Ormat (ORA) 10-K 16 Mar 18 2017 FY Annual report Financial data

Document And Entity Information

Document And Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2017	Feb. 23, 2018	Jun. 30, 2017
Document Information [Line Items]
Entity Registrant Name	ORMAT TECHNOLOGIES, INC.
Entity Central Index Key	1,296,445
Trading Symbol	ora
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	No
Entity Common Stock, Shares Outstanding (in shares)		50,609,051
Entity Public Float			$ 2,315,466,032
Document Type	10-K
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Amendment Flag	false

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands		Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents		$ 47,818	$ 230,214
Restricted cash and cash equivalents (primarily related to VIEs)		48,825	34,262
Receivables:
Trade		110,410	80,807
Other		13,828	17,482
Inventories		19,551	12,000
Costs and estimated earnings in excess of billings on uncompleted contracts		40,945	52,198
Prepaid expenses and other		40,269	45,867
Total current assets		321,646	472,830
Investment in an unconsolidated company		34,084
Deposits and other		21,599	18,553
Deferred income taxes		20,135
Deferred charges		49,834	43,773
Property, plant and equipment, net		1,734,691	1,556,378
Construction-in-process		293,542	306,709
Deferred financing and lease costs, net		4,674	3,923
Intangible assets, net		85,420	52,753
Goodwill		21,037	6,650
Total assets	[1]	2,586,662	2,461,569
Current liabilities:
Accounts payable and accrued expenses		153,796	91,650
Short term revolving credit lines with banks (full recourse)		51,500
Billings in excess of costs and estimated earnings on uncompleted contracts		20,241	31,630
Current portion of long-term debt:
Senior secured notes		33,226	32,234
Other loans		21,495	21,495
Full recourse		3,087	12,242
Total current liabilities		283,345	189,251
Long-term debt, net of current portion:
Senior secured notes (less deferred financing costs of $8,113 and $9,177, respectively)		311,668	350,388
Other loans (less deferred financing costs of $5,258 and $6,409, respectively)		242,385	261,845
Senior unsecured bonds (less deferred financing costs of $580 and $755, respectively)		203,752	203,577
Other loans (less deferred financing costs of $1,011 and $1,346, respectively)		46,489	57,063
Investment in an unconsolidated company			11,081
Liability associated with sale of tax benefits		44,634	54,662
Deferred lease income		51,520	54,561
Deferred income taxes			35,382
Liability for unrecognized tax benefits		8,890	5,738
Liabilities for severance pay		21,141	18,600
Asset retirement obligation		27,110	23,348
Other long-term liabilities		18,853	21,294
Total liabilities		1,259,787	1,286,790
Commitments and contingencies (Note 22)
Redeemable noncontrolling interest		6,416	4,772
Equity:
Common stock, par value $0.001 per share; 200,000,000 shares authorized; 50,609,051 and 49,667,340 shares issued and outstanding as of December 31, 2017 and December 31, 2016, respectively		51	50
Additional paid-in capital		888,778	869,463
Retained earnings		351,622	216,644
Accumulated other comprehensive income (loss)		(4,314)	(7,732)
Total equity attributable to Company's stockholders		1,236,137	1,078,425
Noncontrolling interest		84,322	91,582
Total equity		1,320,459	1,170,007
Total liabilities, redeemable noncontrolling interest and equity		$ 2,586,662	$ 2,461,569
[1]	Electricity segment assets include goodwill in the amount of $21.0 million and $6.7 million as of December 31, 2017 and 2016, respectively.

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Property, plant and equipment, net	$ 1,734,691	$ 1,556,378
Construction-in-process	$ 293,542	$ 306,709
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	200,000,000	200,000,000
Common stock, shares issued (in shares)	50,609,051	49,667,340
Common stock, shares outstanding (in shares)	50,609,051	49,667,340
Senior Secured Notes [Member]
Deferred financing costs	$ 8,113	$ 9,177
Other Loans, Limited and Non-recourse [Member]
Deferred financing costs	5,258	6,409
Senior Unsecured Bonds [Member]
Deferred financing costs	580	755
Other Loans, Full Recourse [Member]
Deferred financing costs	1,011	1,346
Variable Interest Entity, Primary Beneficiary [Member]
Property, plant and equipment, net	1,631,900	1,483,224
Construction-in-process	$ 142,717	$ 120,853

Consolidated Statements of Oper

Consolidated Statements of Operations and Comprehensive Income (Loss) - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues:
Electricity	$ 468,329	$ 436,292	$ 375,920
Product	224,483	226,299	218,724
Total revenues	692,812	662,591	594,644
Cost of revenues:
Electricity	272,266	261,573	242,612
Product	152,094	130,223	133,753
Total cost of revenues	424,360	391,796	376,365
Gross profit	268,452	270,795	218,279
Operating expenses:
Research and development expenses	3,157	2,762	1,780
Selling and marketing expenses	15,600	16,424	16,077
General and administrative expenses	42,881	46,710	34,782
Write-off of unsuccessful exploration activities	1,796	3,017	1,579
Operating income	205,018	201,882	164,061
Other income (expense):
Interest income	988	971	297
Interest expense, net	(54,142)	(67,389)	(72,577)
Derivatives and foreign currency transaction gains (losses)	2,654	(5,534)	(1,622)
Income attributable to sale of tax benefits	17,878	16,503	25,431
Other non-operating expense, net	(1,666)	(5,345)	(1,991)
Income from continuing operations before income taxes and equity in losses of investees	170,730	141,088	113,599
Income tax (provision) benefit	1,411	(31,837)	15,258
Equity in earnings (losses) of investees, net	(1,957)	(7,735)	(5,508)
Income from continuing operations	170,184	101,516	123,349
Net income attributable to noncontrolling interest	(14,695)	(7,586)	(3,776)
Net income attributable to the Company's stockholders	155,489	93,930	119,573
Comprehensive income:
Net income	170,184	101,516	123,349
Other comprehensive income (loss), net of related taxes:
Currency translation adjustments	3,440	(1,648)
Change in unrealized gains or losses in respect of the Company's share in derivatives instruments of unconsolidated investment	804	1,185	1,028
Loss in respect of derivative instruments designated for cash flow hedge	84	87	91
Amortization of unrealized gains in respect of derivative instruments designated for cash flow hedge	(73)	(96)	(118)
Comprehensive income	174,439	101,044	124,350
Comprehensive income attributable to noncontrolling interest	(15,532)	(7,179)	(3,776)
Comprehensive income attributable to the Company's stockholders	$ 158,907	$ 93,865	$ 120,574
Basic:
Net income (in dollars per share)	$ 3.10	$ 1.90	$ 2.46
Diluted:
Net income (in dollars per share)	$ 3.06	$ 1.87	$ 2.43
Weighted average number of shares used in computation of earnings per share attributable to the Company's stockholders:
Basic (in shares)	50,110	49,469	48,562
Diluted (in shares)	50,769	50,140	49,187
Dividend per share declared (in dollars per share)	$ 0.41	$ 0.52	$ 0.26

Consolidated Statements of Equi

Consolidated Statements of Equity - USD ($) shares in Thousands, $ in Thousands	Ormat Nevada ORTP LLC [Member]Common Stock [Member]	Ormat Nevada ORTP LLC [Member]Additional Paid-in Capital [Member]	Ormat Nevada ORTP LLC [Member]Retained Earnings [Member]	Ormat Nevada ORTP LLC [Member]AOCI Attributable to Parent [Member]	Ormat Nevada ORTP LLC [Member]Parent [Member]	Ormat Nevada ORTP LLC [Member]Noncontrolling Interest [Member]	Ormat Nevada ORTP LLC [Member]	OPC LLC [Member]Common Stock [Member]	OPC LLC [Member]Additional Paid-in Capital [Member]	OPC LLC [Member]Retained Earnings [Member]	OPC LLC [Member]AOCI Attributable to Parent [Member]	OPC LLC [Member]Parent [Member]	OPC LLC [Member]Noncontrolling Interest [Member]	OPC LLC [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Parent [Member]	Noncontrolling Interest [Member]	Total
Balance (in shares) at Dec. 31, 2014															45,537
Balance at Dec. 31, 2014															$ 46	$ 742,006	$ 41,539	$ (8,668)	$ 774,923	$ 11,823	$ 786,746
Stock-based compensation																3,955			3,955		3,955
Exercise of options by employees and directors (in shares)															574
Exercise of options by employees and directors																6,085			6,085		6,085
Share exchange with Parent (in shares)															2,996
Share exchange with Parent															$ 3	26,012			26,015		26,015
Cash paid to noncontrolling interest																				(7,196)	(7,196)
Cash dividend declared																	(12,716)		(12,716)		(12,716)
Issuance of shares to noncontrolling interest, net of transaction costs																71,165			71,165	85,470	156,635
Net income																	119,573		119,573	3,776	123,349
Other comprehensive income (loss), net of related taxes:
Loss in respect of derivative instruments designated for cash flow hedge																		91	91		91
Change in unrealized gains or losses in respect of the Company's share in derivatives instruments of unconsolidated investment																		1,028	1,028		1,028
Amortization of unrealized gains in respect of derivative instruments designated for cash flow hedge																		(118)	(118)		(118)
Stock-based compensation																3,955			3,955		3,955
Exercise of options by employees and directors (in shares)															574
Exercise of options by employees and directors																6,085			6,085		6,085
Cash paid to noncontrolling interest																				(7,196)	(7,196)
Cash dividend declared																	(12,716)		(12,716)		(12,716)
Issuance of shares to noncontrolling interest, net of transaction costs																71,165			71,165	85,470	156,635
Net income																	119,573		119,573	3,776	123,349
Currency translation adjustment
Balance (in shares) at Dec. 31, 2015															49,107
Balance at Dec. 31, 2015															$ 49	849,223	148,396	(7,667)	990,001	93,873	1,083,874
Stock-based compensation																5,157			5,157		5,157
Exercise of options by employees and directors (in shares)															560
Exercise of options by employees and directors															$ 1	7,249			7,250		7,250
Cash paid to noncontrolling interest																				(57,391)	(57,391)
Cash dividend declared																	(25,682)		(25,682)		(25,682)
Issuance of shares to noncontrolling interest, net of transaction costs																7,834			7,834	36,268	44,102
Net income																	93,930		93,930	7,302	101,232
Other comprehensive income (loss), net of related taxes:
Loss in respect of derivative instruments designated for cash flow hedge																		87	87		87
Change in unrealized gains or losses in respect of the Company's share in derivatives instruments of unconsolidated investment																		1,185	1,185		1,185
Amortization of unrealized gains in respect of derivative instruments designated for cash flow hedge																		(96)	(96)		(96)
Stock-based compensation																5,157			5,157		5,157
Exercise of options by employees and directors (in shares)															560
Exercise of options by employees and directors															$ 1	7,249			7,250		7,250
Cash paid to noncontrolling interest																				(57,391)	(57,391)
Cash dividend declared																	(25,682)		(25,682)		(25,682)
Increase in noncontrolling interest in Guadeloupe																				8,240	8,240
Increase in noncontrolling interest in Opal Geo																				3,697	3,697
Issuance of shares to noncontrolling interest, net of transaction costs																7,834			7,834	36,268	44,102
Net income																	93,930		93,930	7,302	101,232
Currency translation adjustment																		(1,241)	(1,241)	(407)	(1,648)
Balance (in shares) at Dec. 31, 2016															49,667
Balance at Dec. 31, 2016															$ 50	869,463	216,644	(7,732)	1,078,425	91,582	1,170,007
Stock-based compensation																8,760			8,760		8,760
Exercise of options by employees and directors (in shares)															942
Exercise of options by employees and directors															$ 1	16,111			16,112		16,112
Cash paid to noncontrolling interest																				(21,313)	(21,313)
Cash dividend declared																	(20,511)		(20,511)		(20,511)
Other comprehensive income (loss), net of related taxes:
Loss in respect of derivative instruments designated for cash flow hedge																		84	84		84
Change in unrealized gains or losses in respect of the Company's share in derivatives instruments of unconsolidated investment																		804	804		804
Amortization of unrealized gains in respect of derivative instruments designated for cash flow hedge																		(73)	(73)		(73)
Stock-based compensation																8,760			8,760		8,760
Exercise of options by employees and directors (in shares)															942
Exercise of options by employees and directors															$ 1	16,111			16,112		16,112
Cash paid to noncontrolling interest																				(21,313)	(21,313)
Cash dividend declared																	(20,511)		(20,511)		(20,511)
Increase in noncontrolling interest in Opal Geo																	155,489		155,489	13,643	169,132
Currency translation adjustment																		2,603	2,603	837	3,440
Buyout of Class B membership		$ 2,913			$ 2,913	$ (6,964)	$ (4,051)		$ (8,469)			$ (8,469)	$ 6,537	$ (1,932)
Balance (in shares) at Dec. 31, 2017															50,609
Balance at Dec. 31, 2017															$ 51	$ 888,778	$ 351,622	$ (4,314)	$ 1,236,137	$ 84,322	$ 1,320,459

Consolidated Statements of Equ6

Consolidated Statements of Equity (Parentheticals) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Retained Earnings [Member]
Cash dividend declared, per share (in dollars per share)	$ 0.41	$ 0.52	$ 0.26
Loss in respect of derivative instruments designated for cash flow hedge, related tax	$ 51	$ 54	$ 56
Change in unrealized gains or losses in respect of the Company's share in derivative instruments of unconsolidated investment, tax	0	0	0
Amortization of unrealized gains, tax	$ 46	$ 57	$ 73
Cash dividend declared, per share (in dollars per share)	$ 0.41	$ 0.52	$ 0.26

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net income	$ 170,184	$ 101,516	$ 123,349
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	115,146	105,977	107,206
Amortization of premium from senior unsecured bonds		(513)	(306)
Accretion of asset retirement obligation	1,874	1,649	1,198
Stock-based compensation	8,760	5,157	3,955
Amortization of deferred lease income	(2,685)	(2,685)	(2,685)
Income attributable to sale of tax benefits, net of interest expense	(11,956)	(6,962)	(17,467)
Equity in losses of investees	1,957	7,735	5,508
Mark-to-market of derivative instruments	(1,473)	319	4,129
Write-off of unsuccessful exploration activities	1,796	3,017	1,579
Gain on severance pay fund asset	(1,746)	(304)	(119)
Deferred income tax provision	(64,104)	18,473	(39,530)
Liability for unrecognized tax benefits	3,152	(4,647)	2,874
Deferred lease revenues	(356)	(853)	224
Other	737		484
Changes in operating assets and liabilities, net of amounts acquired:
Receivables	(24,040)	(33,280)	(3,806)
Costs and estimated earnings in excess of billings on uncompleted contracts	11,253	(27,078)	2,673
Inventories	(1,070)	6,297	(1,144)
Prepaid expenses and other	208	(12,540)	(2,579)
Deposits and other	(2,570)	(1,009)	(648)
Accounts payable and accrued expenses	51,641	(1,375)	(339)
Due from/to related entities, net			451
Billings in excess of costs and estimated earnings on uncompleted contracts	11,389	2,262	(9,168)
Liabilities for severance pay	2,541	(786)	(1,076)
Other long-term liabilities	(2,285)	3,310	(2,561)
Due from/to Parent			(513)
Net cash provided by operating activities	245,575	159,285	190,025
Cash flows from investing activities:
Cash acquired in organizational restructuring and share exchange with parent			15,391
Net change in restricted cash, cash equivalents and marketable securities	(14,563)	15,241	43,745
Capital expenditures	(259,234)	(151,930)	(152,450)
Investment in unconsolidated companies	(46,318)	(3,569)
Cash paid for acquisition of controlling interest in a subsidiary, net of cash acquired	(35,300)	(20,135)
Cash paid for achievement of production threshold in Guadeloupe	(8,032)
Intangible assets acquired	(868)		(500)
Decrease (increase) in severance pay fund asset, net of payments made to retired employees	526	1,862	2,843
Net cash used in investing activities	(368,121)	(158,531)	(90,971)
Cash flows from financing activities:
Proceeds from sale of membership interests to noncontrolling interest, net of transaction costs		44,102	156,635
Proceeds from long-term loans, net of transaction costs		142,500	42,000
Proceeds from exercise of options by employees	16,111	7,249	6,085
Proceeds from issuance of senior unsecured notes, net of transaction costs		203,483
Purchase of Senior unsecured notes		(249,468)
Proceeds from the sale of limited liability company interest in Opal Geo LLC, net of transaction costs	2,017	1,972	1,654
Purchase of OFC Senior Secured Notes	(14,270)	(6,815)	(30,638)
Proceeds from revolving credit lines with banks	1,097,500	309,400	598,800
Repayment of revolving credit lines with banks	(1,046,000)	(309,400)	(619,100)
Cash received from noncontrolling interest	2,017	1,972	1,654
Repayments of long-term debt	(66,223)	(62,052)	(71,701)
Cash paid to noncontrolling interest	(21,313)	(64,065)	(19,068)
Payments of capital leases	(1,871)	(1,178)
Deferred debt issuance costs	(5,290)	(6,402)	(5,316)
Cash dividends paid	(20,511)	(25,682)	(12,716)
Net cash provided by (used in) financing activities	(59,850)	43,541	46,635
Net change in cash and cash equivalents	(182,396)	44,295	145,689
Cash and cash equivalents at beginning of period	230,214	185,919	40,230
Cash and cash equivalents at end of period	47,818	230,214	185,919
Supplemental disclosure of cash flow information:
Interest, net of interest capitalized	40,484	55,366	55,492
Income taxes, net	21,878	18,490	10,419
Supplemental non-cash investing and financing activities:
Increase (decrease) in accounts payable related to purchases of property, plant and equipment	4,484	(2,219)	3,810
Accrued liabilities related to financing activities		6,291	1,665
Increase (decrease) in asset retirement cost and asset retirement obligation	1,888	714	516
Opal Transaction [Member]
Cash flows from financing activities:
Proceeds from the sale of limited liability company interest in Opal Geo LLC, net of transaction costs		59,897
Cash received from noncontrolling interest		59,897
Ormat Nevada ORTP LLC [Member]
Cash flows from investing activities:
Buyout of Class B membership	(2,400)
OPC LLC [Member]
Cash flows from investing activities:
Buyout of Class B membership	$ (1,932)

Note 1 - Business and Significa

Note 1 - Business and Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
Notes to Financial Statements
Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block]	NOTE 1 — BUSINESS AND SIGNIFICANT ACCOUNTING POLICIES Business Ormat Technologies, Inc. (the “Company”) is primarily engaged in the geothermal and recovered energy business, including the supply of equipment that is manufactured by the Company and the design and construction of power plants for projects owned by the Company or for third ’s equipment manufacturing operations are located in Israel. Most of the Company ’s domestic power plant facilities are Qualifying Facilities under the Public Utility Regulatory Policies Act of 1978 December 31, 2017. Cash dividends During the years ended December 31, 2017, 2016, 2015, $20.5 $0.41 $25.7 $0.52 $12.7 $0.26 Rounding Dollar amounts, except per share data, in the notes to these financial statements are rounded to the closest $1,000, . Basis of presentation The consolidated financial statements are prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and include the accounts of the Company and of all majority-owned subsidiaries in which the Company exercises control over operating and financial policies, and variable interest entities in which the Company has an interest and is the primary beneficiary. Intercompany accounts and transactions have been eliminated in consolidation . Investments in less-than-majority-owned entities or other entities in which the Company exercises significant influence over operating and financial policies are accounted for using the equity method of accounting or consolidated if they are a variable interest entity in which the Company has an interest and is the primary beneficiary. Under the equity method, original investments are recorded at cost and adjusted by the Company ’s share of undistributed earnings or losses of such companies. The Company’s earnings or losses in investments accounted for under the equity method have been reflected as “equity in earnings (losses) of investees, net” on the Company’s consolidated statements of operations and comprehensive income (loss). Cash and cash equivalents The Company considers all highly liquid instruments, with an original maturity of three . Restricted cash, cash equivalents , and marketable securities Under the terms of certain long-term debt agreements, the Company is required to maintain certain debt service reserves, cash collateral and operating fund accounts that have been classified as restricted cash and cash equivalents. Funds that will be used to satisfy obligations due during the next twelve Concentration of credit risk Financial instruments which potentially subject the Company to 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 U.S. and in foreign countries. At December 31, 2017 2016, $21.2 $72.5 seven $250,000 December 31, 2017 2016, ’s deposits in foreign countries of approximately $32.8 $166.2 not At December 31, 2017 2016, approximately $78.1 $53.3 December 31, 2017, 2016, 19 57% 60%, The Company has historically been able to collect on substantially all of its receivable balances, and believes it will continue to be able to collect all amounts due. Accordingly, no Inventories Inventories consist primarily of raw material parts and sub-assemblies for power units, and are stated at the lower of cost or net realizable value, using the weighted-average cost method. Inventories are reduced by a provision for slow-moving and obsolete inventories. This provision was not December 31, 2017 2016. Deposits and other Deposits and other consist primarily of performance bonds for construction projects, long-term insurance contract and receivables, and derivative instruments. Deferred charges Deferred charges represent prepaid income taxes on intercompany sales. Such amounts are amortized using the straight-line method and included in income tax provision over the life of the related property, plant and equipment. The Company has not 2016 16, For additional information on the new accounting standard related to tax effects associated with intercompany transfers of assets please see "New accounting pronouncements effective in future periods" in Note 1 8 Property, plant and equipment, net Property, plant and equipment are stated at cost. All costs associated with the acquisition, development and construction of power plants operated by the Company are capitalized. Major improvements are capitalized and repairs and maintenance (including major maintenance) costs are expensed. Power plants operated by the Company, which include geothermal wells and exploration and resource development costs, are depreciated using the straight-line method over their estimated useful lives, which range from 15 30 Buildings (in years) 25 Leasehold improvements (in years) 15 - 20 Machinery and equipment — manufacturing and drilling (in years) 10 Machinery and equipment — computers (in years) 3 - 5 Office equipment — furniture and fixtures (in years) 5 - 15 Office equipment — other (in years) 5 - 10 Automobiles (in years) 5 - 7 The cost and accumulated depreciation of items sold or retired are removed from the accounts. Any resulting gain or loss recognized currently and is recorded in the accompanying statements of operations. The Company capitalizes interest costs as part of constructing power plant facilities. Such capitalized interest is recorded as part of the asset to which it relates and is amortized over the asset ’s estimated useful life. Capitalized interest costs amounted to $7.2 $3.3 $4.1 December 31, 2017, 2016, 2015, Exploration and development costs The Company capitalizes costs incurred in connection with the exploration and development of geothermal resources once it acquires land rights to the potential geothermal resource. Prior to acquiring land rights, the Company makes an initial assessment that an economically feasible geothermal reservoir is probable on that land. The Company determines the economic feasibility of potential geothermal resources internally, with all available data and external assessments vetted through the exploration department and occasionally using outside service providers. Costs associated with the initial assessment are expensed and included in cost of electricity revenues in the consolidated statements of operations and comprehensive income (loss). Such costs were immaterial during the years ended December 31, 2017, 2016, 2015. two three may In most cases, the Company obtains the right to conduct the geothermal development and operations on land owned by the Bureau of Land Management (“BLM”), various states or with private parties. In consideration for certain of these leases, the Company may Following the acquisition of land rights to the potential geothermal resource, the Company conducts further studies and surveys, including water and soil analyses among others, and augments its database with the results of these studies. The Company then initiates a suite of geophysical surveys to assess the resource and determine drilling locations. If the results of these activities support the initial assessment of the feasibility of the geothermal resource, the Company then proceeds to exploratory drilling and other related activities which may may not When deciding whether to continue holding lease rights and/or to pursue exploration activity, we diligently prioritize our prospective investments, taking into account resource and probability assessments in order to make informed decisions about whether a particular project will support commercial operation . As a result, write-off of unsuccessful activities for the year ended December 31, 2017, 2016 2015 $1.8 $3.0 $1.6 2017, 2016, no Grants received from the U.S. Department of Energy (“DOE”) are offset against the related exploration and development costs. Such grants amounted to $0.0 $0.3 $0.8 December 31, 2017, 2016, 2015, All exploration and development costs that are being capitalized, including the up-front bonus payments made to secure land leases, will be depreciated over their estimated useful lives when the related geothermal power plant is substantially complete and ready for use. A geothermal power plant is substantially complete and ready for use when electricity generation commences. Asset retirement obligation The Company records the fair value of a legal liability for an asset retirement obligation in the period in which it is incurred. The Company ’s legal liabilities include plugging wells and post-closure costs of power producing sites. When a new liability for asset retirement obligations is recorded, the Company capitalizes the costs of the liability by increasing the carrying amount of the related long-lived asset. The liability is accreted to its present value each period, and the capitalized cost is depreciated over the useful life of the related asset. At retirement, the obligation is settled for its recorded amount at a gain or loss. Deferred financing and lease transaction costs Deferred financing costs are amortized over the term of the related obligation using the effective interest method. Amortization of deferred financing costs is presented as interest expense in the consolidated statements of operations and comprehensive income (loss). Accumulated amortization related to deferred financing costs amounted to $31.0 $31.1 December 31, 2017 2016, December 31, 2017, 2016, 2015 $5.7 $6.9 $8.8 December 31, 2017, 2016 2015, $0.6 $0.1 $0.5 Deferred transaction costs relating to the Puna operating lease (see Note 12 $4.2 23 $2.3 $2.1 December 31, 2017 2016, December 31, 2017, 2016, 2015 $0.2 Goodwill Goodwill represents the excess of the fair value of consideration transferred in the business combination transactions of Guadeloupe and Viridity over the fair value of tangible and intangible assets acquired, net of the fair value of liabilities assumed and the fair value of any noncontrolling interest in the acquisitions. Goodwill is not not entity is permitted to first not no one not first second second 2017 2016, not Intangible assets Intangible assets consist of allocated acquisition costs of PPAs, which are amortized using the straight-line method over the 13 25 9 ) as well as acquisition cost allocation related to Viridity’s storage activities that are amortized over a weighted average amortization period of 19 may not no no not Impairment of long-lived assets and long-lived assets to be disposed of The Company evaluates long-lived assets, such as property, plant and equipment and construction-in-process for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not ’s use of assets or its overall business strategy, negative industry or economic trends, a determination that an exploration project will not not not The Company tests its operating plants that are operated together as a complex for impairment at the complex level because the cash flows of such plants result from significant shared operating activities. For example, the operating power plants in a complex are managed under a combined operation management generally with one one not not not Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to the estimated future net undiscounted cash flows expected to be generated by the asset. The significant assumptions that the Company uses in estimating its undiscounted future cash flows include: (i) projected generating capacity of the complex or power plant and rates to be received under the respective PPA(s) and expected market rates thereafter and (ii) projected operating expenses of the relevant complex or power plant. Estimates of future cash flows used to test recoverability of a long-lived asset under development also include cash flows associated with all future expenditures necessary to develop the asset. If the assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the carrying amount of the assets exceeds their fair value. Assets to be disposed of are reported at the lower of the carrying amount or fair value less costs to sell. Management believes that no may ’s current estimates, a material impairment charge may Derivative instruments Derivative instruments (including certain derivative instruments embedded in other contracts) are measured at their fair value and recorded as either assets or liabilities unless exempted from derivative treatment as a normal purchase and sale. All changes in the fair value of derivatives are recognized in earnings unless specific hedge criteria are met, which requires a company to formally document, designate and assess the effectiveness of transactions that receive hedge accounting. The Company maintains a risk management strategy that incorporates the use of swap contracts and put options on oil and natural gas prices, forward exchange contracts, interest rate swaps, and interest rate caps to minimize significant fluctuation in cash flows and/or earnings that are caused by oil and natural gas prices, exchange rate or interest rate volatility. Gains or losses on contracts that initially qualify for cash flow hedge accounting, net of related taxes, are included as a component of other comprehensive income or loss and accumulated other comprehensive income or loss are subsequently reclassified into earnings when the hedged forecasted transaction affects earnings. Gains or losses on contracts that are not Foreign currency translation The U.S. dollar is the functional currency for all of the Company ’s consolidated operations and those of its equity affiliates except for the Guadeloupe power plant. For those entities, all gains and losses from currency translations are included within the line item “Derivatives and foreign currency transaction gains (losses)” within the consolidated statements of operations and comprehensive income (loss). The Euro is the functional currency of the Guadeloupe power plant and thus gains and losses from currency translation adjustments related to Guadeloupe are included as currency translation adjustments in accumulated other comprehensive income in the consolidated statements of equity and in comprehensive income. The accumulated currency translation adjustments amounted to $1.4 $1.2 December 31, 2017 2016, Comprehensive income (loss) reporting Comprehensive income (loss) includes net income or loss plus other comprehensive income (loss), which for the Company consists of changes in unrealized gains or losses in respect of the Company ’s share in derivatives instruments of unconsolidated investment, foreign currency translation adjustments and amortization of unrealized gains in respect of derivative instruments designated as a cash flow hedge. For the years ended December 31, 2017, 2016 2015, $11,000 $9,000 $27,000 $16,000 $12,000 $44,000 $5,000 $3,000 $17,000 Revenues and cost of revenues Revenues are primarily related to: (i) sale of electricity from geothermal and recovered energy-based power plants owned and operated by the Company and (ii) geothermal and recovered energy-based power plant equipment engineering, sale, construction and installation, and operating services. Revenues related to the sale of electricity from geothermal and recovered energy-based power plants and capacity payments are recorded based upon output delivered and capacity provided at rates specified under relevant contract terms. For PPAs agreed to, modified, or acquired in business combinations on or after July 1, 2003, two 840 8 Revenues from engineering, operating services, and parts and product sales are recorded upon providing the service or delivery of the products and parts and when collectability is reasonably assured. Revenues from the supply and/or construction of geothermal and recovered energy-based power plant equipment and other equipment to third may . In specific instances where there is a lack of dependable estimates or inherent risks cause forecast to be doubtful, then the completed-contract method is followed. Revenue is recognized when the contract is substantially complete and when collectability is reasonably assured. Costs that are closely associated with the project are deferred as contract costs and recognized similarly to the associated revenues. Warranty on products sold The Company generally provides a one December 31, 2017, 2016, 2015 . Research and development Research and development costs incurred by the Company for the development of existing and new geothermal, recovered energy and remote power technologies are expensed as incurred. Grants received from the DOE are offset against the related research and development expenses. There were no December 31, 2017, 2016, 2015 . Stock-based compensation The Company accounts for stock-based compensation using the fair value method whereby compensation cost is measured at the grant date, based on the calculated fair value of the award, and is recognized as an expense over the requisite employee service period (generally the vesting period of the grant). Prior to 2016, 2016, Tax monetization Transactions The Company had three 2017 ’s partners reaching their target after-tax yield on their investment, as further described in Note 13. 470. 810. 835 7. Income taxes Income taxes are accounted for using the asset and liability approach, which requires the recognition of taxes payable or refundable for the current year and deferred tax assets and liabilities for the future tax consequences of events that have been recognized in the Company ’s financial statements or tax returns. The measurement of current and deferred tax assets and liabilities are based on provisions of the enacted tax law. On December 22, 2017, not 1 35 21 2 3 4 5 6 7 8 December 31, 2017. 18 not, not not Earnings (loss) per share Basic earnings (loss) per share attributable to the Company ’s stockholders (“earnings (loss) per share”) 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 The table below shows the reconciliation of the number of shares used in the computation of basic and diluted earnings per share : Year Ended December 31, 2017 2016 2015 (In thousands) Weighted average number of shares used in computation of basic earnings per share 50,110 49,469 48,562 Add: Additional shares from the assumed exercise of employee stock options 659 671 625 Weighted average number of shares used in computation of diluted earnings per share 50,769 50,140 49,187 The number of stock-based awards that could potentially dilute future earnings per share and were not 42,896, 102,793, 467,766, December 31, 2017, 2016, 2015. Use of estimates in preparation of financial statements The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the dates of such financial statements and the reported amounts of revenues and expenses during the reporting periods. Actual results could differ from those estimates. The most significant estimates with regard to the Company ’s consolidated financial statements relate to the useful lives of property, plant and equipment, impairment of goodwill and long-lived assets, including intangible assets, and assets to be disposed of, revenue recognition of product sales using the percentage of completion method, asset retirement obligations, and the provision for income taxes. New Accounting Pronouncements New accounting pronouncements effective in the year ended December 31, 2017 Improvement to Employee Share-Based Payment Accounting In March 2016, 2016 09, 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 1 2 December 15, 2016. The Company elected to not Interests Held through Related Parties that are under Common Control In October 2016, 2016 17, 810 December 15, 2016, not Simplifying the Measurement of Inventory In July 2015, 2015 11, 330. no ‘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, not New accounting pronouncements effective in future periods Derivatives and Hedging In August 2017, 2017 12, December 15, 2018, Intangibles –Goodwill and Other In January 2017, 2017 04, 350 not 2 2 first first December 15, 2019. January 1, 2017. Compensation - Stock Compensation In May 2017, 2017 09, —Stock Compensation (Topic 718 718. 1 2 3 718 December 15, 2017. not Business Combinations In January 2017, 2017 01, 805 not December 15, 2017, The Company is currently evaluating the potential impact of the adoption of these amendments on its consolidated financial statements, however, such impact, if any, is not Statement of Cash Flow In November 2016, 2016 18, 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, not Intra-Entity Transfers of Assets Other than Inventory In October 2016, 2016 16, ’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 December 15, 2017, $9.5 with a corresponding adjustment to deferred charges and deferred income taxes on the consolidated balance sheet of approximately $49.8 $59.3 Statement of Cash Flows: Classification of Certain Cash Receipts and Cash payments (Topic 230 ) In August 2016, 2016 15, 230 eight December 15, 2017, not . Revenues from Contracts with Customers In May 2014, 2014 09, 606, 1 2 3 4 5 2014 09 December 15, 2017, March 2016, 2016 08, not December 15, 2017, To date, we have made substantial progress in our assessment of the impact of adopting this new guidance, and we have taken steps towards implementation. We have utilized internal resources to lead the implementation efforts and supplemented them with external resources. Our approach to implementation has consisted of ( 1 2 3 4 January 1, 2018. 840, $24.1 January 1, 2018. not one $24.1 January 1, 2018, not Leases In February 2016, 2016 02, 842. two 606. December 15, 2018, Recognition and Measurement of Financial Assets and Financial Liabilities In January 2016, 2016 01, December 15, 2017, however, such impact, if any, is not

Note 2 - Business Acquisitions

Note 2 - Business Acquisitions and Others	12 Months Ended
	Dec. 31, 2017
Notes to Financial Statements
Business Combination Disclosure [Text Block]	NOTE 2 —BUSINESS ACQUISITIONS AND OTHERS ORIX transaction On July 26, 2017, 11 ’s common stock, representing an approximately 22% May 4, 2017. May 4, 2017, July 26, 2017. Under the Governance Agreement, ORIX has the right to designate three nine fourth 25% ’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 relationships in Asia and around the world. Viridity transaction On March 15, 2017, $35.3 $12.4 may 2017 2020. first 2017 not $0.6 December 31, 2017, $10.3 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, $34.7 ’s storage activities with a weighted-average amortization period of 19 $0.4 $13.4 810, The revenues of Viridity for the period from March 15, 2017 December 31, 2017 December 31, 2017. Guadeloupe power plant transaction In July 2016, GB”). GB owns and operates the 14.75 . Pursuant to the terms of an Amended and Restated Investment Agreement (“ Investment Agreement”) and Shareholders Agreement with Sageos Holding (“Sageos”), a wholly owned subsidiary of Bureau de Recherches Géologiques et Minières (“BRGM”), the Company together with Caisse des Dépôts et Consignations (“CDC”), a French state-owned financial organization, acquired an approximately 80% 75% 25% Pursuant to the agreements, the Com pany paid approximately $20.6 60% $8.4 €7.5 two 63.75%. may $13.4 2017, $8.0 may $3.6 The Bouillante power plant sells its electricity under a 15 February 2016 The Company accounted for the transaction based on the provision of Accounting Standard Codification 805, corded intangible asset of $33.0 15 $7.1 July 5, 2016 $5.0 $8.3 .

