LONG-TERM DEBT - Components of Convertible Debt Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Debt Instrument [Line Items]
Amortization of debt discount and issuance costs			$ 4,154	$ 4,191
Total interest expense on Notes	$ 9,598	$ 7,314	18,994	14,090
Convertible debt
Debt Instrument [Line Items]
Coupon interest	1,164	2,875	2,328	5,750
Amortization of debt discount and issuance costs	768	1,732	1,534	3,439
Total interest expense on Notes	$ 1,932	$ 4,607	$ 3,862	$ 9,189
Effective interest rate	9.12%	9.12%	9.12%	9.12%