Quarterly report pursuant to Section 13 or 15(d)

Stock-Based Compensation - Weighted-Average Assumptions Used to Estimate Fair Value of Options Granted (Details)

v3.19.2
Stock-Based Compensation - Weighted-Average Assumptions Used to Estimate Fair Value of Options Granted (Details) - Stock options - $ / shares
3 Months Ended 6 Months Ended
Jun. 30, 2019
Jun. 30, 2018
Jun. 30, 2019
Jun. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Volatility (percent)   77.81% 90.15% 77.81%
Risk free interest rate (percent)   2.89% 2.54% 2.89%
Dividend yield (percent) 0.00% 0.00% 0.00% 0.00%
Term (years)   6 years 5 months 25 days 6 years 3 months 26 days 6 years 5 months 25 days
Weighted-average fair value of options granted during the period (usd per share)   $ 0.63 $ 0.34 $ 0.63