Stock-Based Compensation - Schedule of Assumptions to Estimate Fair Value of Stock Options for Employees and Non-Employees Using Black-Scholes Option Pricing Model (Details) - Options Issued and Outstanding - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Employees
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Fair value of common stock	$ 2.23		$ 2.23
Expected term (in years)	5 years 6 months		5 years 6 months
Expected volatility	110.20%		110.20%
Expected volatility, minimum		94.50%		93.70%
Expected volatility, maximum		104.80%		104.80%
Risk-free interest rate	0.40%		0.40%
Risk-free interest rate, minimum		1.90%		1.90%
Risk-free interest rate, maximum		2.40%		2.60%
Expected dividend yield	0.00%	0.00%	0.00%	0.00%
Non-employees
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected volatility, minimum	100.80%	93.40%	99.60%	90.00%
Expected volatility, maximum	103.50%	94.20%	103.50%	94.90%
Risk-free interest rate, minimum	0.50%	1.90%	0.50%	1.90%
Risk-free interest rate, maximum	0.60%	2.10%	0.90%	2.60%
Expected dividend yield	0.00%	0.00%	0.00%	0.00%
Minimum [Member] | Employees
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Fair value of common stock		$ 6.97		$ 6.97
Expected term (in years)		5 years 6 months		5 years 6 months
Minimum [Member] | Non-employees
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Fair value of common stock	$ 2.09	$ 8.90	$ 0.96	$ 6.82
Expected term (in years)	7 years	8 years	7 years	8 years
Maximum | Employees
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Fair value of common stock		$ 8.08		$ 8.90
Expected term (in years)		6 years 1 month 6 days		6 years 1 month 6 days
Maximum | Non-employees
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Fair value of common stock	$ 2.18	$ 10.20	$ 2.18	$ 10.20
Expected term (in years)	8 years 9 months 18 days	9 years 8 months 12 days	9 years	10 years