STOCK-BASED COMPENSATION - Compensation expense (Details) - USD ($) $ in Thousands, shares in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Employee Stock Purchase Plan 2016 [Member]
Discount from market price (as a percent)			15.00%
Allocated Share-based Compensation Expense	$ 32	$ 30	$ 118	$ 90
Stock-based compensation shares available	0.2		0.2
Stock Incentive Plan 2008 [Member]
Allocated Share-based Compensation Expense	$ 2,351	2,440	$ 10,425	6,683
Stock-based compensation shares available	1.1		1.1
Cost of sales [Member] \| Employee Stock Purchase Plan 2016 [Member]
Allocated Share-based Compensation Expense	$ 3	4	$ 14	10
Cost of sales [Member] \| Stock Incentive Plan 2008 [Member]
Allocated Share-based Compensation Expense	34	26	93	75
Research and development Expense [Member] \| Employee Stock Purchase Plan 2016 [Member]
Allocated Share-based Compensation Expense	6	7	25	16
Research and development Expense [Member] \| Stock Incentive Plan 2008 [Member]
Allocated Share-based Compensation Expense	117	213	450	545
Selling, general and administrative Expenses [Member] \| Employee Stock Purchase Plan 2016 [Member]
Allocated Share-based Compensation Expense	23	19	79	64
Selling, general and administrative Expenses [Member] \| Stock Incentive Plan 2008 [Member]
Allocated Share-based Compensation Expense	$ 2,200	$ 2,201	$ 9,882	$ 6,063

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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Discount rate from fair value on purchase date that participants pay for shares.

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The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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