Note 3 - Inventories

Note 3 - Inventories	12 Months Ended
	Dec. 31, 2017
Notes to Financial Statements
Inventory Disclosure [Text Block]	NOTE 3 — INVENTORIES Inventories consist of the following: December 31, 2017 2016 (Dollars in thousands) Raw materials and purchased parts for assembly $ 12,007 $ 5,429 Self-manufactured assembly parts and finished products 7,544 6,571 Total $ 19,551 $ 12,000

Note 4 - Cost and Estimated Ear

Note 4 - Cost and Estimated Earnings on Uncompleted Contracts	12 Months Ended
	Dec. 31, 2017
Notes to Financial Statements
Long-term Contracts or Programs Disclosure [Text Block]	NOTE 4 — COST AND ESTIMATED EARNINGS ON UNCOMPLETED CONTRACTS Cost and estimated earnings on uncompleted contracts consist of the following: December 31, 2017 2016 (Dollars in thousands) Costs and estimated earnings incurred on uncompleted contracts $ 550,823 $ 402,357 Less billings to date (530,119 ) (381,789 ) Total $ 20,704 $ 20,568 These amounts are included in the consolidated balance sheets under the following captions: December 31, 2017 2016 (Dollars in thousands) Costs and estimated earnings in excess of billings on uncompleted contracts $ 40,945 $ 52,198 Billings in excess of costs and estimated earnings on uncompleted contracts (20,241 ) (31,630 ) Total $ 20,704 $ 20,568 The completion costs of the Company ’s construction contracts are subject to estimation. Due to uncertainties inherent in the estimation process, it is reasonably possible that estimated contract earnings will be further revised in the near term.

Note 5 - Investment In an Uncon

Note 5 - Investment In an Unconsolidated Company	12 Months Ended
	Dec. 31, 2017
Notes to Financial Statements
Equity Method Investments and Joint Ventures Disclosure [Text Block]	NOTE 5 — Invesment in an unconsolidated company Investment in an unconsolidated company mainly consist of the following: December 31, 2017 2016 (Dollars in thousands) Sarulla $ 34,084 $ (11,081) The Sarulla Project The Company holds a 12.75% 330 ra, North Sumatra, Indonesia and is owned and operated by the consortium members under the framework of a JOC and ESC that were signed on April 4, 2013. 30 The project is being constructed in three 110 ’s efficiency. The first March 17, 2017 second October 2, 2017. third may third 100% 85% On May 16, 2014, $1.17 six $1.17 $0.1 May 23, 2014) $1.07 may The Sarulla consortium entered into interest rate swap agreements with various international banks in order to fix the LIBOR interest rate on up to $0.96 $1.07 3.4565%. June 4, 2014 second $50.0 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, will be recorded in other comprehensive income. As such, during the years ended December 31, 2017 2016, 6 .3 $9 .3 0 . 8 million and $1.2 December 31, 2017 $5. 1 million. Pursuant to a supply agreement that was signed in October 2013, $255.6 third 2014 During the year ended December 31, 2017, 46 . 3 million for a total of $58.2 .

Note 6 - Variable Interest Enti

Note 6 - Variable Interest Entities	12 Months Ended
	Dec. 31, 2017
Notes to Financial Statements
Disclosure Of Variable Interest Entities [Text Block]	NOTE 6 — VARIABLE INTEREST ENTITIES The Company ’s overall methodology for evaluating transactions and relationships under the variable interest entity (“VIE”) accounting and disclosure requirements includes the following two In performing the first : • The design of the entity, including the nature of its risks and the purpose for which the entity was created, to determine the variability that the entity was designed to create and distribute to its interest holders ; • The nature of the Company ’s involvement with the entity; • Whether control of the entity may not ; • Whether there is sufficient equity investment at risk to finance the activities of the entity; and • Whether parties other than the equity holders have the obligation to absorb expected losses or the right to receive residual returns . If the Company identifies a VIE based on the above considerations, it then performs the second : • Whether the Company has the power to direct the activities of the VIE that most significantly impact the entity ’s economic performance; and • Whether the Company has the obligation to absorb losses of the entity that could potentially be significant to the VIE or the right to receive benefits from the entity that could potentially be significant to the VIE . The Company ’s VIEs include certain of its wholly owned subsidiaries that own one not may The tables below detail the assets and liabilities (excluding intercompany balances which are eliminated in consolidation) for the Company ’s VIEs, combined by VIE classifications, that were included in the consolidated balance sheets as of December 31, 2017 2016: December 31, 2017 Project Debt PPAs (Dollars in thousands) Assets: Restricted cash and cash equivalents $ 48,676 $ — Other current assets 124,322 18,010 Property, plant and equipment, net 1,252,623 379,277 Construction-in-process 129,832 12,885 Other long-term assets 63,667 276 Total assets $ 1,619,120 $ 410,448 Liabilities: Accounts payable and accrued expenses $ 24,887 $ 6,863 Long-term debt 658,726 — Other long-term liabilities 93,682 6,757 Total liabilities $ 777,295 $ 13,620 December 31, 2016 Project Debt PPAs (Dollars in thousands) Assets: Restricted cash, cash equivalents and marketable securities $ 34,262 $ — Other current assets 157,351 7,482 Property, plant and equipment, net 1,305,254 177,970 Construction-in-process 48,128 72,725 Other long-term assets 24,802 — Total assets $ 1,569,797 $ 258,177 Liabilities: Accounts payable and accrued expenses $ 10,900 $ 3,992 Long-term debt 668,815 — Other long-term liabilities 126,879 5,779 Total liabilities $ 806,594 $ 9,771

Note 7 - Fair Value of Financia

Note 7 - Fair Value of Financial Instruments	12 Months Ended
	Dec. 31, 2017
Notes to Financial Statements
Fair Value Disclosures [Text Block]	NOTE 7 — 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 3 three : 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 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 The following table sets forth certain fair value information at December 31, 2017 2016 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. December 31, 2017 Fair Value Carrying Value at December 31, 2017 Total Level 1 Level 2 Level 3 (Dollars in thousands) Assets: Current assets: Cash equivalents (including restricted cash accounts) $ 18,359 $ 18,359 $ 18,359 $ — $ — Derivatives: Contingent receivable (1) 108 108 — — 108 Currency forward contracts (2) 992 992 — 992 — Liabilities: Current liabilities: Derivatives: Contingent payables (1) (13,904 ) (13,904 ) — — (13,904 ) Warrants (1) (3,967 ) (3,967 ) — — (3,967 ) $ 1,588 $ 1,588 $ 18,359 $ 992 $ (17,763 ) 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 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 and warrants pertaining 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 December 31, 2017 December 31, 2016 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" , as applicable, on December 31, 2017 December 31, 2016, 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 The following table presents the amounts of gain (loss) recognized in the consolidated statements of operations and comprehensive income (loss) on derivative instruments not Derivatives not designated as hedging instruments Location of recognized gain (loss) Amount of recognized gain (loss) 2017 2016 2015 (Dollars in thousands) Put options on natural gas price Derivative and foreign currency transaction gains (losses) (350 ) — — Call options on natural gas price Derivative and foreign currency transaction gains (losses) — (1,340 ) — Call and put options on oil price Derivative and foreign currency transaction gains (losses) — (1,313 ) — Swap transactions on natural gas price Electricity revenues — — 1,158 Contingent considerations Derivative and foreign currency transaction gains (losses) (129 ) (1,527 ) — Contingent considerations General and administrative expenses 2,048 — — Currency forward contracts Derivative and foreign currency transaction gains (losses) 3,699 238 (1,206 ) $ 5,268 $ (3,942 ) $ (48 ) In January 2017, 4.1 $3 January 26, 2017 November 27, 2017 $0.7 On February 2, 2016, has written a number of call options covering a notional quantity of approximately 4.1 $2 February 24, 2016 December 27, 2016 $1.9 On February 24, 2016, 185,000 $32.80 $35.50 March 24, 2016 December 22, 2016 $1.1 March 2016, 2 31,800 $41 $42.50 $32.80 $33.50. 16,500 17,000 February 2016 $28.50 $37.50 $28 $38.50, On March 6, 2014, May 14, 2015, 2.2 January 1, 2015 March 31, 2015, 2.4 June 1, 2015 December 31, 2015, $4.95 $3.00 not first January 1, 2015 March 1, 2015 June 1, 2015 December 31, 2015) The foregoing future, forward and swap transactions have not There were no 1, 2 3 December 31, 2017. The fair value of the Company ’s long-term debt is as follows: Fair Value Carrying Amount 2017 2016 2017 2016 (Dollars in millions) (Dollars in millions) Olkaria III Loan - DEG $ — $ 16.3 $ — $ 15.8 Olkaria III Loan - OPIC 234.6 253.4 228.6 246.6 Olkaria IV Loan - DEG 2 50.7 50.9 50.0 50.0 Amatitlan Loan 32.8 37.3 33.3 36.8 Senior Secured Notes: Ormat Funding Corp. ("OFC") — 17.0 — 17.0 OrCal Geothermal Inc. ("OrCal") 34.2 37.4 32.1 35.2 OFC 2 LLC ("OFC 2") 234.6 249.0 232.5 247.2 Don A. Campbell 1 ("DAC 1") 85.5 88.9 88.3 92.4 Senior Unsecured Bonds 200.3 200.1 204.3 204.3 Other long-term debt 7.0 10.4 7.9 11.2 The fair value of the OFC Senior Secured Notes was determined using observable market prices as these securities are traded. The fair value of all the 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 and deposits approximates fair value. The following table presents the fair value of financial instruments as of December 31, 2017: Level 1 Level 2 Level 3 Total (Dollars in millions) Olkaria III - OPIC $ — $ — $ 234.6 $ 234.6 Olkaria IV - DEG 2 — — 50.7 50.7 Amatitlan Loan — 32.8 — 32.8 Senior Secured Notes: OrCal Senior Secured Notes — — 34.2 34.2 OFC 2 Senior Secured Notes — — 234.6 234.6 DAC 1 Senior Secured Notes — — 85.5 85.5 Senior Unsecured Bonds — — 200.3 200.3 Other long-term debt — — 7.0 7.0 Revolving lines of credit — 51.5 — 51.5 Deposits 15.6 — — 15.6 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 Senior Secured Notes — 17.0 — 17.0 OrCal Senior Secured Notes — — 37.4 37.4 OFC 2 Senior Secured Notes — — 249.0 249.0 DAC 1 Senior Secured Notes — — 88.9 88.9 Senior Unsecured Bonds — — 200.1 200.1 Other long-term debt — 3.3 7.1 10.4 Revolving lines of credit — — — — Deposits 14.4 — — 14.4

Note 8 - Property, Plant and Eq

Note 8 - Property, Plant and Equipment and Construction-in-process	12 Months Ended
	Dec. 31, 2017
Notes to Financial Statements
Property, Plant and Equipment Disclosure [Text Block]	NOTE 8 — PROPERTY, PLANT AND EQUIPMENT AND CONSTRUCTION-IN-PROCESS Property, plant and equipment Property, plant and equipment, net, consist of the following: December 31 , 2017 2016 (Dollars in thousands ) Land owned by the Company where the geothermal resource is located $ 32,178 $ 31,904 Leasehold improvements 3,984 3,848 Machinery and equipment 182,121 152,821 Land, buildings and office equipment 31,128 28,634 Automobiles 12,596 11,161 Geothermal and recovered energy generation power plants, including geothermal wells and exploration and resource development costs: United States of America, net of cash grants and impairment charges 1,744,728 1,658,195 Foreign countries 700,498 541,626 Asset retirement cost 10,563 8,669 2,717,797 2,436,858 Less accumulated depreciation (983,106 ) (880,480 ) Property, plant and equipment, net $ 1,734,691 $ 1,556,378 Depreciation expense for the years ended December 31, 2017, 2016, 2015 $98.8 $94.8 $95.2 December 31, 2017, 2016 2015 $5.5 U.S. Operations The net book value of the property, plant and equipment, including construction-in-process, located in the U.S. was approximately $1,447.4 $1,376.1 December 31, 2017 2016, December 31, 2017 2016 $133.2 $138.7 Foreign Operations The net book value of property, plant and equipment, including construction-in-process, located outside of the U.S. was approximately $580.8 $487.0 December 31, 2017 2016, The Company, through its wholly owned subsidiary, OrPower 4, 4” $326.1 $315.0 December 31, 2017 2016, 20 The Company, through its wholly owned subsidiary, Orzunil I de Electricidad, Limitada (“Orzunil”), owns a power plant in Guatemala. On January 22, 2014, 2019 2034. a 3% $9.9 $12.2 December 31, 2017 2016, The Company, through its wholly owned subsidiary, Ortitlan, Limitada (“Ortitlan”), owns a power plant in Guatemala. The net book value of the assets related to the power plant was $40.7 $40.3 December 31, 2017 2016, The Company, through its wholly owned subsidiary, GeoPlatanares, signed a Build, Operate and Transfer (BOT) contract for the Platanares geothermal project in Honduras with ELCOSA, a privately owned Honduran energy company, for 15 Platanares sells the electricity produced by the power plants to ENEE, the national utility of Honduras under a 30 $140.3 $67.5 December 31, 2017 2016, The Company, through its subsidiary, GB, owns a power plant in Guadeloupe. The net book value of the assets related to the power plant was $24.9 $20.3 December 31, 2017 2016, GB sells the electricity produced by the power plants to EDF, the French electric utility, under a 15 Construction-in-process Construction-in-process consists of the following: December 31, 2017 2016 (Dollars in thousands) Projects under exploration and development: Up-front bonus lease costs $ 17,018 $ 17,385 Exploration and development costs 46,154 36,359 Interest capitalized 703 703 63,875 54,447 Projects under construction: Up-front bonus lease costs 27,473 37,713 Drilling and construction costs 198,943 202,211 Interest capitalized 3,251 12,338 229,667 252,262 Total $ 293,542 $ 306,709 Projects under Exploration and Development Up-front Bonus Lease Costs Exploration and Development Costs Interest Capitalized Total (Dollars in thousands) Balance at December 31, 2014 $ 26,618 $ 45,977 $ 836 $ 73,431 Cost incurred during the year 37 10,104 869 11,010 Write off of unsuccessful exploration costs (164 ) (1,415 ) — (1,579 ) Transfer of projects under exploration and development to projects under construction — (18,940 ) (1,002 ) (19,942 ) Balance at December 31, 2015 26,491 35,726 703 62,920 Cost incurred during the year 1,514 25,165 — 26,679 Write off of unsuccessful exploration costs (380 ) (2,637 ) — (3,017 ) Transfer of projects under exploration and development to projects under construction (10,240 ) (21,895 ) — (32,135 ) Balance at December 31, 2016 17,385 36,359 703 54,447 Cost incurred during the year — 11,224 — 11,224 Write off of unsuccessful exploration costs (367 ) (1,429 ) — (1,796 ) Balance at December 31, 2017 $ 17,018 $ 46,154 $ 703 $ 63,875 Projects under Construction Up-front Bonus Lease Costs Drilling and Construction Costs Interest Capitalized Total (Dollars in thousands) Balance at December 31, 2014 $ 27,473 $ 187,545 $ 8,273 $ 223,291 Cost incurred during the year — 140,977 3,556 144,533 Transfer of projects under exploration and development to projects under construction — 18,940 1,002 19,942 Transfer of completed projects to property, plant and equipment — (196,995 ) (4,856 ) (201,851 ) Balance at December 31, 2015 27,473 150,467 7,975 185,915 Cost incurred during the year — 116,247 6,510 122,757 Transfer of exploration and development projects to projects under construction 10,240 21,895 — 32,135 Transfer of completed projects to property, plant and equipment — (86,398 ) (2,147 ) (88,545 ) Balance at December 31, 2016 37,713 202,211 12,338 252,262 Cost incurred during the year — 231,926 7,300 239,226 Transfer of completed projects to property, plant and equipment (10,240 ) (235,194 ) (16,387 ) (261,821 ) Balance at December 31, 2017 $ 27,473 $ 198,943 $ 3,251 $ 229,667

Note 9 - Intangible Assets and

Note 9 - Intangible Assets and Goodwill	12 Months Ended
	Dec. 31, 2017
Notes to Financial Statements
Intangible Assets Disclosure [Text Block]	NOTE 9 — INTANGIBLE ASSETS AND GOODWILL Intangible assets amounting to $85.4 $52.8 $50.0 $42.8 December 31, 2017 2016, 31, 2017, $33.8 $1.7 December 31, 2017, 2016, 2015 $6.9 $4.4 $3.3 December 31, 2017, 2016 2015, $35.6 $33.0 $0.5 2017 2016 no 2017, 2016 2015. Estimated future amortization expense for the intangible assets as of December 31, 2017 (Dollars in thousands) Year ending December 31: 2018 $ 7,129 2019 7,056 2020 6,739 2021 6,739 2022 6,483 Thereafter 51,274 Total $ 85,420 Goodwill Goodwill amounting to $21.0 $6.7 December 31, 2017 2016, Guadeloupe During 2017 2016, $13.5 $7.1 no

Note 10 - Accounts Payable and

Note 10 - Accounts Payable and Accrued Expenses	12 Months Ended
	Dec. 31, 2017
Notes to Financial Statements
Accounts Payable and Accrued Liabilities Disclosure [Text Block]	NOTE 10 — ACCOUNTS PAYABLE AND ACCRUED EXPENSES Accounts payable and accrued expenses consist of the following: December 31, 2017 2016 (Dollars in thousands) Trade payables $ 64,289 $ 48,309 Salaries and other payroll costs 19,888 17,977 Customer advances 1,177 576 Accrued interest 4,462 3,524 Income tax payable 43,682 8,824 Property tax payable 1,860 1,884 Scheduling and transmission 531 964 Royalty accrual 2,909 1,639 Other 14,998 7,953 Total $ 153,796 $ 91,650

Note 11 - Long-term Debt and Cr

Note 11 - Long-term Debt and Credit Agreements	12 Months Ended
	Dec. 31, 2017
Notes to Financial Statements
Long-term Debt [Text Block]	NOTE 11 — LONG-TERM DEBT AND CREDIT AGREEMENTS Long-term debt consists of notes payable under the following agreements: December 31, 2017 2016 (Dollars in thousands) Limited and non-recourse agreements: Loans: Non-recourse: Other loans $ 7,252 $ 6,368 Limited recourse: Loan agreement with OPIC (the Olkaria III power plant) 228,635 246,630 Loan agreement with Banco Industrial S.A. and Westrust Bank (International) Limited 33,251 36,750 Senior Secured Notes: Non-recourse: OFC Senior Secured Notes - 17,026 OrCal Senior Secured Notes 32,142 35,181 DAC 1 Senior Secured Notes 88,339 92,361 Limited recourse: OFC 2 Senior Secured Notes 232,526 247,232 622,145 681,548 Less current portion (54,720 ) (53,729 ) Non current portion $ 567,425 $ 627,819 Full recourse agreements: Senior Unsecured Bonds $ 204,332 $ 204,332 Loans from institutional investors - 3,333 Loan agreements with DEG (the Olkaria III and IV power plants) 50,000 65,789 Loan from a commercial bank 587 1,529 Revolving credit lines with banks 51,500 - 306,419 274,983 Less current portion (54,587 ) (12,242 ) Non current portion $ 251,832 $ 262,741 Loan Agreement with Banco Industrial S.A. and Westrust Bank (International) Limited On July 31, 2015, 12 $42.0 20 The loan is payable in 48 September 30, 2015. per annum 1.25% 4.35% 4.75% March 30, June 30, September 30 December 30 not may 100 50 eighth There are various restrictive covenants under the Amatitlan credit agreement. These include, among others, (i) a financial covenant to maintain a Debt Service Coverage Ratio (as defined in the credit agreement) of not 1.15 1.00 not 1.25 1.00 four As of December 31, 2017, 12 1.49 1.89, The loan is collateralized by substantially all the assets of the borrower and a pledge of all of the membership interests of the borrower. The Company has guaranteed payment of all obligations under the credit agreement and related financing documents. The guaranty is limited in the sense that the Company is only required to pay the guaranteed obligations if a “trigger event” occurs. A trigger event is the occurrence and continuation of a default by INDE in its payment obligations under the PPA for the Amatitlàn power plant or a refusal by INDE to receive capacity and energy sold under that PPA. Th e Company’s may As of December 31, 2017, $33.3 Finance Agreement with OPIC (the Olkaria III Complex) On August 23, 2012, 4, $310.0 November 9, 2012. The OPIC Loan is comprised of up to three • Tranche I in an aggregate principal amount of $85.0 November 2012, $20.5 $1.5 • Tranche II in an aggregate principal amount of $180.0 was used to fund the construction and well field drilling for the expansion of the Olkaria III geothermal power complex (“Plant 2” November 2012, $135.0 February 2013, $45.0 • Tranche III in an aggregate principal amount of $45.0 was used to fund the construction of Plant 3 November 2013, $45.0 I n July 2013, December 31, 2017 $61.4 December 15, 2030, December 31, 2017 $132.4 June 15, 2030, 6.31%. November 2013, December 31, 2017 $34.9 December 15, 2030, 6.12%. OrPower 4 and a prepayment premium of 2.0% first two 2 1% third 2 not 1.7. The OPIC Loan is collateralized by substantially all of OrPower 4’ s assets and by a pledge of all of the equity interests in OrPower 4. The finance agreement includes customary events of default, including failure to pay any principal, interest or other amounts when due, failure to comply with covenants, breach of representations and warranties, non-payment or acceleration of other debt of OrPower 4, 4 4, There are various restrictive covenants under the OPIC Loan, which include a required historical and projected 12 not 1.4 March 15, June 15, September 15 December 15 4 1.1, 4. December 15, 2014. December 31, 2017, 12 2.64 3.09, As of December 31, 2017, $228.6 Debt service reserve As required under the terms of the OPIC Loan, OrPower 4 may six December 31, 2017 2016, was $3.7 $4.3 December 31, 2017, $16.7 22 Well drilling reserve As required under the terms of the OPIC Loan, OrPower 4 may may . OFC Senior Secured Notes In February 2004, ’s wholly owned subsidiary, issued $190.0 8.25% $179.7 $10.3 December 30, 2020. In June 2015, $30.6 $1.7 second 2015. In September 2016, $6.8 $0.6 third 2016. In September 2017, $14.3 $1.3 OrCal Senior Secured Notes In December 2005, ’s w $165.0 6.21% $161.1 $3.9 December 30, 2020. include limitations on additional indebtedness of OrCal and its wholly owned subsidiaries. Failure to comply with these and other covenants will, subject to customary cure rights, constitute an event of default by OrCal. In addition, there are restrictions on the ability of OrCal to make distributions to its shareholders, which include a required historical and projected 12 not 1.25 June 30 December 31 December 31, 2017, 12 1.54 12 2.63. $32.1 $35.2 December 31, 2017 December 31, 2016, OrCal may may 100% . Debt service reserve As required under the terms of the OrCal Senior Secured Notes, OrCal maintains an account which may six December 31, 2017 2016, $1.9 December 31, 2017 2016, $4.6 22 OFC 2 Senior Secured Notes In September 2011, OFC 2, ’s wholly owned subsidiary, and OFC 2’s 2 2 $350.0 2 2 December 31, 2034. Subject to the fulfillment of customary and other specified conditions precedent, the OFC 2 may six 2 The OFC 2 2 not December 31, 2034. ten 80% 2 1705 2005, 2 2 On October 31, 2011, 2 $151.7 of 4.687% 2032 $141.1 March, June, September December On June 20, 2014, 1 Agreement. In accordance with the terms of the Note Purchase Agreement and following recalibration of the financing assumptions, the loan amount was adjusted through a principal prepayment of $4.3 On August 29, 2014, 2 140.0 2 Senior Secured Notes C Notes”) to finance the construction of the second 1705 2005. December 2032, 4.61% 2 In connection with the anticipated sale of the Series C Notes, on August 13, 2014, August 15, 2014. $140.0 as a cash flow hedge. The objective of this cash flow hedge was to eliminate the variability in the changes in the 10 one 2 August 15, 2014. 10 August 18, 2014, $1.5 The Company concluded that the cash flow hedge was fully effective with no no , in 2014, $0.9 $0.6 2 2016 2015, $0.1 The OFC 2 2 2. 2 2 Failure to comply with these and other covenants will, subject to customary cure rights, constitute an event of default by OFC 2. 2 Among other things, the distribution restrictions include a historical debt service coverage ratio requirement of at least 1.2 2 two six 1.5 2 two six As of December 31, 2017, 2.70 2.25, two six 2.04 2.13, two six There were $2 32.5 $247.2 2 December 31, 2017 December 31, 2016, The Company provided a guaranty in connection with the issuance of the Series A Notes and Series C Notes. The guaranty may 2 2 2 2 2 ’s liability under the guaranty with respect to the non-performance trigger is limited to an amount equal to the prepayment amount on the OFC 2 2 not Debt service reserve ; other restricted funds Under the terms of the OFC 2 2 (i) A debt service reserve account which may 2 six December 31, 2017, $18.7 22 (ii) A performance level reserve account, intended to provide additional security for the OFC 2 may project achieves certain milestones. Upon issuance of the Series A Notes, this reserve was funded in the amount of $28.0 December 31, 2017, zero no (iii) Under the terms of the OFC 2 2 project's well field, which may (iv) A performance level reserve account for McGinness Hills Phase II, intended to provide additional security for the OFC 2 may December 31, 2017, no Don A. Campbell Senior Secured Notes — Non-Recourse On November 29, 2016, 47 47” the Company’s subsidiary, 47 47 $92.5 4.03% September 27, 2033 ( 1 1933, 47 first 1” The net proceeds from the sale of the DAC 1 87.1 million and ORNI 47 1 ORNI 47 1 December 27, 2016 27th March, June, September December, 1 The DAC 1 47 47. 47 47 may 1 $2 may 1 100% 47 47 1 ’s notes at 101% not 1 Notes may 47 1 Notes at 100% 47 47 47 47 47 not 1.20 four December 31, 2017, 1.47 1.81, As of December 31, 2017, $88.3 1 Senior Unsecured Bonds In August 2010, $142.0 August 1, 2017. 7%, . In February 2011, $107 .5 million of additional senior unsecured bonds (the “Additional Bonds”) under two 6.75%. In September 2016, two $67 2 $137 3 2 2 3 September 29, 2016 ’s $250 August 1, 2017. The Series 2 September 2020 3.7% 3 September 2022 4.45% 2 3 Loans from institutional investors In July 2009, 8 $20.0 August 1, 2017, 12 February 1, 2012, 6 5.0% . Loan Agreement s with DEG (the Olkaria III Complex ) In March 2009, O rPower 4, ’s wholly owned subsidiary, entered into a project financing loan of $105.0 December 15, 2018, 19 6 4.0%. 6.90%. September 2017, $11.8 $0.1 On October 20, 2016, 4 $50 DEG (the “DEG 2 December 21, 2016, 4 $50 6.28% 2 2 20 December 21, 2018, June 21, 2028. 2 4 4 2 1 3 2 Under the DEG 2 4 may 2 $5 may 2 100% 4 2 100% plus the applicable make-whole amount and certain prepayment premium amount determined for the prepayment date with respect to such principal amount. The DEG 2 4 2 As of December 31, 2017, $50.0 2 Revolving credit lines with commercial banks As of December 31, 2017, eight $468.0 $60.0 $35.0 one $233.0 one $235.0 March 2018 July 2019. As of December 31, 2017, $51.5 of $277.7 Credit Agreements Credit agreement with Union Bank In February 2012, June 30, 2018. December 31. 2017, $6 0 may, There are various restrictive covenants under the credit agreement, which include a requirement to comply with the following financial ratios, which are measured quarterly: (i) a 12 not 4.5; 12 not 1.35; not 2.0. December 31, 2017: ( 12 2.17; 12 2.96; 0.99. As of December 31, 2017, $37.4 . Credit agreement with HSBC In May 2013, one August 31, 2018. $10 $35 $10 may may, There are various restrictive covenants under the credit agreement, including a requirement to comply with the following financial ratios, which are measured quarterly: (i) a 12 not 4.5; 12 not 1.35; not 2.0. December 31, 2017: ( 12 2.17; 12 2.96; 0.99. As of December 31, 2017, $16.2 Chubb Surety Bond In May 2017, agreement (the “Surety Agreement”) with Chubb Limited (“Chubb”) pursuant to which the Company may $200.0 may no may twenty not December 31, 2017, $106.2 Restrictive covenants The Company ’s obligations under the credit agreements, the loan agreements, and the trust instrument governing the bonds, described above, are unsecured, but are subject to a negative pledge in favor of the banks and the other lenders and certain other restrictive covenants. These include, among other things, a prohibition on: (i) creating any floating charge or any permanent pledge, charge or lien over our assets without obtaining the prior written approval of the lender; (ii) guaranteeing the liabilities of any third third $600.0 no 25% 12 not 6; not 35% December 31, 2017: ( $1,320.5 51.1%, 12 2.58. December 31, 2017, $20.5 Future minimum payments Future minimum payments under long-term obligations, excluding revolving credit lines with commercial banks, as of December 31, 2017 (Dollars in thousands) Year ending December 31: 2018 $ 57,807 2019 55,539 2020 123,093 2021 46,579 2022 184,148 Thereafter 409,898 Total $ 877,064

Note 12 - Puna Power Plant Leas

Note 12 - Puna Power Plant Lease Transactions	12 Months Ended
	Dec. 31, 2017
Notes to Financial Statements
Leases of Lessee Disclosure [Text Block]	NOTE 12 — PUNA POWER PLANT LEASE TRANSACTIONS In 2005, ’s wholly owned subsidiary in Hawaii, Puna Geothermal Ventures (“PGV”), entered into transactions involving the original geothermal power plant of the Puna complex located on the Big Island (the “Puna Power Plant” ). Pursuant to a 31 ”), PGV leased the Puna Power Plant to an unrelated company in return for prepaid lease payments in the total amount of $83.0 December 31, 2017 2016 $25.3 $28.0 $35.6 $32.9 23 not The Head Lease and the Project Lease are being accounted for separately. Each was classified as an operating lease in accordance with the accounting standards for leases. The Deferred Lease Income is amortized into revenue, using the straight-line method, over the 31 $4.2 23 Future minimum lease payments under the Project Lease, as of December 31, 2017, (Dollars in thousands) Year ending December 31: 2018 $ 13,317 2019 6,018 2020 2,450 2021 1,723 2022 824 Thereafter 1,917 Total $ 26,249 Depository accounts As required under the terms of the lease agreements, there are certain reserve funds that need to be managed by the indenture trustee in accordance with certain balance requirements. Such reserve funds amounted to $7.9 $2.9 December 31, 2017 2016, . Distribution account PGV maintains an account to deposit its remaining cash, after making all of the necessary payments and transfers as provided for in the lease agreements, in order to make distributions to Ormat Nevada. The distributions are allowed only if PGV maintains various restrictive covenants under the lease agreements, which include limitations on additional indebtedness. As of December 31, 2017 2016, $0.

