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, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Shares, Outstanding, Beginning Balance	5,331
Shares, Granted	548
Shares, Exercised	(1,243)
Shares, Forfeited	(204)
Shares, Outstanding, Ending Balance	4,432
Shares, Vested and expected to vest	4,432
Weighted Average Exercise Price, Outstanding, Beginning balance	$ 25.68
Weighted Average Exercise Price, Granted	$ 121.90
Weighted Average Exercise Price, Exercised	$ 17.64
Weighted Average Exercise Price, Forfeited	$ 48.98
Weighted Average Exercise Price, Outstanding, Ending balance	$ 38.52
Weighted Average Exercise Price, Expected to vest	$ 38.52
Options Exercisable at End of Period, Outstanding, Beginning Balance	2,589
Options Exercisable at End of Period, Outstanding, Ending Balance	2,487
Weighted Average Exercise Price of Exercisable Options, Outstanding, Beginning Balance	$ 16.57
Weighted Average Exercise Price of Exercisable Options, Outstanding, Ending Balance	$ 22.02
Weighted Average Fair Value of Options Granted During the Period, Granted	$ 36.00
Aggregate Intrinsic Value, Outstanding, Beginning Balance	$ 487,673
Aggregate Intrinsic Value, Exercised	154,719
Aggregate Intrinsic Value, Outstanding, Ending Balance	$ 459,142