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, 2010		$ 641	$ 439,712	$ (704,963)	$ 501,713	$ (25)
Balance, beginning of period, shares at Dec. 31, 2010		34,121
Issuance of restricted common stock pursuant to employee stock-based compensation plans		7	(7)
Cancellation of restricted common stock pursuant to employee stock-based compensation plans		(1)	1
Repurchase and cancellation of common stock pursuant to employee stock-based compensation plans		(2)	(4,433)
Issuance of common stock pursuant to employee stock purchase plan			1,442
Exercise of stock options			44
Stock-based compensation expense			12,152
Stock-based compensation income tax benefits			465
Repurchase of common stock pursuant to Board-approved stock repurchase program				(9,930)
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 gains (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, shares		(750)
Issuance of common stock pursuant to employee stock purchase plan, shares		103
Exercise of stock options, shares		3
Issuance of restricted common stock pursuant to employee stock-based compensation plans, shares		746
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, shares		(231)
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
Issuance of restricted common stock pursuant to employee stock-based compensation plans		8	(8)
Cancellation of restricted common stock pursuant to employee stock-based compensation plans		0	0
Repurchase and cancellation of common stock pursuant to employee stock-based compensation plans		0	(3,208)
Issuance of common stock pursuant to employee stock purchase plan			1,394
Exercise of stock options			502
Stock-based compensation expense			13,431
Stock-based compensation income tax benefits			10
Repurchase of common stock pursuant to Board-approved stock repurchase program				(13,350)
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 gains (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, shares		(823)
Issuance of common stock pursuant to employee stock purchase plan, shares		94
Exercise of stock options, shares		40
Issuance of restricted common stock pursuant to employee stock-based compensation plans, shares		873
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, shares		(195)
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
Issuance of restricted common stock pursuant to employee stock-based compensation plans		8	(8)
Cancellation of restricted common stock pursuant to employee stock-based compensation plans		0	0
Repurchase and cancellation of common stock pursuant to employee stock-based compensation plans		(3)	(5,346)
Issuance of common stock pursuant to employee stock purchase plan			1,347
Exercise of stock options			244
Stock-based compensation expense			14,796
Stock-based compensation income tax benefits			660
Repurchase of common stock pursuant to Board-approved stock repurchase program				(10,129)
Net income	51,351				51,351
Declaration of cash dividends					(15,214)
Net unrealized gains (losses) on short-term investments						38
Net unrealized gains (losses) on pension plan and prior service costs						1,761
Net unrealized gains (losses) on change in fair value of interest rate swap contracts	560					560
Foreign currency translation						(600)
Repurchase of common stock pursuant to Board -approved stock repurchase program, shares		(500)
Issuance of common stock pursuant to employee stock purchase plan, shares		68
Exercise of stock options, shares		20
Issuance of restricted common stock pursuant to employee stock-based compensation plans, shares		840
Cancellation of unvested restricted common stock pursuant to employee stock-based compensation plans, shares		(153)
Repurchase and cancellation of common stock pursuant to employee stock-based compensation plans, shares		(264)
Balance, end of period at Dec. 31, 2013	$ 366,104	$ 658	$ 473,190	$ (738,372)	$ 629,011	$ 1,617
Balance, end of period, shares at Dec. 31, 2013	33,745	33,745