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	3 Months Ended
	Mar. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Shares, Outstanding, Beginning Balance	5,131
Shares, Granted	241
Shares, Exercised	(109)
Shares, Forfeited	(25)
Shares, Outstanding, Ending Balance	5,238
Shares,Expected to vest	5,238
Weighted Average Exercise Price, Outstanding, Beginning balance	$ 58.71
Weighted Average Exercise Price, Granted	$ 155.65
Weighted Average Exercise Price, Exercised	$ 23.49
Weighted Average Exercise Price, Forfeited	$ 105.36
Weighted Average Exercise Price, Outstanding, Ending balance	$ 63.68
Weighted Average Exercise Price, Expected to vest	$ 63.68
Options Exercisable at End of Period, Outstanding, Beginning Balance	2,370
Options Exercisable at End of Period, Outstanding, Ending Balance	2,290
Weighted Average Exercise Price of Exercisable Options, Outstanding, Beginning Balance	$ 21.75
Weighted Average Exercise Price of Exercisable Options, Outstanding, Ending Balance	$ 22.40
Weighted Average Fair Value of Options Granted During the Period, Granted	$ 38.12
Aggregate Intrinsic Value, Outstanding, Beginning Balance	$ 461,770
Aggregate Intrinsic Value, Exercised	13,850
Aggregate Intrinsic Value, Outstanding, Ending Balance	$ 456,995