DEBT (Tables)

6 Months Ended

Jun. 30, 2021

Debt Disclosure [Abstract]

Contractual obligation, fiscal year maturity schedule

Carrying value of the Notes:

(in thousands)	June 30, 2021		December 31, 2020
Principal	$	600,000	$	600,000
Unamortized debt discount	—		(71,222)
Unamortized issuance costs	(10,908)		(10,575)
Convertible senior notes, net	$	589,092	$	518,203
Conversion options	$	—	$	84,120
Issuance costs	—		(2,037)
Deferred taxes	—		(20,479)
Additional paid-in capital	$	—	$	61,604

Interest expense related to the Notes:

	Three Months Ended June 30,				Six Months Ended June 30,
(in thousands)	2021		2020		2021		2020
Contractual interest expense (0.75% coupon)	$	1,125	$	1,125	$	2,250	$	1,575
Amortization of debt discount	—		3,757		—		5,253
Amortization of issuance costs	675		558		1,348		780
	$	1,800	$	5,440	$	3,598	$	7,608

The effective interest rate for the Notes:

	Six Months Ended June 30,
	2021		2020
Weighted-average effective interest rate	1.2	%	4.3	%

Future payments of principal and contractual interest:

	June 30, 2021
(in thousands)	Principal		Interest		Total
2021	$	—	$	2,250	$	2,250
2022	—		4,500		4,500
2023	—		4,500		4,500
2024	—		4,500		4,500
2025	600,000		1,488		601,488
	$	600,000	$	17,238	$	617,238

Schedule of derivative instruments

Change in capped call transactions:

	Six Months Ended June 30,
(in thousands)	2021		2020
January 1,	$	83,597	$	—
Issuance	—		51,900
Fair value adjustment	7,192		827
June 30,	$	90,789	$	52,727