part of a contract, that conveys the right to control the use of an identified asset for a period of time in exchange for consideration. Control over the use of the identified asset means that the customer has both (a) the right to obtain substantially all of the economic benefits from the use of the asset and (b) the right to direct the use of the asset. The amendments in this update are effective for annual reporting periods beginning after December 15, 2018, including interim periods within those reporting periods. Early adoption is permitted. The Company is currently evaluating the potential impact, if any, of the adoption of these amendments on its consolidated financial statements. Recognition and Measurement of Financial Assets and Financial Liabilities In January 2016, the FASB issued ASU 2016 - 01, Recognition and Measurement of Financial Assets and Financial Liabilities. The update primarily requires that an entity present separately, in other comprehensive income, the portion of the total change in the fair value of a liability resulting from a change in the instrument-specific credit risk if the entity has elected to measure the liability at fair value in accordance with the fair value option for financial instruments. The application of this update should be by means of cumulative-effect adjustment to the balance sheet as of the beginning of the fiscal year of adoption. The amendments in this update are effective for financial statements issued for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years. Early adoption is permitted as of the beginning of the fiscal year of adoption. The Company is currently evaluating the potential impact, if any, of the adoption of this update on its consolidated financial statements.

Note 3 - Inventories (Tables)

9 Months Ended

Sep. 30, 2017

Schedule of Inventory, Current [Table Text Block]

	September 30,		December 31,
	2017		2016
	(Dollars in thousands)
Raw materials and purchased parts for assembly	$	9,461	$	5,429
Self-manufactured assembly parts and finished products		9,224		6,571
Total	$	18,685	$	12,000

Note 4 - Unconsolidated Investments (Tables)

9 Months Ended

Sep. 30, 2017

Equity Method Investments [Table Text Block]

	September 30,		December 31,
	2017		2016
	(Dollars in thousands)
Sarulla	$	25,367	$	(11,081	)

Note 5 - Fair Value of Financial Instruments (Tables)

9 Months Ended

Sep. 30, 2017

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

				September 30, 2017
				Fair Value
	Carrying Value at September 30, 2017			Total			Level 1		Level 2			Level 3
	(Dollars in thousands)
Assets:
Current assets:
Cash equivalents (including restricted cash accounts)	$	13,497		$	13,497		$	13,497	$	—		$	—
Derivatives:
Put options on gas price (3)		61			61			—		61			—
Contingent receivable (1)		1,125			1,125			—		—			1,125
Currency forward contracts (2)		486			486			—		486			—
Liabilities:
Current and long-term liabilities:
Derivatives:
Contingent payables (1)	$	(25,913	)	$	(25,913	)	$	—	$	—		$	(25,913	)
Warrants (1)		(3,889	)		(3,889	)							(3,889	)
Currency forward contracts (2)		(203	)		(203	)		—		(203	)		—
	$	(14,836	)	$	(14,836	)	$	13,497	$	344		$	(28,677	)

				December 31, 2016
				Fair Value
	Carrying Value at December 31, 2016			Total			Level 1		Level 2			Level 3
	(Dollars in thousands)
Assets
Current assets:
Cash equivalents (including restricted cash accounts)	$	14,922		$	14,922		$	14,922	$	—		$	—
Derivatives:
Contingent receivable (1)		1,443			1,443			—		—			1,443
Liabilities:
Current and long-term liabilities:
Derivatives:
Contingent payables (1)	$	(11,581	)	$	(11,581	)	$	—	$	—		$	(11,581	)
Warrants (1)		(3,429	)		(3,429	)		—		—			(3,429	)
Currency forward contracts (2)		(481	)		(481	)		—		(481	)		—
	$	874		$	874		$	14,922	$	(481	)	$	(13,567	)

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

		Amount of recognized gain (loss)
Derivatives not designated	Location of recognized	Three Months Ended September 30,					Nine Months Ended September 30,
as hedging instruments	gain (loss)	2017			2016		2017			2016

Put options on natural gas price	Derivatives and foreign currency transaction gains (losses)	$	(121	)	$	—	$	(362	)	$	—
Call options on natural gas price	Derivatives and foreign currency transaction gains (losses)		—			32		—			(1,114	)
Call and put options on oil price	Derivatives and foreign currency transaction gains (losses)		—			230		—			(1,312	)
Contingent considerations	Derivative and foreign currency transaction gains (losses)		(19	)		—		(114	)		—
Currency forward contracts	Derivative and foreign currency and transaction gains (losses)		(887	)		689		2,832			1,154
		$	(1,027	)	$	951	$	2,356		$	(1,272	)

