STOCK-BASED COMPENSATION - Stock Options Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Shares
Options granted (in shares)	0
Options exercised (in shares)	0	0
Stock Options | The 2004 Plan
Shares
Options outstanding at the beginning of the period (in shares)	345,206
Options granted (in shares)	0
Options exercised (in shares)	0
Options forfeited (in shares)	0
Options expired (in shares)	(221,706)
Options outstanding at the end of the period (in shares)	123,500	345,206
Options vested and expected to vest at the end of the period (in shares)	123,500
Options exercisable at the end of the period (in shares)	123,500
Weighted- Average Exercise Price
Options outstanding at the beginning of the period (in dollars per share)	$ 7.29
Options granted (in dollars per share)	0
Options exercised (in dollars per share)	0
Options forfeited (in dollars per share)	0
Options expired (in dollars per share)	7.76
Options outstanding at the end of the period (in dollars per share)	6.43	$ 7.29
Options vested and expected to vest at the end of the period (in dollars per share)	6.43
Options exercisable at the end of the period (in dollars per share)	$ 6.43
Weighted- Average Remaining Contractual Term
Options outstanding at the end of the period	1 year 10 months 24 days
Options vested and expected to vest at the end of the period	1 year 10 months 24 days
Options exercisable at the end of the period	1 year 10 months 24 days
Aggregate Intrinsic Value (in thousands)
Options outstanding at the end of the period	$ 0
Options vested and expected to vest at the end of the period	0
Options exercisable at the end of the period	$ 0
Stock Options | The 2014 Plan
Shares
Options outstanding at the beginning of the period (in shares)	1,178,045
Options granted (in shares)	200,000
Options exercised (in shares)	0
Options forfeited (in shares)	(46,285)
Options expired (in shares)	(367,372)
Options outstanding at the end of the period (in shares)	964,388	1,178,045
Options vested and expected to vest at the end of the period (in shares)	964,388
Options exercisable at the end of the period (in shares)	716,501
Weighted- Average Exercise Price
Options outstanding at the beginning of the period (in dollars per share)	$ 12.64
Options granted (in dollars per share)	0.80
Options exercised (in dollars per share)	0
Options forfeited (in dollars per share)	9.17
Options expired (in dollars per share)	13.68
Options outstanding at the end of the period (in dollars per share)	9.14	$ 12.64
Options vested and expected to vest at the end of the period (in dollars per share)	9.14
Options exercisable at the end of the period (in dollars per share)	$ 11.47
Weighted- Average Remaining Contractual Term
Options outstanding at the end of the period	4 years 9 months 29 days
Options vested and expected to vest at the end of the period	4 years 9 months 29 days
Options exercisable at the end of the period	3 years 7 months 6 days
Aggregate Intrinsic Value (in thousands)
Options outstanding at the end of the period	$ 0
Options vested and expected to vest at the end of the period	0
Options exercisable at the end of the period	$ 0
Stock Options | The 2019 Zyla Plan
Shares
Options outstanding at the beginning of the period (in shares)	0
Options granted (in shares)	4,985,875
Options exercised (in shares)	0
Options forfeited (in shares)	(952,101)
Options expired (in shares)	(90,025)
Options outstanding at the end of the period (in shares)	3,943,749	0
Options vested and expected to vest at the end of the period (in shares)	3,943,749
Options exercisable at the end of the period (in shares)	1,933,604
Weighted- Average Exercise Price
Options outstanding at the beginning of the period (in dollars per share)	$ 0
Options granted (in dollars per share)	0.73
Options exercised (in dollars per share)	0
Options forfeited (in dollars per share)	0.70
Options expired (in dollars per share)	1.12
Options outstanding at the end of the period (in dollars per share)	0.73	$ 0
Options vested and expected to vest at the end of the period (in dollars per share)	0.73
Options exercisable at the end of the period (in dollars per share)	$ 0.80
Weighted- Average Remaining Contractual Term
Options outstanding at the end of the period	9 years 3 months 18 days
Options vested and expected to vest at the end of the period	9 years 3 months 18 days
Options exercisable at the end of the period	9 years 6 months
Aggregate Intrinsic Value (in thousands)
Options outstanding at the end of the period	$ 0
Options vested and expected to vest at the end of the period	0
Options exercisable at the end of the period	$ 0