INDEBTEDNESS (Tables)

12 Months Ended

Dec. 31, 2017

Debt Disclosure [Abstract]

Summary of 2024 Notes

The following table summarizes the 2024 Notes for the period indicated:

	As of December 31, 2017
	(in thousand)
Par value of the 2024 Notes	$	570,000
Unamortized discounts	$	(158,890	)
Debt issuance expenses		(10,449	)
Net carrying value of convertible debt	$	400,661
Fair value of convertible debt	$	619,641

Summary of Term Loans

The following table summarizes term loans for each of the periods indicated:

	As of December 31
	2017			2016
	(in thousands)
Principal amount of the 2017 Term Loan	$	30,000		$	—
Principal amount of the 2015 Term Loan		—			15,000
Unamortized debt issuance expense		(918	)		(223	)
Net carrying value of term loan	$	29,082		$	14,777

Summarizes Total Gross Payments Due under Company's Debt Arrangements

The following table summarizes the total gross payments due under the Company’s debt arrangements:

	As of December 31, 2017
	(in thousands)
2018	$	6,328
2019		10,000
2020		10,000
2021		5,000
2022		—
Thereafter		570,000
Total Payments	$	601,328