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

	Fair Value				Carrying Amount
	September 30, 2017		December 31, 2016		September 30, 2017		December 31, 2016
	(Dollars in millions)				(Dollars in millions)
Olkaria III Loan - DEG	$	—	$	16.3	$	—	$	15.8
Olkaria III Loan - OPIC		242.9		253.4		233.1		246.6
Olkaria IV Loan - DEG 2		52.4		50.9		50.0		50.0
Amatitlan Loan		34.2		37.3		34.1		36.8
Senior Secured Notes:
Ormat Funding Corp. ("OFC")		—		17.0		—		17.0
OrCal Geothermal Inc. ("OrCal")		34.1		37.4		32.1		35.2
OFC 2 LLC ("OFC 2")		242.5		249.0		236.6		247.2
Don A. Campbell 1 ("DAC1")		88.2		88.9		89.6		92.4
Senior Unsecured Bonds		201.4		200.1		204.3		204.3
Other long-term debt		7.3		10.4		8.0		11.2

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	$	—	$	—	$	242.9	$	242.9
Olkaria IV - DEG 2		—		—		52.4		52.4
Amatitlan Loan		—		34.2		—		34.2
Senior Secured Notes:
OrCal		—		—		34.1		34.1
OFC 2		—		—		242.5		242.5
Don A. Campbell 1		—		—		88.2		88.2
Senior Unsecured Bonds		—		—		201.4		201.4
Other long-term debt		—		—		7.3		7.3
Revolving lines of credit		—		33.9		—		33.9
Deposits		15.2		—		—		15.2

	Level 1		Level 2		Level 3		Total
	(Dollars in millions)
Olkaria III Loan - DEG	$	—	$	—	$	16.3	$	16.3
Olkaria III Loan - OPIC		—		—		253.4		253.4
Olkaria IV - DEG 2		—		—		50.9		50.9
Amatitlan Loan		—		37.3		—		37.3
Senior Secured Notes:
OFC		—		17.0		—		17.0
OrCal		—		—		37.4		37.4
OFC 2		—		—		249.0		249.0
Don A. Campbell 1		—		—		88.9		88.9
Senior Unsecured Bonds		—		—		200.1		200.1
Other long-term debt		—		3.3		7.1		10.4
Deposits		14.4		—		—		14.4

Note 7 - Interest Expense, Net (Tables)

9 Months Ended

Sep. 30, 2017

Schedule of Other Nonoperating Expense, by Component [Table Text Block]

	Three Months Ended September 30,						Nine Months Ended September 30,
	2017			2016			2017			2016

Interest related to sale of tax benefits	$	1,607		$	2,565		$	5,468		$	6,269
Interest expense		13,299			15,726			41,620			47,214
Less — amount capitalized		(3,214	)		(1,154	)		(5,933	)		(1,922	)
	$	11,692		$	17,137		$	41,155		$	51,561

Note 8 - Earnings Per Share (Tables)

9 Months Ended

Sep. 30, 2017

Schedule of Weighted Average Number of Shares [Table Text Block]

	Three Months Ended September 30,				Nine Months Ended September 30,
	2017		2016		2017		2016

Weighted average number of shares used in computation of basic earnings per share		50,367		49,599		49,942		49,410
Add:
Additional shares from the assumed exercise of employee stock options		500		690		727		687

Weighted average number of shares used in computation of diluted earnings per share		50,867		50,289		50,669		50,097

Note 9 - Business Segments (Tables)

9 Months Ended

Sep. 30, 2017

Schedule of Segment Reporting Information, by Segment [Table Text Block]

	Electricity		Product		Consolidated
	(Dollars in thousands)
Three Months Ended September 30, 2017:
Net revenue from external customers	$	112,273	$	44,912	$	157,185
Intersegment revenue		—		28,248		28,248
Operating income		36,205		7,765		43,970
Segment assets at period end (1)		2,371,855		131,883		2,503,738

Three Months Ended September 30, 2016:
Net revenue from external customers	$	109,795	$	74,822		184,617
Intersegment revenue		—		14,835		14,835
Operating income		23,903		24,320		48,223
Segment assets at period end		2,137,845		141,426		2,279,271

Nine Months Ended September 30, 2017:
Net revenues from external customers	$	339,826	$	186,621		526,447
Intersegment revenues		—		61,026		61,026
Operating income		113,220		43,398		156,618
Segment assets at period end (1)		2,371,855		131,883		2,503,738

Nine Months Ended September 30, 2016:
Net revenues from external customers	$	321,664	$	174,408		496,072
Intersegment revenues		—		36,042		36,042
Operating income		91,502		59,151		150,653
Segment assets at period end		2,137,845		141,426		2,279,271

Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Table Text Block]

	Three Months Ended September 30,						Nine Months Ended September 30,
	2017			2016			2017			2016
Revenue:
Total segment revenue	$	157,185		$	184,617		$	526,447		$	496,072
Intersegment revenue		28,248			14,835			61,026			36,042
Elimination of intersegment revenue		(28,248	)		(14,835	)		(61,026	)		(36,042	)
Total consolidated revenue	$	157,185		$	184,617		$	526,447		$	496,072

