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	6 Months Ended
	Jun. 30, 2013
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Shares, Outstanding, Beginning Balance	6,565
Shares, Granted	150
Shares, Exercised	(661)
Shares, Forfeited	(79)
Shares, Outstanding, Ending Balance	5,975
Shares, Expected to vest	5,975
Weighted Average Exercise Price, Outstanding, Beginning balance	$ 22.17
Weighted Average Exercise Price, Granted	$ 68.22
Weighted Average Exercise Price, Exercised	$ 18.44
Weighted Average Exercise Price, Forfeited	$ 23.00
Weighted Average Exercise Price, Outstanding, Ending balance	$ 23.74
Weighted Average Exercise Price, Expected to vest	$ 23.74
Options Exercisable at End of Period, Outstanding, Beginning Balance	2,666
Options Exercisable at End of Period, Outstanding, Ending Balance	2,459
Weighted Average Exercise Price of Exercisable Options, Outstanding, Beginning Balance	$ 14.71
Weighted Average Exercise Price of Exercisable Options, Outstanding, Ending Balance	$ 16.07
Weighted Average Fair Value of Options Granted During the Period, Granted	$ 19.25
Aggregate Intrinsic Value, Outstanding, Beginning Balance	$ 206,636
Aggregate Intrinsic Value, Exercised	41,550
Aggregate Intrinsic Value, Outstanding, Ending Balance	$ 343,967