CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (USD $) In Thousands, unless otherwise specified	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive (Loss) Income	Retained Earnings (Accumulated Deficit)
Beginning Balance at Dec. 31, 2009	$ 664,579	$ 21,864	$ 1,202,426	$ (2,330)	$ (557,381)
Beginning Balance, Shares at Dec. 31, 2009		174,908
Issuance of stock to employees under benefit plans, net of shares withheld for payroll tax (in shares)		7,127
Issuance of stock to employees under benefit plans, net of shares withheld for payroll tax	37,410	891	36,519
Stock-based compensation expense	30,580		30,580
Net income	384,820				384,820
Unrealized gain on marketable securities
Unrealized gain on marketable securities, net of tax of $(169) in 2012, $666 in 2011 and $0 in 2010	1,466			1,466
Less: reclassification adjustment for gains (losses) included in net income	93			93
Foreign currency translation adjustment	(349)			(349)
Prior service cost arising during period	3,279			3,279
Amortization of prior service costs, net of tax of $(134) in 2012, $9 in 2011 and $ 0 in 2010	310			310
Ending Balance at Dec. 31, 2010	1,122,188	22,755	1,269,525	2,469	(172,561)
Ending Balance, Shares at Dec. 31, 2010		182,035
Issuance of stock to employees under benefit plans, net of shares withheld for payroll tax (in shares)		4,185
Issuance of stock to employees under benefit plans, net of shares withheld for payroll tax	5,088	522	4,566
Stock-based compensation expense	32,337		32,337
Repurchase of common stock, shares		(2,633)
Repurchase of common stock	(31,175)	(329)	(17,770)		(13,076)
Stock options issued in purchase acquisition	4,472		4,472
Net income	369,873				369,873
Unrealized gain on marketable securities
Unrealized gain on marketable securities, net of tax of $(169) in 2012, $666 in 2011 and $0 in 2010	1,293			1,293
Less: reclassification adjustment for gains (losses) included in net income	(1,296)			(1,296)
Foreign currency translation adjustment	2,266			2,266
Amortization of prior service costs, net of tax of $(134) in 2012, $9 in 2011 and $ 0 in 2010	14			14
Ending Balance at Dec. 31, 2011	1,505,060	22,948	1,293,130	4,746	184,236
Ending Balance, Shares at Dec. 31, 2011		183,587
Issuance of stock to employees under benefit plans, net of shares withheld for payroll tax (in shares)		4,321
Issuance of stock to employees under benefit plans, net of shares withheld for payroll tax	6,894	540	6,354
Stock-based compensation expense	39,920		39,920
Tax benefit related to stock options and restricted stock units	8,358		8,358
Net income	217,049				217,049
Unrealized gain on marketable securities
Unrealized gain on marketable securities, net of tax of $(169) in 2012, $666 in 2011 and $0 in 2010	2,106			2,106
Less: reclassification adjustment for gains (losses) included in net income	(799)			(799)
Amortization of prior service costs, net of tax of $(134) in 2012, $9 in 2011 and $ 0 in 2010	(233)			(233)
Ending Balance at Dec. 31, 2012	$ 1,778,355	$ 23,488	$ 1,347,762	$ 5,820	$ 401,285
Ending Balance, Shares at Dec. 31, 2012		187,908