Operating income:
Operating income	$	43,970		$	48,223		$	156,618		$	150,653
Interest income		255			266			861			831
Interest expense, net		(11,692	)		(17,137	)		(41,155	)		(51,561	)
Derivatives and foreign currency transaction gains (losses)		(1,001	)		(222	)		2,040			(2,592	)
Income attributable to sale of tax benefits		3,506			3,463			14,019			12,380
Other non-operating expense, net		(1,592	)		(5,546	)		(1,678	)		(5,306	)
Total consolidated income before income taxes and equity in losses of investees	$	33,446		$	29,047		$	130,705		$	104,405

Note 1 - General and Basis of Presentation (Details Textual) shares in Millions						1 Months Ended	3 Months Ended			9 Months Ended		12 Months Ended
	Sep. 26, 2017 MWh	Jul. 26, 2017 shares	Jul. 10, 2017 USD ($)	Mar. 15, 2017 USD ($)	Dec. 29, 2016 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 MWh $ / MWh	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Repayments of Secured Debt										$ 14,270,000	$ 6,815,000
Repayments of Long-term Debt										55,226,000	40,997,000
Payments to Acquire Additional Interest in Subsidiaries										2,357,000
Goodwill						$ 20,667,000	$ 20,667,000			20,667,000		$ 6,650,000
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax							2,000		$ 2,000	5,000	7,000
Interest Expense							11,692,000		17,137,000	41,155,000	51,561,000
Income Tax Expense (Benefit)							11,003,000		11,988,000	28,258,000	29,387,000
Accumulated Other Comprehensive Income (Loss), Net of Tax						(5,634,000)	(5,634,000)			(5,634,000)		(7,732,000)
Exploration Abandonment and Impairment Expense							0		1,294,000	0	2,714,000
Cash, Cash Equivalents, and Short-term Investments						77,212,000	77,212,000		$ 90,066,000	77,212,000	$ 90,066,000	230,214,000	$ 185,919,000
Accounts Receivable, Net, Current						98,384,000	$ 98,384,000			98,384,000		$ 80,807,000
Provision for Doubtful Accounts										$ 0
Accounts Receivable [Member] \| Customer Concentration Risk [Member] \| Primary Customers [Member]
Concentration Risk, Percentage										48.00%		60.00%
Sales Revenue, Net [Member] \| Customer Concentration Risk [Member] \| Sierra Pacific Power Company And Nevada Power Company [Member]
Concentration Risk, Percentage							16.30%		14.40%	17.40%	18.60%
Sales Revenue, Net [Member] \| Customer Concentration Risk [Member] \| Kenya Power And Lighting Co LTD [Member]
Concentration Risk, Percentage							17.60%		15.10%	15.70%	16.40%
Sales Revenue, Net [Member] \| Customer Concentration Risk [Member] \| Southern California Public Power Authority [Member]
Concentration Risk, Percentage							9.10%		7.70%	8.90%	9.90%
Sales Revenue, Net [Member] \| Customer Concentration Risk [Member] \| Hyundai (Sarulla Goethermal Power Project) [Member]
Concentration Risk, Percentage							0.90%		24.00%	4.70%	14.00%
UNITED STATES
Cash, Cash Equivalents, and Short-term Investments						23,900,000	$ 23,900,000			$ 23,900,000		$ 72,500,000
Foreign Countries [Member]
Cash, Cash Equivalents, and Short-term Investments						56,000,000	56,000,000			56,000,000		166,200,000
Accounts Receivable, Net, Current						67,500,000	67,500,000			67,500,000		53,300,000
Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax						(600,000)	(600,000)			(600,000)
Reclassification out of Accumulated Other Comprehensive Income [Member]
Interest Expense							(6,000)		$ (3,000)	(9,000)	$ (11,000)
Income Tax Expense (Benefit)							(4,000)		$ (1,000)	(4,000)	$ (4,000)
Viridity Energy, Inc. [Member]
Business Combination, Consideration Transferred					$ 35,300,000
Business Combination, Contingent Consideration, Liability				$ 12,800,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill				$ 34,700,000
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life				17 years
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Working Capital				$ 400,000
Goodwill				$ 13,900,000
Maximum [Member]
Cash, FDIC Insured Amount						250,000	$ 250,000			250,000		$ 250,000
Ormat Nevada ORTP LLC [Member] \| ORTP Transaction [Member]
Payments to Acquire Additional Interest in Subsidiaries			$ 2,400,000
Ormat Funding Corp [Member]
Repayments of Secured Debt										14,300,000
Gain (Loss) on Extinguishment of Debt						1,500,000
Amortization of Debt Issuance Costs						200,000
DEG [Member]
Gain (Loss) on Extinguishment of Debt						500,000
Amortization of Debt Issuance Costs										$ 400,000
Repayments of Long-term Debt						$ 11,800,000
ORIX Corporation [Member]
Number of Shares Purchased by Investor \| shares		11
Percentage Ownership in Company Purchased by Investor		22.00%
Voting Rights, Number of Directors Designated		3
Number of Directors after Acquisition Transaction		9
Voting Rights, Effective Rate Cap		25.00%
Southern California Public Power Authority [Member] \| Ormat Nevada ORTP LLC [Member] \| Minimum [Member]
Expected Power Generating Capacity \| MWh								135
Southern California Public Power Authority [Member] \| Ormat Nevada ORTP LLC [Member] \| Maximum [Member]
Expected Power Generating Capacity \| MWh								185
Southern California Public Power Authority [Member] \| ONGP, LLC [Member]
Expected Power Generating Capacity \| MWh								150
Power Plant Usage Agreement Term								5 years
Power Purchase Agreements Term								26 years
Power Purchase Agreements, Number of Power Plants Portfolio								9
Power Purchase Agreements, Fixed Price Per MWh \| $ / MWh								75.5
Geotermica Plantares [Member]
Expected Power Generating Capacity \| MWh	35
Power Plant Usage Agreement Term	15 years
Geotermica Plantares [Member] \| ENEE [Member]
Power Purchase Agreements Term	30 years

