INDEBTEDNESS - Summary of interest expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Debt Disclosure [Abstract]
Interest on debt	$ 1,501	$ 1,441
Net revenue payments on financing arrangement	1,594	0
Paid-in-kind interest on term loans	0	1,590
Amortization of debt financing costs	707	140
Amortization of discount on term loans	0	1,657
Total	$ 3,802	$ 4,828