Consolidated Statements of Cash Flows $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Cash flows from operating activities:
Net income	$ 93,543	$ 110,111	$ 147,109
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	148,761	132,233	115,146
Accretion of asset retirement obligation	2,709	2,474	1,874
Stock-based compensation	9,358	10,218	8,760
Amortization of deferred lease income	(2,685)	(2,685)	(2,685)
Income attributable to sale of tax benefits, net of interest expense	(10,084)	(8,609)	(11,956)
Equity in losses (earnings) of investees, net	(1,853)	(7,663)	1,957
Mark-to-market of derivative instruments	(1,402)	2,032	(1,473)
Write-off of unsuccessful exploration activities	0	126	1,796
Goodwill, Impairment Loss	0	13,464	0
Loss (gain) on severance pay fund asset	(1,016)	1,186	(1,746)
Deferred income tax provision	27,896	19,360	(41,147)
Liability for unrecognized tax benefits	2,874	2,879	3,270
Deferred lease revenues	(574)	(402)	(356)
Gain from insurance recoveries	0	(4,463)	0
Other	914	100	737
Changes in operating assets and liabilities, net of businesses acquired:
Receivables	(15,133)	(29,928)	(24,040)
Costs and estimated earnings in excess of billings on uncompleted contracts	3,765	(1,185)	11,253
Inventories	5,500	(9,318)	(1,070)
Prepaid expenses and other	3,452	(11,172)	208
Change in operating lease right of use asset	8,167	0	0
Deposits and other	(22,525)	18	(2,570)
Accounts payable and accrued expenses	8,738	(56,724)	51,641
Billings in excess of costs and estimated earnings on uncompleted contracts	(15,647)	(1,839)	(11,389)
Liabilities for severance pay	757	(3,147)	2,541
Change in operating lease liabilities	(8,405)	0	0
Other liabilities, net	(617)	(11,244)	(2,285)
Net cash provided by operating activities	236,493	145,822	245,575
Cash flows from investing activities:
Capital expenditures	(279,986)	(258,521)	(259,234)
Cash received from insurance recoveries	35,435	10,427	0
Investment in unconsolidated companies	(10,674)	(3,800)	(46,318)
Buyout of Class B membership in ORTP	0	0	(2,400)
Buyout of Class B membership in OPC	0	2,367	(1,932)
Cash paid for acquisition of controlling interest in a subsidiary, net of cash acquired	0	(95,093)	(35,300)
Intangible assets acquired	0	0	(868)
Decrease (increase) in severance pay fund asset, net of payments made to retired employees	687	2,186	526
Net cash used in investing activities	(254,538)	(342,434)	(345,526)
Cash flows from financing activities:
Proceeds from sale of membership interests to noncontrolling interest, net of transaction costs	0	3,174	0
Proceeds from long-term loans, net of transaction costs	132,847	214,700	0
Proceeds from exercise of options by employees	2,429	0	16,111
Proceeds from the sale of limited liability company interest, net of transaction costs	58,289	32,175	0
Prepayment of long-term debt	(21,073)	0	(14,270)
Proceeds from issuance of commercial paper	50,000	0	0
Proceeds from revolving credit lines with banks	1,450,850	4,097,000	1,097,500
Repayment of revolving credit lines with banks	(1,569,300)	(3,989,500)	(1,046,000)
Cash received from noncontrolling interest	3,346	4,134	2,017
Cash paid for achievement of production threshold in GB	0	0	(8,032)
Repayments of long-term debt	(72,708)	(62,774)	(66,223)
Cash paid to noncontrolling interest	(9,730)	(13,106)	(21,313)
Payments under finance lease obligations	(3,164)	(2,551)	(1,871)
Deferred debt issuance costs	(5,165)	(5,287)	(5,290)
Cash dividends paid	(22,386)	(26,834)	(20,511)
Net cash provided by (used in) financing activities	(5,765)	251,131	(67,882)
Effect of exchange rate changes	(575)	(660)	0
Net change in cash and cash equivalents and restricted cash and cash equivalents	(24,385)	53,859	(167,833)
Restricted cash and cash equivalents acquired in a business combination	0	26,993	0
Cash and cash equivalents and restricted cash and cash equivalents at beginning of period	177,495	96,643	264,476
Cash and cash equivalents and restricted cash and cash equivalents at end of period	153,110	177,495	96,643
Supplemental disclosure of cash flow information:
Interest, net of interest capitalized	61,628	53,864	40,484
Income taxes, net	1,649	18,028	21,878
Supplemental non-cash investing and financing activities:
Increase (decrease) in accounts payable related to purchases of property, plant and equipment	9,423	(6,878)	4,484
Right of use assets obtained in exchange for new lease liabilities	11,626	8,584	0
Increase in asset retirement cost and asset retirement obligation	$ 8,334	$ 881	$ 1,888