Note 3 - Inventories - Inventories, Current (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Raw materials and purchased parts for assembly	$ 9,461	$ 5,429
Self-manufactured assembly parts and finished products	9,224	6,571
Total	$ 18,685	$ 12,000

Note 4 - Unconsolidated Investments (Details Textual) $ in Thousands		3 Months Ended		9 Months Ended		12 Months Ended
	Jun. 04, 2014 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($) MWh	Sep. 30, 2016 USD ($)	Dec. 31, 2014 USD ($)	May 23, 2014 USD ($)	May 16, 2014 USD ($)
Number of Commercial Lenders in Funding Consortium								6
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax		$ 618	$ 1,337	$ 271	$ (3,829)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest		$ 22,780	14,406	$ 100,757	70,284
Intersegment Eliminations [Member]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest						$ 14,100
Sarulla [Member] \| Lenders Consortium [Member]
Senior Notes								$ 1,170,000
Sarulla [Member]
Jointly Owned Utility Plant, Proportionate Ownership Share		12.75%		12.75%
Expected Power Generating Capacity \| MWh				330
Power Plant Usage Agreement Term				30 years
Number Of Phases Of Construction				3
Power Utilization \| MWh				110
Percentage of Required Production Capacity		100.00%		100.00%
Percentage of Required Injection Capacity		85.00%		85.00%
Supply Commitment, Remaining Minimum Amount Committed						$ 255,600
Payments to Acquire Projects		$ 10,500		$ 37,900
Accumulated Cash Contributions to Acquire Projects		49,800		49,800
Sarulla [Member] \| Interest Rate Swap [Member]
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax		600	1,300	(300)	3,800
Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax		5,600		5,600
Sarulla [Member] \| Interest Rate Swap [Member] \| Sarulla Project Company [Member]
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax		$ 4,800	$ 10,500	$ 2,100	$ (30,000)
Sarulla [Member] \| Lenders Consortium [Member] \| Interest Rate Swap [Member] \| London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument, Basis Spread on Variable Rate	3.4565%
Sarulla [Member] \| Lenders Consortium [Member] \| Subject to Fixed Interest Rate [Member]
Senior Notes							$ 100,000
Sarulla [Member] \| Lenders Consortium [Member] \| Subject to Fixed LIBOR Interest Rate [Member]
Senior Notes							$ 1,070,000
Sarulla [Member] \| Lenders Consortium [Member] \| Subject to Fixed LIBOR Interest Rate [Member] \| Interest Rate Swap [Member]
Senior Notes	$ 960,000

Note 4 - Unconsolidated Investments - Unconsolidated Investments Mainly in Power Plants (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Sarulla	$ (6,481)	$ (4,772)
Sarulla [Member]
Sarulla	$ 25,367	$ (11,081)

