Stock-Based Compensation (Narrative) (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Stock-based compensation expense	$ 5,500,000	$ 6,800,000	$ 10,970,000	$ 13,274,000
Stock-based compensation expense, related tax benefits	1,300,000	1,900,000	2,700,000	3,600,000
Options exercisable	5,848,982		5,848,982
Options vested or expected to vest	6,743,459		6,743,459
Stock Options [Member]
Options exercisable	5,848,982		5,848,982
Options unvested			896,000
Options vested or expected to vest	6,743,459		6,743,459
Expected cancellations and forfeitures			1,523
Intrinsic value of options exercised			700,000	6,300,000
Remaining unrecognized compensation cost related to restricted stock	1,300,000		1,300,000
Weighted-average remaining requisite service period, years			0.80
Restricted Stock [Member]
Remaining unrecognized compensation cost related to restricted stock	$ 23,000,000		$ 23,000,000
Weighted-average remaining requisite service period, years			1.50