Stockholders' Equity - Stock Option Activities (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Additional information pertaining to stock options
Fair market value of common stock (in usd per share)	$ 65.58
Stock options outstanding
Number of Shares
Outstanding, beginning balance (in shares)	3,122
Options granted (in shares)	353
Options exercised (in shares)	(932)
Options forfeited or expired (in shares)	(13)
Outstanding, ending balance (in shares)	2,530	3,122
Weighted Average Exercise Price
Outstanding, beginning balance, weighted-average exercise price (in USD per share)	$ 12.52
Options granted, weighted-average exercise price (in USD per share)	51.30
Options exercised, weighted-average exercise price (in USD per share)	8.27
Options forfeited or expired, weighted-average exercise price (in USD per share)	30.18
Outstanding, ending balance, weighted-average exercise price (in USD per share)	$ 19.38	$ 12.52
Weighted average remaining contractual life	6 years
Outstanding, Aggregate intrinsic value	$ 116,874
Vested and expected to vest as of December 31, 2019
Vested and expected to vest (in shares)	2,530
Outstanding, weighted-average exercise price (in USD per share)	$ 19.38
Outstanding, weighted average remaining contractual life	6 years
Vested and expected to vest, aggregate intrinsic value	$ 116,874
Additional information pertaining to stock options
Exercisable (in shares)	1,744
Exercisable, weighted-average exercise price (in USD per share)	$ 11.26
Exercisable, weighted average remaining contractual life	4 years 10 months 24 days
Exercisable, aggregate intrinsic value	$ 94,722
Weighted average grant date fair value per share of options granted (in USD per share)	$ 24.06	$ 16.33	$ 8.81
Intrinsic value of options exercised	$ 42,204	$ 34,785	$ 33,820
Total fair value of options vested during the period	5,342	4,744	7,296
Cash received from options exercised	$ 7,705	$ 7,779	$ 6,047