LOSS PER COMMON SHARE - Shares excluded from the computation of weighted average diluted shares outstanding (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Anti-dilutive securities excluded
Anti-dilutive securities excluded (in shares)	4,872,337	7,056,109	4,952,862	5,950,923
Service-based and earned performance-based stock options
Anti-dilutive securities excluded
Anti-dilutive securities excluded (in shares)	3,634,546	3,907,277	3,556,237	3,983,767
Unearned performance-based stock options
Anti-dilutive securities excluded
Anti-dilutive securities excluded (in shares)	574,138	574,138	574,138	574,138
Weighted average service-based RSUs
Anti-dilutive securities excluded
Anti-dilutive securities excluded (in shares)	663,653	285,386	804,761	367,970
Weighted average performance based RSUs
Anti-dilutive securities excluded
Anti-dilutive securities excluded (in shares)		2,267,384		1,015,331
Weighted average RSAs
Anti-dilutive securities excluded
Anti-dilutive securities excluded (in shares)		21,924	17,726	9,717