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, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Revenues:
Electricity	$ 88,994,000	$ 77,612,000	$ 245,005,000	$ 238,837,000
Product	41,755,000	54,685,000	157,329,000	149,616,000
Total revenues	130,749,000	132,297,000	402,334,000	388,453,000
Cost of revenues:
Electricity	61,356,000	59,924,000	175,085,000	172,785,000
Product	29,637,000	42,130,000	110,335,000	108,575,000
Total cost of revenues	90,993,000	102,054,000	285,420,000	281,360,000
Gross margin	39,756,000	30,243,000	116,914,000	107,093,000
Operating expenses:
Research and development expenses	838,000	1,436,000	3,446,000	3,948,000
Selling and marketing expenses	2,575,000	3,346,000	17,861,000	12,752,000
General and administrative expenses	6,546,000	6,132,000	20,264,000	20,163,000
Impairment charge		7,264,000		7,264,000
Write-off of unsuccessful exploration activities				1,919,000
Operating income	29,797,000	12,065,000	75,343,000	61,047,000
Other income (expense):
Interest income	742,000	280,000	870,000	1,004,000
Interest expense, net	(18,459,000)	(15,400,000)	(51,826,000)	(44,541,000)
Foreign currency translation and transaction gains (losses)	1,258,000	615,000	3,844,000	(1,127,000)
Income attributable to sale of tax benefits	5,027,000	2,311,000	14,342,000	7,417,000
Other non-operating income, net	137,000	215,000	1,583,000	344,000
Income before income taxes and equity in losses of investees	18,502,000	86,000	44,156,000	24,144,000
Income tax provision	(5,201,000)	(1,088,000)	(15,028,000)	(10,148,000)
Equity in losses of investees	(158,000)	(1,245,000)	(149,000)	(1,542,000)
Income (loss) from continuing operations	13,143,000	(2,247,000)	28,979,000	12,454,000
Discontinued operations:
Income from discontinued operations (including gain on disposal of $0, $0, $3,646 and $0, respectively)		2,123,000	5,311,000	4,875,000
Total income from discontinued operations		1,732,000	4,697,000	3,778,000
Net income (loss)	13,143,000	(515,000)	33,676,000	16,232,000
Net income attributable to noncontrolling interest	(193,000)	(67,000)	(600,000)	(278,000)
Net income (loss) attributable to the Company's stockholders	12,950,000	(582,000)	33,076,000	15,954,000
Comprehensive income (loss):
Net income (loss)	13,143,000	(515,000)	33,676,000	16,232,000
Other comprehensive income (loss), net of related taxes:
Amortization of gains or losses in respect of derivative instruments designated for cash flow hedge	(40,000)	(47,000)	(124,000)	(140,000)
Change in fair value of marketable securities available-for-sale		262,000		242,000
Comprehensive income (loss)	13,103,000	(300,000)	33,552,000	16,334,000
Comprehensive income attributable to noncontrolling interest	(211,000)	(67,000)	(600,000)	(278,000)
Comprehensive income (loss) attributable to the Company's stockholders	12,892,000	(367,000)	32,952,000	16,056,000
Basic:
Income (loss) from continuing operations (in Dollars per share)	$ 0.29	$ (0.05)	$ 0.62	$ 0.27
Discontinued operations (in Dollars per share)		$ 0.04	$ 0.10	$ 0.08
Net income (loss) (in Dollars per share)	$ 0.29	$ (0.01)	$ 0.72	$ 0.35
Diluted:
Income (loss) from continuing operations (in Dollars per share)	$ 0.28	$ (0.05)	$ 0.62	$ 0.27
Discontinued operations (in Dollars per share)		$ 0.04	$ 0.10	$ 0.08
Net income (loss) (in Dollars per share)	$ 0.28	$ (0.01)	$ 0.72	$ 0.35
Weighted average number of shares used in computation of earnings per share attributable to the Company's stockholders:
Basic (in Shares)	45,438	45,431	45,433	45,431
Diluted (in Shares)	45,494	45,431	45,454	45,438
Dividend per share declared (in Dollars per share)	$ 0.04	$ 0.04	$ 0.08	$ 0.08
Discontinued Operations [Member]
Other income (expense):
Income tax provision		$ (391,000)	$ (614,000)	$ (1,097,000)