Note 13 - Tax Monetization Tran

Note 13 - Tax Monetization Transactions	12 Months Ended
	Dec. 31, 2017
Notes to Financial Statements
Disclosure Of Investments In And Advances To Affiliates [Text Block]	NOTE 13 —TAX MONETIZATION TRANSACTIONS Opal Geo Transaction On December 16, 2016, December 16, 2016, five In connection with the transactions contemplated by the Equity Contribution Agreement and the LLC Agreement, Ormat Nevada transferred its indirect ownership interest in the McGinness Hills (Phase I and Phase II), Tuscarora, Jersey Valley and second 2” 63 .25% 2 10 0% Pursuant to the Equity Contribution Agreement, JPM contributed approximately $62.1 100% 2 $21 December 31, 2022. Und er the LLC Agreement, until December 31, 2022, 97.5% 2.5% December 31, 2022 10 0% 97.5%, 2.5%, Und er the LLC Agreement, all items of Opal Geo income and loss , gain, deduction and credit (including the federal production tax credits relating to the operation of the two two 99% 1% 5% 95% no two 5% 95% Und er the LLC Agreement, OrLeaf, which owns 1 00% -day management of Opal Geo and its portfolio of five may five 2 . In both cases, these major decisions are generally equivalent to customary minority protection rights. As a result, the Company’s wholly owned subsidiary , Ormat Nevada, which serves as the managing member of OrLeaf and as the managing member of ORPD LLC , will effectively retain the day-to-day control and management of Opal Geo and its portfolio of five The LLC Agreement contains certain customary restrictions on transfer applicable to both OrLeaf and JPM with respect to their respective Membership Interests in Opal Geo, and also provides OrLeaf with a right of first may December 31, 2022 9 $3 Pursuant to the Equity Contribution Agreement, the Company has provided a guaranty for the benefit of JPM of certain of OrLeaf’s indemnification obligations to JPM under the LLC Agreement. In addition, Ormat Nevada also provided a guaranty for the benefit of JPM of all present and future payment and performance obligations of OrLeaf under the LLC Agreement and each ancillary document to which OrLeaf is a party. JPM’s approximately $62.1 $3.7 $58.5 million allocation to liability associated with sale of tax benefits as described in Note 1. 2 OPC TRANSACTION In June 2007, four . The first 2007 ’s Desert Peak 2, 2 $71.8 first second 2008 3 $63.0 second Ormat Nevada continued to operate and maintain the power plants. Under the agreements, Ormat Nevada initially received all of the distributable cash flow generated by the power plants, while the investors received substantially all of the production tax credits and taxable income or loss (together, the “Economic Benefits”). Once Ormat Nevada recovered the capital that it has invested in the power plants, which occurred in the fourth 2010, ’ return was limited by the term of the transaction. Once the investors reached a target after-tax yield on their investment in OPC (the “OPC Flip Date”), Ormat Nevada received 95% On October 30, 2009, LLC all of the Class B membership units of OPC held by Lehman-OPC pursuant to a right of first $18.5 $13.3 December 31, 2009. $1.1 1.5% On February 3, 2011, $24.9 not . A substantial portion of the Class B membership units were accounted for as a financing transaction. As a result, the majority of these proceeds were recorded as a liability. In addition, $2.3 1.5% On May 31, 2017, ’s partners JPM and Morgan Stanley achieved their target after-tax yield on its investment in OPC and on October 31, 2017, $1.9 $6.5 $8.5 O RTP TRANSACTION In January 2013, Under the terms of the transaction, Ormat Nevada transferred the Heber complex, the Mammoth complex, the Ormesa complex, and the Steamboat 2 3, 1 B membership units in ORTP to JPM. In connection with the closing, JPM paid approximately $35.7 25% July 2017 $7.9 In March 2017, July 10, 2017, $2.4 $7.0 $2.9

Note 14 - Asset Retirement Obli

Note 14 - Asset Retirement Obligation	12 Months Ended
	Dec. 31, 2017
Notes to Financial Statements
Asset Retirement Obligation Disclosure [Text Block]	NOTE 14 — ASSET RETIREMENT OBLIGATION The following table presents a reconciliation of the beginning and ending aggregate carrying amount of asset retirement obligation for the years presented below: Year Ended December 31, 2017 2016 (Dollars in thousands) Balance at beginning of year $ 23,348 $ 20,856 Revision in estimated cash flows 1,888 303 Liabilities incurred — 540 Accretion expense 1,874 1,649 Balance at end of year $ 27,110 $ 23,348

Note 15 - Stock-based Compensat

Note 15 - Stock-based Compensation	12 Months Ended
	Dec. 31, 2017
Notes to Financial Statements
Disclosure of Compensation Related Costs, Share-based Payments [Text Block]	NOTE 15 The Company makes an estimate of expected forfeitures and recognizes compensation costs only for those stock-based awards expected to vest. As of December 31, 2017, 7.7 1.2 During the years ended December 31, 2017, 2016 2015, : Year Ended December 31, 2017 2016 2015 (Dollars in thousands, except per share data) Cost of revenues $ 3,369 $ 2,400 $ 1,753 Selling and marketing expenses 452 247 123 General and administrative expenses 4,939 2,510 2,079 Total stock-based compensation expense 8,760 5,157 3,955 Tax effect on stock-based compensation expense 604 617 440 Net effect of stock-based compensation expense $ 8,156 $ 4,540 $ 3,515 During the fourth 2017, 2016 2015, 1.1%, 10.3% 9.66%, 89.3%, 7% 20%, Valuation assumptions Prior to 2016, ’s expected term represented the period that the Company’s stock-based awards were expected to be outstanding. In the absence of enough historical information, the expected term was determined using the simplified method giving consideration to the contractual term and vesting schedule. Starting in 2016, 20% 0.6% December 31, 2017. The Company calculated the fair value of each stock-based award on the date of grant based on the following assumptions : Year Ended December 31, 2017 2016 2015 For stock options issued by the Company: Risk-free interest rates 1.9 % 1.3 % 1.4 % Expected lives (in weighted average years) 3.1 4.5 4.0 Dividend yield 0.62 % 1.10 % 0.70 % Expected volatility (weighted average) 27.2 % 30.7 % 29.2 % Forfeiture rate (weighted average) 0.0 % 8.4 % 0.0 % Stock-based awards The 2004 In 2004, ’s Board of Directors adopted the 2004 “2004 2004 3,750,000 2004 25% 24 25% 36 50% 48 2004 one may ten 2004 May 2012 2012 The 2012 In May 2012, ’s shareholders adopted the 2012 “2012 2012 4,000,000 2012 25% 24 25% 36 50% 48 2012 one may ten The 2012 2012 February 2014 2012 Increase of per grant limit: Section 15 2012 400,000 May 31, 2014; Acceleration of vesting: Section 15 2012 2012 On February 11, 2014, 32,500 2012 $24.57, ’s common stock on the grant date. Such options will expire five three The fair value of each stock option on the grant date was $5.78. Risk-free interest rates 0.81 % Expected life (in years ) 3.375 Dividend yield 0.80 % Expected volatility 33.50 % Forfeiture rat e 0.00 % On April 2, 2014, 400,000 2012 $29.52 ’s common stock on the date of the grant. Options to purchase 300,000 six four 100,000 March 31, 2021, seven The fair value of each option on the grant date was $12.88 300,000 $8.33 100,000 Grant of options to purchase 100,000 shares of common stock Grant of options to purchase 300,000 shares of common stock Risk-free interest rates 2.36 % 1.64 % Expected life (in years) 7.25 4.75 Dividend yield 0.90 % 0.90 % Expected volatility 42.80 % 33.10 % On November 5, 2014, 52,500 2012 $28.23, ’s common stock on the grant date. Such options will expire seven one The fair value of each stock option on the grant date was $7.01. Risk-free interest rates 1.30 % Expected life (in years) 4.0 Dividend yield 0.70 % Expected volatility 32.40 % Forfeiture rate 0.00 % On November 3, 2015, 45,000 2012 $38.24, ’s common stock on the grant date. Such options will expire seven one The fair value of each stock option on the grant date was $8.68. Risk-free interest rates 1.35 % Expected life (in years) 4.0 Dividend yield 0.70 % Expected volatility 29.20 % Forfeiture rate 0.00 % On June 13, 2016, 1,080,000 ’s 2012 $42.87, six 4 50% two 25% three 25% four The fair value of each SAR on the grant date was $11.98 $11.42 Risk-free interest rate 1.29 % Expected life (in years) 6 Dividend yield 1.14 % Expected volatility 30.7 % Forfeiture rate: Senior management 0.0 % Other employees 10.5 % Sub-Optimal Exercise Factor: Senior management 2.5 Other employees 2.0 On November 8, 2016, 60,000 s under the Company’s 2012 $47.46, seven first The fair value of each SAR on the grant date was $14.51. Risk-free interest rate 1.65 % Expected life (in years) 7 Dividend yield 1.1 % Expected volatility 30.6 % Forfeiture rate 0.0 % Sub-Optimal Exercise Factor 2.5 On June 7, 2017, 23,200 ’s under the Company’s 2012 $58.79, five 50% first 25% third fourth he grant date. The fair value of each SAR on the grant date was $13.67. Risk-free interest rate 1.74 % Expected life (in years) 5 Dividend yield 0.66 % Expected volatility 26.3 % Forfeiture rate 10.3 % Sub-Optimal Exercise Factor 2 On August 4, 2017, 30,000 ’s 2012 $57.97, seven one The fair value of each option on the grant date was $18.42. Risk-free interest rate 2.08 % Expected life (in years) 7 Dividend yield 0.69 % Expected volatility 29.4 % Forfeiture rate 0.0 % Sub-Optimal Exercise Factor 2.5 On November 8, 2017, 108,771 22,742 ’s 2012 $63.35, six 100% first the grant date and for members of senior management, 25% third fourth The fair value of each SAR for the directors and members of senior management on the grant date was $17.6 $17.7, $62.9 $62.3, Risk-free interest rate 2.1 % Expected life (in years) 6 Dividend yield 0.6 % Expected volatility 26.9 % Forfeiture rate 0.0 % Sub-Optimal Exercise Factor 2.5 Year Ended December 31, 2017 2016 2015 Shares (In thousands) Weighted Average Exercise Price Shares (In thousands) Weighted Average Exercise Price Shares (In thousands) Weighted Average Exercise Price Outstanding at beginning of year 2,565 $ 33.36 2,438 $ 25.38 4,477 $ 27.48 Granted, at fair value: Stock Options 30 57.97 1,155 43.01 45 38.24 SARs* 132 62.55 — — — — RSUs** 23 — Exercised (1,181 ) 25.92 (967 ) 25.33 (1,589 ) 26.77 Forfeited (21 ) 46.15 (57 ) 24.12 (125 ) 27.33 Expired — — (4 ) 26.84 (370 ) 45.78 Outstanding at end of year 1,548 41.35 2,565 33.36 2,438 25.38 Options and SARs exercisable at end of year 431 32.61 557 25.22 858 26.75 Weighted-average fair value of options and SARs granted during the year $ 22.82 $ 11.61 $ 8.68 __________ * Upon exercise, SARs entitle the recipient to receive shares of common stock with a value equal to the increase in value of the award between the grant date and the exercise date. ** An RSU represents the right to receive one As of December 31, 2017, 894,437 2012 No 2004 The following table summarizes information about stock-based awards outstanding at December 31, 2017 Options Outstanding Options Exercisable Exercise Price Number of Stock-based Awards Outstanding Weighted Average Remaining Contractual Life in Years Aggregate Intrinsic Value Number of Stock-based Awards Exercisable Weighted Average Remaining Contractual Life in Years Aggregate Intrinsic Value $ - 23 3.9 1,455 - - - 20.13 35 1.3 1,533 35 1.3 1,533 23.34 176 1.4 7,150 176 1.4 7,150 25.65 10 0.3 398 10 0.3 398 35.15 15 5.1 432 15 5.1 432 38.24 15 4.8 386 15 4.8 386 42.87 1,074 4.5 22,651 143 4.5 3,005 47.46 38 5.9 619 38 5.9 619 57.97 30 6.6 180 - - - 58.79 23 4.5 120 - - - 63.35 109 5.9 66 - - - 1,548 4.2 $ 34,990 432 3.0 $ 13,523 The following table summarizes information about stock-based awards outstanding at December 31, 2016 Options Outstanding Options Exercisable Exercise Price Number of Stock-based Awards Outstanding Weighted Average Remaining Contractual Life in Years Aggregate Intrinsic Value Number of Stock-based Awards Exercisable Weighted Average Remaining Contractual Life in Years Aggregate Intrinsic Value $ 18.56 15 2.8 526 15 2.8 526 19.69 15 2.6 509 15 2.6 509 20.13 108 2.3 3,608 108 2.3 3,608 20.54 53 2.3 1,761 28 2.3 934 23.34 635 2.4 19,226 140 2.4 4,247 24.57 9 2.1 269 1 2.1 33 25.65 68 1.3 1,905 68 1.3 1,905 26.70 15 3.8 404 15 3.8 404 28.23 30 4.8 762 30 4.8 762 29.52 400 3.6 9,640 75 3.6 1,807 29.95 17 0.3 400 17 0.3 400 35.15 15 6.1 277 - - - 38.24 45 5.8 692 45 5.8 692 42.87 1,080 5.5 11,610 - - - 47.46 60 6.9 370 - - - 2,565 4.1 $ 51,959 557 2.7 $ 15,827 The aggregate intrinsic value in the above tables represents the total pretax intrinsic value, based on the Company ’s stock price of $63.96 $53.62 December 31, 2017 2016, December 31, 2017 2016 431,387 557,350, The total pretax intrinsic value of options exercised during the year ended December 31, 2017 2016 $38.9 $1 8 .0 million, respectively, based on the average stock price of $58.82 $43.99 December 31, 2017 2016,

Note 16 - Power Purchase Agreem

Note 16 - Power Purchase Agreements	12 Months Ended
	Dec. 31, 2017
Notes to Financial Statements
Leases of Lessor Disclosure [Text Block]	NOTE 16 — POWER PURCHASE AGREEMENTS Substantially all of the Company ’s electricity revenues are recognized pursuant to PPAs in the U.S. and in various foreign countries, including Kenya and Guatemala. These PPAs generally provide for the payment of energy payments or both energy and capacity payments through their respective terms which expire in varying periods from 2018 2043. not first Pursuant to the terms of certain of the PPAs, the Company may not not may . As discussed in Note 1, July 1, 2003, December 31, 2017 The PPAs considered to be leases were also assessed for inclusion of embedded derivatives, which required that they be separately accounted for at fair value. However, none

Note 17 - Interest Expense, Net

Note 17 - Interest Expense, Net	12 Months Ended
	Dec. 31, 2017
Notes to Financial Statements
Interest Expense Disclosure [Text Block]	NOTE 17 — INTEREST EXPENSE, NET The components of interest expense are as follows: Year Ended December 31, 2017 2016 2015 (Dollars in thousands) Interest related to sale of tax benefits $ 6,985 $ 9,349 $ 9,620 Interest expense 54,381 61,327 67,032 Less — amount capitalized (7,224 ) (3,287 ) (4,075 ) $ 54,142 $ 67,389 $ 72,577

Note 18 - Income Taxes

Note 18 - Income Taxes	12 Months Ended
	Dec. 31, 2017
Notes to Financial Statements
Income Tax Disclosure [Text Block]	NOTE 18 U.S. and foreign components of income from continuing operations, before income taxes and equity in income (losses) of investees consisted of: Year Ended December 31, 2017 2016 2015 (Dollars in thousands) U.S. $ 13,680 $ (7,109 ) $ (236 ) Non-U.S. (foreign) 157,050 148,197 113,835 Total income from continuing operations, before income taxes and equity in losses of investees $ 170,730 $ 141,088 $ 113,599 The components of the provision (benefit) for income taxes, net are as follows: Year Ended December 31, 2017 2016 2015 (Dollars in thousands) Current: Federal $ 43,850 $ — $ 51 State 108 (276 ) 252 Foreign 10,816 14,040 19,175 Total current income tax expense $ 54,774 $ 13,764 $ 19,478 Deferred: Federal (78,220 ) — — State (4,544 ) — — Foreign 26,579 18,073 (34,736 ) Total deferred tax benefit (56,185 ) 18,073 (34,736 ) Total provision (benefit) for income taxes $ (1,411 ) $ 31,837 $ (15,258 ) The significant components of the deferred income tax expense (benefit) are as follows: Year Ended December 31, 2017 2016 2015 (Dollars in thousands) Other deferred tax expense (exclusive of the effect of other components listed below) $ 1,833 $ (1,105 ) $ 541 Usage (benefit) of operating loss carryforwards - U.S. 73,049 (14,072 ) (30,596 ) Change in valuation allowance (58,757 ) 16,411 (14,324 ) Change in foreign valuation allowance — — (49,701 ) Change in foreign income tax 26,579 18,073 14,965 Change in lease transaction — — (452 ) Change in tax monetization transaction (23,234 ) 48,000 16,386 Change in depreciation 129,408 (55,462 ) 28,370 Change in foreign tax credits (86,206 ) — — Change in withholding tax 14,400 — — Change in state and investment tax credits (144 ) — — Change in intangible drilling costs (118,610 ) 10,227 10,335 Change in production tax credits and alternative minimum tax credit (2,070 ) (11,659 ) 610 Basis difference in partnership interests (12,433 ) 7,660 (10,870 ) $ (56,185 ) $ 18,073 $ (34,736 ) Reconciliation of the U.S. federal statutory tax rate to the Company’s effective income tax rate is as follows: Year Ended December 31, 2017 2016 2015 U.S. federal statutory tax rate 35.0 % 35.0 % 35.0 % Impact of federal tax reform (13.2 ) - - Transition tax inclusion 42.1 - - Foreign tax credits (50.4 ) - - Tax basis adjustment (4.7 ) - - Withholding tax 34.1 - - Valuation allowance - U.S. (30.3 ) 11.1 (1.4 ) Valuation allowance - foreign - - (43.8 ) State income tax, net of federal benefit (2.2 ) (0.2 ) 0.6 Effect of foreign income tax, net (10.3 ) (14.1 ) (5.1 ) Production tax credits (1.2 ) (8.3 ) (0.1 ) Subpart F income 1.7 0.3 1.3 Other, net (1.4 ) (1.3 ) - Effective tax rate (0.8% ) 22.5 % (13.5% ) The net deferred tax assets and liabilities consist of the following: December 31, 2017 2016 (Dollars in thousands) Deferred tax assets (liabilities): Net foreign deferred taxes, primarily depreciation $ (61,961 ) $ (35,382 ) Depreciation (65,312 ) 148,419 Intangible drilling costs 12,934 (112,762 ) Net capital loss carryforward - U.S. 44,619 117,924 Tax monetization transaction (6,465 ) (105,789 ) State and Investment tax credits 813 1,341 Production tax credits 85,193 82,451 Foreign tax credits 86,206 - Withholding tax (14,400 ) - Stock options amortization 1,166 3,241 Basis difference in partnership interest (14,731 ) (24,462 ) Accrued liabilities and other 2,931 (752 ) 70,993 74,229 Less - valuation allowance (50,858 ) (109,611 ) Total $ 20,135 $ (35,382 ) The following table presents a reconciliation of the beginning and ending valuation allowance: Year Ended December 31, 2017 2016 2015 (Dollars in thousands) Balance at beginning of the year $ 109,611 $ 70,536 $ 111,280 Additions to valuation allowance 46,560 39,075 - Release of valuation allowance (105,313 ) - (40,744 ) Balance at end of the year $ 50,858 $ 109,611 $ 70,536 At December 31, 2017, $145.0 $222.2 2029 2037 2018 2037 $0.8 December 31, 2017 $85.2 December 31, 2017 20 2026 2037. $86.2 31, 2017 10 2027. The Company has recorded notable deferred tax assets for net operating losses, foreign tax credits, and production tax credits. 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. Based upon available evidence of the Company’s ability to generate additional taxable income in the future and historical losses in prior years, a valuation allowance in the amount of $50.9 $109.6 December 31, 2017 2016, not not $58.7 $50.9 In October 2016, 2016 16, 2016 16 December 15, 2017, ng entity to recognize the tax expense from intra-entity transfers of assets other than inventory in the selling entity'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 buying entity's jurisdiction would also be recognized at the time of the transfer. For additional information on the new accounting standard related to tax effects associated with intercompany transfers of assets please see New accounting pronouncements effective in future periods” in Note 1 8 The following table presents the deferred taxes on the balance sheet as of the dates indicated: Year Ended December 31, 2017 2016 2015 (Dollars in thousands) Non-current deferred tax assets $ 107,605 $ — $ — Non-current deferred tax liabilities (87,470 ) (35,382 ) (32,654 ) Total Non-current deferred tax assets, net 20,135 (35,382 ) (32,654 ) Uncertain tax benefit offset (1) (95 ) — — $ 20,040 $ (35,382 ) $ (32,654 ) ( 1 $0.1 2013 11, During 2017, The decision was made to distribute $396.0 $300.0 December 2017 $96.0 2018. $58.3 The total amount of undistributed earnings of all other foreign subsidiaries for income tax purposes was approximately $401 December 31, 2017. no may not Uncertain tax positions We are subject to income taxes in the U.S. (federal and state) and numerous foreign jurisdictions. Significant judgment is required in evaluating our tax positions and determining our provision for income taxes. During the ordinary course of business, the re are many transactions and calculations for which the ultimate tax determination is uncertain. We establish reserves for tax-related uncertainties based on estimates of whether, and the extent to which additional taxes will be due. These reserves are established when we believe that certain positions might be challenged despite. We adjust these reserves in light of changing facts and circumstances, such as the outcome of tax audits. The provision for income taxes includes the impact of reserve positions and changes to reserves that are considered probable. At December 31, 2017 2016, $9.0 $5.7 ing authorities on an underpayment of income taxes are included as a component of income tax provision in the consolidated statements of operations and comprehensive income. A reconciliation of our unrecognized tax benefits is as follows: Year Ended December 31, 2017 2016 2015 (Dollars in thousands) Balance at beginning of year $ 5,738 $ 10,385 $ 7,511 Additions based on tax positions taken in prior years 798 675 (198 ) Additions based on tax positions taken in the current year 2,367 1,059 4,386 Reduction based on tax positions taken in prior years (13 ) (6,381 ) (1,314 ) Balance at end of year $ 8,890 $ 5,738 $ 10,385 The Company and its U.S. subsidiaries file consolidated income tax returns for federal and state purposes. As of December 31, 2017, not by the Internal Revenue Service for the years 2000 2017 and by local state jurisdictions for the years 2002 2017. may The reduction of $0.0 $6.4 $1.3 2017, 2016 2015, The Company ’s foreign subsidiaries remain open to examination by the local income tax authorities in the following countries for the years indicated: Israe l 2015 — 2017 Kenya 2012 — 2017 Guatemala 2013 — 2017 Honduras 2012 — 2017 Guadeloupe 2015 — 2017 Philippines 2010 — 2017 New Zealand 2012 — 2017 Management believes that the liability for unrecognized tax benefits is adequate for all open tax years based on its assessment of many factors, including among others, past experience and interpretations of local income tax regulations. This assessment relies on estimates and assumptions and may . Tax benefits in the U.S . The U.S. government encourages production of electricity from geothermal resources through certain tax subsidies under the ARRA which has been extended by the Consolidated Appropriations Act, 2016 On February 9, 2018 2018 2018. 2018 2.4 first 10 may 30% not 10%. 30% January 1, 2018, 1 20 September 27, 2017, first ● 80% Dec. 31, 2022 Jan. 1, 2024 . ● 60% Dec. 31, 2023 Jan. 1, 2025 . ● 40% Dec. 31, 2024 Jan. 1, 2026 . ● 20% Dec. 31, 2025 Jan. 1, 2027 . The Company could also elect in lieu of bonus deprecation to depreciate most of the plant for tax purposes over five may first If the Company claims the ITC, the Company ’s “tax base” in the plant that it can recover through bonus or accelerated depreciation (if elected) must be reduced by half of the ITC. If the Company claims the PTC, there is no 2010, 2011, 2012, 2013, 2014, 2015, 2016 December 31, 2017, may 50% 60 . Income taxes related to foreign operations Guatemala — The enacted tax rate is 25%. ten August 2017. August 2017, 7% December 31, 2017, 2016, 2015 $2.6 $3.3 $3.6 $0.05, $0.07, $0.08 Israel — The Company’s operations in Israel through its wholly owned Israeli subsidiary, Ormat Systems Ltd. (“Ormat Systems”), are taxed at the regular corporate tax rate of 26.5% 2015, 25% 2016, 24% 2017 23% 2018 1959 two January 2011, 16% 2014 2011. In the event of distribution of a cash dividend out of retained earnings which were tax exempt due to prior benefits, Ormat Systems would have to pay tax in respect of the amount distributed. Since the exemptions are contingent upon nondistribution of divid ends and since upon liquidation the Company will have to pay a 25% 25% 2004 2008. may may Ormat Systems tax assessment for fiscal years 2010 2014 January 2017. no Kenya - The Company’s operations in Kenya are taxed at the rate of 37.5%. September 11, 2015, 2015. 150% 17B 5 10 15 4 15 5 January 1, 2016 January 1, 2015 15 4 15 5 50% not five ten $49.4 December 31, 2015. During the fourth 2016, $4.7 used in the calculation of taxable income at its Kenya operations, which principally related to fiscal years prior to 2015. $4.7 fourth 2016 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 2013. June 20, 2017, $2.6 June 2017 150% $1.2 Guadeloupe 34.43% 2017, 28% €0.5 33.3% €0.5 2018, 28% €0.5 31% €0.5 2019, 28% 2020, 26.5% 2021 25% 2022. Honduras - The Company’s operations in Honduras are exempt from income taxes for the first ten Other significant foreign countries — The Company’s operations in New Zealand are taxed at the rate of 28% 2015, 2014 2013. Income taxes related to U.S. tax legislation commonly referred to as the Tax Cuts and Jobs Act On December 22, 2017, Tax Act”). The Tax Act makes broad and complex changes to the U.S. tax code, including, but not 1 35 21 2 one 3 4 ; ( 5 6 7 8 December 31, 2017. The SEC staff issued SAB 118, SAB 118 not one 740. 118, 740 740 Our accounting for the following elements of the Tax Act is incomplete and the Company may However, we are able to make reasonable estimates of certain effects and, therefore, recorded provisional adjustments as follows: Reduction in U.S. federal corporate tax rate: The Tax Act reduces the corporate tax rate of 35 21 January 1, 2018. $22.6 December 31, 2018. may not Deemed Repatriation Transition Tax: The Deemed Repatriation Tax (Transition Tax) is a one To determine the amount of the Transition Tax, we must determine, in addition to other factors, the amount of post- 1986 $71.9 , therefore there is no Transition Tax. Global intangible low taxed income (GILTI): The Tax Act creates a new requirement that certain income (i.e. GILTI) earned by controlled foreign corporations (CFCs) must be included currently in gross income of the CFC ’s U.S. Shareholder. GILTI is the excess of the shareholder’s “net CFC tested income” over the net deemed tangible income return, which is currently defined as the excess of ( 1 10 2 Because of the complexity of the new GILTI rules, we are continuing to evaluate this provision of the Tax Act and the application of ASC 740. As discussed further below, for valuation allowance purposes, GILTI inclusions were determined using estimates of book income, but the Company will calculate the impact of GILTI as a period cost. Valuation Allowance: The Company must assess whether its valuation allowance analyses are affected by various aspects of the Tax Act (e.g. deemed repatriation of deferred foreign income, GILTI inclusions, new categories of FTCs, interest expense limitations). Since, as discussed herein, the Company has recorded provisional amounts related to certain portions of the Tax Act, any corresponding determination of the need for or change in a valuation allowance is provisional . Uncertain Tax Positions: The Company must assess whether its uncertain tax positions a nalyses are affected by various aspects of the Tax Act (e.g. deemed repatriation of deferred foreign income, GILTI inclusions, new categories of FTCs, interest expense limitations). Since, as discussed herein, the Company has recorded provisional amounts related to certain portions of the Tax Act, any corresponding determination of the need for or change in an uncertain tax position is provisional .

Note 19 - Business Segments

Note 19 - Business Segments	12 Months Ended
	Dec. 31, 2017
Notes to Financial Statements
Segment Reporting Disclosure [Text Block]	NOTE 19 — BUSINESS SEGMENTS The Company has two ’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 were determined on current market values or cost plus markup of the seller’s business segment. ORMAT TECHNOLOGIES, INC. AND SUBSIDIARIES NOTES TO CONSOLIDATED FINANCIAL STATEMENTS Summarized financial information concerning the Company ’s reportable segments is shown in the following tables: Electricity Product Consolidated (Dollars in thousands) Year Ended December 31, 2017: Net revenues from external customers $ 468,329 $ 224,483 $ 692,812 Intersegment revenues — 109,040 109,040 Depreciation and amortization expense 111,676 3,470 115,146 Operating income 154,475 50,543 205,018 Segment assets at period end (*) ( 1 2,470,949 115,713 2,586,662 Expenditures for long-lived assets 252,581 6,653 259,234 * Including unconsolidated investments — 34,084 34,084 Year Ended December 31, 2016: Net revenues from external customers $ 436,292 $ 226,299 $ 662,591 Intersegment revenues — 56,075 56,075 Depreciation and amortization expense 102,698 3,279 105,977 Operating income 126,828 75,054 201,882 Segment assets at period end ( 1 2,204,444 257,125 2,461,569 Expenditures for long-lived assets 147,211 4,719 151,930 Year Ended December 31, 2015 : Net revenues from external customers $ 375,920 $ 218,724 $ 594,644 Intersegment revenues — 48,559 48,559 Depreciation and amortization expense 103,892 3,314 107,206 Operating income 99,345 64,716 164,061 Segment assets at period end 2,044,346 229,636 2,273,982 Expenditures for long-lived assets 149,666 2,784 152,450 ( 1 $21.0 $6.7 December 31, 2017 2016, Reconciling information between reportable segments and the Company ’s consolidated totals is shown in the following table: Year Ended December 31, 2017 2016 2015 (Dollars in thousands) Revenues: Total segment revenues $ 692,812 $ 662,591 $ 594,644 Intersegment revenues 109,040 56,075 48,559 Elimination of intersegment revenues (109,040 ) (56,075 ) (48,559 ) Total consolidated revenues $ 692,812 $ 662,591 $ 594,644 Operating income: Operating income $ 205,018 $ 201,882 $ 164,061 Interest income 988 971 297 Interest expense, net (54,142 ) (67,389 ) (72,577 ) Foreign currency translation and transaction losses 2,654 (5,534 ) (1,622 ) Income attributable to sale of equity interest 17,878 16,503 25,431 Other non-operating income, net (1,666 ) (5,345 ) (1,991 ) Total consolidated income before income taxes and equity in income of investees $ 170,730 $ 141,088 $ 113,599 ORMAT TECHNOLOGIES, INC. AND SUBSIDIARIES NOTES TO CONSOLIDATED FINANCIAL STATEMENTS The Company sells electricity and products for power plants and others, mainly to the geographical areas according to location of the customers, as detailed below. The following tables present certain data by geographic area: Year Ended December 31, 2017 2016 2015 (Dollars in thousands) Revenues from external customers attributable to: (1) United States $ 301,132 $ 307,025 $ 286,509 Indonesia 28,968 100,856 93,191 Kenya 110,243 109,270 86,545 Turkey 125,166 46,270 57,356 Chile 8,895 58,032 34,478 Guatemala 27,991 30,086 27,897 New Zealand 33,395 — — Other foreign countries 57,022 11,052 8,668 Consolidated total $ 692,812 $ 662,591 $ 594,644 ( 1 Revenues as reported in the geographic area in which they originate. Year Ended December 31, 2017 2016 2015 (Dollars in thousands) Long-lived assets (primarily power plants and related assets) located in: United States $ 1,510,986 $ 1,414,523 $ 1,374,465 Kenya 340,970 327,157 375,257 Other foreign countries 281,333 199,559 107,407 Consolidated total $ 2,133,289 $ 1,941,239 $ 1,857,129 The following table presents revenues from major customers: Year Ended December 31, 2017 2016 2015 Revenues % Revenues % Revenues % (Dollars in thousands) (Dollars in thousands) (Dollars in thousands) Southern California Edison (1) $ 29,714 4.3 $ 33,552 5.1 $ 56,026 9.4 Southern California Public Power Authority (1) 70,100 10.1 67,566 10.2 30,947 5.2 Sierra Pacific Power Company and Nevada Power Company (1)(2) 125,424 18.1 127,226 19.2 115,876 19.5 Hyundai ( 3 28,968 4.2 100,856 15.2 93,131 15.7 KPLC (1) 110,243 15.9 109,270 16.5 86,545 14.6 ( 1 Revenues reported in Electricity segment. ( 2 Subsidiaries of NV Energy, Inc. ( 3 Revenues related to the Sarulla project that are reported in Product segment. ORMAT TECHNOLOGIES, INC. AND SUBSIDIARIES NOTES TO CONSOLIDATED FINANCIAL STATEMENTS

Note 20 - Transactions With Rel

Note 20 - Transactions With Related Entities	12 Months Ended
	Dec. 31, 2017
Notes to Financial Statements
Related Party Transactions Disclosure [Text Block]	NOTE 20 — TRANSACTIONS WITH RELATED ENTITIES Transactions between the Company and related entities, other than those disclosed elsewhere in these financial are summarized below: Year Ended December 31, 2017 2016 2015 (Dollars in thousands) Property rental fee expense paid to the Parent $ — $ — $ 303 Corporate financial, administrative, executive services, and research and development services provided to the Parent $ — $ — $ 148 Services rendered by an indirect shareholder of the Parent $ — $ — $ 15 Restructuring with the Parent On February 5, 2015, ’s common stock on the TASE. On February 10, 2015, 25 25 On February 12, 2015, Parent entity, Ormat Industries Ltd. ("OIL" or "Parent") following which, the Company became a noncontrolled public company and its public float increased from approximately 40% 76% 0.2592 30.2 3.0 27.2 45.5 48.5 In exchange, the Company also received $15.4 $0.6 $12.1 $0.5 no Corporate and administrative services agreement with the Parent Ormat Systems and the Parent had agreements whereby Ormat Systems provided to the Parent, for a monthly fee of $ 10,000 10%. Lease agreements with the Parent Ormat Systems had a rental agreement with the Parent entered into in July 2004 $52,000, Effective April 1, 2009, July 2004. $77,000, . As of February 12, 2015, no

