LONG-TERM DEBT - Components of Convertible Debt Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Debt Instrument [Line Items]
Amortization of debt discount and issuance costs			$ 6,388	$ 6,493
Total interest expense on Notes	$ 9,974	$ 7,757	28,968	21,847
Convertible debt
Debt Instrument [Line Items]
Coupon interest	1,164	2,875	3,492	8,625
Amortization of debt discount and issuance costs	791	1,785	2,326	5,224
Total interest expense on Notes	$ 1,955	$ 4,660	$ 5,818	$ 13,849
Effective interest rate	9.12%	9.12%	9.12%	9.12%