Consolidated Statements of Equity (USD $) In Thousands, except Share data, unless otherwise specified	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		6,394			6,394		6,394
Exercise of options by employees and directors (in Shares)							0
Cash paid to non controlling interest						(1,244)	(1,244)
Cash dividend declared			(3,636)		(3,636)		(3,636)
Net income (loss)			(213,021)		(213,021)	414	(212,607)
Currency translation adjustment
Amortization of unrealized gains				(190)	(190)		(190)
Change in unrealized gains or losses on marketable securities available-for-sale (net of related tax of $0)				246	246		246
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		6,262			6,262		6,262
Exercise of options by employees and directors		529			529		529
Exercise of options by employees and directors (in Shares)	30						39,000
Cash paid to non controlling interest						(669)	(669)
Cash dividend declared		(3,636)			(3,636)		(3,636)
Increase in noncontrolling interest						5,151	5,151
Net income (loss)			41,238		41,238	793	42,031
of related taxes:
Currency translation adjustment of derivative instruments designated for cash flow hedge (net of related tax of $101)				(164)	(164)		(164)
Currency translation adjustment
Amortization of unrealized gains							(164)
Balance at Dec. 31, 2013	46	735,295	(3,088)	487	732,740	12,371	732,740
Balance (in Shares) at Dec. 31, 2013	45,461
Stock-based compensation		5,571			5,571		5,571
Exercise of options by employees and directors		981			981		981
Exercise of options by employees and directors (in Shares)	76						243,000
Cash paid to non controlling interest						(651)	(651)
Cash dividend declared			(9,555)		(9,555)		(9,555)
Increase in noncontrolling interest						257	257
Acquisition of noncontrolling interest in Crump		159			159	(987)	(828)
Net income (loss)			54,182		54,182	833	55,015
of related taxes:
Loss in respect of derivative instruments designated for cash flow hedge (net of related tax of $554)				(902)	(902)		(902)
Change in unrealized gains or losses in respect of the Company's share in derivative instruments of unconsolidated investment (net of related tax of $0)				(8,112)	(8,112)		(6,302)
Currency translation adjustment
Amortization of unrealized gains				(141)	(141)		(141)
Balance at Dec. 31, 2014	$ 46	$ 742,006	$ 41,539	$ (8,668)	$ 774,923	$ 11,823	$ 774,923
Balance (in Shares) at Dec. 31, 2014	45,537