STOCKHOLDERS' EQUITY (DEFICIT) - Warrants (Details) - $ / shares shares in Thousands	9 Months Ended
	Sep. 30, 2021
Warrant Or Right Outstanding [Roll Forward]
Warrants outstanding, beginning balance (in shares)	2,247
Warrants Issued (in shares)	0
Warrants Exercised (in shares)	(2,048)
Warrants Expired (in shares)	0
Warrants outstanding, ending balance (in shares)	199
Warrants, Expiring March 2023
Warrant Or Right Outstanding [Roll Forward]
Exercise price (in dollars per share)	$ 0.55
Warrants outstanding, beginning balance (in shares)	1,705
Warrants Issued (in shares)	0
Warrants Exercised (in shares)	(1,573)
Warrants Expired (in shares)	0
Warrants outstanding, ending balance (in shares)	132
Warrants, Expiring November 2022
Warrant Or Right Outstanding [Roll Forward]
Exercise price (in dollars per share)	$ 0.55
Warrants outstanding, beginning balance (in shares)	487
Warrants Issued (in shares)	0
Warrants Exercised (in shares)	(475)
Warrants Expired (in shares)	0
Warrants outstanding, ending balance (in shares)	12
Warrants, Expiring November 2024
Warrant Or Right Outstanding [Roll Forward]
Exercise price (in dollars per share)	$ 11.83
Warrants outstanding, beginning balance (in shares)	28
Warrants Issued (in shares)	0
Warrants Exercised (in shares)	0
Warrants Expired (in shares)	0
Warrants outstanding, ending balance (in shares)	28
Warrants, Expiring November 2024
Warrant Or Right Outstanding [Roll Forward]
Exercise price (in dollars per share)	$ 11.04
Warrants outstanding, beginning balance (in shares)	27
Warrants Issued (in shares)	0
Warrants Exercised (in shares)	0
Warrants Expired (in shares)	0
Warrants outstanding, ending balance (in shares)	27