Consolidated Statements of Cash Flows (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Cash flows from operating activities:
Net income (loss)	$ 42,031,000	$ (212,607,000)	$ (42,724,000)
Adjustments to reconcile net income or loss to net cash provided by operating activities:
Depreciation and amortization	92,932,000	102,340,000	96,398,000
Amortization of premium from senior unsecured bonds	(307,000)	(307,000)	(256,000)
Accretion of asset retirement obligation	1,544,000	1,701,000	1,593,000
Stock-based compensation	6,262,000	6,394,000	6,672,000
Amortization of deferred lease income	(2,685,000)	(2,685,000)	(2,685,000)
Income attributable to sale of tax benefits, net of interest expense	(7,999,000)	(4,003,000)	(4,315,000)
Equity in income (losses) of investees	150,000	442,000	959,000
Mark-to-market of derivative instruments	7,813,000
Write-off of unsuccessful exploration activities	4,094,000	2,639,000
Impairment charge		236,377,000
Loss (gain) on severance pay fund asset	(877,000)	(931,000)	588,000
Premium from issuance of senior unsecured bonds			1,957,000
Gain on sale of a subsidiary	(3,646,000)
Deferred income tax provision (benefit)	9,245,000	(4,736,000)	38,061,000
Liability for unrecognized tax benefits	(2,330,000)	1,405,000	444,000
Deferred lease revenues	(217,000)	128,000	376,000
Gain on repurchase of OFC bonds	(819,000)
Changes in operating assets and liabilities, net of amounts acquired:
Receivables	(37,174,000)	(3,623,000)	1,979,000
Costs and estimated earnings in excess of billings on uncompleted contracts	(11,604,000)	(5,647,000)	2,180,000
Inventories	(1,620,000)	(8,128,000)	(3,000)
Prepaid expenses and other	(600,000)	(15,472,000)	(3,743,000)
Deposits and other	621,000	(12,746,000)	(710,000)
Accounts payable and accrued expenses	6,077,000	11,414,000	6,646,000
Due from/to related entities, net	(69,000)	(86,000)	16,000
Billings in excess of costs and estimated earnings on uncompleted contracts	(17,505,000)	(7,696,000)	29,951,000
Liabilities for severance pay	1,267,000	2,340,000	(159,000)
Other long-term liabilities	2,302,000	895,000	(708,000)
Due from/to Parent	(71,000)	(51,000)	12,000
Net cash provided by operating activities	86,760,000	89,471,000	132,734,000
Cash flows from investing activities:
Marketable securities, net		18,763,000	(17,534,000)
Short-term deposit	3,010,000	(3,010,000)
Net change in restricted cash, cash equivalents and marketable securities	25,472,000	(1,016,000)	(50,614,000)
Cash received from sale of a subsidiary	7,699,000
Capital expenditures	(204,628,000)	(233,020,000)	(269,677,000)
Cash grant received	14,685,000	119,199,000
Investment in unconsolidated companies	(4,635,000)	(1,390,000)	(472,000)
Cash paid for investment in a joint venture			(200,000)
Intangible assets acquired			(1,786,000)
Decrease in severance pay fund asset, net of payments made to retired employees	1,244,000	(316,000)	(719,000)
Net cash used in investing activities	(157,153,000)	(100,790,000)	(341,002,000)
Cash flows from financing activities:
Proceeds from issuance of senior unsecured bonds		1,171,000	107,447,000
Proceeds from long-term loans, net of transaction costs	90,000,000	214,051,000
Proceeds from exercise of options by employees	529,000
Proceeds from issuance of senior secured notes, net of transaction costs			141,108,000
Proceeds from the sale of limited liability company interest in OPC LLC, net of transaction costs	31,376,000
Proceeds from the sale of limited liability company interest in ORTP LLC, net of transaction costs	31,376,000
Purchase of OFC Senior Secured Notes	(11,888,000)
Proceeds from revolving credit lines with banks	3,058,956,000	2,953,535,000	891,583,000
Repayment of revolving credit lines with banks	(3,020,545,000)	(3,093,978,000)	(867,000,000)
Repayments of long-term debt	(68,370,000)	(74,502,000)	(50,130,000)
Cash paid to non-controlling interest	(13,384,000)	(15,383,000)	(14,039,000)
Deferred debt issuance costs	(1,919,000)	(3,197,000)	(2,584,000)
Cash dividends paid	(3,636,000)	(3,636,000)	(5,924,000)
Net cash provided by (used in) financing activities	61,119,000	(21,939,000)	225,339,000
Net change in cash and cash equivalents	(9,274,000)	(33,258,000)	17,071,000
Cash and cash equivalents at beginning of year	66,628,000	99,886,000	82,815,000
Cash and cash equivalents at end of year	57,354,000	66,628,000	99,886,000
Cash paid during the year for:
Interest, net of interest capitalized	51,306,000	40,398,000	33,274,000
Income taxes, net	4,114,000	11,570,000	13,575,000
Supplemental non-cash investing and financing activities:
Increase (decrease) in accounts payable related to purchases of property, plant and equipment	4,372,000	(18,813,000)	13,117,000
Increase (decrease) in asset retirement cost and asset retirement obligation	588,000	(3,696,000)	(212,000)
Auction Rate Securities [Member]
Adjustments to reconcile net income or loss to net cash provided by operating activities:
Impairment of investments			205,000
Unconsolidated Investment [Member]
Adjustments to reconcile net income or loss to net cash provided by operating activities:
Impairment of investments		2,114,000
OPC LLC [Member]
Cash flows from financing activities:
Proceeds from the sale of limited liability company interest in OPC LLC, net of transaction costs			24,878,000
Proceeds from the sale of limited liability company interest in ORTP LLC, net of transaction costs			$ 24,878,000