STOCK-BASED COMPENSATION - Option Activity (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Weighted Average Remaining Contractual Terms and Aggregate Intrinsic Value
Aggregate stock-based compensation charges	$ 5.9	$ 3.8	$ 3.6
2017 Omnibus Incentive Plan | Stock Option
Shares
Outstanding, at the beginning (in shares)	2,308,924	2,066,529
Granted (in shares)	2,029,900	631,136
Forfeited or expired (in shares)	(1,223,893)	(388,741)
Outstanding, at the end (in shares)	3,114,931	2,308,924	2,066,529
Exercisable at the end, Shares	1,139,811
Vested and expected to vest (in shares)	3,114,931
Weighted Average Exercise Price
Outstanding, at the beginning (in dollars per shares)	$ 8.39	$ 10.23
Granted (in dollars per shares)	1.75	3.20
Forfeited or expired (in dollars per shares)	2.96	9.73
Outstanding, at the end (in dollars per shares)	6.19	$ 8.39	$ 10.23
Exercisable at the end (in dollars per shares)	9.26
Vested and expected to vest (in dollars per share)	$ 6.19
Weighted Average Remaining Contractual Terms and Aggregate Intrinsic Value
Weighted Average Remaining Contractual Terms (Years)	7 years 10 months 24 days	8 years	8 years 6 months
Exercisable at the end, Weighted Average Remaining Contractual Terms (Years)	6 years 8 months 12 days
Vested and expected to vest (in years)	7 years 10 months 24 days
Aggregate Intrinsic Value, Outstanding, at the beginning (in dollars)	$ 0.2
Aggregate Intrinsic Value, Outstanding at the end (in dollars)	5.9	$ 0.2
Exercisable at the end, Aggregate intrinsic value (in dollars)	0.4
Vested and expected to vest (in dollars)	$ 5.9
Expiration period	10 years