Share Based Compensation - Summary of Changes in Number of Shares of Common Stock Under Option (Detail) $ / shares in Units, shares in Thousands, $ in Thousands	9 Months Ended
	Sep. 30, 2015 USD ($) $ / shares shares
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Shares, Outstanding, Beginning Balance | shares	5,131
Shares, Granted | shares	575
Shares, Exercised | shares	(477)
Shares, Forfeited | shares	(112)
Shares, Outstanding, Ending Balance | shares	5,117
Shares,Expected to vest | shares	5,117
Weighted Average Exercise Price, Outstanding, Beginning balance	$ 58.71
Weighted Average Exercise Price, Granted	155.69
Weighted Average Exercise Price, Exercised	29.31
Weighted Average Exercise Price, Forfeited	106.66
Weighted Average Exercise Price, Outstanding, Ending balance	71.30
Weighted Average Exercise Price, Expected to vest	$ 71.30
Options Exercisable at End of Period, Outstanding, Beginning Balance | shares	2,370
Options Exercisable at End of Period, Outstanding, Ending Balance | shares	2,578
Weighted Average Exercise Price of Exercisable Options, Outstanding, Beginning Balance	$ 21.75
Weighted Average Exercise Price of Exercisable Options, Outstanding, Ending Balance	26.49
Weighted Average Fair Value of Options Granted During the Period, Granted	$ 35.89
Aggregate Intrinsic Value, Outstanding, Beginning Balance | $	$ 461,770
Aggregate Intrinsic Value, Exercised | $	51,624
Aggregate Intrinsic Value, Outstanding, Ending Balance | $	$ 339,387