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, 2013
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Shares, Outstanding, Beginning Balance	6,565
Shares, Granted	271
Shares, Exercised	(1,117)
Shares, Forfeited	(116)
Shares, Outstanding, Ending Balance	5,603
Shares, Expected to vest	5,603
Weighted Average Exercise Price, Outstanding, Beginning balance	$ 22.17
Weighted Average Exercise Price, Granted	$ 76.86
Weighted Average Exercise Price, Exercised	$ 20.30
Weighted Average Exercise Price, Forfeited	$ 28.68
Weighted Average Exercise Price, Outstanding, Ending balance	$ 25.06
Weighted Average Exercise Price, Expected to vest	$ 25.06
Options Exercisable at End of Period, Outstanding, Beginning Balance	2,666
Options Exercisable at End of Period, Outstanding, Ending Balance	2,802
Weighted Average Exercise Price of Exercisable Options, Outstanding, Beginning Balance	$ 14.71
Weighted Average Exercise Price of Exercisable Options, Outstanding, Ending Balance	$ 16.96
Weighted Average Fair Value of Options Granted During the Period, Granted	$ 21.86
Aggregate Intrinsic Value, Outstanding, Beginning Balance	$ 206,636
Aggregate Intrinsic Value, Exercised	100,381
Aggregate Intrinsic Value, Outstanding, Ending Balance	$ 476,854