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		4,837			4,837		4,837
Cash paid to noncontrolling interest						(1,025)	(1,025)
Cash dividend paid			(3,636)		(3,636)		(3,636)
Net income (loss)			15,954		15,954	278	16,232
Amortization of unrealized gains in respect of derivative instruments designated for cash flow hedge (net of related tax)				(140)	(140)		(140)
Change in fair value of marketable securities available-for-sale (net of related tax of $0)				242	242		242
Balance at Sep. 30, 2012	46	730,583	184,649	697	915,975	7,179	923,154
Balance (in Shares) at Sep. 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		4,548			4,548		4,548
Cash paid to noncontrolling interest						(509)	(509)
Cash dividend paid			(1,816)		(1,816)		(1,816)
Exercise of options by employees		437			437		437
Exercise of options by employees (in Shares)	23
Increase in noncontrolling interest due to sale of equity interest in ORTP LLC						5,151	5,151
Net income (loss)			33,076		33,076	600	33,676
Amortization of unrealized gains in respect of derivative instruments designated for cash flow hedge (net of related tax)				(124)	(124)		(124)
Balance at Sep. 30, 2013	$ 46	$ 737,125	$ (13,066)	$ 527	$ 724,632	$ 12,338	$ 736,970
Balance (in Shares) at Sep. 30, 2013	45,454