Stock-Based Compensation Expense (Schedule Of Fixed-Price Stock Options) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011
Stock-Based Compensation Expense [Abstract]
Outstanding at December 31, 2010	1,972,522
Granted, Shares	401,500
Exercised, Shares	(169,350)
Forfeited, Shares	(33,500)
Outstanding at December 31, 2011	2,171,172
Exercisable at December 31, 2011	426,937
Weighted- Average Exercise Price Of Shares, Outstanding at December 31, 2010	$ 24.17
Weighted- Average Exercise Price, Granted	$ 56.34
Weighted- Average Exercise Price, Exercised	$ 13.17
Weighted- Average Exercise Price, Forfeited	$ 34.37
Weighted- Average Exercise Price Of Shares, Outstanding at December 31, 2011	$ 30.82
Weighted- Average Exercise Price, Exercisable at December 31, 2011	$ 22.54
Weighted- Average Remaining Contractual Term (Years), Outstanding at December 31, 2010	7.2
Weighted- Average Remaining Contractual Term (Years), Outstanding at December 31, 2011	7.1
Weighted- Average Remaining Contractual Term (Years), Exercisable at December 31, 2011	4.1
Aggregate Intrinsic Value (in thousands), Outstanding at December 31, 2010	$ 62,357
Aggregate Intrinsic Value (in thousands), Outstanding at December 31, 2011	46,846
Aggregate Intrinsic Value (in thousands), Exercisable at December 31, 2011	$ 12,368