Condensed Consolidated Statements of Operations and Comprehensive Income (Unaudited) (USD $) Share data in Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Revenues:
Electricity	$ 87,713,000	$ 81,882,000	$ 156,011,000	$ 161,225,000
Product	64,966,000	44,826,000	115,574,000	94,931,000
Total revenues	152,679,000	126,708,000	271,585,000	256,156,000
Cost of revenues:
Electricity	58,641,000	56,565,000	113,729,000	112,795,000
Product	43,657,000	31,818,000	80,698,000	66,445,000
Total cost of revenues	102,298,000	88,383,000	194,427,000	179,240,000
Gross margin	50,381,000	38,325,000	77,158,000	76,916,000
Operating expenses:
Research and development expenses	1,608,000	1,464,000	2,608,000	2,512,000
Selling and marketing expenses	3,777,000	4,570,000	15,286,000	9,406,000
General and administrative expenses	7,134,000	6,757,000	13,718,000	14,031,000
Write-off of unsuccessful exploration activities		1,151,000		1,919,000
Operating income	37,862,000	24,383,000	45,546,000	49,048,000
Other income (expense):
Interest income	87,000	336,000	128,000	724,000
Interest expense, net	(17,504,000)	(14,263,000)	(33,367,000)	(29,141,000)
Foreign currency translation and transaction gains (losses)	904,000	(1,756,000)	2,586,000	(1,742,000)
Income attributable to sale of tax benefits	5,783,000	2,589,000	9,315,000	5,106,000
Other non-operating income, net	29,000	286,000	1,446,000	122,000
Income before income taxes and equity in income (losses) of investees	27,161,000	11,575,000	25,654,000	24,117,000
Income tax provision	(5,780,000)	(3,884,000)	(9,827,000)	(9,060,000)
Equity in income (losses) of investees	9,000	(157,000)	9,000	(297,000)
Income from continuing operations	21,390,000	7,534,000	15,836,000	14,760,000
Discontinued operations:
Income from discontinued operations (including gain on disposal of $3,646, $0, $3,646 and $0, repectively)	4,480,000	1,613,000	5,311,000	2,693,000
Total income from discontinued operations	4,117,000	1,188,000	4,697,000	1,987,000
Net income	25,507,000	8,722,000	20,533,000	16,747,000
Net income attributable to noncontrolling interest	(322,000)	(81,000)	(407,000)	(211,000)
Net income attributable to the Company's stockholders	25,185,000	8,641,000	20,126,000	16,536,000
Comprehensive income:
Net income	25,507,000	8,722,000	20,533,000	16,747,000
Other comprehensive income (loss), net of related taxes:
Amortization of unrealized gains or losses in respect of derivative instruments designated for cash flow hedge	(42,000)	(47,000)	(84,000)	(93,000)
Change in unrealized gains or losses on marketable securities available-for-sale		10,000		(20,000)
Comprehensive income	25,465,000	8,685,000	20,449,000	16,634,000
Comprehensive income attributable to noncontrolling interest	(211,000)	(81,000)	(407,000)	(211,000)
Comprehensive income attributable to the Company's stockholders	25,254,000	8,604,000	20,042,000	16,423,000
Earnings per share attributable to the Company's stockholders - basic and diluted:
Income from continuing operations (in Dollars per share)	$ 0.46	$ 0.16	$ 0.34	$ 0.32
Discontinued operations (in Dollars per share)	$ 0.09	$ 0.03	$ 0.10	$ 0.04
Net income (in Dollars per share)	$ 0.55	$ 0.19	$ 0.44	$ 0.36
Weighted average number of shares used in computation of earnings per share attributable to the Company's stockholders:
Basic (in Shares)	45,431	45,431	45,431	45,431
Diluted (in Shares)	45,448	45,438	45,443	45,438
Dividend per share declared (in Dollars per share)	$ 0.04	$ 0.04	$ 0.04	$ 0.04
Discontinued Operations [Member]
Other income (expense):
Income tax provision	$ (363,000)	$ (425,000)	$ (614,000)	$ (706,000)