Stockholders' Equity - Summary of Stock Option Activity (Detail) (Stock options [Member], USD $)	6 Months Ended
	Jun. 30, 2014
Stock options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Options, Outstanding at December 31, 2013	6,614,534
Number of Options, Granted	798,307
Number of Options, Exercised	(812,059)
Number of Options, Forfeited	(179,472)
Number of Options, Expired	(243)
Number of Options, Outstanding at June 30, 2014	6,421,067
Number of Options, Vested and exercisable at June 30, 2014	4,164,218
Weighted Average Exercise Price, Outstanding at December 31, 2013	$ 22.12
Weighted Average Exercise Price, Granted	$ 74.77
Weighted Average Exercise Price, Exercised	$ 10.71
Weighted Average Exercise Price, Forfeited	$ 51.62
Weighted Average Exercise Price, Expired	$ 48.18
Weighted Average Exercise Price, Outstanding at June 30, 2014	$ 29.28
Weighted Average Exercise Price, Vested and exercisable at June 30, 2014	$ 17.71
Weighted Average Remaining Contractual Term (in years), Outstanding at June 30, 2014	6 years 7 months 13 days
Weighted Average Remaining Contractual Term (in years), Vested and exercisable at June 30, 2014	5 years 6 months 18 days
Aggregate Intrinsic Value, Outstanding at June 30, 2014	$ 308.6
Aggregate Intrinsic Value, Vested and exercisable at June 30, 2014	$ 247.2