Note 21 - Employee Benefit Plan

Note 21 - Employee Benefit Plan	12 Months Ended
	Dec. 31, 2017
Notes to Financial Statements
Pension and Other Postretirement Benefits Disclosure [Text Block]	NOTE 21 — EMPLOYEE BENEFIT PLAN 401 ( k) Plan The Company has a 401 one one 60% 2017, 2016 2015, 4%, 3% 2% ’s annual salary, respectively. The Company’s contributions to the Plan were $1.4 $1.0 $0.6 December 31, 2017, 2016, 2015, Severance plan The Company, through Ormat Systems, provides limited non-pension benefits to all current employees in Israel who are entitled to benefits in the event of termination or retirement in accordance with the Israeli Government sponsored programs. These plans generally obligate the Company to pay one ’s salary per year of service to employees in the event of involuntary termination. There is no $13.9 $12.8 December 31, 2017 2016, not may not December 31, 2017, 2016, 2015 $3.2 $2.3 $2.5 $1.8 $0.3 $0.1 The Company expects to pay the following future benefits to its employees upon their reaching normal retirement age : (Dollars in thousands) Year ending December 31 : 201 8 $ 4,258 201 9 1,803 20 20 1,242 20 21 1,418 20 22 2,112 2023-2027 4,338 $ 15,171 The above amounts were determined based on the employees ’ current salary rates and the number of years’ service that will have been accumulated at their retirement date. These amounts do not

Note 22 - Commitments and Conti

Note 22 - Commitments and Contingencies	12 Months Ended
	Dec. 31, 2017
Notes to Financial Statements
Commitments and Contingencies Disclosure [Text Block]	NOTE 22 — COMMITMENTS AND CONTINGENCIES Geothermal resources The Company, through its project subsidiaries in the U.S., controls certain rights to geothermal fluids through certain leases with the Bureau of Land Management (“BLM”) or through private leases. Royalties on the utilization of the geothermal resources are computed and paid to the lessors as defined in the respective agreements. Royalty expense under the geothermal resource agreements were $19.4 $17.1 $15.4 December 31, 2017, 2016, 2015, Letters of credit In the ordinary course of business with customers, vendors, and lenders, the Company is contingently liable for performance under letters of credit totaling $277.7 December 31, 2017. not not Purchase commitments The Company purchases raw materials for inventories, construction-in-process and services from a variety of vendors. During the normal course of business, in order to manage manufacturing lead times and help assure adequate supply, the Company enters into agreements with contract manufacturers and suppliers that either allow them to procure goods and services based upon specifications defined by the Company, or that establish parameters defining the Company ’s requirements. At December 31, 2017, $113.4 $54.2 2018. Grants and royalties The Company, through Ormat Systems, had historically, through December 31, 2003, 3.5% 5.0% No December 31, 2017 , 2016, 2015. not not December 31, 2017 2016, $1.9 $1.8 $0.9 $0.8 Lease commitments At December 31, 201 7, 2016 2015, 12 $0.5 $0.4 $0.4 In 2015, he Company entered into a lease transaction for a fleet of vehicles. The lease transaction was classified as a capital lease and the leased vehicles were classified under Property, Plant and Equipment in total amount of $7.6 2015, 2016 2017. 5 Contingencies ● Jon Olson and Hilary Wilt, together with Puna Pono Alliance filed a complaint on February 17, 2015 16 May 17, 2015, October 10, 2016, ’ 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, April 20, 2017 ● On July 8, 2014, two three 1, June 26, 2015, one ’ causes of action. On January 6, 2017, January 6, 2017 No ● On March 29, 2016, ’s subsidiaries in the 27th $4.8 3.75% 10 11th In February 2018 preliminary defenses, filed by the Company, were denied by the lower court and are pending on appeal. The Company timely filed its answer to the claim on the merits, and the plaintiff filed its response (replication) . The Company believes that it has valid defenses under law and intends to defend itself vigorously . ● On August 5, 2016, ’s fees and statutory interest against PGV and other presently unknown defendants. On December 12, 2016, August 2014. June 14, 2017, ● On June 20, 2016, March 31, 2016. ’s insurer reached an out of court settlement that was approved by the US District Court, Southern District of California, and executed on May 25, 2017. ● On February 18, 2018, January 16, 2018 2 January 2018 3 In 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

Note 23 - Quarterly Financial I

Note 23 - Quarterly Financial Information (Unaudited)	12 Months Ended
	Dec. 31, 2017
Notes to Financial Statements
Quarterly Financial Information [Text Block]	NOTE 23 — QUARTERLY FINANCIAL INFORMATION (UNAUDITED) Three Months Ended Mar. 31, 2016 June 30, 2016 Sept. 30, 2016 Dec. 31, 2016 Mar. 31, 2017 June 30, 2017 Sept. 30, 2017 Dec. 31, 2017 (Dollars in thousands, except per share amounts) Revenues: Electricity $ 107,868 $ 104,001 $ 109,795 $ 114,628 $ 115,776 $ 111,777 $ 112,273 $ 128,503 Product 43,726 55,860 74,822 51,891 74,122 67,587 44,912 37,862 Total revenues 151,594 159,861 184,617 166,519 189,898 179,364 157,185 166,365 Cost of revenues: Electricity 63,686 62,243 66,481 69,163 66,036 65,439 65,774 75,017 Product 24,035 31,822 43,647 30,719 49,452 43,432 32,218 26,992 Total cost of revenues 87,721 94,065 110,128 99,882 115,488 108,871 97,992 102,009 Gross margin 63,873 65,796 74,489 66,637 74,410 70,493 59,193 64,356 Operating expenses: Research and development expenses 349 595 1,086 732 602 1,050 716 789 Selling and marketing expenses 3,675 3,668 4,793 4,288 4,363 4,090 3,630 3,517 General and administrative expenses 8,749 8,783 19,093 10,085 9,949 12,201 10,877 9,854 Write-off of unsuccessful exploration activities 557 863 1,294 303 -- -- -- 1,796 Operating income 50,543 51,887 48,223 51,229 59,496 53,152 43,970 48,400 Other income (expense): Interest income 320 245 266 140 244 362 255 127 Interest expense, net (16,023 ) (18,401 ) (17,137 ) (15,828 ) (14,923 ) (14,540 ) (11,692 ) (12,987 ) Derivatives and foreign currency transaction gains (losses) 1,962 (4,332 ) (222 ) (2,942 ) 1,338 1,703 (1,001 ) 614 Income attributable to sale of tax benefits 4,398 4,519 3,463 4,123 6,157 4,356 3,506 3,859 Other non-operating income (expense), net 191 49 (5,546 ) (39 ) (92 ) 6 (1,592 ) 12 Income (loss) from continuing operations, before income taxes and equity in income of investees 41,391 33,967 29,047 36,683 52,220 45,039 33,446 40,025 Income tax benefit (provision) (9,509 ) (7,890 ) (11,988 ) (2,450 ) (10,886 ) (6,369 ) (11,003 ) 29,669 Equity in income (losses) of investees (937 ) (1,144 ) (2,653 ) (3,001 ) (1,599 ) (428 ) 337 (267 ) Net income (loss) 30,945 24,933 14,406 31,232 39,735 38,242 22,780 69,427 Net loss (income) attributable to noncontrolling interest (1,674 ) (584 ) (2,326 ) (3,002 ) (4,423 ) (3,206 ) (3,599 ) (3,467 ) Net income (loss) attributable to the Company's stockholders $ 29,271 $ 24,349 $ 12,080 $ 28,230 $ 35,312 $ 35,036 $ 19,181 $ 65,960 Earnings (loss) per share attributable to the Company's stockholders Basic: Net income $ 0.60 $ 0.49 $ 0.24 $ 0.57 $ 0.71 $ 0.70 $ 0.38 $ 1.30 Diluted: Net income $ 0.59 $ 0.48 $ 0.21 $ 0.56 $ 0.70 $ 0.69 $ 0.38 $ 1.29 Weighted average number of shares used in computation of earnings per share attributable to the Company's stockholders: Basic 49,173 49,456 49,599 49,647 49,680 49,771 50,367 50,607 Diluted 49,782 50,137 50,289 50,293 50,491 50,624 50,867 51,053

Note 24 - Subsequent Events

Note 24 - Subsequent Events	12 Months Ended
	Dec. 31, 2017
Notes to Financial Statements
Subsequent Events [Text Block]	NOTE 24 Cash dividend On March 1, 2018, ’s Board of Directors declared, approved and authorized payment of a quarterly dividend of $11.5 $0.23 March 14, 2018, March 29, 2018. U.S. Geothermal transaction On January 24, 2018 $5.45 $109.9 second 2018. U.S. Geothermal is currently operating geothermal power projects at Neal Hot Springs, Oregon, San Emidio, Nevada and Raft River, Idaho for a total designed net output of 45 38 , net.

Significant Accounting Policies

Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Description Of Business [Policy Text Block]	Business Ormat Technologies, Inc. (the “Company”) is primarily engaged in the geothermal and recovered energy business, including the supply of equipment that is manufactured by the Company and the design and construction of power plants for projects owned by the Company or for third ’s equipment manufacturing operations are located in Israel. Most of the Company ’s domestic power plant facilities are Qualifying Facilities under the Public Utility Regulatory Policies Act of 1978 December 31, 2017.
Dividend Declared [Policy Text Block]	Cash dividends During the years ended December 31, 2017, 2016, 2015, $20.5 $0.41 $25.7 $0.52 $12.7 $0.26
Rounding [Policy Text Block]	Rounding Dollar amounts, except per share data, in the notes to these financial statements are rounded to the closest $1,000, .
Basis of Accounting, Policy [Policy Text Block]	Basis of presentation The consolidated financial statements are prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and include the accounts of the Company and of all majority-owned subsidiaries in which the Company exercises control over operating and financial policies, and variable interest entities in which the Company has an interest and is the primary beneficiary. Intercompany accounts and transactions have been eliminated in consolidation . Investments in less-than-majority-owned entities or other entities in which the Company exercises significant influence over operating and financial policies are accounted for using the equity method of accounting or consolidated if they are a variable interest entity in which the Company has an interest and is the primary beneficiary. Under the equity method, original investments are recorded at cost and adjusted by the Company ’s share of undistributed earnings or losses of such companies. The Company’s earnings or losses in investments accounted for under the equity method have been reflected as “equity in earnings (losses) of investees, net” on the Company’s consolidated statements of operations and comprehensive income (loss).
Cash and Cash Equivalents, Policy [Policy Text Block]	Cash and cash equivalents The Company considers all highly liquid instruments, with an original maturity of three .
Cash and Cash Equivalents, Restricted Cash and Cash Equivalents, Policy [Policy Text Block]	Restricted cash, cash equivalents , and marketable securities Under the terms of certain long-term debt agreements, the Company is required to maintain certain debt service reserves, cash collateral and operating fund accounts that have been classified as restricted cash and cash equivalents. Funds that will be used to satisfy obligations due during the next twelve
Concentration Risk, Credit Risk, Policy [Policy Text Block]	Concentration of credit risk Financial instruments which potentially subject the Company to 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 U.S. and in foreign countries. At December 31, 2017 2016, $21.2 $72.5 seven $250,000 December 31, 2017 2016, ’s deposits in foreign countries of approximately $32.8 $166.2 not At December 31, 2017 2016, approximately $78.1 $53.3 December 31, 2017, 2016, 19 57% 60%, The Company has historically been able to collect on substantially all of its receivable balances, and believes it will continue to be able to collect all amounts due. Accordingly, no
Inventory, Policy [Policy Text Block]	Inventories Inventories consist primarily of raw material parts and sub-assemblies for power units, and are stated at the lower of cost or net realizable value, using the weighted-average cost method. Inventories are reduced by a provision for slow-moving and obsolete inventories. This provision was not December 31, 2017 2016.
Deposit Contracts, Policy [Policy Text Block]	Deposits and other Deposits and other consist primarily of performance bonds for construction projects, long-term insurance contract and receivables, and derivative instruments.
Deferred Charges, Policy [Policy Text Block]	Deferred charges Deferred charges represent prepaid income taxes on intercompany sales. Such amounts are amortized using the straight-line method and included in income tax provision over the life of the related property, plant and equipment. The Company has not 2016 16, For additional information on the new accounting standard related to tax effects associated with intercompany transfers of assets please see "New accounting pronouncements effective in future periods" in Note 1 8
Property, Plant and Equipment, Policy [Policy Text Block]	Property, plant and equipment, net Property, plant and equipment are stated at cost. All costs associated with the acquisition, development and construction of power plants operated by the Company are capitalized. Major improvements are capitalized and repairs and maintenance (including major maintenance) costs are expensed. Power plants operated by the Company, which include geothermal wells and exploration and resource development costs, are depreciated using the straight-line method over their estimated useful lives, which range from 15 30 Buildings (in years) 25 Leasehold improvements (in years) 15 - 20 Machinery and equipment — manufacturing and drilling (in years) 10 Machinery and equipment — computers (in years) 3 - 5 Office equipment — furniture and fixtures (in years) 5 - 15 Office equipment — other (in years) 5 - 10 Automobiles (in years) 5 - 7 The cost and accumulated depreciation of items sold or retired are removed from the accounts. Any resulting gain or loss recognized currently and is recorded in the accompanying statements of operations. The Company capitalizes interest costs as part of constructing power plant facilities. Such capitalized interest is recorded as part of the asset to which it relates and is amortized over the asset ’s estimated useful life. Capitalized interest costs amounted to $7.2 $3.3 $4.1 December 31, 2017, 2016, 2015,
Exploratory Drilling Costs Capitalization and Impairment, Policy [Policy Text Block]	Exploration and development costs The Company capitalizes costs incurred in connection with the exploration and development of geothermal resources once it acquires land rights to the potential geothermal resource. Prior to acquiring land rights, the Company makes an initial assessment that an economically feasible geothermal reservoir is probable on that land. The Company determines the economic feasibility of potential geothermal resources internally, with all available data and external assessments vetted through the exploration department and occasionally using outside service providers. Costs associated with the initial assessment are expensed and included in cost of electricity revenues in the consolidated statements of operations and comprehensive income (loss). Such costs were immaterial during the years ended December 31, 2017, 2016, 2015. two three may In most cases, the Company obtains the right to conduct the geothermal development and operations on land owned by the Bureau of Land Management (“BLM”), various states or with private parties. In consideration for certain of these leases, the Company may Following the acquisition of land rights to the potential geothermal resource, the Company conducts further studies and surveys, including water and soil analyses among others, and augments its database with the results of these studies. The Company then initiates a suite of geophysical surveys to assess the resource and determine drilling locations. If the results of these activities support the initial assessment of the feasibility of the geothermal resource, the Company then proceeds to exploratory drilling and other related activities which may may not When deciding whether to continue holding lease rights and/or to pursue exploration activity, we diligently prioritize our prospective investments, taking into account resource and probability assessments in order to make informed decisions about whether a particular project will support commercial operation . As a result, write-off of unsuccessful activities for the year ended December 31, 2017, 2016 2015 $1.8 $3.0 $1.6 2017, 2016, no Grants received from the U.S. Department of Energy (“DOE”) are offset against the related exploration and development costs. Such grants amounted to $0.0 $0.3 $0.8 December 31, 2017, 2016, 2015, All exploration and development costs that are being capitalized, including the up-front bonus payments made to secure land leases, will be depreciated over their estimated useful lives when the related geothermal power plant is substantially complete and ready for use. A geothermal power plant is substantially complete and ready for use when electricity generation commences.
Asset Retirement Obligation [Policy Text Block]	Asset retirement obligation The Company records the fair value of a legal liability for an asset retirement obligation in the period in which it is incurred. The Company ’s legal liabilities include plugging wells and post-closure costs of power producing sites. When a new liability for asset retirement obligations is recorded, the Company capitalizes the costs of the liability by increasing the carrying amount of the related long-lived asset. The liability is accreted to its present value each period, and the capitalized cost is depreciated over the useful life of the related asset. At retirement, the obligation is settled for its recorded amount at a gain or loss.
Deferred Financing And Lease Transaction Costs [Policy Text Block]	Deferred financing and lease transaction costs Deferred financing costs are amortized over the term of the related obligation using the effective interest method. Amortization of deferred financing costs is presented as interest expense in the consolidated statements of operations and comprehensive income (loss). Accumulated amortization related to deferred financing costs amounted to $31.0 $31.1 December 31, 2017 2016, December 31, 2017, 2016, 2015 $5.7 $6.9 $8.8 December 31, 2017, 2016 2015, $0.6 $0.1 $0.5 Deferred transaction costs relating to the Puna operating lease (see Note 12 $4.2 23 $2.3 $2.1 December 31, 2017 2016, December 31, 2017, 2016, 2015 $0.2
Goodwill and Intangible Assets, Goodwill, Policy [Policy Text Block]	Goodwill Goodwill represents the excess of the fair value of consideration transferred in the business combination transactions of Guadeloupe and Viridity over the fair value of tangible and intangible assets acquired, net of the fair value of liabilities assumed and the fair value of any noncontrolling interest in the acquisitions. Goodwill is not not entity is permitted to first not no one not first second second 2017 2016, not
Intangible Assets, Finite-Lived, Policy [Policy Text Block]	Intangible assets Intangible assets consist of allocated acquisition costs of PPAs, which are amortized using the straight-line method over the 13 25 9 ) as well as acquisition cost allocation related to Viridity’s storage activities that are amortized over a weighted average amortization period of 19 may not no no not
Impairment or Disposal of Long-Lived Assets, Policy [Policy Text Block]	Impairment of long-lived assets and long-lived assets to be disposed of The Company evaluates long-lived assets, such as property, plant and equipment and construction-in-process for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not ’s use of assets or its overall business strategy, negative industry or economic trends, a determination that an exploration project will not not not The Company tests its operating plants that are operated together as a complex for impairment at the complex level because the cash flows of such plants result from significant shared operating activities. For example, the operating power plants in a complex are managed under a combined operation management generally with one one not not not Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to the estimated future net undiscounted cash flows expected to be generated by the asset. The significant assumptions that the Company uses in estimating its undiscounted future cash flows include: (i) projected generating capacity of the complex or power plant and rates to be received under the respective PPA(s) and expected market rates thereafter and (ii) projected operating expenses of the relevant complex or power plant. Estimates of future cash flows used to test recoverability of a long-lived asset under development also include cash flows associated with all future expenditures necessary to develop the asset. If the assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the carrying amount of the assets exceeds their fair value. Assets to be disposed of are reported at the lower of the carrying amount or fair value less costs to sell. Management believes that no may ’s current estimates, a material impairment charge may
Derivatives, Policy [Policy Text Block]	Derivative instruments Derivative instruments (including certain derivative instruments embedded in other contracts) are measured at their fair value and recorded as either assets or liabilities unless exempted from derivative treatment as a normal purchase and sale. All changes in the fair value of derivatives are recognized in earnings unless specific hedge criteria are met, which requires a company to formally document, designate and assess the effectiveness of transactions that receive hedge accounting. The Company maintains a risk management strategy that incorporates the use of swap contracts and put options on oil and natural gas prices, forward exchange contracts, interest rate swaps, and interest rate caps to minimize significant fluctuation in cash flows and/or earnings that are caused by oil and natural gas prices, exchange rate or interest rate volatility. Gains or losses on contracts that initially qualify for cash flow hedge accounting, net of related taxes, are included as a component of other comprehensive income or loss and accumulated other comprehensive income or loss are subsequently reclassified into earnings when the hedged forecasted transaction affects earnings. Gains or losses on contracts that are not
Foreign Currency Transactions and Translations Policy [Policy Text Block]	Foreign currency translation The U.S. dollar is the functional currency for all of the Company ’s consolidated operations and those of its equity affiliates except for the Guadeloupe power plant. For those entities, all gains and losses from currency translations are included within the line item “Derivatives and foreign currency transaction gains (losses)” within the consolidated statements of operations and comprehensive income (loss). The Euro is the functional currency of the Guadeloupe power plant and thus gains and losses from currency translation adjustments related to Guadeloupe are included as currency translation adjustments in accumulated other comprehensive income in the consolidated statements of equity and in comprehensive income.
Comprehensive Income, Policy [Policy Text Block]	Comprehensive income (loss) reporting Comprehensive income (loss) includes net income or loss plus other comprehensive income (loss), which for the Company consists of changes in unrealized gains or losses in respect of the Company ’s share in derivatives instruments of unconsolidated investment, foreign currency translation adjustments and amortization of unrealized gains in respect of derivative instruments designated as a cash flow hedge. For the years ended December 31, 2017, 2016 2015, $11,000 $9,000 $27,000 $16,000 $12,000 $44,000 $5,000 $3,000 $17,000
Revenue Recognition, Policy [Policy Text Block]	Revenues and cost of revenues Revenues are primarily related to: (i) sale of electricity from geothermal and recovered energy-based power plants owned and operated by the Company and (ii) geothermal and recovered energy-based power plant equipment engineering, sale, construction and installation, and operating services. Revenues related to the sale of electricity from geothermal and recovered energy-based power plants and capacity payments are recorded based upon output delivered and capacity provided at rates specified under relevant contract terms. For PPAs agreed to, modified, or acquired in business combinations on or after July 1, 2003, Revenues from engineering, operating services, and parts and product sales are recorded upon providing the service or delivery of the products and parts and when collectability is reasonably assured. Revenues from the supply and/or construction of geothermal and recovered energy-based power plant equipment and other equipment to third may . In specific instances where there is a lack of dependable estimates or inherent risks cause forecast to be doubtful, then the completed-contract method is followed. Revenue is recognized when the contract is substantially complete and when collectability is reasonably assured. Costs that are closely associated with the project are deferred as contract costs and recognized similarly to the associated revenues.
Standard Product Warranty, Policy [Policy Text Block]	Warranty on products sold The Company generally provides a one December 31, 2017, 2016, 2015 .
Research and Development Expense, Policy [Policy Text Block]	Research and development Research and development costs incurred by the Company for the development of existing and new geothermal, recovered energy and remote power technologies are expensed as incurred. Grants received from the DOE are offset against the related research and development expenses. There were no December 31, 2017, 2016, 2015 .
Tax Monetization Transactions Policy [Policy Text Block]	Tax monetization Transactions The Company had three 2017 ’s partners reaching their target after-tax yield on their investment, as further described in Note 13. 470. 810. 835 7.
Share-based Compensation, Option and Incentive Plans Policy [Policy Text Block]	Stock-based compensation The Company accounts for stock-based compensation using the fair value method whereby compensation cost is measured at the grant date, based on the calculated fair value of the award, and is recognized as an expense over the requisite employee service period (generally the vesting period of the grant). Prior to 2016, 2016,
Income Tax, Policy [Policy Text Block]	Income taxes Income taxes are accounted for using the asset and liability approach, which requires the recognition of taxes payable or refundable for the current year and deferred tax assets and liabilities for the future tax consequences of events that have been recognized in the Company ’s financial statements or tax returns. The measurement of current and deferred tax assets and liabilities are based on provisions of the enacted tax law. On December 22, 2017, not 1 35 21 2 3 4 5 6 7 8 December 31, 2017. 18 not, not not
Earnings Per Share, Policy [Policy Text Block]	Earnings (loss) per share Basic earnings (loss) per share attributable to the Company ’s stockholders (“earnings (loss) per share”) 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 The table below shows the reconciliation of the number of shares used in the computation of basic and diluted earnings per share : Year Ended December 31, 2017 2016 2015 (In thousands) Weighted average number of shares used in computation of basic earnings per share 50,110 49,469 48,562 Add: Additional shares from the assumed exercise of employee stock options 659 671 625 Weighted average number of shares used in computation of diluted earnings per share 50,769 50,140 49,187 The number of stock-based awards that could potentially dilute future earnings per share and were not 42,896, 102,793, 467,766, December 31, 2017, 2016, 2015.
Use of Estimates, Policy [Policy Text Block]	Use of estimates in preparation of financial statements The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the dates of such financial statements and the reported amounts of revenues and expenses during the reporting periods. Actual results could differ from those estimates. The most significant estimates with regard to the Company ’s consolidated financial statements relate to the useful lives of property, plant and equipment, impairment of goodwill and long-lived assets, including intangible assets, and assets to be disposed of, revenue recognition of product sales using the percentage of completion method, asset retirement obligations, and the provision for income taxes.
New Accounting Pronouncements, Policy [Policy Text Block]	New Accounting Pronouncements New accounting pronouncements effective in the year ended December 31, 2017 Improvement to Employee Share-Based Payment Accounting In March 2016, 2016 09, 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 1 2 December 15, 2016. The Company elected to not Interests Held through Related Parties that are under Common Control In October 2016, 2016 17, 810 December 15, 2016, not Simplifying the Measurement of Inventory In July 2015, 2015 11, 330. no ‘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, not New accounting pronouncements effective in future periods Derivatives and Hedging In August 2017, 2017 12, December 15, 2018, Intangibles –Goodwill and Other In January 2017, 2017 04, 350 not 2 2 first first December 15, 2019. January 1, 2017. Compensation - Stock Compensation In May 2017, 2017 09, —Stock Compensation (Topic 718 718. 1 2 3 718 December 15, 2017. not Business Combinations In January 2017, 2017 01, 805 not December 15, 2017, The Company is currently evaluating the potential impact of the adoption of these amendments on its consolidated financial statements, however, such impact, if any, is not Statement of Cash Flow In November 2016, 2016 18, 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, not Intra-Entity Transfers of Assets Other than Inventory In October 2016, 2016 16, ’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 December 15, 2017, $9.5 with a corresponding adjustment to deferred charges and deferred income taxes on the consolidated balance sheet of approximately $49.8 $59.3 Statement of Cash Flows: Classification of Certain Cash Receipts and Cash payments (Topic 230 ) In August 2016, 2016 15, 230 eight December 15, 2017, not . Revenues from Contracts with Customers In May 2014, 2014 09, 606, 1 2 3 4 5 2014 09 December 15, 2017, March 2016, 2016 08, not December 15, 2017, To date, we have made substantial progress in our assessment of the impact of adopting this new guidance, and we have taken steps towards implementation. We have utilized internal resources to lead the implementation efforts and supplemented them with external resources. Our approach to implementation has consisted of ( 1 2 3 4 January 1, 2018. 840, $24.1 January 1, 2018. not one $24.1 January 1, 2018, not Leases In February 2016, 2016 02, 842. two 606. December 15, 2018, Recognition and Measurement of Financial Assets and Financial Liabilities In January 2016, 2016 01, December 15, 2017, however, such impact, if any, is not

Note 1 - Business and Signifi33

Note 1 - Business and Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2017
Notes Tables
Schedule Of Estimated Useful Lives [Table Text Block]	Buildings (in years) 25 Leasehold improvements (in years) 15 - 20 Machinery and equipment — manufacturing and drilling (in years) 10 Machinery and equipment — computers (in years) 3 - 5 Office equipment — furniture and fixtures (in years) 5 - 15 Office equipment — other (in years) 5 - 10 Automobiles (in years) 5 - 7
Schedule of Weighted Average Number of Shares [Table Text Block]	Year Ended December 31, 2017 2016 2015 (In thousands) Weighted average number of shares used in computation of basic earnings per share 50,110 49,469 48,562 Add: Additional shares from the assumed exercise of employee stock options 659 671 625 Weighted average number of shares used in computation of diluted earnings per share 50,769 50,140 49,187

Note 3 - Inventories (Tables)

Note 3 - Inventories (Tables)	12 Months Ended
	Dec. 31, 2017
Notes Tables
Schedule of Inventory, Current [Table Text Block]	December 31, 2017 2016 (Dollars in thousands) Raw materials and purchased parts for assembly $ 12,007 $ 5,429 Self-manufactured assembly parts and finished products 7,544 6,571 Total $ 19,551 $ 12,000

Note 4 - Cost and Estimated E35

Note 4 - Cost and Estimated Earnings on Uncompleted Contracts (Tables)	12 Months Ended
	Dec. 31, 2017
Notes Tables
Cost And Estimated Earnings On Uncompleted Contracts [Table Text Block]	December 31, 2017 2016 (Dollars in thousands) Costs and estimated earnings incurred on uncompleted contracts $ 550,823 $ 402,357 Less billings to date (530,119 ) (381,789 ) Total $ 20,704 $ 20,568
Cost and Estimated Earnings on Uncompleted Contracts Included in Consolidated Balance Sheets [Table Text Block]	December 31, 2017 2016 (Dollars in thousands) Costs and estimated earnings in excess of billings on uncompleted contracts $ 40,945 $ 52,198 Billings in excess of costs and estimated earnings on uncompleted contracts (20,241 ) (31,630 ) Total $ 20,704 $ 20,568

Note 5 - Investment In an Unc36

Note 5 - Investment In an Unconsolidated Company (Tables)	12 Months Ended
	Dec. 31, 2017
Notes Tables
Equity Method Investments [Table Text Block]	December 31, 2017 2016 (Dollars in thousands) Sarulla $ 34,084 $ (11,081)

Note 6 - Variable Interest En37

Note 6 - Variable Interest Entities (Tables)	12 Months Ended
	Dec. 31, 2017
Notes Tables
Schedule of Variable Interest Entities [Table Text Block]	December 31, 2017 Project Debt PPAs (Dollars in thousands) Assets: Restricted cash and cash equivalents $ 48,676 $ — Other current assets 124,322 18,010 Property, plant and equipment, net 1,252,623 379,277 Construction-in-process 129,832 12,885 Other long-term assets 63,667 276 Total assets $ 1,619,120 $ 410,448 Liabilities: Accounts payable and accrued expenses $ 24,887 $ 6,863 Long-term debt 658,726 — Other long-term liabilities 93,682 6,757 Total liabilities $ 777,295 $ 13,620 December 31, 2016 Project Debt PPAs (Dollars in thousands) Assets: Restricted cash, cash equivalents and marketable securities $ 34,262 $ — Other current assets 157,351 7,482 Property, plant and equipment, net 1,305,254 177,970 Construction-in-process 48,128 72,725 Other long-term assets 24,802 — Total assets $ 1,569,797 $ 258,177 Liabilities: Accounts payable and accrued expenses $ 10,900 $ 3,992 Long-term debt 668,815 — Other long-term liabilities 126,879 5,779 Total liabilities $ 806,594 $ 9,771

Note 7 - Fair Value of Financ38

Note 7 - Fair Value of Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2017
Notes Tables
Fair Value, by Balance Sheet Grouping [Table Text Block]	December 31, 2017 Fair Value Carrying Value at December 31, 2017 Total Level 1 Level 2 Level 3 (Dollars in thousands) Assets: Current assets: Cash equivalents (including restricted cash accounts) $ 18,359 $ 18,359 $ 18,359 $ — $ — Derivatives: Contingent receivable (1) 108 108 — — 108 Currency forward contracts (2) 992 992 — 992 — Liabilities: Current liabilities: Derivatives: Contingent payables (1) (13,904 ) (13,904 ) — — (13,904 ) Warrants (1) (3,967 ) (3,967 ) — — (3,967 ) $ 1,588 $ 1,588 $ 18,359 $ 992 $ (17,763 ) 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 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]	Derivatives not designated as hedging instruments Location of recognized gain (loss) Amount of recognized gain (loss) 2017 2016 2015 (Dollars in thousands) Put options on natural gas price Derivative and foreign currency transaction gains (losses) (350 ) — — Call options on natural gas price Derivative and foreign currency transaction gains (losses) — (1,340 ) — Call and put options on oil price Derivative and foreign currency transaction gains (losses) — (1,313 ) — Swap transactions on natural gas price Electricity revenues — — 1,158 Contingent considerations Derivative and foreign currency transaction gains (losses) (129 ) (1,527 ) — Contingent considerations General and administrative expenses 2,048 — — Currency forward contracts Derivative and foreign currency transaction gains (losses) 3,699 238 (1,206 ) $ 5,268 $ (3,942 ) $ (48 )
Schedule of Carrying Values and Estimated Fair Values of Debt Instruments [Table Text Block]	Fair Value Carrying Amount 2017 2016 2017 2016 (Dollars in millions) (Dollars in millions) Olkaria III Loan - DEG $ — $ 16.3 $ — $ 15.8 Olkaria III Loan - OPIC 234.6 253.4 228.6 246.6 Olkaria IV Loan - DEG 2 50.7 50.9 50.0 50.0 Amatitlan Loan 32.8 37.3 33.3 36.8 Senior Secured Notes: Ormat Funding Corp. ("OFC") — 17.0 — 17.0 OrCal Geothermal Inc. ("OrCal") 34.2 37.4 32.1 35.2 OFC 2 LLC ("OFC 2") 234.6 249.0 232.5 247.2 Don A. Campbell 1 ("DAC 1") 85.5 88.9 88.3 92.4 Senior Unsecured Bonds 200.3 200.1 204.3 204.3 Other long-term debt 7.0 10.4 7.9 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 $ — $ — $ 234.6 $ 234.6 Olkaria IV - DEG 2 — — 50.7 50.7 Amatitlan Loan — 32.8 — 32.8 Senior Secured Notes: OrCal Senior Secured Notes — — 34.2 34.2 OFC 2 Senior Secured Notes — — 234.6 234.6 DAC 1 Senior Secured Notes — — 85.5 85.5 Senior Unsecured Bonds — — 200.3 200.3 Other long-term debt — — 7.0 7.0 Revolving lines of credit — 51.5 — 51.5 Deposits 15.6 — — 15.6 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 Senior Secured Notes — 17.0 — 17.0 OrCal Senior Secured Notes — — 37.4 37.4 OFC 2 Senior Secured Notes — — 249.0 249.0 DAC 1 Senior Secured Notes — — 88.9 88.9 Senior Unsecured Bonds — — 200.1 200.1 Other long-term debt — 3.3 7.1 10.4 Revolving lines of credit — — — — Deposits 14.4 — — 14.4

