Stockholders' Equity - Activity Related to Stock Option Plans (Details) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2020 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Shares available for grant, beginning balance (in shares)	6,111,561
Options outstanding, number of shares, beginning balance (in shares)	20,859,326
Options outstanding, number of shares granted (in shares)	(581,455)
Options outstanding, number of shares granted (in shares)	581,455
Options outstanding, number of shares, exercised (in shares)	(973,969)
Options outstanding, number of shares expired (in shares)	(48)
Shares available for grant, ending balance (in shares)	5,530,106
Options outstanding, number of shares, ending balance (in shares)	20,466,764
Options vested and exercisable, number of shares, ending balance (in shares)	20,466,764
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	$ 124.28
Options outstanding, weighted-average exercise price, granted (dollars per share) | $ / shares	354.55
Options outstanding, weighted-average exercise price, exercised (dollars per share) | $ / shares	45.77
Options expired, weighted-average exercise price (dollars per share) | $ / shares	9.96
Options outstanding, weighted-average exercise price, ending balance (dollars per share) | $ / shares	134.56
Options outstanding, weighted-average exercise price, vested and exercisable (dollars per share) | $ / shares	$ 134.56
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Aggregate intrinsic value | $	$ 4,937
Weighted-average remaining contractual term (in years)	5 years 6 months 25 days