INDEBTEDNESS (Tables)

12 Months Ended

Dec. 31, 2019

Debt Disclosure [Abstract]

Convertible Notes

The net carrying amount of the Notes were as follows (in thousands):

	Principal outstanding		Unamortized debt discount		Unamortized debt issuance costs		Net carrying value
December 31, 2019
2023 Notes	$	862,500	$	(110,518)	$	(3,418)	$	748,564
2022 Notes	211,726		(19,312)		(2,146)		190,268
Total	$	1,074,226	$	(129,830)	$	(5,564)	$	938,832
December 31, 2018
2023 Notes	$	862,500	$	(138,924)	$	(5,054)	$	718,522
2022 Notes	211,728		(27,569)		(2,986)		181,173
Total	$	1,074,228	$	(166,493)	$	(8,040)	$	899,695

The net carrying amount of the equity component of the Notes were as follows (in thousands):

	Amount allocated to conversion option		Less: allocated issuance costs		Equity component, net
December 31, 2019 and December 31, 2018
2023 Notes	$	155,250	$	(1,231)	$	154,019
2022 Notes	41,481		(1,108)		40,373
Total	$	196,731	$	(2,339)	$	194,392

Interest Expense on Convertible Notes

The Company recognized interest expense on the Notes as follows (in thousands, except for percentages):

	Year Ended December 31,
	2019		2018		2017
Contractual interest expense	$	5,108	$	4,023	$	1,351
Amortization of debt discount and issuance costs	39,139		32,855		14,223
Total	$	44,247	$	36,878	$	15,574