STOCK-BASED COMPENSATION - Stock Options Activity (Details) - USD ($)
$ / shares in Units, $ in Thousands
 12 Months Ended
Dec. 31, 2021
Dec. 31, 2020
Shares    
Options exercised (in shares) (72,750) 0
Stock Options | The 2004 Plan    
Shares    
Options outstanding at the beginning of the period (in shares) 30,875  
Options granted (in shares) 0  
Options exercised (in shares) 0  
Options forfeited (in shares) 0  
Options expired (in shares) (10,875)  
Options outstanding at the end of the period (in shares) 20,000 30,875
Options vested and expected to vest at the end of the period (in shares) 20,000  
Options exercisable at the end of the period (in shares) 20,000  
Weighted- Average Exercise Price    
Options outstanding at the beginning of the period (in dollars per share) $ 25.71  
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) 20.52  
Options outstanding at the end of the period (in dollars per share) 28.54 $ 25.71
Options vested and expected to vest at the end of the period (in dollars per share) 28.54  
Options exercisable at the end of the period (in dollars per share) $ 28.54  
Weighted- Average Remaining Contractual Term    
Options outstanding at the end of the period 1 year 4 months 24 days  
Options vested and expected to vest at the end of the period 1 year 4 months 24 days  
Options exercisable at the end of the period 1 year 4 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) 232,956  
Options granted (in shares) 2,100,000  
Options exercised (in shares) 0  
Options forfeited (in shares) (259)  
Options expired (in shares) (128,856)  
Options outstanding at the end of the period (in shares) 2,203,841 232,956
Options vested and expected to vest at the end of the period (in shares) 2,203,841  
Options exercisable at the end of the period (in shares) 103,841  
Weighted- Average Exercise Price    
Options outstanding at the beginning of the period (in dollars per share) $ 36.18  
Options granted (in dollars per share) 1.31  
Options exercised (in dollars per share) 0  
Options forfeited (in dollars per share) 25.73  
Options expired (in dollars per share) 44.84  
Options outstanding at the end of the period (in dollars per share) 2.45 $ 36.18
Options vested and expected to vest at the end of the period (in dollars per share) 2.45  
Options exercisable at the end of the period (in dollars per share) $ 25.46  
Weighted- Average Remaining Contractual Term    
Options outstanding at the end of the period 9 years 9 months 18 days  
Options vested and expected to vest at the end of the period 9 years 9 months 18 days  
Options exercisable at the end of the period 6 years 6 months  
Aggregate Intrinsic Value (in thousands)    
Options outstanding at the end of the period $ 1,827  
Options vested and expected to vest at the end of the period 1,827  
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) 985,944  
Options granted (in shares) 0  
Options exercised (in shares) (72,750)  
Options forfeited (in shares) (402,296)  
Options expired (in shares) (476,340)  
Options outstanding at the end of the period (in shares) 34,558 985,944
Options vested and expected to vest at the end of the period (in shares) 34,558  
Options exercisable at the end of the period (in shares) 25,029  
Weighted- Average Exercise Price    
Options outstanding at the beginning of the period (in dollars per share) $ 2.93  
Options granted (in dollars per share) 0  
Options exercised (in dollars per share) 2.40  
Options forfeited (in dollars per share) 2.73  
Options expired (in dollars per share) 2.73  
Options outstanding at the end of the period (in dollars per share) 3.23 $ 2.93
Options vested and expected to vest at the end of the period (in dollars per share) 3.23  
Options exercisable at the end of the period (in dollars per share) $ 3.23  
Weighted- Average Remaining Contractual Term    
Options outstanding at the end of the period 7 years  
Options vested and expected to vest at the end of the period 7 years  
Options exercisable at the end of the period 6 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 $ 54