Condensed Consolidated Statements of Operations and Comprehensive Income (Unaudited) - USD ($) shares in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Revenues:
Electricity	$ 115,776,000	$ 107,868,000
Product	74,122,000	43,726,000
Total revenues	189,898,000	151,594,000
Cost of revenues:
Electricity	66,036,000	63,686,000
Product	49,452,000	24,035,000
Total cost of revenues	115,488,000	87,721,000
Gross profit	74,410,000	63,873,000
Operating expenses:
Research and development expenses	602,000	349,000
Selling and marketing expenses	4,363,000	3,675,000
General and administrative expenses	9,949,000	8,749,000
Write-off of unsuccessful exploration activities	0	557,000
Operating income	59,496,000	50,543,000
Other income (expense):
Interest income	244,000	320,000
Interest expense, net	(14,923,000)	(16,023,000)
Derivatives and foreign currency transaction gains (losses)	1,338,000	1,962,000
Income attributable to sale of tax benefits	6,157,000	4,398,000
Other non-operating income (expense), net	(92,000)	191,000
Income from continuing operations before income taxes and equity in losses of investees	52,220,000	41,391,000
Income tax (provision) benefit	(10,886,000)	(9,509,000)
Equity in losses of investees, net	(1,599,000)	(937,000)
Income from continuing operations	39,735,000	30,945,000
Net income attributable to noncontrolling interest	(4,423,000)	(1,674,000)
Net income attributable to the Company's stockholders	35,312,000	29,271,000
Comprehensive income:
Net income	39,735,000	30,945,000
Other comprehensive income (loss), net of related taxes:
Change in unrealized gains or losses in respect of the Company's share in derivatives instruments of unconsolidated investment	569,000	(3,179,000)
Loss in respect of derivative instruments designated for cash flow hedge	22,000	21,000
Amortization of unrealized gains in respect of derivative instruments designated for cash flow hedge	(24,000)	(24,000)
Comprehensive income	40,302,000	27,763,000
Comprehensive income attributable to noncontrolling interest	(4,412,000)	(1,674,000)
Comprehensive income attributable to the Company's stockholders	$ 35,890,000	$ 26,089,000
Basic:
Net income (in dollars per share)	$ 0.71	$ 0.60
Diluted:
Net income (in dollars per share)	$ 0.70	$ 0.59
Weighted average number of shares used in computation of earnings per share attributable to the Company's stockholders:
Basic (in shares)	49,680	49,173
Diluted (in shares)	50,491	49,782
Dividend per share declared (in dollars per share)	$ 0.17	$ 0.31