Note 5 - Fair Value of Financial Instruments (Details Textual) BTU in Millions, $ in Millions				1 Months Ended
	Jan. 12, 2017 USD ($) BTU $ / item	Feb. 24, 2016 USD ($) Boe $ / item	Feb. 02, 2016 USD ($) BTU $ / item	Mar. 31, 2016 Boe $ / item	Feb. 28, 2016 $ / item
Derivative, Number of Options Rolled				2
Henry Hub Natural Gas Future ("NG") Contracts [Member] \| Put Option [Member]
Derivative, Nonmonetary Notional Amount, Energy Measure \| BTU	4.1
Derivative, Price Risk Option Strike Price	3
Payments for Derivative Instrument, Investing Activities \| $	$ 0.7
Henry Hub Natural Gas Future ("NG") Contracts [Member] \| Call Option [Member]
Derivative, Nonmonetary Notional Amount, Energy Measure \| BTU			4.1
Derivative, Price Risk Option Strike Price			2
Proceeds from Derivative Instrument, Investing Activities \| $			$ 1.9
Brent Oil Future Contracts [Member]
Derivative, Nonmonetary Notional Amount, Energy Measure \| Boe		185,000
Brent Oil Future Contracts [Member] \| Minimum [Member]
Derivative, Price Risk Option Strike Price		32.8
Brent Oil Future Contracts [Member] \| Maximum [Member]
Derivative, Price Risk Option Strike Price		35.5
Brent Oil Future Contracts [Member] \| Call Option [Member]
Proceeds from Derivative Instrument, Investing Activities \| $		$ 1.1
Rolled Two Existing Options [Member]
Derivative, Nonmonetary Notional Amount, Energy Measure \| Boe				31,800
Rolled Two Existing Options [Member] \| Minimum [Member]
Derivative, Price Risk Option Strike Price				41
Rolled Two Existing Options [Member] \| Maximum [Member]
Derivative, Price Risk Option Strike Price				42.5
Before Rolling Two Existing Options [Member] \| Minimum [Member]
Derivative, Price Risk Option Strike Price					32.8
Before Rolling Two Existing Options [Member] \| Maximum [Member]
Derivative, Price Risk Option Strike Price					33.5
Short Risk Reversal Transactions, Rolling Existing Call Option 1 [Member]
Derivative, Nonmonetary Notional Amount, Energy Measure \| Boe				16,500
Short Risk Reversal Transactions, Rolling Existing Call Option 1 [Member] \| Minimum [Member]
Derivative, Price Risk Option Strike Price				28.5
Short Risk Reversal Transactions, Rolling Existing Call Option 1 [Member] \| Maximum [Member]
Derivative, Price Risk Option Strike Price				37.5
Short Risk Reversal Transactions, Rolling Existing Call Option 2 [Member]
Derivative, Nonmonetary Notional Amount, Energy Measure \| Boe				17,000
Short Risk Reversal Transactions, Rolling Existing Call Option 2 [Member] \| Minimum [Member]
Derivative, Price Risk Option Strike Price				28
Short Risk Reversal Transactions, Rolling Existing Call Option 2 [Member] \| Maximum [Member]
Derivative, Price Risk Option Strike Price				38.5

Note 5 - Fair Value of Financial Instruments - Financial Assets and Liabilities at Fair Value (Details) - USD ($)
$ in Thousands

Sep. 30, 2017

Dec. 31, 2016

Reported Value Measurement [Member]

Cash equivalents (including restricted cash accounts)

$ 13,497

$ 14,922

(14,836)

874

Reported Value Measurement [Member] | Put Options on Natural Gas Price [Member]

Reported Value Measurement [Member] | Contingent Receivable [Member]

^[1]

61

Reported Value Measurement [Member] | Contingent Payable [Member]

^[2]

1,125

1,443

Reported Value Measurement [Member] | Currency Forward Contracts [Member]

^[2]

(25,913)

(11,581)

^[3]

486

Reported Value Measurement [Member] | Warrant [Member]

^[3]

(203)

(481)

Estimate of Fair Value Measurement [Member]

^[2]

(3,889)

(3,429)

Cash equivalents (including restricted cash accounts)

13,497

14,922

(14,836)

874

Estimate of Fair Value Measurement [Member] | Put Options on Natural Gas Price [Member]

Estimate of Fair Value Measurement [Member] | Contingent Receivable [Member]

^[1]

61

Estimate of Fair Value Measurement [Member] | Contingent Payable [Member]

^[2]

1,125

1,443

Estimate of Fair Value Measurement [Member] | Currency Forward Contracts [Member]

^[2]

(25,913)

(11,581)

^[3]

486

Estimate of Fair Value Measurement [Member] | Warrant [Member]

^[3]

(203)

(481)

Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]

^[2]

(3,889)

(3,429)

Cash equivalents (including restricted cash accounts)

13,497

14,922

13,497

14,922

Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member] | Put Options on Natural Gas Price [Member]

Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member] | Contingent Receivable [Member]

^[1]

Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member] | Contingent Payable [Member]

^[2]

Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member] | Currency Forward Contracts [Member]

^[2]

^[3]

Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member] | Warrant [Member]

^[3]

Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]

^[2]

Cash equivalents (including restricted cash accounts)

344

(481)

Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Put Options on Natural Gas Price [Member]

Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Contingent Receivable [Member]

^[1]

61

Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Contingent Payable [Member]

^[2]

Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Currency Forward Contracts [Member]

^[2]

^[3]

486

Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Warrant [Member]

^[3]

(203)

(481)

Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member]

^[2]

Cash equivalents (including restricted cash accounts)

(28,677)

(13,567)

Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member] | Put Options on Natural Gas Price [Member]

Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member] | Contingent Receivable [Member]

^[1]

Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member] | Contingent Payable [Member]

^[2]

1,125

1,443

Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member] | Currency Forward Contracts [Member]

^[2]

(25,913)

(11,581)

^[3]

Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member] | Warrant [Member]

^[3]

^[2]

$ (3,889)

$ (3,429)

