Stockholders' Equity - Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Stock-Based Compensation Expense
Total stock-based compensation expense	$ 742	$ 621
Cost of goods sold
Stock-Based Compensation Expense
Total stock-based compensation expense	60
Research and development
Stock-Based Compensation Expense
Total stock-based compensation expense	107	198
Selling and marketing
Stock-Based Compensation Expense
Total stock-based compensation expense	35	17
General and administrative
Stock-Based Compensation Expense
Total stock-based compensation expense	$ 540	$ 406