Condensed Consolidated Statements of Operations and Comprehensive Income (Unaudited) (USD $) Share data in Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Revenues:
Electricity	$ 102,506,000	$ 88,994,000	$ 289,015,000	$ 245,005,000
Product	37,736,000	41,755,000	121,266,000	157,329,000
Total revenues	140,242,000	130,749,000	410,281,000	402,334,000
Cost of revenues:
Electricity	61,727,000	61,356,000	186,083,000	175,085,000
Product	23,040,000	29,637,000	75,307,000	110,335,000
Total cost of revenues	84,767,000	90,993,000	261,390,000	285,420,000
Gross margin	55,475,000	39,756,000	148,891,000	116,914,000
Operating expenses:
Research and development expenses	250,000	838,000	395,000	3,446,000
Selling and marketing expenses	4,258,000	2,575,000	10,853,000	17,861,000
General and administrative expenses	7,179,000	6,546,000	20,847,000	20,264,000
Write-off of unsuccessful exploration activities	8,100,000		8,107,000
Operating income	43,788,000	29,797,000	108,689,000	75,343,000
Other income (expense):
Interest income	35,000	742,000	236,000	870,000
Interest expense, net	(22,494,000)	(18,459,000)	(65,084,000)	(51,826,000)
Foreign currency translation and transaction gains (losses)	(2,946,000)	1,258,000	(3,639,000)	3,844,000
Income attributable to sale of tax benefits	5,487,000	5,027,000	18,334,000	14,342,000
Gain from sale of property, plant and equipment			7,628,000
Other non-operating income, net	243,000	137,000	649,000	1,583,000
Income before income taxes and equity in losses of investees	24,113,000	18,502,000	66,813,000	44,156,000
Income tax provision	(6,444,000)	(5,201,000)	(17,731,000)	(15,028,000)
Equity in losses of investees	(899,000)	(158,000)	(1,210,000)	(149,000)
Income from continuing operations	16,770,000	13,143,000	47,872,000	28,979,000
Discontinued operations:
Income from discontinued operations (including gain on disposal of $0, $0, $0 and $3,646, respectively)				5,311,000
Total income from discontinued operations				4,697,000
Net income	16,770,000	13,143,000	47,872,000	33,676,000
Net income attributable to noncontrolling interest	(256,000)	(193,000)	(670,000)	(600,000)
Net income attributable to the Company's stockholders	16,514,000	12,950,000	47,202,000	33,076,000
Comprehensive income:
Net income	16,770,000	13,143,000	47,872,000	33,676,000
Other comprehensive income (loss), net of related taxes:
Change in unrealized gains or losses in respect of the Company's share in derivative instruments of unconsolidated investment	(1,069,000)		(5,157,000)
Loss in respect of derivative instruments designated for cash flow hedge	(933,000)		(933,000)
Amortization of unrealized gains or losses in respect of derivative instruments designated for cash flow hedge	(35,000)	(40,000)	(107,000)	(124,000)
Comprehensive income	14,733,000	13,103,000	41,675,000	33,552,000
Comprehensive income attributable to noncontrolling interest	(256,000)	(193,000)	(670,000)	(600,000)
Comprehensive income attributable to the Company's stockholders	14,477,000	12,910,000	41,005,000	32,952,000
Basic:
Income from continuing operations (in Dollars per share)	$ 0.37	$ 0.29	$ 1.04	$ 0.62
Discontinued operations (in Dollars per share)				$ 0.10
Net income (in Dollars per share)	$ 0.37	$ 0.29	$ 1.04	$ 0.72
Diluted:
Income from continuing operations (in Dollars per share)	$ 0.36	$ 0.28	$ 1.03	$ 0.62
Discontinued operations (in Dollars per share)				$ 0.10
Net income (in Dollars per share)	$ 0.36	$ 0.28	$ 1.03	$ 0.72
Weighted average number of shares used in computation of earnings per share attributable to the Company's stockholders:
Basic (in Shares)	45,690	45,438	45,594	45,433
Diluted (in Shares)	46,102	45,494	45,917	45,454
Dividend per share declared (in Dollars per share)	$ 0.05	$ 0.04	$ 0.16	$ 0.04
Discontinued Operations [Member]
Other income (expense):
Income tax provision				$ (614,000)