LONG-TERM DEBT - Summary of interest expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Debt Disclosure [Abstract]
Interest on debt	$ 6,488	$ 2,975
Net revenue payments on financing arrangement	888	0
Paid-in-kind interest on term loans	1,590	12,213
Amortization of debt financing costs	803	3,241
Amortization of discount on term loans	1,657	14,398
Total	$ 11,426	$ 32,827