Stock Compensation - Components of Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 3,598	$ 2,714	$ 2,897
Cost of sales
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	95	142	191
Selling, general and administrative expenses
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	3,192	2,384	2,413
Research and development expenses
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 311	$ 188	$ 293