Stockholders' Equity - Summary of Activity Related to Stock Option Plans (Details) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2017 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Shares available for grant, beginning balance	13,289,953
Options outstanding, number of shares, beginning balance	22,437,347
Shares available for grant, granted	(1,988,266)
Options outstanding, number of shares, exercised	(2,676,918)
Shares available for grant, expired	(1,561)
Options outstanding, number of shares, ending balance	21,747,134
Shares available for grant, ending balance	11,301,687
Options vested and exercisable, number of shares, ending balance	21,747,134
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Options outstanding, weighted-average exercise price, beginning balance (dollars per share) | $ / shares	$ 44.83
Options outstanding, weighted-average exercise price, granted (dollars per share) | $ / shares	151.82
Options outstanding, weighted-average exercise price, exercised (dollars per share) | $ / shares	27.53
Options outstanding, weighted-average exercise price, canceled (dollars per share) | $ / shares	3.25
Options outstanding, weighted-average exercise price, ending balance (dollars per share) | $ / shares	56.74
Options outstanding, weighted-average exercise price, vested and exercisable (dollars per share) | $ / shares	$ 56.74
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Weighted-average remaining contractual term, ending balance (in years)	6 years 16 days
Weighted-average remaining contractual term, vested and exercisable (in years)	6 years 16 days
Aggregate intrinsic value, ending balance | $	$ 2,709,943
Aggregate intrinsic value, vested and exercisable | $	$ 2,709,943