STOCKHOLDERS' EQUITY (Common Stock, 2018 Purchase Agreement and LP Purchase Agreement) (Details) - USD ($)					3 Months Ended		6 Months Ended		14 Months Ended
	Jun. 26, 2020	Apr. 08, 2020	Mar. 26, 2020	Sep. 07, 2018	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Jun. 14, 2021	Dec. 31, 2020	Jan. 01, 2019	Dec. 20, 2018
Class of Stock [Line Items]
Common stock, shares authorized (in shares)					150,000,000		150,000,000			150,000,000	250,000,000	150,000,000
Proceeds from exercise of warrants							$ 400,000
Issuance of common stock in connection with at the market offering, net of issuance costs					$ 14,947,000		$ 14,947,000
Shares issued (in shares)					22,707,063		22,707,063			17,576,916
Common stock, shares outstanding (in shares)					22,707,063		22,707,063			17,576,916
Issuance of common stock, net of issuance costs							$ 16,207,000	$ 2,607,000
Issuance of common stock for consulting services							$ 150,000
Conversion of debt into stock								$ 2,176,000
Common Stock [Member]
Class of Stock [Line Items]
Proceeds upon issuance of common stock from exercise of warrants (in shares)					74,000		74,000
Proceeds from exercise of warrants					$ 400,000
Common stock issued in connection with the conversion of convertible notes					0	3,480,148	0	3,908,145
Issuance of common stock in connection with at the market offering, net of issuance costs					$ 45,000		$ 45,000
Shares issued (in shares)					4,501,000		4,501,000
Issuance of common stock for consulting services (in shares)					0		55,147
Issuance of common stock for consulting services					$ 0		$ 200,000
Number of shares converted from debt instrument (in shares)						3,480,148		3,908,145
Conversion of debt into stock						$ 1,800,000		$ 2,200,000
Preferred Class B
Class of Stock [Line Items]
Conversion price (in dollars per share)					$ 0.40		$ 0.40
Lincoln Park [Member]
Class of Stock [Line Items]
Issuance of common stock in connection with at the market offering, net of issuance costs			$ 10,000,000.0	$ 10,000,000
Shares issued (in shares)	4,500,000
Shares issued (in shares)					3,460,000		3,460,000
Shares sold in offering (in shares)						110,642		1,040,654	4,980,000
Issuance of common stock, net of issuance costs						$ 100,000		$ 1,400,000
LP 2020 Purchase Agreement [Member]
Class of Stock [Line Items]
Issuance of common stock, net of issuance costs							$ 8,800,000
LP 2020 Purchase Agreement [Member] | Lincoln Park [Member]
Class of Stock [Line Items]
Issuance of common stock in connection with at the market offering, net of issuance costs			$ 10,000,000
Shares issued (in shares)		1,770,000	250,000
Shares sold in offering (in shares)					0		500,000
Issuance of common stock, net of issuance costs					$ 0		$ 1,300,000