DEBT - Summary of Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Long-term Debt, Unclassified [Abstract]
Stated coupon interest	$ 2,938	$ 7,976	$ 7,714	$ 27,096
Amortization of debt discount, debt issuance costs and royalty rights (Non-cash)	103	5,870	5,614	18,090
Other interest expense	0	26	0	82
Total interest expense	$ 3,041	$ 13,872	$ 13,328	$ 45,268