Statements of Operations and Comprehensive Loss (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Operating expenses include stock-based compensation as follows:
Total stock-based compensation	$ 743	$ 805
Research and development
Operating expenses include stock-based compensation as follows:
Total stock-based compensation	181	162
General and administrative
Operating expenses include stock-based compensation as follows:
Total stock-based compensation	485	585
Sales and marketing
Operating expenses include stock-based compensation as follows:
Total stock-based compensation	$ 77	$ 58