[1]	These amounts relate to natural gas put options, valued primarily based on observable inputs, including spot prices on related commodity indices, and are included within Prepaid expenses and other on September 30, 2017 in the consolidated balance sheets with the corresponding gain or loss being recognized within Derivatives and foreign currency transaction gains (losses) in the consolidated statement of operations and comprehensive income.
[2]	These amounts relate to contingent receivables and payables relating to the Viridity acquisition and Guadeloupe power plant purchase transaction, valued primarily based on unobservable inputs and are included within Prepaid expenses and other, Accounts payable and accrued expenses and Other long-term liabilities on September 30, 2017 and within Prepaid expenses and other and Other long-term liabilities on December 31, 2016 in the consolidated balance sheets with the corresponding gain or loss being recognized within Derivatives and foreign currency transaction gains (losses) in the consolidated statement of operations and comprehensive income.
[3]	These amounts relate to currency forward contracts valued primarily based on observable inputs, including forward and spot prices for currencies, net of contracted rates and then multiplied by notional amounts, and are included within Prepaid expenses and other and Accounts payable and accrued expenses on September 30, 2017 and December 31, 2016, in the consolidated balance sheet with the corresponding gain or loss being recognized within Derivatives and foreign currency transaction gains (losses) in the consolidated statement of operations and comprehensive income.

Note 5 - Fair Value of Financial Instruments - Amounts of Gain (Loss) Recognized in Condensed Consolidated Statements on Derivative Instruments Not Designated as Hedges (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Amount of gain (loss) recognized	$ (1,027)	$ 951	$ 2,356	$ (1,272)
Foreign Currency Gain (Loss) [Member] \| Put Options on Natural Gas Price [Member]
Amount of gain (loss) recognized	(121)		(362)
Foreign Currency Gain (Loss) [Member] \| Call Option on Natural Gas Price [Member]
Amount of gain (loss) recognized		32		(1,114)
Foreign Currency Gain (Loss) [Member] \| Call and Put Options on Oil Price [Member]
Amount of gain (loss) recognized		230		(1,312)
Foreign Currency Gain (Loss) [Member] \| Contingent Considerations [Member]
Amount of gain (loss) recognized	(19)		(114)
Foreign Currency Gain (Loss) [Member] \| Currency Forward Contracts [Member]
Amount of gain (loss) recognized	$ (887)	$ 689	$ 2,832	$ 1,154

Note 5 - Fair Value of Financial Instruments - Fair Value of Long-term Debt Approximates Its Carrying Amount, Exceptions (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Estimate of Fair Value Measurement [Member]
Other long-term debt	$ 7.3	$ 10.4
Reported Value Measurement [Member]
Other long-term debt	8.0	11.2
Olkaria III DEG [Member]
Loans		16.3
Olkaria III DEG [Member] \| Estimate of Fair Value Measurement [Member]
Loans		16.3
Olkaria III DEG [Member] \| Reported Value Measurement [Member]
Loans		15.8
Olkaria III OPIC [Member]
Loans	242.9	253.4
Olkaria III OPIC [Member] \| Estimate of Fair Value Measurement [Member]
Loans	242.9	253.4
Olkaria III OPIC [Member] \| Reported Value Measurement [Member]
Loans	233.1	246.6
Olkaria IV Loan - DEG 2 [Member]
Loans	52.4	50.9
Olkaria IV Loan - DEG 2 [Member] \| Estimate of Fair Value Measurement [Member]
Loans	52.4	50.9
Olkaria IV Loan - DEG 2 [Member] \| Reported Value Measurement [Member]
Loans	50.0	50.0
Amatitlan Loan [Member]
Loans	34.2	37.3
Amatitlan Loan [Member] \| Estimate of Fair Value Measurement [Member]
Loans	34.2	37.3
Amatitlan Loan [Member] \| Reported Value Measurement [Member]
Loans	34.1	36.8
Ormat Funding Corp [Member]
Notes		17.0
Ormat Funding Corp [Member] \| Estimate of Fair Value Measurement [Member]
Notes		17.0
Ormat Funding Corp [Member] \| Reported Value Measurement [Member]
Notes		17.0
OrCal Geothermal Inc [Member]
Notes	34.1	37.4
OrCal Geothermal Inc [Member] \| Estimate of Fair Value Measurement [Member]
Notes	34.1	37.4
OrCal Geothermal Inc [Member] \| Reported Value Measurement [Member]
Notes	32.1	35.2
OFC Two Senior Secured Notes [Member]
Notes	242.5	249.0
OFC Two Senior Secured Notes [Member] \| Estimate of Fair Value Measurement [Member]
Notes	242.5	249.0
OFC Two Senior Secured Notes [Member] \| Reported Value Measurement [Member]
Notes	236.6	247.2
Don A. Campbell 1 ("DAC1") [Member]
Notes	88.2	88.9
Don A. Campbell 1 ("DAC1") [Member] \| Estimate of Fair Value Measurement [Member]
Notes	88.2	88.9
Don A. Campbell 1 ("DAC1") [Member] \| Reported Value Measurement [Member]
Notes	89.6	92.4
Senior Unsecured Bonds [Member]
Notes		200.1
Senior Unsecured Bonds	201.4
Senior Unsecured Bonds [Member] \| Estimate of Fair Value Measurement [Member]
Senior Unsecured Bonds	201.4	200.1
Senior Unsecured Bonds [Member] \| Reported Value Measurement [Member]
Senior Unsecured Bonds	$ 204.3	$ 204.3

