NET LOSS PER COMMON SHARE - Antidilutive Shares (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Total anti-dilutive shares
Anti-dilutive shares excluded from the calculation (in shares)	17,984,802	16,911,846	18,012,120	16,849,452
Restricted stock
Total anti-dilutive shares
Anti-dilutive shares excluded from the calculation (in shares)	1,538,792	1,400,555	1,588,737	1,384,748
Convertible debt
Total anti-dilutive shares
Anti-dilutive shares excluded from the calculation (in shares)	7,113,402	7,113,402	7,113,402	7,113,402
Options
Total anti-dilutive shares
Anti-dilutive shares excluded from the calculation (in shares)	9,332,608	8,397,889	9,309,981	8,351,302