Stock Compensation (Tables)

9 Months Ended

Sep. 30, 2020

Share-based Payment Arrangement [Abstract]

Schedule of Other Share-based Compensation, Activity

A summary of unvested restricted stock unit activity for the nine months ended September 30, 2020 is as follows:

	Number of Shares	Weighted- Average Grant Date Fair Value
Balance as of December 31, 2019	11,615,884	$	2.44
Granted	14,164,946	$	0.91
Vested	(4,925,493)	$	1.98
Forfeited and canceled	(4,224,836)	$	2.24
Balance as of September 30, 2020	16,630,501	$	1.32

Schedule of Share-based Compensation, Stock Options, Activity

A summary of stock option activity for the nine months ended September 30, 2020 is as follows: 

	Options Outstanding	Weighted- Average Exercise Price		Aggregate Intrinsic Value (in thousands)
Balance as of December 31, 2019	7,207,733	$	1.94	$	412
Granted	1,927,111	$	1.18
Exercised	(172,729)	$	1.03
Forfeited and canceled	(2,787,141)	$	1.71
Balance as of September 30, 2020	6,174,974	$	1.83	$	227

Schedule of Share-based Payment Award, Valuation Assumptions

The fair value of each option grant was estimated on the date of grant using the Black-Scholes option-valuation model with the following assumptions:

	Nine Months Ended September 30,
	2020	2019
Volatility	73% - 75%	57% - 58%
Expected life (in years)	6.1	6.1
Risk-free interest rate	0.34% - 1.47%	1.62% - 2.57%
Dividend yield	—%	—%

The Company used the following Black-Scholes assumptions in estimating the fair value of the shares under the 2014 Employee Stock Purchase Plan (the “ESPP”):

	Nine Months Ended September 30, 2020
Volatility	71% - 103%
Expected life equals length of offering period (in years)	0.5
Risk-free interest rate	0.13% - 0.95%
Dividend yield	—%