Stock Incentive Plans - Stock-Based Compensation (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Stock Based Compensation
Total stock-based compensation expense	$ 749,000	$ 446,000	$ 1,509,000	$ 873,000
Research and development expense
Stock Based Compensation
Total stock-based compensation expense	203,000	149,000	405,000	216,000
Sales and marketing expense
Stock Based Compensation
Total stock-based compensation expense	57,000	12,000	113,000	46,000
General and administrative expense
Stock Based Compensation
Total stock-based compensation expense	489,000	$ 285,000	991,000	$ 611,000
Stock options and RSUs
Stock Based Compensation
Unrecognized stock-based compensation expense	$ 3,693,000		$ 3,693,000
Expected weighted average period to be recognized			1 year 7 months 21 days
Employee stock options
Estimated grant-date fair value of stock options calculated using the Black-Scholes option-pricing model
Weighted-average expected term (years)		5 years 9 months 18 days	5 years
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%	150.10%
Risk-free interest rate (as a percent)		2.50%	0.30%
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%	172.40%
Risk-free interest rate (as a percent)		2.60%	0.50%