Summary of Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016
Compensation Related Costs [Abstract]
Shares, Options outstanding as of December 31, 2016		8,856,208
Shares, Granted		801,170
Shares, Exercised		(1,367,307)
Shares, Expired and forfeited		(182,090)
Shares, Options outstanding as of December 31, 2017		8,107,981	8,856,208
Shares, Options unvested at December 31, 2017		1,462,941
Shares, Exercisable at December 31, 2017		6,645,032
Weighted Average Exercise Price, Outstanding as of December 31, 2016		$ 51.13
Weighted Average Exercise Price, Granted		87.74
Weighted Average Exercise Price, Exercised		34.96
Weighted Average Exercise Price, Expired and forfeited		92.98
Weighted Average Exercise Price, Outstanding as of December 31, 2017		56.53	$ 51.13
Weighted Average Exercise Price, Options unvested at December 31, 2017		88.19
Weighted Average Exercise Price, Exercisable at December 31, 2017		$ 49.56
Weighted Average Remaining Years, Options outstanding		5 years 1 month 6 days	5 years 4 months 24 days
Weighted Average Remaining Years, Options unvested at December 31, 2017		8 years 6 months
Weighted Average Remaining Years, Exercisable at December 31, 2017		4 years 3 months 18 days
Aggregate Intrinsic Value, Options outstanding	[1]	$ 281,141	$ 304,356
Aggregate Intrinsic Value, Options unvested at December 31, 2017	[1]	6,313
Aggregate Intrinsic Value, Exercisable at December 31, 2017	[1]	$ 274,828

[1] The aggregate intrinsic value for outstanding options is calculated as the difference between the exercise price of the underlying awards and the quoted price of the Company’s common stock on the Nasdaq Global Select Market as of the last trading day for the respective year. The aggregate intrinsic value of options outstanding and exercisable includes options with an exercise price below $89.17, the closing price of the Company’s common stock on the Nasdaq Global Select Market on December 29, 2017, the last trading day of the year.