INCOME TAXES - Deferred Tax Assets (Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Loss and credit carry-forwards	$ 4,779	$ 0	$ 7,722
Stock-based compensation	1,004	721	549
Inventory Reserve	99	115	494
Intangibles	34	146	0
Other	1,000	910	178
Total deferred tax assets	6,916	1,892	8,943
Valuation allowance	(6,472)	(1,742)	(8,756)
Total deferred tax assets, net of valuation allowance	444	150	187
Deferred tax liabilities:
State taxes (capital)	0	0	(17)
Property and equipment	(245)	(150)	(294)
Intangibles	0	0	(244)
Lease right-of-use assets	(199)
Total deferred tax liabilities	(444)	(150)	(555)
Net deferred tax liabilities	$ 0	$ 0	$ (368)