NET LOSS PER COMMON SHARE - Antidilutive Shares (Details) - shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares excluded from the calculation (in shares)	16,911,846	15,449,154	16,849,452	16,218,443
Restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares excluded from the calculation (in shares)	1,400,555	808,939	1,384,748	704,023
Convertible debt
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares excluded from the calculation (in shares)	7,113,402	7,113,402	7,113,402	7,805,418
Options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares excluded from the calculation (in shares)	8,397,889	7,526,813	8,351,302	7,709,002