Share-Based Compensation (Stock Option Activity) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011 years	Dec. 31, 2010	Dec. 31, 2009
Share-Based Compensation [Abstract]
Number of Shares, Outstanding Ending Balance	5,836	5,704	5,309
Number of Shares, Granted	831	765	835
Number of Shares, Exercised	(582)	(615)	(425)
Number of Shares, Forfeited	(26)	(18)	(15)
Number of Shares, Outstanding Beginning Balance	6,059	5,836	5,704
Number of Shares, Exercisable at December 31, 2011	3,177
Weighted Average Exercise Price, Outstanding	$ 12.74	$ 11.12	$ 9.69
Weighted Average Exercise Price, Granted	$ 26.83	$ 18.82	$ 17.25
Weighted Average Exercise Price, Exercised	$ 6.10	$ 5.17	$ 5.40
Weighted Average Exercise Price, Forfeited	$ 15.78	$ 16.59	$ 7.80
Weighted Average Exercise Price, Outstanding	$ 15.31	$ 12.74	$ 11.12
Weighted Average Exercise Price, Exercisable at December 31, 2011	$ 11.44
Weighted Average Remaining Contractual Life (Years), Outstanding at December 31, 2011	6
Weighted Average Remaining Contractual Life (Years), Exercisable at December 31, 2011	5
Aggregate Intrinsic Value, Outstanding at December 31, 2011	$ 89,646
Aggregate Intrinsic Value, Exercisable at December 31, 2011	$ 59,293