WARRANTS - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands										1 Months Ended					2 Months Ended	9 Months Ended	12 Months Ended			31 Months Ended	34 Months Ended
	Sep. 28, 2020	Jun. 17, 2020	Feb. 11, 2020	Aug. 09, 2019	Jul. 31, 2019	Apr. 25, 2019	Sep. 28, 2017	Apr. 25, 2016	Jun. 17, 2013	Aug. 31, 2020	Jun. 30, 2018	Dec. 31, 2017	Sep. 30, 2016	Apr. 30, 2016	Oct. 31, 2017	Sep. 30, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2017	Apr. 30, 2019	Nov. 30, 2017	Oct. 02, 2017	Sep. 30, 2017
Warrant liabilities
Sales of common stock, net of offering costs (in shares)			201,000	396,000	3,960,560											2,766,798
Sale of common stock, net of offering costs			$ 28,800	$ 3,000	$ 10,000												$ 37,447	$ 9,919
Proceeds from exercises of warrants																	$ 0	$ 1,387
Common stock options
Warrant liabilities
Sales of common stock, net of offering costs (in shares)																	23,776,000	3,961,000
Sale of common stock, net of offering costs																	$ 24	$ 4
Placement Agents
Warrant liabilities
Implied unit price/stock price (in dollars per share)							$ 4.85
Period start after closing																	6 months
Placement Agents | Common stock options
Warrant liabilities
Period end after closing																	2 years
Placement Agents | Private Placement, Offering One
Warrant liabilities
Sold in private placement (in shares)							87,279
Placement Agents | Private Placement, Offering Two
Warrant liabilities
Sold in private placement (in shares)							11,567
Financing Warrant | MDB
Warrant liabilities
Warrants to purchase shares of common stock or units (in shares)									208,763
Exercise price (in dollars per share)									$ 3.35
Warrant exercised/expired (in shares)		62,530																			146,233
Warrants exercisable period from underwriting agreement									6 months
Warrant term									7 years
Underwriting Warrant
Warrant liabilities
Sales of common stock, net of offering costs (in shares)							1,976,919
Underwriting Warrant | Common stock options
Warrant liabilities
Warrants to purchase shares of common stock or units (in shares)																							2,715,000
Warrant exercised/expired (in shares)																			13,575
Underwriting Warrant | Investors, Executives and Board Members
Warrant liabilities
Exercise price (in dollars per share)																							$ 4.25
Underwriting Warrant | Investors, Executives and Board Members | Private Placement
Warrant liabilities
Sales of common stock, net of offering costs (in shares)													135,750
Underwriting Warrant | Placement Agents
Warrant liabilities
Sales of common stock, net of offering costs (in shares)							98,846
Underwriting Warrant | MDB
Warrant liabilities
Warrants to purchase shares of common stock or units (in shares)									310,500
Exercise price (in dollars per share)									$ 7.50
Warrants exercisable period from underwriting agreement									180 days
Warrant term									5 years
Private Placement Warrants
Warrant liabilities
Warrant exercised/expired (in shares)						288,135														971,809
Sale of common stock, net of offering costs												$ 2,400
Non-cash warrant inducement expense												239
Proceeds from exercises of warrants												$ 2,200
Private Placement Warrants | Private Placement
Warrant liabilities
Warrants to purchase shares of common stock or units (in shares)														1,996,880				836,780
Private Placement Warrants | Investors, Executives and Board Members
Warrant liabilities
Exercise price (in dollars per share)								$ 2.86										$ 2.86
Period start after closing								6 months
Period end after closing								36 months
Private Placement Warrants | Investors, Executives and Board Members | Private Placement
Warrant liabilities
Sales of common stock, net of offering costs (in shares)														1,996,880
Private Placement Warrants | Placement Agents
Warrant liabilities
Sales of common stock, net of offering costs (in shares)								99,844				836,780
Implied unit price/stock price (in dollars per share)								$ 2.86
Private Placement Warrants, September 2017
Warrant liabilities
Warrant exercised/expired (in shares)	1,961,000										10,600
Cancellation of warrants (in shares)										5,319
Private Placement Warrants, September 2017 | Private Placement
Warrant liabilities
Warrants to purchase shares of common stock or units (in shares)							1,745,581								1,976,919							231,338
Period start after closing																	6 months
Private Placement Warrants, September 2017 | Investors, Executives and Board Members | Capital Units
Warrant liabilities
Exercise price (in dollars per share)															$ 4.85
Private Placement Warrants, September 2017 | Investors, Executives and Board Members | Private Placement | Capital Units
Warrant liabilities
Sales of common stock, net of offering costs (in shares)															1,976,919
Consulting Warrant | MDB
Warrant liabilities
Warrants to purchase shares of common stock or units (in shares)									222,222
Exercise price (in dollars per share)									$ 0.01
Warrants exercisable period from underwriting agreement									6 months
Warrant term									7 years