Stock-Based Compensation - Stock Option Activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Number of Shares
Number of shares outstanding, beginning of period (in shares)	19,219	14,573	9,336
Number of shares, granted (in shares)	0	6,108	9,022
Number of shares, exercised (in shares)	(4,205)	(740)	(1,870)
Number of shares, forfeited/canceled (in shares)	(2,075)	(722)	(1,915)
Number of shares outstanding, end of period (in shares)	12,939	19,219	14,573	9,336
Number of shares exercisable (in shares)	6,473
Weighted Average Exercise Price
Weighted average exercise price, outstanding, beginning of period (in USD per share)	$ 7.78	$ 4.38	$ 2.77
Weighted average exercise price, granted (in USD per share)	0	15.17	5.22
Weighted average exercise price, exercised (in USD per share)	4.53	2.26	1.62
Weighted average exercise price, forfeited/canceled (in USD per share)	10.63	7.23	3.21
Weighted average exercise price, outstanding, end of period (in USD per share)	8.38	$ 7.78	$ 4.38	$ 2.77
Weighted average exercise price, exercisable (in USD per share)	$ 6.04
Weighted average remaining contractual term (in years), outstanding	7 years 1 month 6 days	8 years	8 years 2 months 12 days	7 years 2 months 12 days
Weighted average remaining contractual term (in years), exercisable	6 years 4 months 24 days
Aggregate intrinsic value, outstanding, beginning of period	$ 277,114	$ 77,020	$ 15,374
Aggregate intrinsic value, exercised	98,378	9,902	7,667
Aggregate intrinsic value, outstanding, end of period	201,608	$ 277,114	$ 77,020	$ 15,374
Aggregate intrinsic value, exercisable	$ 116,016