STOCK-BASED COMPENSATION - Expense (Details) - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Allocated share-based compensation expense	$ 12,800	$ 9,100	$ 6,700
Employee service share-based compensation, tax benefit from compensation expense	$ 1,600	$ 1,400	$ 1,200
Employee Stock Purchase Plan 2016 [Member]
Discount from market price (as a percent)	15.00%
Employee share plan issued (in shares)	13	6	5
Allocated share-based compensation expense	$ 180	$ 147	$ 102
Stock-based compensation shares available	200
Stock Incentive Plan 2008 [Member]
Allocated share-based compensation expense	$ 12,756	9,070	6,680
Stock-based compensation shares available	1,100
Cost of sales [Member] | Employee Stock Purchase Plan 2016 [Member]
Allocated share-based compensation expense	$ 21	18	11
Cost of sales [Member] | Stock Incentive Plan 2008 [Member]
Allocated share-based compensation expense	115	101	87
Research and development Expense [Member] | Employee Stock Purchase Plan 2016 [Member]
Allocated share-based compensation expense	36	29	16
Research and development Expense [Member] | Stock Incentive Plan 2008 [Member]
Allocated share-based compensation expense	561	756	771
Selling, general and administrative Expenses [Member] | Employee Stock Purchase Plan 2016 [Member]
Allocated share-based compensation expense	123	100	75
Selling, general and administrative Expenses [Member] | Stock Incentive Plan 2008 [Member]
Allocated share-based compensation expense	$ 12,080	$ 8,213	$ 5,822