Stockholders' Equity (Summary Of Activity Under Stock Incentive Plans) (Details) (USD $)	3 Months Ended
	Mar. 31, 2013
Number of Shares [Roll Forward]
Outstanding, Number of Shares, Beginning Balance	8,824,705
Granted, Number of Shares	583,045
Exercised, number of shares	(552,072)
Forfeited, Number of Shares	(398,373)
Expired, Number of Shares	(19,770)
Outstanding, Number of Shares, Ending Balance	8,437,535
Vested and expected to vest, end of period, Number of Shares	7,990,187
Exercisable, end of period, Number of Shares	4,909,164
Weighted Average Exercise Price [Roll Forward]
Outstanding, Weighted Average Exercise Price, Beginning Balance	$ 27.92
Granted, Weighted Average Exercise Price	$ 30.70
Exercised, Weighted Average Exercise Price	$ 23.21
Forfeited, Weighted Average Exercise Price	$ 32.85
Expired, Weighted Average Exercise Price	$ 29.83
Outstanding, Weighted Average Exercise Price, Ending Balance	$ 28.24
Vested and expected to vest, end of period, Weighted Average Exercise Price	$ 28.01
Exercisable, end of period, Weighted Average Exercise Price	$ 25.78
Weighted Average Remaining Contractual Term [Abstract]
Outstanding, ending balance, Weighted Average Remaining Contractual Term	5 years 8 months 20 days
Vested and expected to vest, end of period, Weighted Average Remaining Contractual Term	5 years 7 months 7 days
Exercisable, end of period, Weighted Average Remaining Contractual Term	4 years 5 months 20 days
Outstanding, end of period, Aggregate Intrinsic Value	$ 33,933,099
Vested and expected to vest, end of period, Aggregate Intrinsic Value	33,587,010
Exercisable, end of period, Aggregate Intrinsic Value	$ 28,552,541