Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2020

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Schedule of performance-based awards

Period Granted	Options Granted	RSUs Granted	Options Vested	RSUs Vested	Milestone	Valuation Method
(in thousands)
Q1 2019	200	300	38	69	(1)	Monte-Carlo Simulation
Q2 2019	—	188	—	—	(2)	Fair Market Value
Q3 2019	—	50	—	—	(1)	Monte-Carlo Simulation
Q1 2020	150	300	—	—	(1)	Monte-Carlo Simulation
Q1 2020	—	436	—	—	(3)	Fair Market Value
Q1 2020	129	—	—	—	(3)	Black-Scholes-Merton

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(1) The awards will vest based on the achievement of certain values of the Company’s common stock at multiple thresholds within certain periods and are contingent upon the completion of requisite service through the date of such vesting.

(2) The vesting of the awards will be triggered after the end of the achievement milestone, as measured by the Company.

(3) The awards will vest based on achievement of certain revenue target and are contingent upon the completion of requisite service through the date of such vesting.

Summary of stock option activity

	Outstanding Options
					Weighted-
			Weighted-		Average
	Shares		Average		Remaining	Aggregate
	Available for	Number of	Exercise		Contractual	Intrinsic
(in thousands, except for contractual life and exercise price)	Grant	Shares	Price		Life	Value
					(In years)
Balance at December 31, 2019	6,416	8,497	$	10.39	6.88	$	197,955
Additional shares authorized	3,120	—
Options granted	(409)	409	$	25.51
Options exercised	—	(356)	$	10.74
Options forfeited/cancelled	45	(45)	$	17.76
RSUs granted	(4,140)	—
RSUs forfeited/cancelled	88	—
Balance at March 31, 2020	5,120	8,505	$	11.07	6.78	$	159,957
Exercisable at March 31, 2020		5,078	$	7.85	5.54	$	111,759
Vested and expected to vest at March 31, 2020		8,316	$	10.96	6.74	$	157,297

Restricted stock units

		Weighted-
		Average
		Grant Date
(in thousands, except for grant date fair value)	Shares	Fair Value
Balance at December 31, 2019	2,404	$	19.86
Granted	2,071	$	26.67
Vested	(291)	$	16.88
Cancelled/forfeited	(44)	$	21.35
Balance at March 31, 2020	4,140	$	22.48

Performance-based awards

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Schedule of assumptions used in valuation of fair value

	March 31,
	2020
Risk-free interest rate		0.61	%	—	1.64	%
Expected dividend yield					0.00	%
Expected volatility		55	%	—	65	%
Expected term (years)		5.25		—	7.25

Employee stock options

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Schedule of assumptions used in valuation of fair value

	Three months ended March 31,
	2020					2019
Expected term (years)	5.27		—	10.0		5.33		—	5.53
Expected volatility	49.94	%	—	58.53	%	42.53	%	—	42.75	%
Expected dividend rate				0.00	%				0.00	%
Risk-free interest rate	0.44	%	—	1.70	%	2.26	%	—	2.60	%