DEBT (Tables)

12 Months Ended

Dec. 31, 2017

Senior Notes

Debt

Schedule of principal amount of the Senior Notes is repayable

The remaining principal amount of the Senior Notes, following the amendment on December 4, 2017 is repayable each year is as follows (in thousands):

2018	$	82,500
2019		120,000
2020		80,000
2021		82,500
Total	$	365,000

Summary of the carrying value of the Senior Notes

The following is a summary of the carrying value of the Senior Notes as of December 31, 2017 (in thousands):

	December 31,		December 31,
	2017		2016
Principal amount of the Senior Notes	$	365,000	$	475,000
Unamortized debt discount balance		(4,717)		(8,605)
Unamortized debt issuance costs		(3,063)		(344)
Total Senior Notes	$	357,220	$	466,051

Summary of interest expense for the Notes

The following is a summary of Senior Notes interest expense (in thousands):

	December 31,
	2017		2016		2015
Contractual interest expense	$	44,212	$	54,722	$	46,874
Amortization of debt discount and debt issuance costs		2,631		2,261		1,466
Total interest expense	$	46,843	$	56,983	$	48,340

Convertible Notes

Debt

Summary of the liability component of the Convertible Notes

The following is a summary of the liability component of the Convertible Notes as of December 31, 2017 and 2016 (in thousands):

	December 31,		December 31,
	2017		2016
Principal amount of the Convertible Notes	$	345,000	$	345,000
Unamortized discount of the liability component		(71,799)		(87,570)
Unamortized debt issuance costs		(3,691)		(4,705)
Total Convertible Notes	$	269,510	$	252,725

Summary of interest expense for the Notes

The following is a summary of interest expense for 2017, 2016 and 2015 (in thousands):

	December 31,
	2017		2016		2015
Stated coupon interest	$	8,625	$	8,625	$	8,625
Amortization of debt discount and debt issuance costs		16,784		15,412		14,163
Total interest expense	$	25,409	$	24,037	$	22,788