CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME [Abstract]
Revenues	$ 318,124	$ 333,081	$ 641,409	$ 667,894
Cost of revenues	261,979	259,021	530,842	505,407
Research and development expenses	7,399	23,191	14,264	55,324
Selling, general and administrative expenses	33,486	24,563	58,061	49,750
Income from operations	15,260	26,306	38,242	57,413
Interest income and other, net	11,913	476	11,793	1,042
Interest expense	(1,109)	(1,184)	(2,210)	(2,294)
Income before income taxes	26,064	25,598	47,825	56,161
Income tax provision	(9,531)	(9,319)	(17,481)	(20,280)
Net income	16,533	16,279	30,344	35,881
Basic income per share	$ 0.27	$ 0.27	$ 0.50	$ 0.60
Diluted income per share	$ 0.27	$ 0.27	$ 0.50	$ 0.59
Net income	16,533	16,279	30,344	35,881
Other comprehensive income (loss):
Defined benefit plans, net of tax of $28, $(206), $(24) and $(42), respectively	50	(329)	(33)	(67)
Unrealized gain (loss) on investments	0	300	0	600
Net gain (loss) on foreign exchange derivative instruments, net of tax of $0, $(176), $206 and $298, respectively	0	(282)	326	474
Total other comprehensive income (loss)	50	(311)	293	1,007
Comprehensive Income	$ 16,583	$ 15,968	$ 30,637	$ 36,888