Share Based Compensation (Summary Of Changes In Number Of Shares Of Common Stock Under Option) (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	9 Months Ended
	Sep. 30, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, Outstanding, Beginning Balance	8,341
Shares, Granted	1,158
Shares, Exercised	(2,425)
Shares, Forfeited	(44)
Shares, Outstanding, Ending Balance	7,031
Shares, Expected to vest	7,031
Weighted Average Exercise Price, Outstanding, Beginning balance	$ 15.51
Weighted Average Exercise Price, Granted	$ 36.34
Weighted Average Exercise Price, Exercised	$ 8.71
Weighted Average Exercise Price, Forfeited	$ 15.54
Weighted Average Exercise Price, Outstanding, Ending balance	$ 21.22
Weighted Average Exercise Price, Expected to vest	$ 21.22
Options Exercisable at End of Period, Outstanding, Beginning Balance	4,394
Options Exercisable at End of Year, Outstanding, Ending Balance	3,052
Weighted Average Exercise Price of Exercisable Options, Outstanding, Beginning Balance	$ 10.13
Weighted Average Exercise Price of Exercisable Options, Outstanding, Ending Balance	$ 13.72
Weighted Average Fair Value of Options Granted During the Period, Granted	$ 10.65
Outstanding at December 31, 2011	$ 119,802
Exercised	87,521
Outstanding at September 30, 2012	$ 165,792