Note 8 - Property, Plant and 39

Note 8 - Property, Plant and Equipment and Construction-in-process (Tables)	12 Months Ended
	Dec. 31, 2017
Notes Tables
Property, Plant and Equipment [Table Text Block]	December 31 , 2017 2016 (Dollars in thousands ) Land owned by the Company where the geothermal resource is located $ 32,178 $ 31,904 Leasehold improvements 3,984 3,848 Machinery and equipment 182,121 152,821 Land, buildings and office equipment 31,128 28,634 Automobiles 12,596 11,161 Geothermal and recovered energy generation power plants, including geothermal wells and exploration and resource development costs: United States of America, net of cash grants and impairment charges 1,744,728 1,658,195 Foreign countries 700,498 541,626 Asset retirement cost 10,563 8,669 2,717,797 2,436,858 Less accumulated depreciation (983,106 ) (880,480 ) Property, plant and equipment, net $ 1,734,691 $ 1,556,378
Construction In Progress [Table Text Block]	December 31, 2017 2016 (Dollars in thousands) Projects under exploration and development: Up-front bonus lease costs $ 17,018 $ 17,385 Exploration and development costs 46,154 36,359 Interest capitalized 703 703 63,875 54,447 Projects under construction: Up-front bonus lease costs 27,473 37,713 Drilling and construction costs 198,943 202,211 Interest capitalized 3,251 12,338 229,667 252,262 Total $ 293,542 $ 306,709
Rollforward Of Construction In Process [Table Text Block]	Projects under Exploration and Development Up-front Bonus Lease Costs Exploration and Development Costs Interest Capitalized Total (Dollars in thousands) Balance at December 31, 2014 $ 26,618 $ 45,977 $ 836 $ 73,431 Cost incurred during the year 37 10,104 869 11,010 Write off of unsuccessful exploration costs (164 ) (1,415 ) — (1,579 ) Transfer of projects under exploration and development to projects under construction — (18,940 ) (1,002 ) (19,942 ) Balance at December 31, 2015 26,491 35,726 703 62,920 Cost incurred during the year 1,514 25,165 — 26,679 Write off of unsuccessful exploration costs (380 ) (2,637 ) — (3,017 ) Transfer of projects under exploration and development to projects under construction (10,240 ) (21,895 ) — (32,135 ) Balance at December 31, 2016 17,385 36,359 703 54,447 Cost incurred during the year — 11,224 — 11,224 Write off of unsuccessful exploration costs (367 ) (1,429 ) — (1,796 ) Balance at December 31, 2017 $ 17,018 $ 46,154 $ 703 $ 63,875 Projects under Construction Up-front Bonus Lease Costs Drilling and Construction Costs Interest Capitalized Total (Dollars in thousands) Balance at December 31, 2014 $ 27,473 $ 187,545 $ 8,273 $ 223,291 Cost incurred during the year — 140,977 3,556 144,533 Transfer of projects under exploration and development to projects under construction — 18,940 1,002 19,942 Transfer of completed projects to property, plant and equipment — (196,995 ) (4,856 ) (201,851 ) Balance at December 31, 2015 27,473 150,467 7,975 185,915 Cost incurred during the year — 116,247 6,510 122,757 Transfer of exploration and development projects to projects under construction 10,240 21,895 — 32,135 Transfer of completed projects to property, plant and equipment — (86,398 ) (2,147 ) (88,545 ) Balance at December 31, 2016 37,713 202,211 12,338 252,262 Cost incurred during the year — 231,926 7,300 239,226 Transfer of completed projects to property, plant and equipment (10,240 ) (235,194 ) (16,387 ) (261,821 ) Balance at December 31, 2017 $ 27,473 $ 198,943 $ 3,251 $ 229,667

Note 9 - Intangible Assets an40

Note 9 - Intangible Assets and Goodwill (Tables)	12 Months Ended
	Dec. 31, 2017
Notes Tables
Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block]	(Dollars in thousands) Year ending December 31: 2018 $ 7,129 2019 7,056 2020 6,739 2021 6,739 2022 6,483 Thereafter 51,274 Total $ 85,420

Note 10 - Accounts Payable an41

Note 10 - Accounts Payable and Accrued Expenses (Tables)	12 Months Ended
	Dec. 31, 2017
Notes Tables
Schedule of Accounts Payable and Accrued Liabilities [Table Text Block]	December 31, 2017 2016 (Dollars in thousands) Trade payables $ 64,289 $ 48,309 Salaries and other payroll costs 19,888 17,977 Customer advances 1,177 576 Accrued interest 4,462 3,524 Income tax payable 43,682 8,824 Property tax payable 1,860 1,884 Scheduling and transmission 531 964 Royalty accrual 2,909 1,639 Other 14,998 7,953 Total $ 153,796 $ 91,650

Note 11 - Long-term Debt and 42

Note 11 - Long-term Debt and Credit Agreements (Tables)	12 Months Ended
	Dec. 31, 2017
Notes Tables
Schedule of Long-term Debt Instruments [Table Text Block]	December 31, 2017 2016 (Dollars in thousands) Limited and non-recourse agreements: Loans: Non-recourse: Other loans $ 7,252 $ 6,368 Limited recourse: Loan agreement with OPIC (the Olkaria III power plant) 228,635 246,630 Loan agreement with Banco Industrial S.A. and Westrust Bank (International) Limited 33,251 36,750 Senior Secured Notes: Non-recourse: OFC Senior Secured Notes - 17,026 OrCal Senior Secured Notes 32,142 35,181 DAC 1 Senior Secured Notes 88,339 92,361 Limited recourse: OFC 2 Senior Secured Notes 232,526 247,232 622,145 681,548 Less current portion (54,720 ) (53,729 ) Non current portion $ 567,425 $ 627,819 Full recourse agreements: Senior Unsecured Bonds $ 204,332 $ 204,332 Loans from institutional investors - 3,333 Loan agreements with DEG (the Olkaria III and IV power plants) 50,000 65,789 Loan from a commercial bank 587 1,529 Revolving credit lines with banks 51,500 - 306,419 274,983 Less current portion (54,587 ) (12,242 ) Non current portion $ 251,832 $ 262,741
Schedule of Maturities of Long-term Debt [Table Text Block]	(Dollars in thousands) Year ending December 31: 2018 $ 57,807 2019 55,539 2020 123,093 2021 46,579 2022 184,148 Thereafter 409,898 Total $ 877,064

Note 12 - Puna Power Plant Le43

Note 12 - Puna Power Plant Lease Transactions (Tables)	12 Months Ended
	Dec. 31, 2017
Notes Tables
Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block]	(Dollars in thousands) Year ending December 31: 2018 $ 13,317 2019 6,018 2020 2,450 2021 1,723 2022 824 Thereafter 1,917 Total $ 26,249

Note 14 - Asset Retirement Ob44

Note 14 - Asset Retirement Obligation (Tables)	12 Months Ended
	Dec. 31, 2017
Notes Tables
Schedule of Asset Retirement Obligations [Table Text Block]	Year Ended December 31, 2017 2016 (Dollars in thousands) Balance at beginning of year $ 23,348 $ 20,856 Revision in estimated cash flows 1,888 303 Liabilities incurred — 540 Accretion expense 1,874 1,649 Balance at end of year $ 27,110 $ 23,348

Note 15 - Stock-based Compens45

Note 15 - Stock-based Compensation (Tables)	12 Months Ended
	Dec. 31, 2017
Notes Tables
Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table Text Block]	Year Ended December 31, 2017 2016 2015 (Dollars in thousands, except per share data) Cost of revenues $ 3,369 $ 2,400 $ 1,753 Selling and marketing expenses 452 247 123 General and administrative expenses 4,939 2,510 2,079 Total stock-based compensation expense 8,760 5,157 3,955 Tax effect on stock-based compensation expense 604 617 440 Net effect of stock-based compensation expense $ 8,156 $ 4,540 $ 3,515
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]	Year Ended December 31, 2017 2016 2015 For stock options issued by the Company: Risk-free interest rates 1.9 % 1.3 % 1.4 % Expected lives (in weighted average years) 3.1 4.5 4.0 Dividend yield 0.62 % 1.10 % 0.70 % Expected volatility (weighted average) 27.2 % 30.7 % 29.2 % Forfeiture rate (weighted average) 0.0 % 8.4 % 0.0 %
Schedule of Share-based Compensation, Stock Options and Stock Appreciation Rights Award Activity [Table Text Block]	Year Ended December 31, 2017 2016 2015 Shares (In thousands) Weighted Average Exercise Price Shares (In thousands) Weighted Average Exercise Price Shares (In thousands) Weighted Average Exercise Price Outstanding at beginning of year 2,565 $ 33.36 2,438 $ 25.38 4,477 $ 27.48 Granted, at fair value: Stock Options 30 57.97 1,155 43.01 45 38.24 SARs* 132 62.55 — — — — RSUs** 23 — Exercised (1,181 ) 25.92 (967 ) 25.33 (1,589 ) 26.77 Forfeited (21 ) 46.15 (57 ) 24.12 (125 ) 27.33 Expired — — (4 ) 26.84 (370 ) 45.78 Outstanding at end of year 1,548 41.35 2,565 33.36 2,438 25.38 Options and SARs exercisable at end of year 431 32.61 557 25.22 858 26.75 Weighted-average fair value of options and SARs granted during the year $ 22.82 $ 11.61 $ 8.68
Schedule of Share-based Compensation, Shares Authorized under Stock Option Plans, by Exercise Price Range [Table Text Block]	Options Outstanding Options Exercisable Exercise Price Number of Stock-based Awards Outstanding Weighted Average Remaining Contractual Life in Years Aggregate Intrinsic Value Number of Stock-based Awards Exercisable Weighted Average Remaining Contractual Life in Years Aggregate Intrinsic Value $ - 23 3.9 1,455 - - - 20.13 35 1.3 1,533 35 1.3 1,533 23.34 176 1.4 7,150 176 1.4 7,150 25.65 10 0.3 398 10 0.3 398 35.15 15 5.1 432 15 5.1 432 38.24 15 4.8 386 15 4.8 386 42.87 1,074 4.5 22,651 143 4.5 3,005 47.46 38 5.9 619 38 5.9 619 57.97 30 6.6 180 - - - 58.79 23 4.5 120 - - - 63.35 109 5.9 66 - - - 1,548 4.2 $ 34,990 432 3.0 $ 13,523 Options Outstanding Options Exercisable Exercise Price Number of Stock-based Awards Outstanding Weighted Average Remaining Contractual Life in Years Aggregate Intrinsic Value Number of Stock-based Awards Exercisable Weighted Average Remaining Contractual Life in Years Aggregate Intrinsic Value $ 18.56 15 2.8 526 15 2.8 526 19.69 15 2.6 509 15 2.6 509 20.13 108 2.3 3,608 108 2.3 3,608 20.54 53 2.3 1,761 28 2.3 934 23.34 635 2.4 19,226 140 2.4 4,247 24.57 9 2.1 269 1 2.1 33 25.65 68 1.3 1,905 68 1.3 1,905 26.70 15 3.8 404 15 3.8 404 28.23 30 4.8 762 30 4.8 762 29.52 400 3.6 9,640 75 3.6 1,807 29.95 17 0.3 400 17 0.3 400 35.15 15 6.1 277 - - - 38.24 45 5.8 692 45 5.8 692 42.87 1,080 5.5 11,610 - - - 47.46 60 6.9 370 - - - 2,565 4.1 $ 51,959 557 2.7 $ 15,827
Chief Financial Officer [Member]
Notes Tables
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]	Risk-free interest rates 0.81 % Expected life (in years ) 3.375 Dividend yield 0.80 % Expected volatility 33.50 % Forfeiture rat e 0.00 % Grant of options to purchase 100,000 shares of common stock Grant of options to purchase 300,000 shares of common stock Risk-free interest rates 2.36 % 1.64 % Expected life (in years) 7.25 4.75 Dividend yield 0.90 % 0.90 % Expected volatility 42.80 % 33.10 % Risk-free interest rates 1.30 % Expected life (in years) 4.0 Dividend yield 0.70 % Expected volatility 32.40 % Forfeiture rate 0.00 % Risk-free interest rates 1.35 % Expected life (in years) 4.0 Dividend yield 0.70 % Expected volatility 29.20 % Forfeiture rate 0.00 %
Stock Appreciation Rights (SARs) [Member]
Notes Tables
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]	Risk-free interest rate 1.29 % Expected life (in years) 6 Dividend yield 1.14 % Expected volatility 30.7 % Forfeiture rate: Senior management 0.0 % Other employees 10.5 % Sub-Optimal Exercise Factor: Senior management 2.5 Other employees 2.0 Risk-free interest rate 1.65 % Expected life (in years) 7 Dividend yield 1.1 % Expected volatility 30.6 % Forfeiture rate 0.0 % Sub-Optimal Exercise Factor 2.5 Risk-free interest rate 1.74 % Expected life (in years) 5 Dividend yield 0.66 % Expected volatility 26.3 % Forfeiture rate 10.3 % Sub-Optimal Exercise Factor 2 Risk-free interest rate 2.08 % Expected life (in years) 7 Dividend yield 0.69 % Expected volatility 29.4 % Forfeiture rate 0.0 % Sub-Optimal Exercise Factor 2.5 Risk-free interest rate 2.1 % Expected life (in years) 6 Dividend yield 0.6 % Expected volatility 26.9 % Forfeiture rate 0.0 % Sub-Optimal Exercise Factor 2.5

Note 17 - Interest Expense, N46

Note 17 - Interest Expense, Net (Tables)	12 Months Ended
	Dec. 31, 2017
Notes Tables
Schedule of Other Nonoperating Expense, by Component [Table Text Block]	Year Ended December 31, 2017 2016 2015 (Dollars in thousands) Interest related to sale of tax benefits $ 6,985 $ 9,349 $ 9,620 Interest expense 54,381 61,327 67,032 Less — amount capitalized (7,224 ) (3,287 ) (4,075 ) $ 54,142 $ 67,389 $ 72,577

Note 18 - Income Taxes (Tables)

Note 18 - Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2017
Notes Tables
Schedule of Income before Income Tax, Domestic and Foreign [Table Text Block]	Year Ended December 31, 2017 2016 2015 (Dollars in thousands) U.S. $ 13,680 $ (7,109 ) $ (236 ) Non-U.S. (foreign) 157,050 148,197 113,835 Total income from continuing operations, before income taxes and equity in losses of investees $ 170,730 $ 141,088 $ 113,599
Schedule of Components of Income Tax Expense (Benefit) [Table Text Block]	Year Ended December 31, 2017 2016 2015 (Dollars in thousands) Current: Federal $ 43,850 $ — $ 51 State 108 (276 ) 252 Foreign 10,816 14,040 19,175 Total current income tax expense $ 54,774 $ 13,764 $ 19,478 Deferred: Federal (78,220 ) — — State (4,544 ) — — Foreign 26,579 18,073 (34,736 ) Total deferred tax benefit (56,185 ) 18,073 (34,736 ) Total provision (benefit) for income taxes $ (1,411 ) $ 31,837 $ (15,258 )
Components Of Deferred Income Tax Expense (Benefit) [Table Text Block]	Year Ended December 31, 2017 2016 2015 (Dollars in thousands) Other deferred tax expense (exclusive of the effect of other components listed below) $ 1,833 $ (1,105 ) $ 541 Usage (benefit) of operating loss carryforwards - U.S. 73,049 (14,072 ) (30,596 ) Change in valuation allowance (58,757 ) 16,411 (14,324 ) Change in foreign valuation allowance — — (49,701 ) Change in foreign income tax 26,579 18,073 14,965 Change in lease transaction — — (452 ) Change in tax monetization transaction (23,234 ) 48,000 16,386 Change in depreciation 129,408 (55,462 ) 28,370 Change in foreign tax credits (86,206 ) — — Change in withholding tax 14,400 — — Change in state and investment tax credits (144 ) — — Change in intangible drilling costs (118,610 ) 10,227 10,335 Change in production tax credits and alternative minimum tax credit (2,070 ) (11,659 ) 610 Basis difference in partnership interests (12,433 ) 7,660 (10,870 ) $ (56,185 ) $ 18,073 $ (34,736 )
Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]	Year Ended December 31, 2017 2016 2015 U.S. federal statutory tax rate 35.0 % 35.0 % 35.0 % Impact of federal tax reform (13.2 ) - - Transition tax inclusion 42.1 - - Foreign tax credits (50.4 ) - - Tax basis adjustment (4.7 ) - - Withholding tax 34.1 - - Valuation allowance - U.S. (30.3 ) 11.1 (1.4 ) Valuation allowance - foreign - - (43.8 ) State income tax, net of federal benefit (2.2 ) (0.2 ) 0.6 Effect of foreign income tax, net (10.3 ) (14.1 ) (5.1 ) Production tax credits (1.2 ) (8.3 ) (0.1 ) Subpart F income 1.7 0.3 1.3 Other, net (1.4 ) (1.3 ) - Effective tax rate (0.8% ) 22.5 % (13.5% )
Schedule of Deferred Tax Assets and Liabilities [Table Text Block]	December 31, 2017 2016 (Dollars in thousands) Deferred tax assets (liabilities): Net foreign deferred taxes, primarily depreciation $ (61,961 ) $ (35,382 ) Depreciation (65,312 ) 148,419 Intangible drilling costs 12,934 (112,762 ) Net capital loss carryforward - U.S. 44,619 117,924 Tax monetization transaction (6,465 ) (105,789 ) State and Investment tax credits 813 1,341 Production tax credits 85,193 82,451 Foreign tax credits 86,206 - Withholding tax (14,400 ) - Stock options amortization 1,166 3,241 Basis difference in partnership interest (14,731 ) (24,462 ) Accrued liabilities and other 2,931 (752 ) 70,993 74,229 Less - valuation allowance (50,858 ) (109,611 ) Total $ 20,135 $ (35,382 )
Summary of Valuation Allowance [Table Text Block]	Year Ended December 31, 2017 2016 2015 (Dollars in thousands) Balance at beginning of the year $ 109,611 $ 70,536 $ 111,280 Additions to valuation allowance 46,560 39,075 - Release of valuation allowance (105,313 ) - (40,744 ) Balance at end of the year $ 50,858 $ 109,611 $ 70,536
Schedule of Deferred Taxes Classified in Balance Sheet [Table Text Block]	Year Ended December 31, 2017 2016 2015 (Dollars in thousands) Non-current deferred tax assets $ 107,605 $ — $ — Non-current deferred tax liabilities (87,470 ) (35,382 ) (32,654 ) Total Non-current deferred tax assets, net 20,135 (35,382 ) (32,654 ) Uncertain tax benefit offset (1) (95 ) — — $ 20,040 $ (35,382 ) $ (32,654 )
Summary of Income Tax Contingencies [Table Text Block]	Year Ended December 31, 2017 2016 2015 (Dollars in thousands) Balance at beginning of year $ 5,738 $ 10,385 $ 7,511 Additions based on tax positions taken in prior years 798 675 (198 ) Additions based on tax positions taken in the current year 2,367 1,059 4,386 Reduction based on tax positions taken in prior years (13 ) (6,381 ) (1,314 ) Balance at end of year $ 8,890 $ 5,738 $ 10,385
Summary of Income Tax Examinations [Table Text Block]	Israe l 2015 — 2017 Kenya 2012 — 2017 Guatemala 2013 — 2017 Honduras 2012 — 2017 Guadeloupe 2015 — 2017 Philippines 2010 — 2017 New Zealand 2012 — 2017

Note 19 - Business Segments (Ta

Note 19 - Business Segments (Tables)	12 Months Ended
	Dec. 31, 2017
Notes Tables
Schedule of Segment Reporting Information, by Segment [Table Text Block]	Electricity Product Consolidated (Dollars in thousands) Year Ended December 31, 2017: Net revenues from external customers $ 468,329 $ 224,483 $ 692,812 Intersegment revenues — 109,040 109,040 Depreciation and amortization expense 111,676 3,470 115,146 Operating income 154,475 50,543 205,018 Segment assets at period end (*) ( 1 2,470,949 115,713 2,586,662 Expenditures for long-lived assets 252,581 6,653 259,234 * Including unconsolidated investments — 34,084 34,084 Year Ended December 31, 2016: Net revenues from external customers $ 436,292 $ 226,299 $ 662,591 Intersegment revenues — 56,075 56,075 Depreciation and amortization expense 102,698 3,279 105,977 Operating income 126,828 75,054 201,882 Segment assets at period end ( 1 2,204,444 257,125 2,461,569 Expenditures for long-lived assets 147,211 4,719 151,930 Year Ended December 31, 2015 : Net revenues from external customers $ 375,920 $ 218,724 $ 594,644 Intersegment revenues — 48,559 48,559 Depreciation and amortization expense 103,892 3,314 107,206 Operating income 99,345 64,716 164,061 Segment assets at period end 2,044,346 229,636 2,273,982 Expenditures for long-lived assets 149,666 2,784 152,450
Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Table Text Block]	Year Ended December 31, 2017 2016 2015 (Dollars in thousands) Revenues: Total segment revenues $ 692,812 $ 662,591 $ 594,644 Intersegment revenues 109,040 56,075 48,559 Elimination of intersegment revenues (109,040 ) (56,075 ) (48,559 ) Total consolidated revenues $ 692,812 $ 662,591 $ 594,644 Operating income: Operating income $ 205,018 $ 201,882 $ 164,061 Interest income 988 971 297 Interest expense, net (54,142 ) (67,389 ) (72,577 ) Foreign currency translation and transaction losses 2,654 (5,534 ) (1,622 ) Income attributable to sale of equity interest 17,878 16,503 25,431 Other non-operating income, net (1,666 ) (5,345 ) (1,991 ) Total consolidated income before income taxes and equity in income of investees $ 170,730 $ 141,088 $ 113,599
Schedule of Revenue from External Customers and Long-Lived Assets, by Geographical Areas [Table Text Block]	Year Ended December 31, 2017 2016 2015 (Dollars in thousands) Revenues from external customers attributable to: (1) United States $ 301,132 $ 307,025 $ 286,509 Indonesia 28,968 100,856 93,191 Kenya 110,243 109,270 86,545 Turkey 125,166 46,270 57,356 Chile 8,895 58,032 34,478 Guatemala 27,991 30,086 27,897 New Zealand 33,395 — — Other foreign countries 57,022 11,052 8,668 Consolidated total $ 692,812 $ 662,591 $ 594,644
Schedule of Disclosure on Geographic Areas, Long-Lived Assets in Individual Foreign Countries by Country [Table Text Block]	Year Ended December 31, 2017 2016 2015 (Dollars in thousands) Long-lived assets (primarily power plants and related assets) located in: United States $ 1,510,986 $ 1,414,523 $ 1,374,465 Kenya 340,970 327,157 375,257 Other foreign countries 281,333 199,559 107,407 Consolidated total $ 2,133,289 $ 1,941,239 $ 1,857,129
Schedule of Revenue by Major Customers by Reporting Segments [Table Text Block]	Year Ended December 31, 2017 2016 2015 Revenues % Revenues % Revenues % (Dollars in thousands) (Dollars in thousands) (Dollars in thousands) Southern California Edison (1) $ 29,714 4.3 $ 33,552 5.1 $ 56,026 9.4 Southern California Public Power Authority (1) 70,100 10.1 67,566 10.2 30,947 5.2 Sierra Pacific Power Company and Nevada Power Company (1)(2) 125,424 18.1 127,226 19.2 115,876 19.5 Hyundai ( 3 28,968 4.2 100,856 15.2 93,131 15.7 KPLC (1) 110,243 15.9 109,270 16.5 86,545 14.6

Note 20 - Transactions With R49

Note 20 - Transactions With Related Entities (Tables)	12 Months Ended
	Dec. 31, 2017
Notes Tables
Schedule of Related Party Transactions [Table Text Block]	Year Ended December 31, 2017 2016 2015 (Dollars in thousands) Property rental fee expense paid to the Parent $ — $ — $ 303 Corporate financial, administrative, executive services, and research and development services provided to the Parent $ — $ — $ 148 Services rendered by an indirect shareholder of the Parent $ — $ — $ 15

Note 21 - Employee Benefit Pl50

Note 21 - Employee Benefit Plan (Tables)	12 Months Ended
	Dec. 31, 2017
Notes Tables
Schedule of Expected Benefit Payments [Table Text Block]	(Dollars in thousands) Year ending December 31 : 201 8 $ 4,258 201 9 1,803 20 20 1,242 20 21 1,418 20 22 2,112 2023-2027 4,338 $ 15,171

Note 23 - Quarterly Financial51

Note 23 - Quarterly Financial Information (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2017
Notes Tables
Quarterly Financial Information [Table Text Block]	Three Months Ended Mar. 31, 2016 June 30, 2016 Sept. 30, 2016 Dec. 31, 2016 Mar. 31, 2017 June 30, 2017 Sept. 30, 2017 Dec. 31, 2017 (Dollars in thousands, except per share amounts) Revenues: Electricity $ 107,868 $ 104,001 $ 109,795 $ 114,628 $ 115,776 $ 111,777 $ 112,273 $ 128,503 Product 43,726 55,860 74,822 51,891 74,122 67,587 44,912 37,862 Total revenues 151,594 159,861 184,617 166,519 189,898 179,364 157,185 166,365 Cost of revenues: Electricity 63,686 62,243 66,481 69,163 66,036 65,439 65,774 75,017 Product 24,035 31,822 43,647 30,719 49,452 43,432 32,218 26,992 Total cost of revenues 87,721 94,065 110,128 99,882 115,488 108,871 97,992 102,009 Gross margin 63,873 65,796 74,489 66,637 74,410 70,493 59,193 64,356 Operating expenses: Research and development expenses 349 595 1,086 732 602 1,050 716 789 Selling and marketing expenses 3,675 3,668 4,793 4,288 4,363 4,090 3,630 3,517 General and administrative expenses 8,749 8,783 19,093 10,085 9,949 12,201 10,877 9,854 Write-off of unsuccessful exploration activities 557 863 1,294 303 -- -- -- 1,796 Operating income 50,543 51,887 48,223 51,229 59,496 53,152 43,970 48,400 Other income (expense): Interest income 320 245 266 140 244 362 255 127 Interest expense, net (16,023 ) (18,401 ) (17,137 ) (15,828 ) (14,923 ) (14,540 ) (11,692 ) (12,987 ) Derivatives and foreign currency transaction gains (losses) 1,962 (4,332 ) (222 ) (2,942 ) 1,338 1,703 (1,001 ) 614 Income attributable to sale of tax benefits 4,398 4,519 3,463 4,123 6,157 4,356 3,506 3,859 Other non-operating income (expense), net 191 49 (5,546 ) (39 ) (92 ) 6 (1,592 ) 12 Income (loss) from continuing operations, before income taxes and equity in income of investees 41,391 33,967 29,047 36,683 52,220 45,039 33,446 40,025 Income tax benefit (provision) (9,509 ) (7,890 ) (11,988 ) (2,450 ) (10,886 ) (6,369 ) (11,003 ) 29,669 Equity in income (losses) of investees (937 ) (1,144 ) (2,653 ) (3,001 ) (1,599 ) (428 ) 337 (267 ) Net income (loss) 30,945 24,933 14,406 31,232 39,735 38,242 22,780 69,427 Net loss (income) attributable to noncontrolling interest (1,674 ) (584 ) (2,326 ) (3,002 ) (4,423 ) (3,206 ) (3,599 ) (3,467 ) Net income (loss) attributable to the Company's stockholders $ 29,271 $ 24,349 $ 12,080 $ 28,230 $ 35,312 $ 35,036 $ 19,181 $ 65,960 Earnings (loss) per share attributable to the Company's stockholders Basic: Net income $ 0.60 $ 0.49 $ 0.24 $ 0.57 $ 0.71 $ 0.70 $ 0.38 $ 1.30 Diluted: Net income $ 0.59 $ 0.48 $ 0.21 $ 0.56 $ 0.70 $ 0.69 $ 0.38 $ 1.29 Weighted average number of shares used in computation of earnings per share attributable to the Company's stockholders: Basic 49,173 49,456 49,599 49,647 49,680 49,771 50,367 50,607 Diluted 49,782 50,137 50,289 50,293 50,491 50,624 50,867 51,053

Note 1 - Business and Signifi52

Note 1 - Business and Significant Accounting Policies (Details Textual) - USD ($)	Mar. 01, 2018	Mar. 15, 2017	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jan. 01, 2018
Dividends, Common Stock, Cash												$ 20,500,000	$ 25,700,000	$ 12,700,000
Common Stock, Dividends, Per Share, Declared												$ 0.41	$ 0.52	$ 0.26
Accounts Receivable, Net, Current			$ 110,410,000				$ 80,807,000					$ 110,410,000	$ 80,807,000
Provision for Doubtful Accounts												0
Interest Costs Capitalized												7,224,000	3,287,000	$ 4,075,000
Exploration Abandonment and Impairment Expense			1,796,000				303,000	$ 1,294,000	$ 863,000	$ 557,000		1,796,000	3,017,000	1,579,000
Grants Received to Offset Exploration and Development Costs Incurred												0	300,000	800,000
Accumulated Amortization, Debt Issuance Costs			31,000,000				31,100,000					31,000,000	31,100,000
Amortization of Debt Issuance Costs												5,700,000	6,900,000	8,800,000
Write off of Deferred Debt Issuance Cost												600,000	100,000	500,000
Deferred Costs, Leasing, Gross			4,200,000									$ 4,200,000
Lease Payment Term												23 years
Goodwill, Impairment Loss												$ 0	0
Impairment of Long-Lived Assets to be Disposed of												0
Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax			1,400,000				1,200,000					1,400,000	1,200,000
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax												11,000,000	9,000,000	27,000,000
Interest Expense			12,987,000	11,692,000	14,540,000	14,923,000	15,828,000	17,137,000	18,401,000	16,023,000		54,142,000	67,389,000	72,577,000
Income Tax Expense (Benefit)			(29,669,000)	$ 11,003,000	$ 6,369,000	$ 10,886,000	2,450,000	$ 11,988,000	$ 7,890,000	$ 9,509,000		$ (1,411,000)	$ 31,837,000	$ (15,258,000)
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent												35.00%	35.00%	35.00%
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount												42,896	102,793	467,766
Research and Development Arrangement with Federal Government, Customer Funding to Offset Costs Incurred												$ 0	$ 0	$ 0
Retained Earnings [Member]
Common Stock, Dividends, Per Share, Declared												$ 0.41	$ 0.52	$ 0.26
Subsequent Event [Member]
Common Stock, Dividends, Per Share, Declared	$ 0.23
Subsequent Event [Member] | Accounting Standards Update 2016-16 [Member]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets															$ 9.50
Subsequent Event [Member] | Accounting Standards Update 2014-09 [Member] | Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption															24,100,000
Scenario, Forecast [Member]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent											21.00%
Reclassification out of Accumulated Other Comprehensive Income [Member]
Interest Expense												$ (16,000,000)	$ (12,000,000)	$ (44,000,000)
Income Tax Expense (Benefit)												$ (5,000,000)	(3,000,000)	(17,000,000)
Viridity Energy, Inc. [Member]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life		19 years										19 years
Puna Geothermal Ventures [Member]
Deferred Costs, Leasing, Gross			4,200,000									$ 4,200,000
Lease Payment Term												23 years
Deferred Costs, Leasing, Accumulated Amortization			2,300,000				2,100,000					$ 2,300,000	2,100,000
Amortization of Deferred Leasing Fees												$ 200,000	$ 200,000	$ 200,000
Accounts Receivable [Member] | Customer Concentration Risk [Member] | Primary Customers [Member]
Concentration Risk, Percentage												57.00%	60.00%
Maximum [Member]
Cash, FDIC Insured Amount			250,000									$ 250,000
Finite-Lived Intangible Asset, Useful Life												25 years
Maximum [Member] | Subsequent Event [Member] | Accounting Standards Update 2016-16 [Member]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets															59.30
Maximum [Member] | Power Plants [Member]
Property, Plant and Equipment, Useful Life												30 years
Minimum [Member]
Finite-Lived Intangible Asset, Useful Life												13 years
Minimum [Member] | Subsequent Event [Member] | Accounting Standards Update 2016-16 [Member]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets															$ 49.80
Minimum [Member] | Power Plants [Member]
Property, Plant and Equipment, Useful Life												15 years
UNITED STATES
Cash, Cash Equivalents, and Short-term Investments			21,200,000				72,500,000					$ 21,200,000	$ 72,500,000
Foreign Countries [Member]
Cash, Cash Equivalents, and Short-term Investments			32,800,000				166,200,000					32,800,000	166,200,000
Accounts Receivable, Net, Current			$ 78,100,000				$ 53,300,000					$ 78,100,000	$ 53,300,000

