Consolidated Statements Of Stockholders' Equity (USD $)	Class A Common Stock [Member]	Additional Paid-in Capital [Member]	Treasury Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Total
Beginning Balance at Dec. 31, 2008	$ 722,000	$ 144,861,000	$ (344,147,000)	$ 922,091,000	$ (12,789,000)	$ 710,738,000
Repurchase of Class A Common Stock			(65,445,000)			(65,445,000)
Issuance of treasury shares upon exercise of stock options, purchases under stock purchase plan and grants of restricted stock awards		(18,789,000)	23,761,000			4,972,000
Additional tax benefit resulting from exercise of options		(1,435,000)				(1,435,000)
Equity-based compensation		11,467,000				11,467,000
Net income				47,104,000		47,104,000
Unrealized holding gain (loss) on investments (net of income taxes)					737,000	737,000
Unrealized holding gain (loss) on hedging transactions (net of income taxes)					19,000	19,000
Foreign currency translation adjustment					3,972,000	3,972,000
Ending Balance at Dec. 31, 2009	722,000	136,104,000	(385,831,000)	969,195,000	(8,061,000)	712,129,000
Repurchase of Class A Common Stock			(102,091,000)			(102,091,000)
Issuance of treasury shares upon exercise of stock options, purchases under stock purchase plan and grants of restricted stock awards		(16,918,000)	25,893,000			8,975,000
Additional tax benefit resulting from exercise of options		(1,342,000)				(1,342,000)
Equity-based compensation		11,871,000				11,871,000
Net income				101,778,000		101,778,000
Unrealized holding gain (loss) on investments (net of income taxes)					(406,000)	(406,000)
Unrealized holding gain (loss) on hedging transactions (net of income taxes)					(949,000)	(949,000)
Foreign currency translation adjustment					67,000	67,000
Ending Balance at Dec. 31, 2010	722,000	129,715,000	(462,029,000)	1,070,973,000	(9,349,000)	730,032,000
Repurchase of Class A Common Stock			(160,200,000)			(160,200,000)
Issuance of treasury shares upon exercise of stock options, purchases under stock purchase plan and grants of restricted stock awards		(12,598,000)	25,607,000			13,009,000
Additional tax benefit resulting from exercise of options		210,000				210,000
Equity-based compensation		14,095,000				14,095,000
Net income				174,643,000		174,643,000
Unrealized holding gain (loss) on investments (net of income taxes)					(385,000)	(385,000)
Unrealized holding gain (loss) on hedging transactions (net of income taxes)					6,209,000	6,209,000
Foreign currency translation adjustment					(688,000)	(688,000)
Ending Balance at Dec. 31, 2011	$ 722,000	$ 131,422,000	$ (596,622,000)	$ 1,245,616,000	$ (4,213,000)	$ 776,925,000