Convertible Senior Notes (Tables)

9 Months Ended

Sep. 30, 2015

The 2022 Notes consist of the following:



Liability component	September 30, 2015			December 31, 2014
	(in thousands)
Principal	$	400,000		$	—
Less: Debt discount, net⁽¹⁾	(81,536		)	—
Net carrying amount	$	318,464		$	—

⁽¹⁾ Included in the accompanying consolidated balance sheets within convertible senior notes (due 2022) and amortized to interest expense over the remaining life of the 2022 Notes using the effective interest rate method.

The 2017 Notes consist of the following:



Liability component	September 30, 2015			December 31, 2014
	(in thousands)
Principal	$	275,000		$	275,000
Less: Debt discount, net⁽¹⁾	(19,953		)	(28,324		)
Net carrying amount	$	255,047		$	246,676

⁽¹⁾ Included in the accompanying consolidated balance sheets within convertible senior notes (due 2017) and amortized to interest expense over the remaining life of the 2017 Notes using the effective interest rate method.

Schedule of Debt Interest Expense

The following table sets forth total interest expense recognized related to the 2017 Notes:



	Three Months Ended September 30,						Nine Months Ended September 30,
	2015			2014			2015			2014
	(in thousands)
Contractual interest expense	$	945		$	945		$	2,836		$	2,836
Amortization of debt issuance costs	382			340			1,110			985
Amortization of debt discount	2,836			2,673			8,370			7,889
Total	$	4,163		$	3,958		$	12,316		$	11,710
Effective interest rate of the liability component	6.02		%	6.02		%	6.02		%	6.02		%

The following table sets forth total interest expense recognized related to the 2022 Notes:



	Three Months Ended September 30,						Nine Months Ended September 30,
	2015			2014			2015			2014
	(in thousands)
Contractual interest expense	$	2,505		$	—		$	7,139		$	—
Amortization of debt issuance costs	248			—			684			—
Amortization of debt discount	2,630			—			7,369			—
Total	$	5,383		$	—		$	15,192		$	—
Effective interest rate of the liability component	6.5		%	—		%	6.5		%	—		%