CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME [Abstract]
Revenues	$ 1,365,271	$ 1,436,769	$ 1,345,923
Cost of revenues	1,062,466	1,097,190	1,074,389
Research and development expenses	89,233	114,205	102,751
Selling, general and administrative expenses	100,027	112,803	88,989
Income from operations	113,545	112,571	79,794
Interest income and other, net	(5,368)	749	19,335
Interest expense	(4,556)	(11,275)	(11,096)
Debt extinguishment expense	0	(10,261)	0
Income before income taxes	103,621	91,784	88,033
Income tax provision	(35,255)	(30,778)	(20,639)
Net income	68,366	61,006	67,394
Basic income per share	$ 1.13	$ 1.03	$ 1.14
Diluted income per share	$ 1.13	$ 1.02	$ 1.13
Net income	68,366	61,006	67,394
Other comprehensive income (loss):
Defined benefit plans, net of tax of $813, $263 and $(773), respectively	1,278	418	(1,248)
Unrealized gain (loss) on investments	(50)	700	(100)
Unrealized gain (loss) on foreign exchange derivative instruments, net of tax of $135 and $(339)	212	(540)	0
Total other comprehensive income (loss)	1,440	578	(1,348)
Comprehensive Income	$ 69,806	$ 61,584	$ 66,046