Stock Incentive Plans - Stock-Based Compensation (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Stock Based Compensation
Total stock-based compensation expense	$ 760	$ 427
Research and development expense
Stock Based Compensation
Total stock-based compensation expense	202	67
Sales and marketing expense
Stock Based Compensation
Total stock-based compensation expense	56	34
General and administrative expense
Stock Based Compensation
Total stock-based compensation expense	$ 502	$ 326
Stock options and RSUs
Stock Based Compensation
Expected weighted average period to be recognized	1 year 9 months 29 days
Employee stock options
Estimated grant-date fair value of stock options calculated using the Black-Scholes option-pricing model
Weighted-average volatility (as a percent)	150.10%
Weighted-average expected term (years)	5 years	5 years 9 months 18 days
Risk-free interest rate (as a percent)	0.50%
Minimum | Employee stock options
Estimated grant-date fair value of stock options calculated using the Black-Scholes option-pricing model
Weighted-average volatility (as a percent)		108.30%
Risk-free interest rate (as a percent)		2.50%
Maximum | Employee stock options
Estimated grant-date fair value of stock options calculated using the Black-Scholes option-pricing model
Weighted-average volatility (as a percent)		108.50%
Risk-free interest rate (as a percent)		2.60%