Note 1 - Business and Signifi53

Note 1 - Business and Significant Accounting Policies - Property, Plant, and Equipment Estimated Useful Life (Details)	12 Months Ended
	Dec. 31, 2017
Building [Member]
Property, plant, and equipment estimated useful lives (Year)	25 years
Leasehold Improvements [Member] | Minimum [Member]
Property, plant, and equipment estimated useful lives (Year)	15 years
Leasehold Improvements [Member] | Maximum [Member]
Property, plant, and equipment estimated useful lives (Year)	20 years
Machinery And Equipment - Manufacturing And Drilling [Member]
Property, plant, and equipment estimated useful lives (Year)	10 years
Machinery and Equipment - Computers [Member] | Minimum [Member]
Property, plant, and equipment estimated useful lives (Year)	3 years
Machinery and Equipment - Computers [Member] | Maximum [Member]
Property, plant, and equipment estimated useful lives (Year)	5 years
Furniture and Fixtures [Member] | Minimum [Member]
Property, plant, and equipment estimated useful lives (Year)	5 years
Furniture and Fixtures [Member] | Maximum [Member]
Property, plant, and equipment estimated useful lives (Year)	15 years
Office Equipment - Other [Member] | Minimum [Member]
Property, plant, and equipment estimated useful lives (Year)	5 years
Office Equipment - Other [Member] | Maximum [Member]
Property, plant, and equipment estimated useful lives (Year)	10 years
Automobiles [Member] | Minimum [Member]
Property, plant, and equipment estimated useful lives (Year)	5 years
Automobiles [Member] | Maximum [Member]
Property, plant, and equipment estimated useful lives (Year)	7 years

Note 1 - Business and Signifi54

Note 1 - Business and Significant Accounting Policies - Shares Used to Calculate Earnings Per Share (Details) - shares shares in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Weighted average number of shares used in computation of basic earnings per share (in shares)	50,607	50,367	49,771	49,680	49,647	49,599	49,456	49,173	50,110	49,469	48,562
Additional shares from the assumed exercise of employee stock options (in shares)									659	671	625
Weighted average number of shares used in computation of diluted earnings per share (in shares)	51,053	50,867	50,624	50,491	50,293	50,289	50,137	49,782	50,769	50,140	49,187

Note 2 - Business Acquisition55

Note 2 - Business Acquisitions and Others (Details Textual) € in Millions, shares in Millions	Jul. 26, 2017shares	Mar. 15, 2017USD ($)	Jul. 31, 2016USD ($)MWh	Jul. 31, 2016EUR (€)MWh	Dec. 31, 2017USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Goodwill					$ 21,037,000	$ 21,037,000	$ 6,650,000
Payments to Acquire Businesses, Net of Cash Acquired						35,300,000	20,135,000
Payments for Achievement of Production Goal						8,032,000
Redeemable Noncontrolling Interest, Equity, Carrying Amount							11,081,000
Stockholders' Equity Attributable to Noncontrolling Interest					84,322,000	84,322,000	$ 91,582,000
Viridity Energy, Inc. [Member]
Business Combination, Consideration Transferred		$ 35,300,000
Business Combination, Contingent Consideration, Liability		12,400,000			10,300,000	$ 10,300,000
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		19 years				19 years
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Working Capital		$ 400,000
Goodwill		$ 13,400,000
Viridity Energy, Inc. [Member] | General and Administrative Expense [Member]
Business Combination, Contingent Consideration Arrangements, Change in Amount of Contingent Consideration, Liability					(600,000)
Geothermie Bouillante SA (“GB”) [Member]
Goodwill			$ 7,100,000
Expected Power Generating Capacity | MWh			14.75	14.75
Business Acquisition, Percentage of Voting Interests Acquired			60.00%
Payments to Acquire Businesses, Net of Cash Acquired			$ 20.60
Payments to Acquire Businesses, Additional Amount Subject to Achievement of Agreed upon Production Thresholds			$ 13,400,000			$ 3,600,000
Payments for Achievement of Production Goal						8,000,000
Power Purchase Agreements Term			15 years	15 years
Redeemable Noncontrolling Interest, Equity, Carrying Amount					5,000,000	5,000,000
Stockholders' Equity Attributable to Noncontrolling Interest					$ 8,300,000	$ 8,300,000
Geothermie Bouillante SA (“GB”) [Member] | Service Agreements [Member]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles			$ 33,000,000
Geothermie Bouillante SA (“GB”) [Member] | After Further Invest in Two Years [Member]
Payments to Acquire Additional Interest in Subsidiaries			$ 8,400,000	€ 7.5
Business Combination, Expected Ownership Interest			63.75%
Geothermie Bouillante SA (“GB”) [Member] | Ormat Systems LTD and Caisse des Depots et Consignations (CDC) [Member]
Business Acquisition, Percentage of Voting Interests Acquired			80.00%
Business Combination, Co-acquisition, Percentage of Ownership Interest Allocated			75.00%
Geothermie Bouillante SA (“GB”) [Member] | Caisse des Depots et Consignations (CDC) [Member]
Business Combination, Co-acquisition, Percentage of Ownership Interest Allocated			25.00%
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%

Note 3 - Inventories - Inventor

Note 3 - Inventories - Inventories, Current (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Raw materials and purchased parts for assembly	$ 12,007	$ 5,429
Self-manufactured assembly parts and finished products	7,544	6,571
Total	$ 19,551	$ 12,000

Note 4 - Cost and Estimated E57

Note 4 - Cost and Estimated Earnings on Uncompleted Contracts - Cost and Estimated Earnings on Uncompleted Contracts (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Costs and estimated earnings incurred on uncompleted contracts	$ 550,823	$ 402,357
Less billings to date	(530,119)	(381,789)
Total	$ 20,704	$ 20,568

Note 4 - Cost and Estimated E58

Note 4 - Cost and Estimated Earnings on Uncompleted Contracts - Cost and Estimated Earnings on Uncompleted Contracts Included in Consolidated Balance Sheets (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Costs and estimated earnings in excess of billings on uncompleted contracts	$ 40,945	$ 52,198
Billings in excess of costs and estimated earnings on uncompleted contracts	(20,241)	(31,630)
Total	$ 20,704	$ 20,568

Note 5 - Investment In an Unc59

Note 5 - Investment In an Unconsolidated Company (Details Textual) $ in Thousands	Jun. 04, 2014USD ($)	Dec. 31, 2017USD ($)MWh	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	May 23, 2014USD ($)	May 16, 2014USD ($)	Oct. 31, 2013USD ($)
Number of Commercial Lenders in Funding Consortium						6
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax		$ 804	$ 1,185	$ 1,028
Sarulla [Member] | Lenders Consortium [Member]
Senior Notes						$ 1,170,000
Sarulla [Member]
Jointly Owned Utility Plant, Proportionate Ownership Share		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%
Percentage of Required Injection Capacity		85.00%
Supply Commitment, Remaining Minimum Amount Committed							$ 255,600
Payments to Acquire Projects		$ 46,300
Accumulated Cash Contributions to Acquire Projects		$ 58,200
Contract Effective Date		April 4, 2013
Sarulla [Member] | Interest Rate Swap [Member]
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax		$ 800	1,200
Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax		(5,100)
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		$ 6,300	$ 9,300
Sarulla [Member] | Lenders Consortium [Member] | Interest Rate Swap [Member]
Proceeds from Issuance of Senior Long-term Debt	$ 50,000
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 5 - Unconsolidated Investm

Note 5 - Unconsolidated Investments - Unconsolidated Investments Mainly in Power Plants (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Sarulla	$ (6,416)	$ (4,772)
Sarulla [Member]
Sarulla	$ 34,084	$ (11,081)

Note 6 - Variable Interest En61

Note 6 - Variable Interest Entities - Assets and Liabilities for the Company's 2015 Variable Interest Entity (Details) - USD ($) $ in Thousands	Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
Restricted cash and cash equivalents (primarily related to VIEs)	$ 48,825		$ 34,262
Property, plant and equipment, net	1,734,691		1,556,378
Construction-in-process	293,542		306,709
Total assets	2,586,662	[1]	2,461,569	[1]	$ 2,273,982
Accounts payable and accrued expenses	153,796		91,650
Long-term debt	877,064
Other long-term liabilities	18,853		21,294
Total liabilities	1,259,787		1,286,790
Variable Interest Entity, Primary Beneficiary [Member]
Property, plant and equipment, net	1,631,900		1,483,224
Construction-in-process	142,717		120,853
Variable Interest Entity, Primary Beneficiary [Member] | Project Debt [Member]
Restricted cash and cash equivalents (primarily related to VIEs)	48,676		34,262
Other current assets	124,322		157,351
Property, plant and equipment, net	1,252,623		1,305,254
Construction-in-process	129,832		48,128
Other long-term assets	63,667		24,802
Total assets	1,619,120		1,569,797
Accounts payable and accrued expenses	24,887		10,900
Long-term debt	658,726		668,815
Other long-term liabilities	93,682		126,879
Total liabilities	777,295		806,594
Variable Interest Entity, Primary Beneficiary [Member] | Power Purchase Agreements [Member]
Restricted cash and cash equivalents (primarily related to VIEs)
Other current assets	18,010		7,482
Property, plant and equipment, net	379,277		177,970
Construction-in-process	12,885		72,725
Other long-term assets	276
Total assets	410,448		258,177
Accounts payable and accrued expenses	6,863		3,992
Long-term debt
Other long-term liabilities	6,757		5,779
Total liabilities	$ 13,620		$ 9,771
[1]	Electricity segment assets include goodwill in the amount of $21.0 million and $6.7 million as of December 31, 2017 and 2016, respectively.

Note 7 - Fair Value of Financ62

Note 7 - Fair Value of Financial Instruments (Details Textual) BTU in Millions, $ in Millions	Jan. 12, 2017USD ($)BTU$ / BTU	Feb. 24, 2016USD ($)Boe$ / Boe	Feb. 02, 2016USD ($)BTU$ / BTU	May 14, 2015BTU$ / item	Mar. 06, 2014BTU$ / BTU	Mar. 31, 2016Boe$ / Boe$ / item	Feb. 28, 2016$ / Boe
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 | $ / BTU	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 | $ / BTU			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 | $ / item						28.5
Short Risk Reversal Transactions, Rolling Existing Call Option 1 [Member] | Maximum [Member]
Derivative, Price Risk Option Strike Price | $ / item						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 | $ / item						28
Short Risk Reversal Transactions, Rolling Existing Call Option 2 [Member] | Maximum [Member]
Derivative, Price Risk Option Strike Price | $ / item						38.5
NGI Swap Contract [Member]
Derivative, Nonmonetary Notional Amount, Energy Measure | BTU				2.4	2.2
Underlying, Derivative Energy Measure				3	4.95

Note 7 - Fair Value of Financ63

Note 7 - Fair Value of Financial Instruments - Financial Assets and Liabilities at Fair Value (Details) - USD ($) $ in Thousands		Dec. 31, 2017	Dec. 31, 2016
Reported Value Measurement [Member]
Cash equivalents (including restricted cash accounts)		$ 18,359	$ 14,922
		1,588	874
Reported Value Measurement [Member] | Contingent Receivable [Member]
Derivative Asset, Current	[1]	108	1,443
Reported Value Measurement [Member] | Currency Forward Contracts [Member]
Derivative Asset, Current	[2]	992
Derivative Liability, Current	[2]		(481)
Reported Value Measurement [Member] | Contingent Payable [Member]
Derivative Liability, Current	[1]	(13,904)	(11,581)
Reported Value Measurement [Member] | Warrant [Member]
Derivative Liability, Current	[1]	(3,967)	(3,429)
Estimate of Fair Value Measurement [Member]
Cash equivalents (including restricted cash accounts)		18,359	14,922
		1,588	874
Estimate of Fair Value Measurement [Member] | Contingent Receivable [Member]
Derivative Asset, Current	[1]	108	1,443
Estimate of Fair Value Measurement [Member] | Currency Forward Contracts [Member]
Derivative Asset, Current	[2]	992
Derivative Liability, Current	[2]		(481)
Estimate of Fair Value Measurement [Member] | Contingent Payable [Member]
Derivative Liability, Current	[1]	(13,904)	(11,581)
Estimate of Fair Value Measurement [Member] | Warrant [Member]
Derivative Liability, Current	[1]	(3,967)	(3,429)
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Cash equivalents (including restricted cash accounts)		18,359	14,922
		18,359	14,922
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member] | Contingent Receivable [Member]
Derivative Asset, Current	[1]
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member] | Currency Forward Contracts [Member]
Derivative Asset, Current	[2]
Derivative Liability, Current	[2]
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member] | Contingent Payable [Member]
Derivative Liability, Current	[1]
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member] | Warrant [Member]
Derivative Liability, Current	[1]
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
Cash equivalents (including restricted cash accounts)
		992	(481)
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Contingent Receivable [Member]
Derivative Asset, Current	[1]
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Currency Forward Contracts [Member]
Derivative Asset, Current	[2]	992
Derivative Liability, Current	[2]		(481)
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Contingent Payable [Member]
Derivative Liability, Current	[1]
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Warrant [Member]
Derivative Liability, Current	[1]
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member]
Cash equivalents (including restricted cash accounts)
		(17,763)	(13,567)
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member] | Contingent Receivable [Member]
Derivative Asset, Current	[1]	108	1,443
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member] | Currency Forward Contracts [Member]
Derivative Asset, Current	[2]
Derivative Liability, Current	[2]
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member] | Contingent Payable [Member]
Derivative Liability, Current	[1]	(13,904)	(11,581)
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member] | Warrant [Member]
Derivative Liability, Current	[1]	$ (3,967)	$ (3,429)
[1]	These amounts relate to contingent receivables and payables pertaining 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 December 31, 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", as applicable, on December 31, 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 7 - Fair Value of Financ64

Note 7 - 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	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Amount of gain (loss) recognized	$ 5,268	$ (3,942)	$ (48)
Foreign Currency Gain (Loss) [Member] | Put Options on Natural Gas Price [Member]
Amount of gain (loss) recognized	(350)
Foreign Currency Gain (Loss) [Member] | Call Option on Natural Gas Price [Member]
Amount of gain (loss) recognized		(1,340)
Foreign Currency Gain (Loss) [Member] | Call and Put Options on Oil Price [Member]
Amount of gain (loss) recognized		(1,313)
Foreign Currency Gain (Loss) [Member] | Contingent Considerations [Member]
Amount of gain (loss) recognized	(129)	(1,527)
Foreign Currency Gain (Loss) [Member] | Currency Forward Contracts [Member]
Amount of gain (loss) recognized	3,699	238	(1,206)
Electricity Revenues [Member] | Natural Gas Price Swap [Member]
Amount of gain (loss) recognized			1,158
General and Administrative Expense [Member] | Contingent Considerations [Member]
Amount of gain (loss) recognized	$ 2,048

Note 7 - Fair Value of Financ65

Note 7 - Fair Value of Financial Instruments - Fair Value of Long-term Debt Approximates Its Carrying Amount, Exceptions (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Estimate of Fair Value Measurement [Member]
Other long-term debt	$ 7	$ 10.4
Reported Value Measurement [Member]
Other long-term debt	7.9	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	234.6	253.4
Olkaria III OPIC [Member] | Estimate of Fair Value Measurement [Member]
Loans	234.6	253.4
Olkaria III OPIC [Member] | Reported Value Measurement [Member]
Loans	228.6	246.6
Olkaria IV Loan - DEG 2 [Member]
Loans	50.7	50.9
Olkaria IV Loan - DEG 2 [Member] | Estimate of Fair Value Measurement [Member]
Loans	50.7	50.9
Olkaria IV Loan - DEG 2 [Member] | Reported Value Measurement [Member]
Loans	50	50
Amatitlan Loan [Member]
Loans	32.8	37.3
Amatitlan Loan [Member] | Estimate of Fair Value Measurement [Member]
Loans	32.8	37.3
Amatitlan Loan [Member] | Reported Value Measurement [Member]
Loans	33.3	36.8
Ormat Funding Corp [Member] | Estimate of Fair Value Measurement [Member]
Notes		17
Ormat Funding Corp [Member] | Reported Value Measurement [Member]
Notes		17
OrCal Geothermal Inc [Member]
Notes	34.2	37.4
OrCal Geothermal Inc [Member] | Estimate of Fair Value Measurement [Member]
Notes	34.2	37.4
OrCal Geothermal Inc [Member] | Reported Value Measurement [Member]
Notes	32.1	35.2
OFC Two Senior Secured Notes [Member]
Notes	234.6	249
OFC Two Senior Secured Notes [Member] | Estimate of Fair Value Measurement [Member]
Notes	234.6	249
OFC Two Senior Secured Notes [Member] | Reported Value Measurement [Member]
Notes	232.5	247.2
Don A. Campbell 1 ("DAC1") [Member]
Notes	85.5	88.9
Don A. Campbell 1 ("DAC1") [Member] | Estimate of Fair Value Measurement [Member]
Notes	85.5	88.9
Don A. Campbell 1 ("DAC1") [Member] | Reported Value Measurement [Member]
Notes	88.3	92.4
Senior Unsecured Bonds [Member]
Senior Unsecured Bonds	200.3	200.1
Senior Unsecured Bonds [Member] | Estimate of Fair Value Measurement [Member]
Senior Unsecured Bonds	200.3	200.1
Senior Unsecured Bonds [Member] | Reported Value Measurement [Member]
Senior Unsecured Bonds	$ 204.3	$ 204.3

Note 7 - Fair Value of Financ66

Note 7 - Fair Value of Financial Instruments - Fair Value of Financial Instruments (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Revolving lines of credit	$ 51.5
Deposits	15.6	14.4
Fair Value, Inputs, Level 1 [Member]
Revolving lines of credit
Deposits	15.6	14.4
Fair Value, Inputs, Level 2 [Member]
Revolving lines of credit	51.5
Deposits
Fair Value, Inputs, Level 3 [Member]
Revolving lines of credit
Deposits
Olkaria III OPIC [Member]
Loans	234.6	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	234.6	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	50.7	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	50.7	50.9
Amatitlan Loan [Member]
Loans	32.8	37.3
Amatitlan Loan [Member] | Fair Value, Inputs, Level 1 [Member]
Loans
Amatitlan Loan [Member] | Fair Value, Inputs, Level 2 [Member]
Loans	32.8	37.3
Amatitlan Loan [Member] | Fair Value, Inputs, Level 3 [Member]
Loans
OrCal Geothermal Inc [Member]
Notes	34.2	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	34.2	37.4
OFC Two Senior Secured Notes [Member]
Notes	234.6	249
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	234.6	249
OFC Senior Secured Notes [Member]
Notes		17
OFC Senior Secured Notes [Member] | Fair Value, Inputs, Level 1 [Member]
Notes
OFC Senior Secured Notes [Member] | Fair Value, Inputs, Level 2 [Member]
Notes		17
OFC Senior Secured Notes [Member] | Fair Value, Inputs, Level 3 [Member]
Notes
Don A. Campbell 1 ("DAC1") [Member]
Notes	85.5	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	85.5	88.9
Senior Unsecured Bonds [Member]
Senior Unsecured Bonds	200.3	200.1
Senior Unsecured Bonds [Member] | Fair Value, Inputs, Level 1 [Member]
Senior Unsecured Bonds
Senior Unsecured Bonds [Member] | Fair Value, Inputs, Level 2 [Member]
Senior Unsecured Bonds
Senior Unsecured Bonds [Member] | Fair Value, Inputs, Level 3 [Member]
Senior Unsecured Bonds	200.3	200.1
Other Long-term Debt [Member]
Other long-term debt	7	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	$ 7.1

Note 8 - Property, Plant and 67

Note 8 - Property, Plant and Equipment and Construction-in-process (Details Textual) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Depreciation	$ 98.8	$ 94.8	$ 95.2
Depreciation Net Of Amortization Of Cash Grant	5.5	5.5	$ 5.5
Property, Plant and Equipment Including Construction In Progress, Net	1,447.4	1,376.1
Property, Plant and Equipment, Cash Grant, Net	133.2	138.7
Geotermica Platanares [Member]
Property, Plant and Equipment Including Construction In Progress, Net	$ 140.3	67.5
Power Plant Usage Agreement Term	15 years
Geothermie Bouillante SA (“GB”) [Member]
Property, Plant and Equipment Including Construction In Progress, Net	$ 24.9	20.3
Orzunil I de Electricidad, Limitada [Member]
Property, Plant and Equipment Including Construction In Progress, Net	9.9	12.2
Ortitlan Limitada [Member]
Property, Plant and Equipment Including Construction In Progress, Net	$ 40.7	$ 40.3
Kenya Power and Lighting Co Limited [Member]
Power Purchase Agreements Term	20 years
Zunil Power Plant In Guatemala [Member] | Instituto Nacional de Electrificacion (INDE) [Member]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners		3.00%
ENEE [Member] | Geotermica Platanares [Member]
Power Purchase Agreements Term	30 years
EDF [Member] | Geothermie Bouillante SA (“GB”) [Member]
Power Purchase Agreements Term	15 years
Foreign Countries [Member]
Property, Plant and Equipment Including Construction In Progress, Net	$ 580.8	$ 487
KENYA | Power Plants [Member]
Property, Plant and Equipment Including Construction In Progress, Net	$ 326.1	$ 315

Note 8 - Property, Plant and 68

Note 8 - Property, Plant and Equipment and Construction-in-process - Property, Plant and Equipment, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Property, plant and equipment	$ 2,717,797	$ 2,436,858
Asset retirement cost	10,563	8,669
Less accumulated depreciation	(983,106)	(880,480)
Property, plant and equipment, net	1,734,691	1,556,378
Land [Member]
Property, plant and equipment	32,178	31,904
Leasehold Improvements [Member]
Property, plant and equipment	3,984	3,848
Machinery and Equipment [Member]
Property, plant and equipment	182,121	152,821
Office Equipment [Member]
Property, plant and equipment	31,128	28,634
Automobiles [Member]
Property, plant and equipment	12,596	11,161
Geothermal And Recovered Energy Generation Power Plants [Member] | UNITED STATES
Property, plant and equipment	1,744,728	1,658,195
Geothermal And Recovered Energy Generation Power Plants [Member] | Foreign Countries [Member]
Property, plant and equipment	$ 700,498	$ 541,626

Note 8 - Property, Plant and 69

Note 8 - Property, Plant and Equipment and Construction-in-process - Construction-in-process (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Construction-in-process	$ 293,542	$ 306,709
Projects Under Exploration and Development [Member]
Construction-in-process	63,875	54,447	$ 62,920	$ 73,431
Projects Under Exploration and Development [Member] | Up-front Bonus Lease Costs [Member]
Construction-in-process	17,018	17,385	26,491	26,618
Projects Under Exploration and Development [Member] | Exploration and Development Costs [Member]
Construction-in-process	46,154	36,359	35,726	45,977
Projects Under Exploration and Development [Member] | Interest Capitalized [Member]
Construction-in-process	703	703	$ 703	$ 836
Projects Under Construction [Member]
Construction-in-process	229,667	252,262
Projects Under Construction [Member] | Up-front Bonus Lease Costs [Member]
Construction-in-process	27,473	37,713
Projects Under Construction [Member] | Interest Capitalized [Member]
Construction-in-process	3,251	12,338
Projects Under Construction [Member] | Drilling And Construction Costs [Member]
Construction-in-process	$ 198,943	$ 202,211

Note 8 - Property, Plant and 70

Note 8 - Property, Plant and Equipment and Construction-in-process - Activity in Construction and Development (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Balance				$ 306,709					$ 306,709
Write off of unsuccessful exploration costs	$ (1,796)				$ (303)	$ (1,294)	$ (863)	$ (557)	(1,796)	$ (3,017)	$ (1,579)
Balance	293,542				306,709				293,542	306,709
Projects Under Exploration and Development [Member]
Balance				54,447				62,920	54,447	62,920	73,431
Cost incurred during the year									11,224	26,679	11,010
Write off of unsuccessful exploration costs									(1,796)	(3,017)	(1,579)
Transfer of projects under exploration and development to projects under construction										(32,135)	(19,942)
Balance	63,875				54,447				63,875	54,447	62,920
Projects Under Exploration and Development [Member] | Up-front Bonus Lease Costs [Member]
Balance				17,385				26,491	17,385	26,491	26,618
Cost incurred during the year										1,514	37
Write off of unsuccessful exploration costs									(367)	(380)	(164)
Transfer of projects under exploration and development to projects under construction										(10,240)
Balance	17,018				17,385				17,018	17,385	26,491
Projects Under Exploration and Development [Member] | Exploration and Development Costs [Member]
Balance				36,359				35,726	36,359	35,726	45,977
Cost incurred during the year									11,224	25,165	10,104
Write off of unsuccessful exploration costs									(1,429)	(2,637)	(1,415)
Transfer of projects under exploration and development to projects under construction										(21,895)	(18,940)
Balance	46,154				36,359				46,154	36,359	35,726
Projects Under Exploration and Development [Member] | Interest Capitalized [Member]
Balance				703				703	703	703	836
Cost incurred during the year											869
Write off of unsuccessful exploration costs
Transfer of projects under exploration and development to projects under construction											(1,002)
Balance	703				703				703	703	703
Construction in Progress [Member]
Balance				252,262				185,915	252,262	185,915	223,291
Cost incurred during the year									239,226	122,757	144,533
Transfer of projects under exploration and development to projects under construction										32,135	19,942
Transfer of completed projects to property, plant and equipment									(261,821)	(88,545)	(201,851)
Balance	229,667				252,262				229,667	252,262	185,915
Construction in Progress [Member] | Up-front Bonus Lease Costs [Member]
Balance				37,713				27,473	37,713	27,473	27,473
Cost incurred during the year
Transfer of projects under exploration and development to projects under construction										10,240
Transfer of completed projects to property, plant and equipment									(10,240)
Balance	27,473				37,713				27,473	37,713	27,473
Construction in Progress [Member] | Drilling And Construction Costs [Member]
Balance				202,211				150,467	202,211	150,467	187,545
Cost incurred during the year									231,926	116,247	140,977
Transfer of projects under exploration and development to projects under construction										21,895	18,940
Transfer of completed projects to property, plant and equipment									(235,194)	(86,398)	(196,995)
Balance	198,943				202,211				198,943	202,211	150,467
Construction in Progress [Member] | Interest Capitalized [Member]
Balance				$ 12,338				$ 7,975	12,338	7,975	8,273
Cost incurred during the year									7,300	6,510	3,556
Transfer of projects under exploration and development to projects under construction											1,002
Transfer of completed projects to property, plant and equipment									(16,387)	(2,147)	(4,856)
Balance	$ 3,251				$ 12,338				$ 3,251	$ 12,338	$ 7,975

Note 9 - Intangible Assets an71

Note 9 - Intangible Assets and Goodwill (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Mar. 15, 2017
Finite-Lived Intangible Assets, Net	$ 85,420,000
Amortization of Intangible Assets	6,900,000	$ 4,400,000	$ 3,300,000
Increase (Decrease) in Intangible Assets, Current	35,600,000	33,000,000	500,000
Finite Lived Intangible Assets, Disposals	0	0	$ 0
Goodwill	21,037,000	6,650,000
Viridity Energy, Inc. [Member]
Goodwill				$ 13,400,000
Goodwill, Acquired During Period	13,500,000
Guadeloupe Power Plant Transaction [Member]
Goodwill, Acquired During Period		7,100,000
Power Purchase Agreements and Intangible Assets Related to Storage Activities [Member]
Finite-Lived Intangible Assets, Net	85,400,000	52,800,000
Finite-Lived Intangible Assets, Accumulated Amortization	50,000,000	$ 42,800,000
Intangible Assets Related to Storage Activities [Member]
Finite-Lived Intangible Assets, Net	33,800,000
Finite-Lived Intangible Assets, Accumulated Amortization	$ 1,700,000

Note 9 - Intangible Assets an72

Note 9 - Intangible Assets and Goodwill - Estimated Future Amortization Expense (Details) $ in Thousands	Dec. 31, 2017USD ($)
2,018	$ 7,129
2,019	7,056
2,020	6,739
2,021	6,739
2,022	6,483
Thereafter	51,274
Total	$ 85,420

Note 10 - Accounts Payable an73

Note 10 - Accounts Payable and Accrued Expenses - Accounts Payable and Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Trade payables	$ 64,289	$ 48,309
Salaries and other payroll costs	19,888	17,977
Customer advances	1,177	576
Accrued interest	4,462	3,524
Income tax payable	43,682	8,824
Property tax payable	1,860	1,884
Scheduling and transmission	531	964
Royalty accrual	2,909	1,639
Other	14,998	7,953
Total	$ 153,796	$ 91,650

