STOCKHOLDERS' EQUITY (Common Stock, 2018 Purchase Agreement and LP Purchase Agreement) (Details) - USD ($)									1 Months Ended	3 Months Ended	12 Months Ended			36 Months Ended
	Jun. 20, 2020	Apr. 08, 2020	Mar. 26, 2020	Jan. 14, 2020	Aug. 09, 2019	Feb. 01, 2019	Sep. 14, 2018	Sep. 07, 2018	Apr. 30, 2020	Mar. 25, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2020	Apr. 06, 2020	Jan. 29, 2019	Jan. 01, 2019	Dec. 20, 2018	Dec. 19, 2018	Sep. 06, 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	150,000,000
Proceeds from exercise of warrants												$ 1,575,000
Conversion of convertible debt, plus interest, into common stock											$ 2,176,000	$ 7,553,000
Shares issued (in shares)											17,576,916	7,898,117		17,576,916
Common stock, shares outstanding (in shares)			8,870,129								17,576,916	7,898,117		17,576,916						1,543,724
Issuance of common stock, net of issuance costs											$ 8,929,000	$ 6,628,000
Conversion of debt into stock											$ 2,176,000	$ 7,553,000
Common Stock [Member]
Class of Stock [Line Items]
Common stock issued in connection with the conversion of convertible notes											3,980,145	2,511,173
Conversion of convertible notes into common stock (in shares)											3,908,145	2,511,173
Number of shares converted from debt instrument (in shares)											3,908,145	2,511,173
Common Stock [Member]
Class of Stock [Line Items]
Common stock issued for exercise of warrants												310,200
Warrant exercises in period												310,200
Proceeds from exercise of warrants												$ 1,600,000
Conversion of convertible debt, plus interest, into common stock											$ 2,200,000	7,600,000
Conversion of debt into stock											$ 2,200,000	$ 7,600,000
Preferred Class B
Class of Stock [Line Items]
Number of shares converted (in shares)											0	0
Leviston Resources LLC
Class of Stock [Line Items]
Conversion of convertible debt, plus interest, into common stock												$ 700,000
Conversion of convertible notes into common stock (in shares)												184,357
Number of shares converted from debt instrument (in shares)												184,357
Conversion of debt into stock												$ 700,000
Leviston Resources LLC | Settled Litigation
Class of Stock [Line Items]
Issuance of convertible notes																$ 700,000
Lincoln Park [Member]
Class of Stock [Line Items]
Value of shares issued			$ 10,000,000					$ 10,000,000
New shares issued (in shares)	4,500,000			920,654	1,800,000	1,000,000	466,667	40,000
Shares issued (in shares)											2,960,000			2,960,000	920,654
Share price (in dollars per share)								$ 7.05
Floor price (in dollars per share)								$ 0.10
Shares sold in offering (in shares)			4,980,000								1,040,654	2,778,077	328,590
Maximum percentage of shares issued								19.99%
Maximum number of shares issued								308,590
Beneficial Ownership Cap								4.99%
Issuance of common stock, net of issuance costs											$ 1,400,000		$ 1,400,000	$ 9,400,000
Proceeds from sale of stock												$ 6,600,000
Lincoln Park [Member] | Subsequent Events
Class of Stock [Line Items]
Shares sold in offering (in shares)										500,000
Issuance of common stock, net of issuance costs										$ 1,300,000
Minimum | Lincoln Park [Member]
Class of Stock [Line Items]
Share price (in dollars per share)			$ 1.50					$ 1.50
Maximum | Lincoln Park [Member]
Class of Stock [Line Items]
Value of shares issued								$ 1,000,000
Shares sold in offering (in shares)								30,000
Shares sold in offering based on market price								36,666
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]
Value of shares issued			$ 10,000,000
New shares issued (in shares)		1,770,000	250,000
Share price (in dollars per share)			$ 0.7306
Shares sold in offering (in shares)											4,480,000
Maximum percentage of shares issued			19.99%
Maximum number of shares issued			1,774,024
Beneficial Ownership Cap									4.99%
Issuance of common stock, net of issuance costs											$ 7,500,000
LP 2020 Purchase Agreement [Member] | Minimum | Lincoln Park [Member]
Class of Stock [Line Items]
Share price (in dollars per share)			$ 1.00
LP 2020 Purchase Agreement [Member] | Maximum | Lincoln Park [Member]
Class of Stock [Line Items]
Value of shares issued			$ 1,000,000
Shares sold in offering based on market price			50,000
LP 2020 Purchase Agreement [Member] | Closing Sale Price Above 1.00 [Member] | Maximum
Class of Stock [Line Items]
Shares sold in offering based on market price			80,000
LP 2020 Purchase Agreement [Member] | Closing Sale Price Above 1.50 [Member] | Maximum | Lincoln Park [Member]
Class of Stock [Line Items]
Shares sold in offering based on market price			100,000