Stock-Based Compensation - Valuation Assumptions (Details) - $ / shares	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Employee stock options
Valuation Assumptions
Expected term (in years)	6 years 29 days
Expected volatility, low end of range (as a percent)	51.90%	48.30%
Expected volatility, high end of range (as a percent)	51.90%	66.50%
Risk-free interest rate, low end of range (as a percent)	1.30%	2.40%
Risk-free interest rate, high end of range (as a percent)	1.40%	2.50%
Performance-based stock options
Valuation Assumptions
Asset volatility (as a percent)	40.00%
Equity volatility (as a percent)	45.00%
Discount rate (as a percent)	14.00%
Stock price at grant date (in dollars per share)	$ 31.7
Minimum | Employee stock options
Valuation Assumptions
Fair value of common stock (in dollars per share)	117.9	$ 111.3
Expected term (in years)		3 months 29 days
Maximum | Employee stock options
Valuation Assumptions
Fair value of common stock (in dollars per share)	$ 126.7	$ 130.7
Expected term (in years)		6 years 29 days