Note 11 - Long-term Debt and 74

Note 11 - Long-term Debt and Credit Agreements (Details Textual) $ in Thousands	Dec. 21, 2016USD ($)	Nov. 29, 2016USD ($)	Sep. 14, 2016USD ($)	Jul. 31, 2015USD ($)MWh	Feb. 28, 2013USD ($)	Nov. 30, 2012USD ($)	Sep. 30, 2017USD ($)	Aug. 18, 2014USD ($)	Jun. 20, 2014USD ($)	Nov. 30, 2013USD ($)	May 31, 2013USD ($)	Feb. 29, 2012USD ($)	Oct. 31, 2011USD ($)	Jul. 31, 2009USD ($)	Mar. 31, 2009	Dec. 31, 2005USD ($)	Feb. 29, 2004USD ($)	Sep. 30, 2016USD ($)	Jun. 30, 2015USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Jun. 30, 2017	May 31, 2017USD ($)	Oct. 20, 2016USD ($)	Aug. 29, 2014USD ($)	Aug. 23, 2012USD ($)	Sep. 30, 2011USD ($)	Feb. 28, 2011USD ($)	Aug. 31, 2010USD ($)	Mar. 30, 2009USD ($)
Letters of Credit Outstanding, Amount																				$ 277,700
Repayments of Secured Debt																				14,270	$ 6,815	$ 30,638
Repayments of Long-term Debt																				66,223	62,052	71,701
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax																				84	87	91
Proceeds from Issuance of Unsecured Debt																					203,483
Debt To Earnings Before Interest Tax Depreciation And Amortization Ratio																				2.58
Stockholders' Equity Attributable to Parent																				$ 1,236,137	1,078,425
Percentage Of Company Assets																				51.10%
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest																				$ 1,320,459	1,170,007	1,083,874	$ 786,746
Payments of Dividends																				$ 20,500
Interest Rate Cap [Member]
Payments for Derivative Instrument, Financing Activities								$ 1,500
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax																							900
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Tax																							$ 600
Interest Rate Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months, Net																					100	$ 100
Covenant Requirement Minimum [Member]
Amount Available For Dividend Distribution Percent Of Cumulative Net Income																				0.35
Stockholders' Equity Attributable to Parent																				$ 600,000
Percentage Of Company Assets																				25.00%
Maximum [Member] | Covenant Requirement Minimum [Member]
Debt To Earnings Before Interest Tax Depreciation And Amortization Ratio																				6
Loan Agreement with Banco Industrial S.A. and Westrust Bank (International) Limited [Member]
Debt Instrument, Term				12 years
Debt Instrument, Face Amount				$ 42,000
Power Utilization | MWh				20
Debt Instrument, Payment Frequency				12 years
Long-term Debt, Gross																				$ 33,300
Loan Agreement with Banco Industrial S.A. and Westrust Bank (International) Limited [Member] | Historical [Member]
Debt Services, Coverage Ratio																				1.49
Loan Agreement with Banco Industrial S.A. and Westrust Bank (International) Limited [Member] | Projected [Member]
Debt Services, Coverage Ratio																				1.89
Loan Agreement with Banco Industrial S.A. and Westrust Bank (International) Limited [Member] | Covenant Requirement Minimum [Member]
Debt Services, Coverage Ratio				1.15
Loan Agreement with Banco Industrial S.A. and Westrust Bank (International) Limited [Member] | Covenant Required to not Limit Dividends [Member]
Debt Services, Coverage Ratio				1.25
Loan Agreement with Banco Industrial S.A. and Westrust Bank (International) Limited [Member] | Minimum [Member]
Debt Instrument, Prepayment Premium Percentage				0.50%
Loan Agreement with Banco Industrial S.A. and Westrust Bank (International) Limited [Member] | Maximum [Member]
Debt Instrument, Prepayment Premium Percentage				1.00%
Loan Agreement with Banco Industrial S.A. and Westrust Bank (International) Limited [Member] | London Interbank Offered Rate (LIBOR) [Member] | Guaranteed [Member]
Debt Instrument, Basis Spread on Variable Rate				4.35%
Loan Agreement with Banco Industrial S.A. and Westrust Bank (International) Limited [Member] | London Interbank Offered Rate (LIBOR) [Member] | Not Guaranteed [Member]
Debt Instrument, Basis Spread on Variable Rate				4.75%
Loan Agreement with Banco Industrial S.A. and Westrust Bank (International) Limited [Member] | London Interbank Offered Rate (LIBOR) [Member] | Minimum [Member]
Debt Instrument, Basis Spread on Variable Rate				1.25%
Loan Agreement With OPIC [Member]
Debt Instrument, Face Amount																												$ 310,000
Debt Services, Coverage Ratio																				1.7
Long-term Debt, Gross																				$ 228,600
Restricted Cash and Cash Equivalents, Current																				3,700	4,300
Letters of Credit Outstanding, Amount																				$ 16,700
Loan Agreement With OPIC [Member] | In The First Two Years After the Plant Commercial Operation Date [Member]
Debt Instrument, Prepayment Premium Percentage																				2.00%
Loan Agreement With OPIC [Member] | Third Year After the Plant 2 Commercial Operation Date [Member]
Debt Instrument, Prepayment Premium Percentage																				1.00%
Loan Agreement With OPIC [Member] | Historical [Member]
Debt Services, Coverage Ratio																				2.64
Loan Agreement With OPIC [Member] | Projected [Member]
Debt Services, Coverage Ratio																				3.09
Loan Agreement With OPIC [Member] | Tranche One [Member]
Debt Instrument, Face Amount						$ 85,000
Long-term Debt, Gross																				$ 61,400
Debt Instrument, Interest Rate, Stated Percentage																				6.31%
Loan Agreement With OPIC [Member] | Tranche Two [Member]
Debt Instrument, Face Amount						180,000
Long-term Debt, Gross						135,000														$ 132,400
Proceeds from Issuance of Debt					$ 45,000
Debt Instrument, Interest Rate, Stated Percentage																				6.31%
Loan Agreement With OPIC [Member] | Tranche Three [Member]
Debt Instrument, Face Amount						45,000
Long-term Debt, Gross																				$ 34,900
Proceeds from Issuance of Debt										$ 45,000
Debt Instrument, Interest Rate, Stated Percentage																				6.12%
Loan Agreement With OPIC [Member] | Threshold For Loan Default [Member]
Debt Services, Coverage Ratio																				1.1
Loan Agreement With OPIC [Member] | Minimum [Member] | Historical [Member]
Debt Services, Coverage Ratio																				1.4
Olkaria III DEG [Member]
Debt Instrument, Face Amount																																$ 105,000
Debt Instrument, Basis Spread on Variable Rate															4.00%
Debt Instrument, Interest Rate, Stated Percentage															6.90%
Payment for Debt Extinguishment or Debt Prepayment Cost							$ 100
Repayments of Long-term Debt							11,800
Olkaria III DEG [Member] | Tranche One [Member]
Prepayment Deposit On Debt						20,500
Prepayment Penalty Charges						$ 1,500
Ormat Funding Corp [Member]
Debt Instrument, Face Amount																	$ 190,000
Proceeds from Issuance of Debt																	$ 179,700
Debt Instrument, Interest Rate, Stated Percentage																	8.25%
Debt Instrument, Issuance Costs																	$ 10,300
Repayments of Secured Debt							14,300
Payment for Debt Extinguishment or Debt Prepayment Cost							$ 1,300
Ormat Funding Corp [Member] | Senior Notes [Member]
Debt Instrument, Repurchase Amount																		$ 6,800	$ 30,600
Gain (Loss) on Extinguishment of Debt																		$ (600)	$ (1,700)
OrCal Senior Secured Notes [Member]
Debt Instrument, Face Amount																$ 165,000
Proceeds from Issuance of Debt																$ 161,100
Debt Instrument, Interest Rate, Stated Percentage																6.21%
Restricted Cash and Cash Equivalents, Current																					1,900
Letters of Credit Outstanding, Amount																				$ 32,100	35,200
Debt Instrument, Issuance Costs																$ 3,900
Debt Instrument, Redemption Price, Percentage																				100.00%
OrCal Senior Secured Notes [Member] | Historical [Member]
Debt Services, Coverage Ratio																				1.54
OrCal Senior Secured Notes [Member] | Projected [Member]
Debt Services, Coverage Ratio																				2.63
OrCal Senior Secured Notes [Member] | Debt Service Reserve Backing [Member]
Letters of Credit Outstanding, Amount																				$ 4,600
OrCal Senior Secured Notes [Member] | Minimum [Member]
Debt Services, Coverage Ratio																1.25
OFC Two Senior Secured Notes [Member]
Debt Instrument, Face Amount																													$ 350,000
Government Guarantee Percent																				80.00%
Debtor-in-Possession Financing, Letters of Credit Outstanding																				$ 18,700
OFC Two Senior Secured Notes [Member] | Wholly Owned Subsidiaries With Project Debt [Member]
Debt Instrument, Face Amount																											$ 140,000
Debt Instrument, Interest Rate, Stated Percentage																											4.61%
OFC Two Senior Secured Notes [Member] | Senior Notes [Member]
Secured Debt																				$ 232,500	$ 247,200
OFC Two Senior Secured Notes [Member] | Historical [Member]
Debt Services, Coverage Ratio																				2.7				2.25
OFC Two Senior Secured Notes [Member] | Projected [Member]
Debt Services, Coverage Ratio																				2.04				2.13
OFC Two Senior Secured Notes [Member] | Phase One Series A Senior Notes [Member]
Debt Instrument, Face Amount													$ 151,700
Proceeds from Issuance of Debt													$ 141,100
Debt Instrument, Interest Rate, Stated Percentage													4.687%
Repayments of Long-term Debt									$ 4,300
Other Reserves																				$ 0							$ 28,000
OFC Two Senior Secured Notes [Member] | Minimum [Member] | Historical [Member]
Debt Services, Coverage Ratio																				1.2
OFC Two Senior Secured Notes [Member] | Minimum [Member] | Projected [Member]
Debt Services, Coverage Ratio																				1.5
Don A. Cambell Senior Secured Notes [Member]
Debt Instrument, Face Amount		$ 92,500
Proceeds from Issuance of Debt		$ 87,100
Debt Instrument, Interest Rate, Stated Percentage		4.03%
Secured Debt																				$ 88,300
Debt Instrument, Minimum Prepay Amount		$ 2,000
Don A. Cambell Senior Secured Notes [Member] | Historical [Member]
Debt Services, Coverage Ratio																				1.47
Don A. Cambell Senior Secured Notes [Member] | Projected [Member]
Debt Services, Coverage Ratio																				1.81
Don A. Cambell Senior Secured Notes [Member] | Minimum [Member]
Debt Services, Coverage Ratio		1.2
Senior Unsecured Bonds [Member]
Debt Instrument, Face Amount																														$ 107,500	$ 142,000
Debt Instrument, Interest Rate, Stated Percentage																														6.75%	7.00%
Proceeds from Issuance of Unsecured Debt			$ 250,000
Senior Unsecured Bonds [Member] | Series 3 Bonds [Member]
Debt Instrument, Face Amount			137,000
Senior Unsecured Bonds, Series 2 [Member]
Debt Instrument, Face Amount			$ 67,000
Debt Instrument, Interest Rate, Stated Percentage			3.70%
Senior Unsecured Bonds, Series 3 [Member]
Debt Instrument, Interest Rate, Stated Percentage			4.45%
Institutional Investors [Member] | Second Loan [Member]
Debt Instrument, Term														8 years
Debt Instrument, Face Amount														$ 20,000
Debt Instrument, Basis Spread on Variable Rate														5.00%
DEG 2 Facility Agreement [Member]
Debt Instrument, Interest Rate, Stated Percentage	6.28%
Debt Instrument, Minimum Prepay Amount	$ 5,000
Line of Credit Facility, Maximum Borrowing Capacity																										$ 50,000
Proceeds from Lines of Credit	$ 50,000
Long-term Line of Credit																				$ 50,000
Credit Agreements With Eight Commercial Banks [Member]
Letters of Credit Outstanding, Amount																				277,700
Line of Credit Facility, Maximum Borrowing Capacity																				468,000
Long-term Line of Credit																				51,500
Credit Agreements With Eight Commercial Banks [Member] | Extensions of Credit in The Form of Loans and/or Letters of Credit [Member]
Line of Credit Facility, Maximum Borrowing Capacity																				233,000
Credit Agreements With Eight Commercial Banks [Member] | Letter of Credit [Member]
Line of Credit Facility, Maximum Borrowing Capacity																				235,000
Credit Agreements With Eight Commercial Banks [Member] | Union Bank, N.A. [Member]
Line of Credit Facility, Maximum Borrowing Capacity																				60,000
Credit Agreements With Eight Commercial Banks [Member] | HSBC Bank USA, N.A. [Member]
Line of Credit Facility, Maximum Borrowing Capacity																				$ 35,000
Union Bank, N.A. [Member]
Debt Services, Coverage Ratio																				2.96
Letters of Credit Outstanding, Amount																				$ 37,400
Debt To Earnings Before Interest Tax Depreciation And Amortization Ratio																				2.17
Amount Available For Dividend Distribution Percent Of Cumulative Net Income																				0.99
Union Bank, N.A. [Member] | Minimum [Member]
Debt Services, Coverage Ratio												1.35
Union Bank, N.A. [Member] | Maximum [Member]
Line of Credit Facility, Maximum Borrowing Capacity												$ 60,000
Debt To Earnings Before Interest Tax Depreciation And Amortization Ratio												4.5
Amount Available For Dividend Distribution Percent Of Cumulative Net Income												2
HSBC Bank USA, N.A. [Member]
Debt Services, Coverage Ratio																				2.96
Letters of Credit Outstanding, Amount																				$ 16,200
Line of Credit Facility, Maximum Borrowing Capacity											$ 35,000
Debt To Earnings Before Interest Tax Depreciation And Amortization Ratio																				2.17
Amount Available For Dividend Distribution Percent Of Cumulative Net Income																				0.99
Line of Credit Facility, Borrowing Capacity Increase											10,000
Line of Credit Facility, Capacity Available for Specific Purpose Other than for Trade Purchases											$ 10,000
HSBC Bank USA, N.A. [Member] | Minimum [Member]
Debt Services, Coverage Ratio											1.35
HSBC Bank USA, N.A. [Member] | Maximum [Member]
Debt To Earnings Before Interest Tax Depreciation And Amortization Ratio											4.5
Amount Available For Dividend Distribution Percent Of Cumulative Net Income											2
Surety Agreement [Member] | Chubb [Member]
Surety Bonds Available																									$ 200,000
Surety Bonds Outstanding																				$ 106,200

Note 11 - Long-term Debt and 75

Note 11 - Long-term Debt and Credit Agreements - Long-term Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
	$ 622,145	$ 681,548
Less current portion	(54,720)	(53,729)
Non current portion	567,425	627,819
Recourse Debt	306,419	274,983
Less current portion	(54,587)	(12,242)
Non current portion	251,832	262,741
Other Loans, Limited and Non-recourse [Member]
Non-Recourse Debt	7,252	6,368
Loan Agreement With OPIC the Olkaria III Power Plant [Member]
Non-Recourse Debt	228,635	246,630
Loan Agreement with Banco Industrial S.A. and Westrust Bank (International) Limited [Member]
Non-Recourse Debt	33,251	36,750
Ormat Funding Corp [Member]
Non-Recourse Debt		17,026
OrCal Geothermal Inc [Member]
Non-Recourse Debt	32,142	35,181
Don A. Campbell 1 ("DAC1") [Member]
Non-Recourse Debt	88,339	92,361
OFC Two Senior Secured Notes [Member]
Non-Recourse Debt	232,526	247,232
Senior Unsecured Bonds [Member]
Recourse Debt	204,332	204,332
Institutional Investors [Member]
Recourse Debt		3,333
Olkaria III DEG [Member]
Recourse Debt	50,000	65,789
Loan From Commercial Bank [Member]
Recourse Debt	587	1,529
Revolving Credit Lines With Banks [Member]
Recourse Debt	$ 51,500

Note 11 - Long-term Debt and 76

Note 11 - Long-term Debt and Credit Agreements - Future Minimum Payments Under Long-term Obligations (Details) $ in Thousands	Dec. 31, 2017USD ($)
2,018	$ 57,807
2,019	55,539
2,020	123,093
2,021	46,579
2,022	184,148
Thereafter	409,898
Total	$ 877,064

Note 12 - Puna Power Plant Le77

Note 12 - Puna Power Plant Lease Transactions (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2005	Dec. 31, 2016
Lease Term		31 years
Deferred Revenue, Leases, Gross		$ 83,000,000
Capital Leases, Balance Sheet, Assets by Major Class, Net	$ 25,300,000		$ 28,000,000
Capital Leases, Lessee Balance Sheet, Assets by Major Class, Accumulated Depreciation	$ 35,600,000		32,900,000
Lease Payment Term	23 years
Deferred Costs, Leasing, Gross	$ 4,200,000
Restricted Cash and Cash Equivalents	7,900,000		2,900,000
Cash	$ 0		$ 0

Note 12 - Puna Power Plant Le78

Note 12 - Puna Power Plant Lease Transactions - Future Minimum Lease Payments Under the Project Lease (Details) $ in Thousands	Dec. 31, 2017USD ($)
2,018	$ 13,317
2,019	6,018
2,020	2,450
2,021	1,723
2,022	824
Thereafter	1,917
Total	$ 26,249

Note 13 - Tax Monetization Tr79

Note 13 - Tax Monetization Transactions (Details Textual) - USD ($) $ in Thousands

Dec. 31, 2022

Oct. 31, 2017

Jul. 10, 2017

Dec. 16, 2016

Feb. 03, 2011

Oct. 30, 2009

Jan. 31, 2013

Dec. 31, 2009

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2015

Dec. 31, 2008

Dec. 31, 2007

Jul. 31, 2017

Dec. 31, 2022

Dec. 15, 2016

Dec. 31, 2010

Proceeds from Noncontrolling Interests

$ 2,017

$ 1,972

$ 1,654

Noncontrolling Interest, Increase from Subsidiary Equity Issuance

44,102

156,635

OPC LLC [Member]

Payments to Acquire Additional Interest in Subsidiaries

1,932

Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests

(1,932)

Ormat Nevada ORTP LLC [Member]

Payments to Acquire Additional Interest in Subsidiaries

2,400

Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests

(4,051)

Noncontrolling Interest [Member]

Noncontrolling Interest, Increase from Subsidiary Equity Issuance

36,268

85,470

Noncontrolling Interest [Member] | OPC LLC [Member]

Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests

6,537

Noncontrolling Interest [Member] | Ormat Nevada ORTP LLC [Member]

Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests

(6,964)

Additional Paid-in Capital [Member]

Noncontrolling Interest, Increase from Subsidiary Equity Issuance

$ 7,834

$ 71,165

Additional Paid-in Capital [Member] | OPC LLC [Member]

Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests

(8,469)

Additional Paid-in Capital [Member] | Ormat Nevada ORTP LLC [Member]

Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests

$ 2,913

Opal Geo LLC [Member]

Percentage Of Distributable Cash to Controlling Interest

97.50%

Percentage of Income (Loss), Gain, Deduction and Credit Allocated to Controlling Interests

1.00%

Percentage of Income (Loss), Gain, Deduction and Credit Allocated to Controlling Interests, PTCs Not Available

95.00%

Opal Geo LLC [Member] | Scenario, Forecast [Member]

Percentage of Income (Loss), Gain, Deduction and Credit Allocated to Controlling Interests

95.00%

Opal Geo LLC [Member] | JPM Capital Corporation [Member]

Proceeds from Noncontrolling Interests

$ 62,100

Percentage Of Distributable Cash to Nontrolling Interests

2.50%

Percentage of Income (Loss), Gain, Deduction and Credit Allocated to Noncontrolling Interests

99.00%

Percentage of Income (Loss), Gain, Deduction and Credit Allocated to Noncontrolling Interests, PTCs Not Available

5.00%

Opal Geo LLC [Member] | JPM Capital Corporation [Member] | Noncontrolling Interest [Member]

Proceeds from Noncontrolling Interests

$ 3,700

Opal Geo LLC [Member] | JPM Capital Corporation [Member] | Liability for Sale of Tax Benefit [Member]

Proceeds from Noncontrolling Interests

$ 58,500

Opal Geo LLC [Member] | JPM Capital Corporation [Member] | Scenario, Forecast [Member]

Proceeds from Noncontrolling Interests

$ 21,000

Percentage Of Distributable Cash to Nontrolling Interests

100.00%

Percentage of Income (Loss), Gain, Deduction and Credit Allocated to Noncontrolling Interests

5.00%

Opal Geo LLC [Member] | JPM Capital Corporation [Member] | Capital Unit, Class B [Member]

Percentage of Equity Interest Sold

100.00%

Ormat Nevada ORTP LLC [Member]

Proceeds From Sale Of Equity Units

$ 63,000

$ 71,800

Percentage Of Ownership Interests Flip Date

95.00%

Payments for Repurchase of Redeemable Noncontrolling Interest

$ 18,500

Gain From Repurchase Of Interests At Discount

$ 13,300

Adjustments To Additional Paid In Capital Purchase Of Noncontrolling Interest

$ 1,100

Percentage Of Ownership Interests Purchased From Noncontrolling Owners

1.50%

1.50%

Proceeds Sale Minority Interest

$ 24,900

Noncontrolling Interest, Increase from Subsidiary Equity Issuance

$ 2,300

Proceeds from Sales of Business, Affiliate and Productive Assets

$ 35,700

$ 7,900

Additional Proceeds As Percentage Of Production Tax Credit

25.00%

Ormat Nevada ORTP LLC [Member] | ORTP Transaction [Member]

Payments to Acquire Interest in Joint Venture

$ 2,400

Ormat Nevada, OPC LLC [Member] | OPC Transaction [Member]

Payments to Acquire Additional Interest in Subsidiaries

$ 1,900

DAC 2 [Member]

Percentage Of Ownership Interests

63.25%

Other Geothermal Power Plants [Member]

Percentage Of Ownership Interests

100.00%

Opal Geo LLC [Member] | Capital Unit, Class A [Member]

Percentage Of Ownership Interests

100.00%

OPC LLC [Member] | JPM Capital Corporation [Member] | Capital Unit, Class B [Member]

Fair Value of Equity Interest Sold

$ 3,000

Note 14 - Asset Retirement Ob80

Note 14 - Asset Retirement Obligations - Reconciliation of the Beginning and Ending Aggregate Carrying Amount of Asset Retirement Obligation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Balance at beginning of year	$ 23,348	$ 20,856
Revision in estimated cash flows	1,888	303
Liabilities incurred		540
Accretion expense	1,874	1,649	$ 1,198
Balance at end of year	$ 27,110	$ 23,348	$ 20,856

Note 15 - Stock-based Compens81

Note 15 - Stock-based Compensation (Details Textual) - USD ($) $ / shares in Units, $ in Millions

Nov. 08, 2017

Aug. 04, 2017

Jun. 07, 2017

Nov. 08, 2016

Jun. 13, 2016

Nov. 03, 2015

Nov. 05, 2014

Apr. 02, 2014

Feb. 11, 2014

May 31, 2012

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2015

Dec. 31, 2004

Mar. 31, 2021

Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized

$ 7.7

Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition

1 year 73 days

Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Annual Forfeiture Rate

1.10%

10.30%

9.66%

Increase (Decrease) In Stock Based Compensation Expense Due To Forfeitures, Percent

(89.30%)

7.00%

20.00%

Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Dividends Growth Rate

20.00%

Sharebased Compensation Arrangement By Sharebased Payment Award Fair Value Assumptions Weighted Average Expected Dividend Rate

0.60%

Share Price

$ 63.96

$ 53.62

Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Number

431,387

557,350

Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value

$ 38.9

$ 18

Weighted Average [Member]

Share Price

$ 58.82

$ 43.99

2004 Stock Incentive Plan [Member]

Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant

0

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]

Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant

894,437

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] | Chief Financial Officer [Member]

Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross

32,500

Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price

$ 24.57

Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value

$ 5.78

2012 Stock Incentive Plan [Member] | Chief Executive Officer [Member]

Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross

400,000

Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price

$ 29.52

2012 Stock Incentive Plan [Member] | 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

7 years

Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross

30,000

45,000

52,500

Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price

$ 57.97

$ 38.24

$ 28.23

Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value

$ 7.01

Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value

$ 8.68

2012 Stock Incentive Plan [Member] | Share-based Compensation Award, Tranche One [Member] | Chief Executive Officer [Member]

Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period

4 years

Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period

6 years

Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross

300,000

Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value

$ 12.88

2012 Stock Incentive Plan [Member] | Share-based Compensation Award, Tranche Two [Member] | Chief Executive Officer [Member]

Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period

7 years 182 days

Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value

$ 8.33

2012 Stock Incentive Plan [Member] | Share-based Compensation Award, Tranche Two [Member] | Chief Executive Officer [Member] | Scenario, Forecast [Member]

Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number

100,000

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

2012 Stock Incentive Plan [Member] | Employee Stock Option [Member] | Chief Financial Officer [Member]

Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period

3 years

Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period

5 years

2012 Stock Incentive Plan [Member] | Employee Stock Option [Member] | Director [Member]

Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period

1 year

1 year

Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period

7 years

7 years

Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value

$ 18.42

2012 Stock Incentive Plan [Member] | Stock Appreciation Rights (SARs) [Member]

Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period

4 years

Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period

5 years

6 years

Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value

$ 13.67

Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period

23,200

1,080,000

Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Exercise Price

$ 58.79

$ 42.87

2012 Stock Incentive Plan [Member] | Stock Appreciation Rights (SARs) [Member] | 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

7 years

Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value

$ 17.60

$ 14.51

Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period

60,000

Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Exercise Price

$ 47.46

2012 Stock Incentive Plan [Member] | Stock Appreciation Rights (SARs) [Member] | Senior Management [Member]

Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value

$ 17.70

11.98

2012 Stock Incentive Plan [Member] | Stock Appreciation Rights (SARs) [Member] | Other Employees [Member]

Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value

$ 11.42

2012 Stock Incentive Plan [Member] | Stock Appreciation Rights (SARs) [Member] | Directors and Senior Management [Member]

Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period

108,771

Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Exercise Price

$ 63.35

2012 Stock Incentive Plan [Member] | Stock Appreciation Rights (SARs) [Member] | Share-based Compensation Award, Tranche One [Member]

Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage

50.00%

50.00%

Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period

2 years

2012 Stock Incentive Plan [Member] | Stock Appreciation Rights (SARs) [Member] | Share-based Compensation Award, Tranche Two [Member]

Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage

25.00%

25.00%

Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period

3 years

2012 Stock Incentive Plan [Member] | Stock Appreciation Rights (SARs) [Member] | Share-based Compensation Award, Tranche Three [Member]

Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage

25.00%

25.00%

Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period

4 years

2012 Stock Incentive Plan [Member] | Restricted Stock Units (RSUs) [Member] | Director [Member]

Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value

62.90

2012 Stock Incentive Plan [Member] | Restricted Stock Units (RSUs) [Member] | Senior Management [Member]

Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value

$ 62.30

2012 Stock Incentive Plan [Member] | Restricted Stock Units (RSUs) [Member] | Directors and Senior Management [Member]

Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period

22,742

2012 Stock Incentive Plan [Member] | SARs and RSUs [Member] | Directors and Senior Management [Member]

Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period

6 years

2012 Stock Incentive Plan [Member] | SARs and RSUs [Member] | Vesting After the First Year from the Grant Date [Member] | Director [Member]

Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage

100.00%

2012 Stock Incentive Plan [Member] | SARs and RSUs [Member] | Vesting Each Year [Member] | Senior Management [Member]

Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage

25.00%

Note 15 - Stock-based Compens82

Note 15 - Stock-based Compensation - Compensation Related to Stock-based Awards (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Total stock-based compensation expense	$ 8,760	$ 5,157	$ 3,955
Tax effect on stock-based compensation expense	604	617	440
Net effect of stock-based compensation expense	8,156	4,540	3,515
Cost of Sales [Member]
Total stock-based compensation expense	3,369	2,400	1,753
Selling and Marketing Expense [Member]
Total stock-based compensation expense	452	247	123
General and Administrative Expense [Member]
Total stock-based compensation expense	$ 4,939	$ 2,510	$ 2,079

Note 15 - Stock-based Compens83

Note 15 - Stock-based Compensation - Fair Value of Stock-based Award on the Date of Grant (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Risk-free interest rates	1.90%	1.30%	1.40%
Expected lives (in weighted average years) (Year)	3 years 36 days	4 years 182 days	4 years
Dividend yield	0.62%	1.10%	0.70%
Expected volatility	27.20%	30.70%	29.20%
Forfeiture rate (weighted average)	0.00%	8.40%	0.00%

Note 15 - Stock-based Compens84

Note 15 - Stock-based Compensation - Fair Value of Each Option Using Black-scholes Valuation Model Assumptions (Details)	Apr. 02, 2017	Nov. 03, 2015	Nov. 05, 2014	Feb. 11, 2014	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Apr. 02, 2017
Risk-free interest rates					1.90%	1.30%	1.40%
Expected life (in years) (Year)					3 years 36 days	4 years 182 days	4 years
Dividend yield					0.62%	1.10%	0.70%
Expected volatility					27.20%	30.70%	29.20%
Chief Executive Officer [Member] | Options to Purchase 300,000 Shares of Common Stock [Member]
Risk-free interest rates								2.36%
Expected life (in years) (Year)								7 years 91 days
Dividend yield								0.90%
Expected volatility								42.80%
Chief Executive Officer [Member] | Options to Purchase 100,000 Shares of Common Stock [Member]
Risk-free interest rates	1.64%
Expected life (in years) (Year)	4 years 273 days
Dividend yield	0.90%
Expected volatility	33.10%
2012 Incentive Plan [Member] | Chief Financial Officer [Member]
Risk-free interest rates		1.35%	1.30%	0.81%
Expected life (in years) (Year)		4 years	4 years	3 years 136 days
Dividend yield		0.70%	0.70%	0.80%
Expected volatility		29.20%	32.40%	33.50%
Forfeiture rate		0.00%	0.00%	0.00%

Note 15 - Stock-based Compens85

Note 15 - Stock-based Compensation - Fair Value of Stock-based Award Using Exercise Multiple-based Lattice SAR Pricing Model Assumptions (Details)	Nov. 08, 2017	Aug. 04, 2017	Nov. 08, 2016	Jun. 13, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Risk-free interest rate					1.90%	1.30%	1.40%
Expected life (in years) (Year)					3 years 36 days	4 years 182 days	4 years
Dividend yield					0.62%	1.10%	0.70%
Expected volatility					27.20%	30.70%	29.20%
Forfeiture rate					0.00%	8.40%	0.00%
Stock Appreciation Rights (SARs) [Member]
Risk-free interest rate		1.74%
Expected life (in years) (Year)		5 years
Dividend yield		0.66%
Expected volatility		26.30%
Forfeiture rate		10.30%
Sub-optimal Exercise Factor		2
Stock Appreciation Rights (SARs) [Member] | Senior Management and Other Employees [Member]
Risk-free interest rate				1.29%
Expected life (in years) (Year)				6 years
Dividend yield				1.14%
Expected volatility				30.70%
Stock Appreciation Rights (SARs) [Member] | Directors [Member]
Risk-free interest rate			1.65%
Expected life (in years) (Year)			7 years
Dividend yield			1.10%
Expected volatility			30.60%
Forfeiture rate			0.00%
Sub-optimal Exercise Factor			2.5
Stock Appreciation Rights (SARs) [Member] | Senior Management [Member]
Forfeiture rate				0.00%
Sub-optimal Exercise Factor				2.5
Stock Appreciation Rights (SARs) [Member] | Other Employees [Member]
Forfeiture rate				10.50%
Sub-optimal Exercise Factor				2
Employee Stock Option [Member] | Director [Member]
Risk-free interest rate		2.08%
Expected life (in years) (Year)		7 years
Dividend yield		0.69%
Expected volatility		29.40%
Forfeiture rate		0.00%
Sub-optimal Exercise Factor		2.5
SARs and RSUs [Member] | Directors and Senior Management [Member]
Risk-free interest rate	2.10%
Expected life (in years) (Year)	6 years
Dividend yield	0.60%
Expected volatility	26.90%
Forfeiture rate	0.00%
Sub-optimal Exercise Factor	2.5

Note 15 - Stock-based Compens86

Note 15 - Stock-based Compensation - Summary of the Status of the 2012 Incentive Plan (Details) - $ / shares shares in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Outstanding at beginning of year (in shares)		2,565
Outstanding at end of year (in shares)		1,548	2,565
2012 Incentive Plan [Member]
Outstanding at beginning of year (in shares)		2,565	2,438	4,477
Outstanding at beginning of year (in dollars per share)		$ 33.36	$ 25.38	$ 27.48
Stock Options (in shares)		30	1,155	45
Stock Options (in dollars per share)		$ 57.97	$ 43.01	$ 38.24
Exercised (in shares)		(1,181)	(967)	(1,589)
Exercised (in dollars per share)		$ 25.92	$ 25.33	$ 26.77
Forfeited (in shares)		(21)	(57)	(125)
Forfeited (in dollars per share)		$ 46.15	$ 24.12	$ 27.33
Expired (in shares)			(4)	(370)
Expired (in dollars per share)			$ 26.84	$ 45.78
Outstanding at end of year (in shares)		1,548	2,565	2,438
Outstanding at end of year (in dollars per share)		$ 41.35	$ 33.36	$ 25.38
Options and SARs exercisable at end of year (in shares)		431	557	858
Options and SARs exercisable at end of year (in dollars per share)		$ 32.61	$ 25.22	$ 26.75
Weighted-average fair value of options and SARs granted during the year (in dollars per share)		$ 22.82	$ 11.61	$ 8.68
2012 Incentive Plan [Member] | Stock Appreciation Rights (SARs) [Member]
Other than Options (in shares)	[1]	132
Other than Options (in dollars per share)	[1]	$ 62.55
2012 Incentive Plan [Member] | Restricted Stock Units (RSUs) [Member]
Other than Options (in shares)	[2]	23
Other than Options (in dollars per share)	[2]
[1]	Upon exercise, SARs entitle the recipient to receive shares of common stock with a value equal to the increase in value of the award between the grant date and the exercise date.
[2]	An RSU represents the right to receive one share of common stock once certain vesting conditions are met. The value of an RSU is identical to the value of the underlying stock.

