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	$ 147,109	$ 96,294	$ 124,148
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	1,779	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 (benefit) and deferred charges	(41,147)	23,222	(39,962)
Liability for unrecognized tax benefits	3,270	(4,174)	3,107
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)	(939)
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)