Summary of Significant Accounting Policies - (Tables)

6 Months Ended

Jun. 30, 2019

Accounting Policies [Abstract]

Schedule of weighted-average assumptions used to estimate grant date fair value of stock options

The weighted-average assumptions used to estimate grant date fair value of stock options using the Black-Scholes option pricing model were as follows for the three and six months ended June 30, 2019 and 2018:

	Three Months Ended June 30,		Six Months Ended June 30,
	2019	2018	2019	2018
Expected common stock price volatility	88%	85%	87%	83%
Risk-free interest rate	2.15%-2.31%	2.83%-2.83%	2.15%-2.54%	2.39%-2.83%
Expected term of options (years)	5.3	5.3	5.6	5.6
Expected dividend yield	—	—	—	—