Note 15 - Stock-based Compens87

Note 15 - Stock-based Compensation - Summary of Information About Stock-based Awards Outstanding (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Number of shares outstanding (in shares)	1,548	2,565
Weighted average remaining contractual life in years, options outstanding (Year)	4 years 73 days	4 years 36 days
Aggregate intrinsic value, options outstanding	$ 34,990	$ 51,959
Number of shares exercisable (in shares)	432	557
Weighted average remaining contractual life in years, options exercisable (Year)	3 years	2 years 255 days
Aggregate intrinsic value, options exercisable	$ 13,523	$ 15,827
Exercise Price 1 [Member]
Exercise price (in dollars per share)		$ 18.56
Number of shares outstanding (in shares)	23	15
Weighted average remaining contractual life in years, options outstanding (Year)	3 years 328 days	2 years 292 days
Aggregate intrinsic value, options outstanding	$ 1,455	$ 526
Number of shares exercisable (in shares)		15
Weighted average remaining contractual life in years, options exercisable (Year)		2 years 292 days
Aggregate intrinsic value, options exercisable		$ 526
Exercise Price 2 [Member]
Exercise price (in dollars per share)	$ 20.13	$ 19.69
Number of shares outstanding (in shares)	35	15
Weighted average remaining contractual life in years, options outstanding (Year)	1 year 109 days	2 years 219 days
Aggregate intrinsic value, options outstanding	$ 1,533	$ 509
Number of shares exercisable (in shares)	35	15
Weighted average remaining contractual life in years, options exercisable (Year)	1 year 109 days	2 years 219 days
Aggregate intrinsic value, options exercisable	$ 1,533	$ 509
Exercise Price 3 [Member]
Exercise price (in dollars per share)	$ 23.34	$ 20.13
Number of shares outstanding (in shares)	176	108
Weighted average remaining contractual life in years, options outstanding (Year)	1 year 146 days	2 years 109 days
Aggregate intrinsic value, options outstanding	$ 7,150	$ 3,608
Number of shares exercisable (in shares)	176	108
Weighted average remaining contractual life in years, options exercisable (Year)	1 year 146 days	2 years 109 days
Aggregate intrinsic value, options exercisable	$ 7,150	$ 3,608
Exercise Price 4 [Member]
Exercise price (in dollars per share)	$ 25.65	$ 20.54
Number of shares outstanding (in shares)	10	53
Weighted average remaining contractual life in years, options outstanding (Year)	109 days	2 years 109 days
Aggregate intrinsic value, options outstanding	$ 398	$ 1,761
Number of shares exercisable (in shares)	10	28
Weighted average remaining contractual life in years, options exercisable (Year)	109 days	2 years 109 days
Aggregate intrinsic value, options exercisable	$ 398	$ 934
Exercise Price 5 [Member]
Exercise price (in dollars per share)	$ 35.15	$ 23.34
Number of shares outstanding (in shares)	15	635
Weighted average remaining contractual life in years, options outstanding (Year)	5 years 36 days	2 years 146 days
Aggregate intrinsic value, options outstanding	$ 432	$ 19,226
Number of shares exercisable (in shares)	15	140
Weighted average remaining contractual life in years, options exercisable (Year)	5 years 36 days	2 years 146 days
Aggregate intrinsic value, options exercisable	$ 432	$ 4,247
Exercise Price 6 [Member]
Exercise price (in dollars per share)	$ 38.24	$ 24.57
Number of shares outstanding (in shares)	15	9
Weighted average remaining contractual life in years, options outstanding (Year)	4 years 292 days	2 years 36 days
Aggregate intrinsic value, options outstanding	$ 386	$ 269
Number of shares exercisable (in shares)	15	1
Weighted average remaining contractual life in years, options exercisable (Year)	4 years 292 days	2 years 36 days
Aggregate intrinsic value, options exercisable	$ 386	$ 33
Exercise Price 7 [Member]
Exercise price (in dollars per share)	$ 42.87	$ 25.65
Number of shares outstanding (in shares)	1,074	68
Weighted average remaining contractual life in years, options outstanding (Year)	4 years 182 days	1 year 109 days
Aggregate intrinsic value, options outstanding	$ 22,651	$ 1,905
Number of shares exercisable (in shares)	143	68
Weighted average remaining contractual life in years, options exercisable (Year)	4 years 182 days	1 year 109 days
Aggregate intrinsic value, options exercisable	$ 3,005	$ 1,905
Exercise Price 8 [Member]
Exercise price (in dollars per share)	$ 47.46	$ 26.70
Number of shares outstanding (in shares)	38	15
Weighted average remaining contractual life in years, options outstanding (Year)	5 years 328 days	3 years 292 days
Aggregate intrinsic value, options outstanding	$ 619	$ 404
Number of shares exercisable (in shares)	38	15
Weighted average remaining contractual life in years, options exercisable (Year)	5 years 328 days	3 years 292 days
Aggregate intrinsic value, options exercisable	$ 619	$ 404
Exercise Price 9 [Member]
Exercise price (in dollars per share)	$ 57.97	$ 28.23
Number of shares outstanding (in shares)	30	30
Weighted average remaining contractual life in years, options outstanding (Year)	6 years 219 days	4 years 292 days
Aggregate intrinsic value, options outstanding	$ 180	$ 762
Number of shares exercisable (in shares)		30
Weighted average remaining contractual life in years, options exercisable (Year)		4 years 292 days
Aggregate intrinsic value, options exercisable		$ 762
Exercise Price 10 [Member]
Exercise price (in dollars per share)	$ 58.79	$ 29.52
Number of shares outstanding (in shares)	23	400
Weighted average remaining contractual life in years, options outstanding (Year)	4 years 182 days	3 years 219 days
Aggregate intrinsic value, options outstanding	$ 120	$ 9,640
Number of shares exercisable (in shares)		75
Weighted average remaining contractual life in years, options exercisable (Year)		3 years 219 days
Aggregate intrinsic value, options exercisable		$ 1,807
Exercise Price 11 [Member]
Exercise price (in dollars per share)	$ 63.35	$ 29.95
Number of shares outstanding (in shares)	109	17
Weighted average remaining contractual life in years, options outstanding (Year)	5 years 328 days	109 days
Aggregate intrinsic value, options outstanding	$ 66	$ 400
Number of shares exercisable (in shares)		17
Weighted average remaining contractual life in years, options exercisable (Year)		109 days
Aggregate intrinsic value, options exercisable		$ 400
Exercise Price 12 [Member]
Exercise price (in dollars per share)		$ 35.15
Number of shares outstanding (in shares)		15
Weighted average remaining contractual life in years, options outstanding (Year)		6 years 36 days
Aggregate intrinsic value, options outstanding		$ 277
Number of shares exercisable (in shares)
Weighted average remaining contractual life in years, options exercisable (Year)
Aggregate intrinsic value, options exercisable
Exercise Price 13 [Member]
Exercise price (in dollars per share)		$ 38.24
Number of shares outstanding (in shares)		45
Weighted average remaining contractual life in years, options outstanding (Year)		5 years 292 days
Aggregate intrinsic value, options outstanding		$ 692
Number of shares exercisable (in shares)		45
Weighted average remaining contractual life in years, options exercisable (Year)		5 years 292 days
Aggregate intrinsic value, options exercisable		$ 692
Exercise Price 14 [Member]
Exercise price (in dollars per share)		$ 42.87
Number of shares outstanding (in shares)		1,080
Weighted average remaining contractual life in years, options outstanding (Year)		5 years 182 days
Aggregate intrinsic value, options outstanding		$ 11,610
Number of shares exercisable (in shares)
Weighted average remaining contractual life in years, options exercisable (Year)
Aggregate intrinsic value, options exercisable
Exercise Price 15 [Member]
Exercise price (in dollars per share)		$ 47.46
Number of shares outstanding (in shares)		60
Weighted average remaining contractual life in years, options outstanding (Year)		6 years 328 days
Aggregate intrinsic value, options outstanding		$ 370
Number of shares exercisable (in shares)
Weighted average remaining contractual life in years, options exercisable (Year)
Aggregate intrinsic value, options exercisable

Note 17 - Interest Expense, N88

Note 17 - Interest Expense, Net - Components of Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Interest related to sale of tax benefits									$ 6,985	$ 9,349	$ 9,620
Interest expense									54,381	61,327	67,032
Less — amount capitalized									(7,224)	(3,287)	(4,075)
Interest Expense	$ 12,987	$ 11,692	$ 14,540	$ 14,923	$ 15,828	$ 17,137	$ 18,401	$ 16,023	$ 54,142	$ 67,389	$ 72,577

Note 18 - Income Taxes (Details

Note 18 - Income Taxes (Details Textual) - USD ($)		Jun. 20, 2017	Sep. 11, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2018
Deferred Tax Assets, Investments				$ 813,000	$ 1,341,000						$ 813,000	$ 1,341,000
Deferred Tax Assets, Tax Credit Carryforwards, General Business				85,193,000	82,451,000						85,193,000	82,451,000
Deferred Tax Assets, Tax Credit Carryforwards, Foreign				86,206,000							86,206,000
Deferred Tax Assets, Valuation Allowance				50,858,000	109,611,000						50,858,000	109,611,000	$ 70,536,000	$ 111,280,000
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount											(58,700,000)
Uncertain Tax Benefit, Reudction to Deferred Tax Asset	[1]			95,000							95,000
Foreign Earnings Repatriated				300,000,000
Income Tax Expense (Benefit), Impact of Reinvestment of Undistributed Foreign Earnings, Withholding Tax											58,300,000
Undistributed Earnings of Foreign Subsidiaries				401,000,000							401,000,000
Unrecognized Tax Benefits that Would Impact Effective Tax Rate				9,000,000	5,700,000						9,000,000	5,700,000
Unrecognized Tax Benefits, Reduction Resulting from Lapse of Applicable Statute of Limitations											$ 0	$ 6,400,000	$ 1,300,000
Depreciation Bonus Permitted Write Off Equipment Cost Percentage											50.00%
Depreciation Bonus Period to Write Off The Reminder of Equipment Cost											60 days
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent											35.00%	35.00%	35.00%
Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability											$ 22,600,000
Effective Income Tax Rate Reconciliation, Repatriation of Foreign Earnings, Amount											$ 71,900,000
Placed in Service After December 31, 2022 and Before January 1, 2024 [Member]
Depreciation Bonus Permitted Write Off Equipment Cost Percentage											80.00%
Placed in Service After December 31, 2023 and Before January 1, 2025 [Member]
Depreciation Bonus Permitted Write Off Equipment Cost Percentage											60.00%
Placed in Service After December 31, 2024 and Before January 1, 2026 [Member]
Depreciation Bonus Permitted Write Off Equipment Cost Percentage											40.00%
Placed in Service After December 31, 2025 and Before January 1, 2027 [Member]
Depreciation Bonus Permitted Write Off Equipment Cost Percentage											20.00%
Scenario, Forecast [Member]
Foreign Earnings Repatriated																$ 396,000,000
Distribution of Earnings in Foreign Subsidiaries										$ 96,000,000
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent										21.00%
Accounting Standards Update 2013-11 [Member]
Uncertain Tax Benefit, Reudction to Deferred Tax Asset				100,000							$ 100,000
Investment Tax Credit Carryforward [Member]
Deferred Tax Assets, Investments				800,000							$ 800,000
General Business Tax Credit Carryforward [Member]
Tax Credit Carryforward Expiration Period											20 years
Minimum [Member] | General Business Tax Credit Carryforward [Member]
Tax Credit Carryforward Expiration Year											2,026
Maximum [Member] | General Business Tax Credit Carryforward [Member]
Tax Credit Carryforward Expiration Year											2,037
Deferred Tax Assets, Tax Credit Carryforwards, General Business				85,200,000							$ 85,200,000
Domestic Tax Authority [Member]
Operating Loss Carryforwards				145,000,000							$ 145,000,000
Domestic Tax Authority [Member] | Placed in Service Before January 2018 [Member]
Investment Tax Credit, Percentage of Eligible Cost											30.00%
Domestic Tax Authority [Member] | Placed in Service After January 2018 [Member]
Investment Tax Credit, Percentage of Eligible Cost											10.00%
Domestic Tax Authority [Member] | Minimum [Member]
Tax Credit Carryforward Expiration Year											2,029
Domestic Tax Authority [Member] | Maximum [Member]
Tax Credit Carryforward Expiration Year											2,037
State and Local Jurisdiction [Member]
Operating Loss Carryforwards				222,200,000							$ 222,200,000
State and Local Jurisdiction [Member] | Minimum [Member]
Tax Credit Carryforward Expiration Year											2,018
State and Local Jurisdiction [Member] | Maximum [Member]
Tax Credit Carryforward Expiration Year											2,037
Foreign Tax Authority [Member]
Tax Credit Carryforward Expiration Period											10 years
Deferred Tax Assets, Tax Credit Carryforwards, Foreign				$ 86,200,000							$ 86,200,000
Foreign Tax Authority [Member] | Tax Authority of Guatemala in Guatemala [Member]
National Corporate Tax Rate											25.00%
Tax Exemption Period											10 years
Effective Income Tax Rate											7.00%
Effective Income Tax Rate Reconciliation, Tax Exempt Income, Amount											$ 2,600,000	$ 3,300,000	$ 3,600,000
Income Tax Benefit From Examination Per Share											0.05	0.07	0.08
Foreign Tax Authority [Member] | Israel Tax Authority [Member]
National Corporate Tax Rate											24.00%	25.00%	26.50%
Foreign Tax Authority [Member] | Israel Tax Authority [Member] | Ormat Systems Ltd [Member]
Effective Income Tax Rate, Year Four and Thereafter														16.00%
Tax Rate on Exempt Income, in Event of Distribution											25.00%
Deferred Tax Liability, Rate, Respect of Tax Exempt Income											25.00%
Foreign Tax Authority [Member] | Kenya Revenue Authority [Member]
National Corporate Tax Rate											37.50%
Investment Deduction Percentage		150.00%	150.00%
Income Tax Examination, Penalties Paid		$ 2,600,000
Income Tax Examination, Interest Accrued and Waiver Requested		$ 1,200,000
Foreign Tax Authority [Member] | Kenya Revenue Authority [Member] | Reduction of Income Tax Expense and Deferred Liabilities Due to Overstatement of Tax Position [Member]
Current Period Reclassification Adjustment					$ 4,700,000
Foreign Tax Authority [Member] | Ministry of the Economy, Finance and Industry, France [Member]
National Corporate Tax Rate											34.43%
Foreign Tax Authority [Member] | Sistema de Administración de Rentas [Member]
Income Taxes Exempt Period											10 years
Foreign Tax Authority [Member] | Inland Revenue Department, New Zealand [Member]
National Corporate Tax Rate													28.00%	28.00%	28.00%
Foreign Tax Authority [Member] | Scenario, Forecast [Member] | Israel Tax Authority [Member]
National Corporate Tax Rate										23.00%
Foreign Tax Authority [Member] | Scenario, Forecast [Member] | Ministry of the Economy, Finance and Industry, France [Member]
National Corporate Tax Rate						25.00%	26.50%	28.00%
Corporate Income Tax Rate, Taxable Income of Euro 0.5 Million									28.00%	28.00%
Corporate Income Tax Rate, Taxable Income Exceeding Euro 0.5 Million									31.00%	33.30%
Foreign Tax Authority [Member] | Minimum [Member]
Tax Credit Carryforward Expiration Year											2,027
Foreign Tax Authority [Member] | Minimum [Member] | Kenya Revenue Authority [Member]
Tax Losses Carryforward Period			5 years
Foreign Tax Authority [Member] | Maximum [Member] | Kenya Revenue Authority [Member]
Tax Losses Carryforward Period			10 years
[1]	The non-current deferred tax asset has been reduced by the uncertain tax benefit of $0.1 million in accordance with ASU 2013-11

Note 18 - Income Taxes - Income

Note 18 - Income Taxes - Income From Continuing Operations Before Income Taxes and Equity in Income (Losses) of Investees (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
U.S.									$ 13,680	$ (7,109)	$ (236)
Non-U.S. (foreign)									157,050	148,197	113,835
Income from continuing operations before income taxes and equity in losses of investees	$ 40,025	$ 33,446	$ 45,039	$ 52,220	$ 36,683	$ 29,047	$ 33,967	$ 41,391	$ 170,730	$ 141,088	$ 113,599

Note 18 - Income Taxes - Compon

Note 18 - Income Taxes - Components of Income Tax Provision (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current:
Federal									$ 43,850		$ 51
State									108	(276)	252
Foreign									10,816	14,040	19,175
Total current income tax expense									54,774	13,764	19,478
Deferred:
Federal									(78,220)
State									(4,544)
Foreign									26,579	18,073	(34,736)
Total deferred tax benefit									(56,185)	18,073	(34,736)
Total provision (benefit) for income taxes	$ (29,669)	$ 11,003	$ 6,369	$ 10,886	$ 2,450	$ 11,988	$ 7,890	$ 9,509	$ (1,411)	$ 31,837	$ (15,258)

Note 18 - Income Taxes - Signif

Note 18 - Income Taxes - Significant Components of Deferred Income Tax Expense (Benefit) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other deferred tax expense (exclusive of the effect of other components listed below)	$ 1,833	$ (1,105)	$ 541
Usage (benefit) of operating loss carryforwards - U.S.	73,049	(14,072)	(30,596)
Change in valuation allowance	(58,757)	16,411	(14,324)
Change in foreign valuation allowance			(49,701)
Change in foreign income tax	26,579	18,073	14,965
Change in lease transaction			(452)
Change in tax monetization transaction	(23,234)	48,000	16,386
Change in depreciation	129,408	(55,462)	28,370
Change in foreign tax credits	(86,206)
Change in withholding tax	14,400
Change in state and investment tax credits	(144)
Change in intangible drilling costs	(118,610)	10,227	10,335
Change in production tax credits and alternative minimum tax credit	(2,070)	(11,659)	610
Basis difference in partnership interests	(12,433)	7,660	(10,870)
	$ (56,185)	$ 18,073	$ (34,736)

Note 18 - Income Taxes - Differ

Note 18 - Income Taxes - Difference Between US Federal Statutory Tax Rate and Company's Effective Tax Rate (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
U.S. federal statutory tax rate	35.00%	35.00%	35.00%
Impact of federal tax reform	(13.20%)
Transition tax inclusion	42.10%
Foreign tax credits	(50.40%)
Tax basis adjustment	(4.70%)
Withholding tax	34.10%
State income tax, net of federal benefit	(2.20%)	(0.20%)	0.60%
Effect of foreign income tax, net	(10.30%)	(14.10%)	(5.10%)
Production tax credits	(1.20%)	(8.30%)	(0.10%)
Subpart F income	1.70%	0.30%	1.30%
Other, net	(1.40%)	(1.30%)
Effective tax rate	(0.80%)	22.50%	(13.50%)
Domestic Tax Authority [Member]
Valuation allowance	(30.30%)	11.10%	(1.40%)
Foreign Tax Authority [Member]
Valuation allowance			(43.80%)

Note 18 - Income Taxes - Net De

Note 18 - Income Taxes - Net Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Deferred tax assets (liabilities):
Net foreign deferred taxes, primarily depreciation	$ (61,961)	$ (35,382)
Depreciation, deferred tax liability	(65,312)
Depreciation, deferred tax asset		148,419
Intangible drilling costs	12,934	(112,762)
Net capital loss carryforward - U.S.	44,619	117,924
Tax monetization transaction	(6,465)	(105,789)
State and Investment tax credits	813	1,341
Production tax credits	85,193	82,451
Foreign tax credits	86,206
Withholding tax	(14,400)
Stock options amortization	1,166	3,241
Basis difference in partnership interest	(14,731)	(24,462)
Accrued liabilities and other	2,931	(752)
	70,993	74,229
Less - valuation allowance	(50,858)	(109,611)	$ (70,536)	$ (111,280)
Total	$ 20,135
Total		$ (35,382)	$ (32,654)

Note 18 - Income Taxes - Reconc

Note 18 - Income Taxes - Reconciliation of Beginning and Ending Valuation Allowance (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Balance at beginning of the year	$ 109,611	$ 70,536	$ 111,280
Additions to valuation allowance	46,560	39,075
Release of valuation allowance	(105,313)		(40,744)
Balance at end of the year	$ 50,858	$ 109,611	$ 70,536

Note 18 - Income Taxes - Balanc

Note 18 - Income Taxes - Balance Sheet Presentation of Deferred Taxes (Details) - USD ($) $ in Thousands		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Non-current deferred tax assets		$ 107,605
Non-current deferred tax liabilities			(35,382)	(32,654)
Total Non-current deferred tax assets, net		20,135
Total			(35,382)	(32,654)
Uncertain tax benefit offset (1)	[1]	(95)
Total		$ 20,135
[1]	The non-current deferred tax asset has been reduced by the uncertain tax benefit of $0.1 million in accordance with ASU 2013-11

Note 18 - Income Taxes - Reco97

Note 18 - Income Taxes - Reconciliation of Beginning and Ending Amounts of Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Balance at beginning of year	$ 5,738	$ 10,385	$ 7,511
Additions based on tax positions taken in prior years	798	675	(198)
Additions based on tax positions taken in the current year	2,367	1,059	4,386
Reduction based on tax positions taken in prior years	(13)	(6,381)	(1,314)
Balance at end of year	$ 8,890	$ 5,738	$ 10,385

Note 18 - Income Taxes - Foreig

Note 18 - Income Taxes - Foreign Subsidiaries Income Tax Years Open to Examination (Details)	12 Months Ended
	Dec. 31, 2017
ISRAEL | Earliest Tax Year [Member]
Countries	2,015
ISRAEL | Latest Tax Year [Member]
Countries	2,017
KENYA | Earliest Tax Year [Member]
Countries	2,012
KENYA | Latest Tax Year [Member]
Countries	2,017
GUATEMALA | Earliest Tax Year [Member]
Countries	2,013
GUATEMALA | Latest Tax Year [Member]
Countries	2,017
HONDURAS | Earliest Tax Year [Member]
Countries	2,012
HONDURAS | Latest Tax Year [Member]
Countries	2,017
GUADELOUPE | Earliest Tax Year [Member]
Countries	2,015
GUADELOUPE | Latest Tax Year [Member]
Countries	2,017
PHILIPPINES | Earliest Tax Year [Member]
Countries	2,010
PHILIPPINES | Latest Tax Year [Member]
Countries	2,017
NEW ZEALAND | Earliest Tax Year [Member]
Countries	2,012
NEW ZEALAND | Latest Tax Year [Member]
Countries	2,017

Note 19 - Business Segments (De

Note 19 - Business Segments (Details Textual) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Number of Reportable Segments	2
Goodwill	$ 21,037	$ 6,650
Electricity [Member]
Goodwill	$ 21,000	$ 6,700

Note 19 - Business Segments - S

Note 19 - Business Segments - Summarized Financial Information Concerning Reportable Segments (Details) - USD ($) $ in Thousands	3 Months Ended										12 Months Ended
	Dec. 31, 2017		Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016		Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
Net revenues	$ 166,365		$ 157,185	$ 179,364	$ 189,898	$ 166,519		$ 184,617	$ 159,861	$ 151,594	$ 692,812		$ 662,591		$ 594,644
Depreciation and amortization expense											115,146		105,977		107,206
Operating income	48,400		$ 43,970	$ 53,152	$ 59,496	51,229		$ 48,223	$ 51,887	$ 50,543	205,018		201,882		164,061
Segment assets at period end	2,586,662	[1]				2,461,569	[1]				2,586,662	[1]	2,461,569	[1]	2,273,982
Expenditures for long-lived assets											259,234		151,930		152,450
Unconsolidated Investments [Member]
Segment assets at period end	34,084										34,084
Intersegment Eliminations [Member]
Net revenues											109,040		56,075		48,559
Electricity [Member]
Net revenues											468,329		436,292		375,920
Depreciation and amortization expense											111,676		102,698		103,892
Operating income											154,475		126,828		99,345
Segment assets at period end	2,470,949	[1]				2,204,444	[1]				2,470,949	[1]	2,204,444	[1]	2,044,346
Expenditures for long-lived assets											252,581		147,211		149,666
Electricity [Member] | Unconsolidated Investments [Member]
Segment assets at period end
Electricity [Member] | Intersegment Eliminations [Member]
Net revenues
Product Segment [Member]
Net revenues											224,483		226,299		218,724
Depreciation and amortization expense											3,470		3,279		3,314
Operating income											50,543		75,054		64,716
Segment assets at period end	115,713	[1]				$ 257,125	[1]				115,713	[1]	257,125	[1]	229,636
Expenditures for long-lived assets											6,653		4,719		2,784
Product Segment [Member] | Unconsolidated Investments [Member]
Segment assets at period end	$ 34,084										34,084
Product Segment [Member] | Intersegment Eliminations [Member]
Net revenues											$ 109,040		$ 56,075		$ 48,559
[1]	Electricity segment assets include goodwill in the amount of $21.0 million and $6.7 million as of December 31, 2017 and 2016, respectively.

Note 19 - Business Segments - R

Note 19 - Business Segments - Reconciling Information Between Reportable Segments and Consolidated Totals (Details) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Total segment revenues	[1]									$ 692,812	$ 662,591	$ 594,644
Operating income		$ 48,400	$ 43,970	$ 53,152	$ 59,496	$ 51,229	$ 48,223	$ 51,887	$ 50,543	205,018	201,882	164,061
Interest income		127	255	362	244	140	266	245	320	988	971	297
Interest expense, net		(12,987)	(11,692)	(14,540)	(14,923)	(15,828)	(17,137)	(18,401)	(16,023)	(54,142)	(67,389)	(72,577)
Derivatives and foreign currency transaction gains (losses)		614	(1,001)	1,703	1,338	(2,942)	(222)	(4,332)	1,962	2,654	(5,534)	(1,622)
Income attributable to sale of tax benefits		3,859	3,506	4,356	6,157	4,123	3,463	4,519	4,398	17,878	16,503	25,431
Other non-operating income (expense), net		12	(1,592)	6	(92)	(39)	(5,546)	49	191	(1,666)	(5,345)	(1,991)
Income (loss) from continuing operations, before income taxes and equity in income of investees		$ 40,025	$ 33,446	$ 45,039	$ 52,220	$ 36,683	$ 29,047	$ 33,967	$ 41,391	170,730	141,088	113,599
Intersegment Eliminations [Member]
Total segment revenues										109,040	56,075	48,559
Consolidation, Eliminations [Member]
Total segment revenues										$ (109,040)	$ (56,075)	$ (48,559)
[1]	Revenues as reported in the geographic area in which they originate.

Note 19 - Business Segments 102

Note 19 - Business Segments - Revenues as Reported in the Geographic Area (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues	[1]	$ 692,812	$ 662,591	$ 594,644
UNITED STATES
Revenues	[1]	301,132	307,025	286,509
INDONESIA
Revenues	[1]	28,968	100,856	93,191
KENYA
Revenues	[1]	110,243	109,270	86,545
TURKEY
Revenues	[1]	125,166	46,270	57,356
CHILE
Revenues	[1]	8,895	58,032	34,478
GUATEMALA
Revenues	[1]	27,991	30,086	27,897
NEW ZEALAND
Revenues	[1]	33,395
Other Foreign Countries [Member]
Revenues	[1]	$ 57,022	$ 11,052	$ 8,668
[1]	Revenues as reported in the geographic area in which they originate.

Note 19 - Business Segments - L

Note 19 - Business Segments - Long Lived Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Long Lived Assets, Geographic Area	$ 2,133,289	$ 1,941,239	$ 1,857,129
UNITED STATES
Long Lived Assets, Geographic Area	1,510,986	1,414,523	1,374,465
KENYA
Long Lived Assets, Geographic Area	340,970	327,157	375,257
Other Foreign Countries [Member]
Long Lived Assets, Geographic Area	$ 281,333	$ 199,559	$ 107,407

Note 19 - Business Segments 104

Note 19 - Business Segments - Revenue From Major Customers (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues	[1]	$ 692,812	$ 662,591	$ 594,644
Southern California Edison Company [Member]
Revenues	[2]	$ 29,714	$ 33,552	$ 56,026
Percentage of revenues	[2]	4.30%	5.10%	9.40%
Hawaii Electric Light Company [Member]
Revenues	[2]	$ 70,100	$ 67,566	$ 30,947
Percentage of revenues	[2]	10.10%	10.20%	5.20%
Sierra Pacific Power Company And Nevada Power Company [Member]
Revenues	[2],[3]	$ 125,424	$ 127,226	$ 115,876
Percentage of revenues	[2],[3]	18.10%	19.20%	19.50%
Hyundai [Member]
Revenues	[4]	$ 28,968	$ 100,856	$ 93,131
Percentage of revenues	[4]	4.20%	15.20%	15.70%
Kenya Power and Lighting Co LTD [Member]
Revenues	[2]	$ 110,243	$ 109,270	$ 86,545
Percentage of revenues	[2]	15.90%	16.50%	14.60%
[1]	Revenues as reported in the geographic area in which they originate.
[2]	Revenues reported in Electricity segment.
[3]	Subsidiaries of NV Energy, Inc.
[4]	Revenues related to the Sarulla project that are reported in Products segment.

Note 20 - Transactions With 105

Note 20 - Transactions With Related Entities (Details Textual) - USD ($)	Feb. 12, 2015	Apr. 01, 2009	Jul. 31, 2004	Dec. 31, 2017	Dec. 31, 2016	Feb. 11, 2015
Common Stock, Shares, Outstanding				50,609,051	49,667,340
Corporate Costs And Other				$ 10,000
Other Research and Development Expense, Percentage				10.00%
Ormat Systems Ltd [Member]
Operating Lease, Monthly Rent		$ 77,000	$ 52,000
Ormat Industries Ltd. [Member]
Percentage of Public Float Before Transition to Noncontrolled Public Company						40.00%
Percentage of Public Float After Transition to Noncontrolled Public Company	76.00%
Share Exchange Shares Granted Per Share	0.2592
Conversion of Stock, Shares Issued	30,200,000
Stock Issued During Period, Shares, New Issues	3,000,000
Common Stock, Shares, Outstanding	48,500,000					45,500,000
Sale of Stock, Consideration Received on Transaction	$ 15,400,000
Ormat Industries Ltd. [Member] | Shares Issued to Self, Deducted [Member]
Conversion of Stock, Shares Issued	27,200,000
Ormat Industries Ltd. [Member] | Sale of Stock, Other Assets Received [Member]
Sale of Stock, Consideration Received Per Transaction	$ 600,000
Ormat Industries Ltd. [Member] | Sale of Stock, Land and Buildings Received [Member]
Sale of Stock, Consideration Received Per Transaction	12,100,000
Ormat Industries Ltd. [Member] | Sale of Stock, Liabilities Assumed [Member]
Sale of Stock, Consideration Received Per Transaction	$ 500,000

Note 20 - Transactions With 106

Note 20 - Transactions With Related Entities - Summary of Transactions Between Company and Related Entities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property rental fee expense paid to the Parent			$ 303
Corporate financial, administrative, executive services, and research and development services provided to the Parent			148
Services rendered by an indirect shareholder of the Parent			$ 15

Note 21 - Employee Benefit P107

Note 21 - Employee Benefit Plan (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent		60.00%
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	4.00%	3.00%	2.00%
Defined Contribution Plan, Employer Discretionary Contribution Amount	$ 1,400	$ 1,000	$ 600
Deposits And Other Assets Noncurrent	21,599	18,553
Severance Costs	3,200	2,300	2,500
Gain (Loss) Of Severance Fund	1,800	300	$ 100
Israeli Severance Funds [Member]
Deposits And Other Assets Noncurrent	$ 13,900	$ 12,800

Note 21 - Employee Benefit P108

Note 21 - Employee Benefit Plan - Expected Future Benefit Payments (Details) $ in Thousands	Dec. 31, 2017USD ($)
2,018	$ 4,258
2,019	1,803
2,020	1,242
2,021	1,418
2,022	2,112
2023-2027	4,338
	$ 15,171

Note 22 - Commitments and Co109

Note 22 - Commitments and Contingencies (Details Textual) - USD ($) $ in Thousands	Mar. 29, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Royalty Expense		$ 0	$ 0	$ 0
Letters of Credit Outstanding, Amount		277,700
Letter Of Credit Fair Value Disclosure		0
Recorded Unconditional Purchase Obligation		113,400
Royalty Cap Amount		1,900	1,800
Royalty Cap Amount LIBOR Rate		900	800
Operating Leases, Rent Expense		500	400	$ 400
Capital Leased Assets, Gross		$ 7,600
Capital Lease, Period of Payments				5 years
Former Local Sales Representative vs. Ormat [Member] | Pending Litigation [Member]
Loss Contingency, Damages Sought, Value	$ 4,800
Loss Contingency, Additional Damages Sought for Ormat Geothermal Products Sales in Chile, Percent	3.75%
Loss Contingency, Damages Sought, Ormat Geothermal Products Sales in Chile, Period	10 years
Minimum [Member]
Percentage For Royalty To Be Paid		3.50%
Maximum [Member]
Percentage For Royalty To Be Paid		5.00%
Construction In Process [Member]
Recorded Unconditional Purchase Obligation		$ 54,200
Geothermal Resource Agreement [Member]
Royalty Expense		$ 19,400	$ 17,100	$ 15,400

Note 23 - Quarterly Financia110

Note 23 - Quarterly Financial Information (Unaudited) - Quarterly Financial Information (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues:
Electricity	$ 128,503	$ 112,273	$ 111,777	$ 115,776	$ 114,628	$ 109,795	$ 104,001	$ 107,868	$ 468,329	$ 436,292	$ 375,920
Product	37,862	44,912	67,587	74,122	51,891	74,822	55,860	43,726	224,483	226,299	218,724
Total revenues	166,365	157,185	179,364	189,898	166,519	184,617	159,861	151,594	692,812	662,591	594,644
Cost of revenues:
Electricity	75,017	65,774	65,439	66,036	69,163	66,481	62,243	63,686	272,266	261,573	242,612
Product	26,992	32,218	43,432	49,452	30,719	43,647	31,822	24,035	152,094	130,223	133,753
Total cost of revenues	102,009	97,992	108,871	115,488	99,882	110,128	94,065	87,721	424,360	391,796	376,365
Gross margin	64,356	59,193	70,493	74,410	66,637	74,489	65,796	63,873	268,452	270,795	218,279
Operating expenses:
Research and development expenses	789	716	1,050	602	732	1,086	595	349	3,157	2,762	1,780
Selling and marketing expenses	3,517	3,630	4,090	4,363	4,288	4,793	3,668	3,675	15,600	16,424	16,077
General and administrative expenses	9,854	10,877	12,201	9,949	10,085	19,093	8,783	8,749	42,881	46,710	34,782
Write-off of unsuccessful exploration activities	1,796				303	1,294	863	557	1,796	3,017	1,579
Operating income	48,400	43,970	53,152	59,496	51,229	48,223	51,887	50,543	205,018	201,882	164,061
Interest income	127	255	362	244	140	266	245	320	988	971	297
Interest expense, net	(12,987)	(11,692)	(14,540)	(14,923)	(15,828)	(17,137)	(18,401)	(16,023)	(54,142)	(67,389)	(72,577)
Derivatives and foreign currency transaction gains (losses)	614	(1,001)	1,703	1,338	(2,942)	(222)	(4,332)	1,962	2,654	(5,534)	(1,622)
Income attributable to sale of tax benefits	3,859	3,506	4,356	6,157	4,123	3,463	4,519	4,398	17,878	16,503	25,431
Other non-operating income (expense), net	12	(1,592)	6	(92)	(39)	(5,546)	49	191	(1,666)	(5,345)	(1,991)
Income (loss) from continuing operations, before income taxes and equity in income of investees	40,025	33,446	45,039	52,220	36,683	29,047	33,967	41,391	170,730	141,088	113,599
Income tax (provision) benefit	29,669	(11,003)	(6,369)	(10,886)	(2,450)	(11,988)	(7,890)	(9,509)	1,411	(31,837)	15,258
Equity in income (losses) of investees	(267)	337	(428)	(1,599)	(3,001)	(2,653)	(1,144)	(937)	(1,957)	(7,735)	(5,508)
Net income (loss)	69,427	22,780	38,242	39,735	31,232	14,406	24,933	30,945	170,184	101,516	123,349
Net loss (income) attributable to noncontrolling interest	(3,467)	(3,599)	(3,206)	(4,423)	(3,002)	(2,326)	(584)	(1,674)	14,695	7,586	3,776
Net income (loss) attributable to the Company's stockholders	$ 65,960	$ 19,181	$ 35,036	$ 35,312	$ 28,230	$ 12,080	$ 24,349	$ 29,271	$ 155,489	$ 93,930	$ 119,573
Net income (in dollars per share)	$ 1.30	$ 0.38	$ 0.70	$ 0.71	$ 0.57	$ 0.24	$ 0.49	$ 0.60	$ 3.10	$ 1.90	$ 2.46
Net income (in dollars per share)	$ 1.29	$ 0.38	$ 0.69	$ 0.70	$ 0.56	$ 0.21	$ 0.48	$ 0.59	$ 3.06	$ 1.87	$ 2.43
Basic (in shares)	50,607	50,367	49,771	49,680	49,647	49,599	49,456	49,173	50,110	49,469	48,562
Diluted (in shares)	51,053	50,867	50,624	50,491	50,293	50,289	50,137	49,782	50,769	50,140	49,187

Note 24 - Subsequent Events (De

Note 24 - Subsequent Events (Details Textual) $ / shares in Units, $ in Thousands	Mar. 01, 2018USD ($)$ / shares	Jan. 24, 2018USD ($)MWh$ / shares	Dec. 31, 2017USD ($)$ / shares	Dec. 31, 2016USD ($)$ / shares	Dec. 31, 2015USD ($)$ / shares
Dividends, Common Stock | $			$ 20,511	$ 25,682	$ 12,716
Common Stock, Dividends, Per Share, Declared | $ / shares			$ 0.41	$ 0.52	$ 0.26
Subsequent Event [Member]
Dividends, Common Stock | $	$ 11,500
Common Stock, Dividends, Per Share, Declared | $ / shares	$ 0.23
Subsequent Event [Member] | U.S. Geothermal [Member]
Expected Power Generating Capacity | MWh		45
Current Power Generation | MWh		38
Subsequent Event [Member] | U.S. Geothermal [Member]
Business Acquisition, Share Price | $ / shares		$ 5.45
Business Combination, Consideration Transferred | $		$ 109,900