Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash flows from operating activities:
Net income	$ 28,130	$ 74,256
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	36,901	30,553
Accretion of asset retirement obligation	651	529
Stock-based compensation	2,360	1,707
Amortization of deferred lease income	(775)	(775)
Income attributable to sale of tax benefits, net of interest expense	(4,314)	(6,295)
Equity in losses (earnings) of investees	(1,047)	(1,210)
Mark-to-market of derivative instruments	(1,209)	962
Loss on disposal of property, plant and equipment	377
Write-off of unsuccessful exploration activities	0	123
Loss (gain) on severance pay fund asset	(330)	129
Deferred income tax provision	10,469	(29,467)
Liability for unrecognized tax benefits	713	184
Changes in operating assets and liabilities, net of businesses acquired:
Receivables	(1,119)	9,777
Costs and estimated earnings in excess of billings on uncompleted contracts	12,368	(189)
Inventories	2,018	(503)
Prepaid expenses and other	(2,105)	(2,005)
Operating lease right of use asset	1,698
Deposits and other	26	62
Accounts payable and accrued expenses	(4,271)	(49,027)
Billings in excess of costs and estimated earnings on uncompleted contracts	(2,894)	(9,783)
Liabilities for severance pay	406	(267)
Other long-term liabilities	(616)	1,008
Net cash provided by operating activities	77,437	19,769
Cash flows from investing activities:
Capital expenditures	(51,303)	(66,962)
Investment in unconsolidated companies		(1,275)
Decrease (increase) in severance pay fund asset, net of payments made to retired employees	359	203
Net cash used in investing activities	(50,944)	(68,034)
Cash flows from financing activities:
Proceeds from long-term loans, net of transaction costs	91,500	100,000
Proceeds from revolving credit lines with banks	914,700	860,800
Repayment of revolving credit lines with banks	(1,012,800)	(873,800)
Cash received from noncontrolling interest	3,346	4,134
Repayments of long-term debt	(15,757)	(16,687)
Cash paid to noncontrolling interest	(4,459)	(4,674)
Payments of finance leases	(767)	(436)
Deferred debt issuance costs	(1,223)	(1,020)
Cash dividends paid	(5,579)	(11,640)
Net cash provided by (used in) financing activities	(31,039)	56,677
Effect of exchange rate changes	(485)
Net change in cash and cash equivalents and restricted cash and cash equivalents	(5,031)	8,412
Cash and cash equivalents and restricted cash and cash equivalents at beginning of period	177,495	96,643
Cash and cash equivalents and restricted cash and cash equivalents at end of period	172,464	105,055
Supplemental non-cash investing and financing activities:
Increase (decrease) in accounts payable related to purchases of property, plant and equipment	153	(1,673)
Accrued liabilities related to financing activities	$ 2,154