Consolidated Statements of Stockholder's Equity (USD $) In Thousands	Total	Common stock:	Paid-in capital:	Treasury Stock:	Accumulated Earnings:	Accumulated Other Comprehensive Income:
Balance, beginning of period at Dec. 31, 2009		$ 636	$ 408,722	$ (675,623)	$ 479,284	$ (909)
Balance, beginning of period, Shares at Dec. 31, 2009		35,126
Net income	22,429				22,429
Net unrealized gains (losses) on short-term investments						(6)
Net unrealized gains (losses) on pension plan and prior service costs						22
Foreign currency translation						868
Repurchase of common stock pursuant to Board-approved stock repurchase program				(29,340)
Repurchase of common stock pursuant to Board-approved stock repurchase program, shares				(1,500)
Issuance of common stock pursuant to employee stock purchase plan			1,172
Issuance of common stock pursuant to employee stock purchase plan, shares		70
Exercise of stock options			233
Exercise of stock options, shares		19
Issuance of restricted common stock pursuant to employee stock-based compensation plans		8	(8)
Issuance of restricted common stock pursuant to employee stock-based compensation plans, Shares		748
Cancellation of restricted common stock pursuant to employee stock-based compensation plans		(2)	2
Cancellation of unvested restricted common stock pursuant to employee stock-based compensation plans, Shares		(109)
Repurchase and cancellation of common stock pursuant to employee stock-based compensation plans		(1)	(4,689)
Repurchase and cancellation of common stock pursuant to employee stock-based compensation plans , Shares		(233)
Issuance of 2010 Convertible Debt Securities			22,928
Stock-based compensation expense			12,338
Stock-based compensation income tax benefits			627
Repurchase of convertible debt			(1,613)
Balance, end of period at Dec. 31, 2010	237,078	641	439,712	(704,963)	501,713	(25)
Balance, end of period, Shares at Dec. 31, 2010		34,121
Net income	42,282				42,282
Net unrealized gains (losses) on short-term investments						(3)
Net unrealized gains (losses) on pension plan and prior service costs						(897)
Net unrealized losses on change in fair value of interest rate swap contracts	(618)					(618)
Foreign currency translation						(2,866)
Repurchase of common stock pursuant to Board-approved stock repurchase program				(9,930)
Repurchase of common stock pursuant to Board-approved stock repurchase program, shares				(750)
Issuance of common stock pursuant to employee stock purchase plan			1,442
Issuance of common stock pursuant to employee stock purchase plan, shares		103
Exercise of stock options			44
Exercise of stock options, shares		3
Issuance of restricted common stock pursuant to employee stock-based compensation plans		7	(7)
Issuance of restricted common stock pursuant to employee stock-based compensation plans, Shares		746
Cancellation of restricted common stock pursuant to employee stock-based compensation plans		(1)	1
Cancellation of unvested restricted common stock pursuant to employee stock-based compensation plans, Shares		(170)
Repurchase and cancellation of common stock pursuant to employee stock-based compensation plans		(2)	(4,433)
Repurchase and cancellation of common stock pursuant to employee stock-based compensation plans , Shares		(231)
Stock-based compensation expense			12,152
Stock-based compensation income tax benefits			465
Balance, end of period at Dec. 31, 2011	274,714	645	449,376	(714,893)	543,995	(4,409)
Balance, end of period, Shares at Dec. 31, 2011	33,822	33,822
Net income	48,879				48,879
Net unrealized gains (losses) on short-term investments						2
Net unrealized gains (losses) on pension plan and prior service costs						33
Net unrealized losses on change in fair value of interest rate swap contracts	(40)					(40)
Foreign currency translation						4,272
Repurchase of common stock pursuant to Board-approved stock repurchase program				(13,350)
Repurchase of common stock pursuant to Board-approved stock repurchase program, shares				(823)
Issuance of common stock pursuant to employee stock purchase plan			1,394
Issuance of common stock pursuant to employee stock purchase plan, shares		94
Exercise of stock options			502
Exercise of stock options, shares		40
Issuance of restricted common stock pursuant to employee stock-based compensation plans		8	(8)
Issuance of restricted common stock pursuant to employee stock-based compensation plans, Shares		873
Cancellation of restricted common stock pursuant to employee stock-based compensation plans
Cancellation of unvested restricted common stock pursuant to employee stock-based compensation plans, Shares		(77)
Repurchase and cancellation of common stock pursuant to employee stock-based compensation plans			(3,208)
Repurchase and cancellation of common stock pursuant to employee stock-based compensation plans , Shares		(195)
Issuance of 2010 Convertible Debt Securities
Stock-based compensation expense			13,431
Stock-based compensation income tax benefits			10
Repurchase of convertible debt
Balance, end of period at Dec. 31, 2012	$ 326,639	$ 653	$ 461,497	$ (728,243)	$ 592,874	$ (142)
Balance, end of period, Shares at Dec. 31, 2012	33,734	33,734