Convertible Notes (Tables)

The carrying value and unamortized discount of the December 2021 Notes were as follows:



(In thousands)	March 31, 2018			December 31, 2017
Principal amount of the December 2021 Notes	$	150,000		$	150,000
Unamortized discount of liability component	(30,834		)	(32,585		)
Net carrying value of the December 2021 Notes	$	119,166		$	117,415



		Principal Balance Outstanding		Carrying Value
		March 31,		March 31,		December 31,
Description	Maturity Date	2018		2018		2017
(In thousands)
Convertible Notes
February 2018 Notes	February 1, 2018	$	—	$	—	$	126,066
December 2021 Notes	December 1, 2021	$	150,000	119,166		117,415
Total				$	119,166	$	243,481

The carrying value and unamortized discount of the February 2018 Notes were as follows:



(In thousands)	March 31, 2018		December 31, 2017
Principal amount of the February 2018 Notes	$	—	$	126,447
Unamortized discount of liability component	—		(381		)
Net carrying value of the February 2018 Notes	$	—	$	126,066

Interest expense for the February 2018 Notes on the Company’s Condensed Consolidated Statements of Income was as follows:



	Three Months Ended
	March 31,
(In thousands)	2018		2017
Contractual coupon interest	$	421	$	1,265
Amortization of debt issuance costs	88		249
Amortization of debt discount	293		848
Total	$	802	$	2,362

Interest expense for the December 2021 Notes on the Company’s Condensed Consolidated Statements of Income was as follows:



	Three Months Ended
	March 31,
(In thousands)	2018		2017
Contractual coupon interest	$	1,031	$	1,031
Amortization of debt issuance costs	19		18
Amortization of debt discount	134		130
Amortization of conversion feature	1,598		1,430
Total	$	2,782	$	2,609