Condensed Consolidated Statements of Operations and Comprehensive Income (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Revenues:
Revenues	$ 199,038	$ 184,023
Cost of revenues:
Cost of revenues	124,859	110,651
Gross profit	74,179	73,372
Operating expenses:
Research and development expenses	900	1,108
Selling and marketing expenses	3,865	3,699
General and administrative expenses	15,689	13,849
Write-off of unsuccessful exploration activities	0	123
Operating income	53,725	54,593
Other income (expense):
Interest income	293	113
Interest expense, net	(21,223)	(14,344)
Derivatives and foreign currency transaction gains (losses)	472	(1,599)
Income attributable to sale of tax benefits	7,764	7,361
Other non-operating income (expense), net	91	(20)
Income from operations before income tax and equity in earnings (losses) of investees	41,122	46,104
Income tax (provision) benefit	(14,039)	26,942
Equity in earnings (losses) of investees, net	1,047	1,210
Net income	28,130	74,256
Net income attributable to noncontrolling interest	(2,184)	(4,748)
Net income attributable to the Company's stockholders	25,946	69,508
Comprehensive income:
Net income	28,130	74,256
Other comprehensive income (loss), net of related taxes:
Change in foreign currency translation adjustments	(1,348)	1,528
Change in unrealized gains or losses in respect of the Company's share in derivatives instruments of unconsolidated investment	(1,145)	2,634
Loss in respect of derivative instruments designated for cash flow hedge	22	20
Amortization of unrealized gains in respect of derivative instruments designated for cash flow hedge	(8)	(15)
Comprehensive income	25,651	78,423
Comprehensive income attributable to noncontrolling interest	(1,862)	(5,118)
Comprehensive income attributable to the Company's stockholders	$ 23,789	$ 73,305
Basic:
Net income (in dollars per share)	$ 0.51	$ 1.37
Diluted:
Net income (in dollars per share)	$ 0.51	$ 1.36
Weighted average number of shares used in computation of earnings per share attributable to the Company's stockholders:
Basic (in shares)	50,709	50,614
Diluted (in shares)	51,012	51,051
Electricity [Member]
Revenues:
Revenue	$ 142,908	$ 132,489
Cost of revenues:
Cost of revenues	77,543	73,482
Product [Member]
Revenues:
Revenue	52,128	48,672
Cost of revenues:
Cost of revenues	42,106	33,726
Other Revenue [Member]
Revenues:
Revenue	4,002	2,862
Cost of revenues:
Cost of revenues	$ 5,210	$ 3,443