Condensed Consolidated Statements of Equity (Unaudited) (USD $) In Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Parent [Member]	Noncontrolling Interest [Member]	Total
Balance at Dec. 31, 2011	$ 46	$ 725,746	$ 172,331	$ 595	$ 898,718	$ 7,926	$ 906,644
Balance (in Shares) at Dec. 31, 2011	45,431
Stock-based compensation		3,127			3,127		3,127
Cash paid to noncontrolling interest						(375)	(375)
Cash dividend declared, $0.04 per share			(1,819)		(1,819)		(1,819)
Net income (loss)			16,536		16,536	211	16,747
Amortization of unrealized gains in respect of derivative instruments designated for cash flow hedge (net of related tax)				(93)	(93)		(93)
Change in unrealized gains or losses on marketable securities available-for-sale (net of related tax of $0)				(20)	(20)		(20)
Balance at Jun. 30, 2012	46	728,873	187,048	482	916,449	7,762	924,211
Balance (in Shares) at Jun. 30, 2012	45,431
Balance at Dec. 31, 2012	46	732,140	(44,326)	651	688,511	7,096	695,607
Balance (in Shares) at Dec. 31, 2012	45,431
Stock-based compensation		2,857			2,857		2,857
Cash paid to noncontrolling interest						(349)	(349)
Increase in noncontrolling interest due to sale of equity interest in ORTP LLC						5,151	5,151
Net income (loss)			20,126		20,126	407	20,533
Amortization of unrealized gains in respect of derivative instruments designated for cash flow hedge (net of related tax)				(84)	(84)		(84)
Balance at Jun. 30, 2013	$ 46	$ 734,997	$ (24,200)	$ 567	$ 711,410	$ 12,305	$ 723,715
Balance (in Shares) at Jun. 30, 2013	45,431