STOCK-BASED COMPENSATION - Stock-based compensation expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Employee Stock Purchase Plan 2016 [Member]
Allocated Share-based Compensation Expense	$ 29	$ 30
Stock Incentive Plan 2008 [Member]
Allocated Share-based Compensation Expense	2,395	1,680
Cost of sales [Member] | Employee Stock Purchase Plan 2016 [Member]
Allocated Share-based Compensation Expense	4	3
Cost of sales [Member] | Stock Incentive Plan 2008 [Member]
Allocated Share-based Compensation Expense	26	21
Research and development Expense [Member] | Employee Stock Purchase Plan 2016 [Member]
Allocated Share-based Compensation Expense	7	5
Research and development Expense [Member] | Stock Incentive Plan 2008 [Member]
Allocated Share-based Compensation Expense	187	113
Selling, general and administrative Expenses [Member] | Employee Stock Purchase Plan 2016 [Member]
Allocated Share-based Compensation Expense	18	22
Selling, general and administrative Expenses [Member] | Stock Incentive Plan 2008 [Member]
Allocated Share-based Compensation Expense	$ 2,182	$ 1,546