Stock Compensation (Tables)

6 Months Ended

Jun. 30, 2020

Share-based Payment Arrangement [Abstract]

Schedule of Other Share-based Compensation, Activity

A summary of unvested restricted stock unit activity for the six months ended June 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	12,299,276	$	0.88
Vested	(2,032,476)	$	2.77
Forfeited and canceled	(3,268,027)	$	2.51
Balance as of June 30, 2020	18,614,657	$	1.36

Schedule of Share-based Compensation, Stock Options, Activity

A summary of stock option activity for the six months ended June 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	749,111	$	1.17
Exercised	(142,729)	$	1.08
Forfeited and canceled	(2,117,240)	$	1.71
Balance as of June 30, 2020	5,696,875	$	1.94	$	2

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:

	Six Months Ended June 30,
	2020	2019
Volatility	73%	57%
Expected life (in years)	6.11 - 6.12	6.06
Risk-free interest rate	0.84% - 1.47%	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”):

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