Note 5 - Fair Value of Financial Instruments - Fair Value of Financial Instruments (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Revolving lines of credit	$ 33.9
Deposits	15.2
Deposits		$ 14.4
Fair Value, Inputs, Level 1 [Member]
Revolving lines of credit
Deposits	15.2
Deposits		14.4
Fair Value, Inputs, Level 2 [Member]
Revolving lines of credit	33.9
Deposits
Deposits
Fair Value, Inputs, Level 3 [Member]
Revolving lines of credit
Deposits
Deposits
Olkaria III OPIC [Member]
Loans	242.9	253.4
Olkaria III OPIC [Member] \| Fair Value, Inputs, Level 1 [Member]
Loans
Olkaria III OPIC [Member] \| Fair Value, Inputs, Level 2 [Member]
Loans
Olkaria III OPIC [Member] \| Fair Value, Inputs, Level 3 [Member]
Loans	242.9	253.4
Olkaria III DEG [Member]
Loans		16.3
Olkaria III DEG [Member] \| Fair Value, Inputs, Level 1 [Member]
Loans
Olkaria III DEG [Member] \| Fair Value, Inputs, Level 2 [Member]
Loans
Olkaria III DEG [Member] \| Fair Value, Inputs, Level 3 [Member]
Loans		16.3
Olkaria IV Loan - DEG 2 [Member]
Loans	52.4	50.9
Olkaria IV Loan - DEG 2 [Member] \| Fair Value, Inputs, Level 1 [Member]
Loans
Olkaria IV Loan - DEG 2 [Member] \| Fair Value, Inputs, Level 2 [Member]
Loans
Olkaria IV Loan - DEG 2 [Member] \| Fair Value, Inputs, Level 3 [Member]
Loans	52.4	50.9
Amatitlan Loan [Member]
Loans	34.2	37.3
Amatitlan Loan [Member] \| Fair Value, Inputs, Level 1 [Member]
Loans
Amatitlan Loan [Member] \| Fair Value, Inputs, Level 2 [Member]
Loans	34.2	37.3
Amatitlan Loan [Member] \| Fair Value, Inputs, Level 3 [Member]
Loans
OrCal Geothermal Inc [Member]
Notes	34.1	37.4
OrCal Geothermal Inc [Member] \| Fair Value, Inputs, Level 1 [Member]
Notes
OrCal Geothermal Inc [Member] \| Fair Value, Inputs, Level 2 [Member]
Notes
OrCal Geothermal Inc [Member] \| Fair Value, Inputs, Level 3 [Member]
Notes	34.1	37.4
OFC Two Senior Secured Notes [Member]
Notes	242.5	249.0
OFC Two Senior Secured Notes [Member] \| Fair Value, Inputs, Level 1 [Member]
Notes
OFC Two Senior Secured Notes [Member] \| Fair Value, Inputs, Level 2 [Member]
Notes
OFC Two Senior Secured Notes [Member] \| Fair Value, Inputs, Level 3 [Member]
Notes	242.5	249.0
Ormat Funding Corp [Member]
Notes		17.0
Ormat Funding Corp [Member] \| Fair Value, Inputs, Level 1 [Member]
Notes
Ormat Funding Corp [Member] \| Fair Value, Inputs, Level 2 [Member]
Notes		17.0
Ormat Funding Corp [Member] \| Fair Value, Inputs, Level 3 [Member]
Notes
Don A. Campbell 1 ("DAC1") [Member]
Notes	88.2	88.9
Don A. Campbell 1 ("DAC1") [Member] \| Fair Value, Inputs, Level 1 [Member]
Notes
Don A. Campbell 1 ("DAC1") [Member] \| Fair Value, Inputs, Level 2 [Member]
Notes
Don A. Campbell 1 ("DAC1") [Member] \| Fair Value, Inputs, Level 3 [Member]
Notes	88.2	88.9
Senior Unsecured Bonds [Member]
Notes		200.1
Senior Unsecured Bonds	201.4
Senior Unsecured Bonds [Member] \| Fair Value, Inputs, Level 1 [Member]
Notes
Senior Unsecured Bonds
Senior Unsecured Bonds [Member] \| Fair Value, Inputs, Level 2 [Member]
Notes
Senior Unsecured Bonds
Senior Unsecured Bonds [Member] \| Fair Value, Inputs, Level 3 [Member]
Notes		200.1
Senior Unsecured Bonds	201.4
Other Long-term Debt [Member]
Other long-term debt	7.3	10.4
Other Long-term Debt [Member] \| Fair Value, Inputs, Level 1 [Member]
Other long-term debt
Other Long-term Debt [Member] \| Fair Value, Inputs, Level 2 [Member]
Other long-term debt		3.3
Other Long-term Debt [Member] \| Fair Value, Inputs, Level 3 [Member]
Other long-term debt	$ 7.3	$ 7.1

