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DEBT - Summary of Long-term Debt (Details) - USD ($) $ in Thousands	Jun. 30, 2020	May 20, 2020	Dec. 31, 2019	Aug. 13, 2019	Sep. 09, 2014
Debt Instrument [Line Items]
Gross, long-term debt	$ 99,234		$ 427,500
Unamortized debt discounts	(24)		(70,699)
Unamortized debt issuance costs	(2)		(5,543)
Carrying value	99,208		351,258
Less: current portion of long-term debt	(7,374)		(80,000)
Net, long-term debt	91,834		271,258
Senior Notes
Debt Instrument [Line Items]
Gross, long-term debt	0		162,500
Senior Notes \| Series A-1 Notes
Debt Instrument [Line Items]
Gross, long-term debt	50,000		0
Senior Notes \| Series A-2 Notes
Debt Instrument [Line Items]
Gross, long-term debt	45,000		0
Senior Notes \| Royalty rights obligation
Debt Instrument [Line Items]
Gross, long-term debt	3,899		0
Senior Notes \| 13% Senior Secured Notes due 2024
Debt Instrument [Line Items]
Interest rate		13.00%
Convertible debt \| 2.50% Convertible Notes due 2021
Debt Instrument [Line Items]
Gross, long-term debt	$ 335		145,000
Interest rate	2.50%				2.50%
Convertible debt \| 5.0% Convertible Notes debt 2024
Debt Instrument [Line Items]
Gross, long-term debt	$ 0		$ 120,000
Interest rate	5.00%			5.00%