Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($)	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Cash flows from operating activities:
Net income	$ 55,878,000	$ 25,540,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	51,258,000	52,559,000
Amortization of premium from senior unsecured bonds	(154,000)	(154,000)
Accretion of asset retirement obligation	821,000	752,000
Stock-based compensation	1,659,000	2,156,000
Amortization of deferred lease income	(1,343,000)	(1,342,000)
Income attributable to sale of tax benefits, net of interest expense	(5,076,000)	(6,720,000)
Equity in losses of investees	2,081,000	1,759,000
Mark-to-market of derivative instruments	(162,000)	4,140,000
Loss on disposal of property, plant and equipment		531,000
Write-off of unsuccessful exploration activities	1,420,000	174,000
Gain on severance pay fund asset	(253,000)	(572,000)
Deferred income tax provision	13,254,000	7,024,000
Liability for unrecognized tax benefits	(411,000)	(360,000)
Deferred lease revenues	169,000	(148,000)
Other		484,000
Changes in operating assets and liabilities, net of amounts acquired:
Receivables	(10,206,000)	(12,775,000)
Costs and estimated earnings in excess of billings on uncompleted contracts	9,861,000	20,700,000
Inventories	1,384,000	529,000
Prepaid expenses and other	(11,007,000)	(300,000)
Deposits and other	(153,000)	(362,000)
Accounts payable and accrued expenses	1,808,000	(2,600,000)
Due from/to related entities, net		451,000
Billings in excess of costs and estimated earnings on uncompleted contracts	(9,020,000)	(25,007,000)
Liabilities for severance pay	(297,000)	(975,000)
Other long-term liabilities	22,000	(2,259,000)
Due from/to Parent		(513,000)
Net cash provided by operating activities	119,573,000	112,726,000
Cash flows from investing activities:
Cash acquired in organizational restructuring and share exchange with parent		15,391,000
Net change in restricted cash, cash equivalents and marketable securities	11,498,000	(11,622,000)
Capital expenditures	(67,779,000)	(86,142,000)
Decrease in severance pay fund asset, net of payments made to retired employees	992,000	2,940,000
Net cash used in investing activities	(55,289,000)	(79,433,000)
Cash flows from financing activities:
Proceeds from sale of membership interests to noncontrolling interest, net of transaction costs		156,761,000
Proceeds from exercise of options by employees	5,945,000	3,966,000
Purchase of OFC Senior Secured Notes		(30,638,000)
Proceeds from revolving credit lines with banks	134,500,000	598,800,000
Repayment of revolving credit lines with banks	(134,500,000)	(619,100,000)
Cash received from non-controlling interest	1,972,000	1,654,000
Repayments of long-term debt	(31,386,000)	(29,404,000)
Cash paid to non-controlling interest	(12,249,000)	(7,418,000)
Deferred debt issuance costs	(2,931,000)	(3,649,000)
Cash dividends paid	(18,998,000)	(6,830,000)
Net cash provided by (used in) financing activities	(57,647,000)	64,142,000
Net change in cash and cash equivalents	6,637,000	97,435,000
Cash and cash equivalents at beginning of period	185,919,000	40,230,000
Cash and cash equivalents at end of period	192,556,000	137,665,000
Supplemental non-cash investing and financing activities:
Increase (decrease) in accounts payable related to purchases of property, plant and equipment	(6,956,000)	12,612,000
Accrued liabilities related to financing activities	$ 6,128,000