Note 6 - Stock-based Compensation (Details Textual) - shares	1 Months Ended	12 Months Ended
	May 31, 2012	Dec. 31, 2004
2004 Stock Incentive Plan [Member] \| Stock Options And Stock Appreciation Rights [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized		3,750,000
2004 Stock Incentive Plan [Member] \| Stock Options And Stock Appreciation Rights [Member] \| Share-based Compensation Award, Tranche One [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage		25.00%
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period		2 years
2004 Stock Incentive Plan [Member] \| Stock Options And Stock Appreciation Rights [Member] \| Share-based Compensation Award, Tranche Two [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage		25.00%
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period		3 years
2004 Stock Incentive Plan [Member] \| Stock Options And Stock Appreciation Rights [Member] \| Share-based Compensation Award, Tranche Three [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage		50.00%
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period		4 years
2004 Stock Incentive Plan [Member] \| Employee Stock Option [Member] \| Non Employee Director [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period		1 year
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period		10 years
2012 Stock Incentive Plan [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period	6 years
2012 Stock Incentive Plan [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period	10 years
2012 Stock Incentive Plan [Member] \| Officer [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized	400,000
2012 Stock Incentive Plan [Member] \| Stock Options And Stock Appreciation Rights [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized	4,000,000
2012 Stock Incentive Plan [Member] \| Stock Options And Stock Appreciation Rights [Member] \| Share-based Compensation Award, Tranche One [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage	25.00%
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	2 years
2012 Stock Incentive Plan [Member] \| Stock Options And Stock Appreciation Rights [Member] \| Share-based Compensation Award, Tranche Two [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage	25.00%
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	3 years
2012 Stock Incentive Plan [Member] \| Stock Options And Stock Appreciation Rights [Member] \| Share-based Compensation Award, Tranche Three [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage	50.00%
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	4 years
2012 Stock Incentive Plan [Member] \| Employee Stock Option [Member] \| Non Employee Director [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	1 year

Note 7 - Interest Expense, Net - Components of Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Interest related to sale of tax benefits	$ 1,607	$ 2,565	$ 5,468	$ 6,269
Interest expense	13,299	15,726	41,620	47,214
Less — amount capitalized	(3,214)	(1,154)	(5,933)	(1,922)
Interest Expense	$ 11,692	$ 17,137	$ 41,155	$ 51,561

Note 8 - Earnings Per Share (Details Textual) - shares	3 Months Ended		9 Months Ended
Note 8 - Earnings Per Share (Details Textual) - shares	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	8,851	225,191	6,494	116,641

Note 8 - Earnings Per Share - Shares Used to Calculate Earnings Per Share (Details) - shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Weighted average number of shares used in computation of basic earnings per share (in shares)	50,367	49,599	49,942	49,410
Additional shares from the assumed exercise of employee stock options (in shares)	500	690	727	687
Weighted average number of shares used in computation of diluted earnings per share (in shares)	50,867	50,289	50,669	50,097

Note 9 - Business Segments (Details Textual) $ in Thousands	9 Months Ended
Note 9 - Business Segments (Details Textual) $ in Thousands	Sep. 30, 2017 USD ($)	Dec. 31, 2016 USD ($)
Number of Reportable Segments	2
Goodwill	$ 20,667	$ 6,650
Electricity [Member]
Goodwill	$ 20,700

Note 9 - Business Segments - Summarized Financial Information Concerning Reportable Segments (Details) - USD ($)
$ in Thousands

3 Months Ended

9 Months Ended

Sep. 30, 2017

Sep. 30, 2016

Sep. 30, 2017

Sep. 30, 2016

Dec. 31, 2016

Segment assets at period end

$ 157,185

$ 184,617

$ 526,447

$ 496,072

Operating income

43,970

48,223

156,618

150,653

2,503,738

^[1]

2,279,271

2,503,738

^[1]

2,279,271

$ 2,461,569

Intersegment Eliminations [Member]

28,248

14,835

61,026

36,042

Electricity [Member]

Segment assets at period end

112,273

109,795

339,826

321,664

Operating income

36,205

23,903

113,220

91,502

2,371,855

^[1]

2,137,845

2,371,855

^[1]

2,137,845

Electricity [Member] | Intersegment Eliminations [Member]

Product Segment [Member]

Segment assets at period end

44,912

74,822

186,621

174,408

Operating income

7,765

24,320

43,398

59,151

131,883

^[1]

141,426

131,883

^[1]

141,426

Product Segment [Member] | Intersegment Eliminations [Member]