Convertible Senior Notes (Tables)

6 Months Ended

Jun. 30, 2015

The 2022 Notes consist of the following:



Liability component	June 30, 2015			December 31, 2014
	(in thousands)
Principal	$	400,000		$	—
Less: Debt discount, net⁽¹⁾	(84,166		)	—
Net carrying amount	$	315,834		$	—

⁽¹⁾ Included in the 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	June 30, 2015			December 31, 2014
	(in thousands)
Principal	$	275,000		$	275,000
Less: Debt discount, net⁽¹⁾	(22,790		)	(28,324		)
Net carrying amount	$	252,210		$	246,676

⁽¹⁾ Included in the 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 June 30,						Six Months Ended June 30,
	2015			2014			2015			2014
	(in thousands)
Contractual interest expense	$	945		$	945		$	1,891		$	1,890
Amortization of debt issuance costs	367			326			728			646
Amortization of debt discount	2,781			2,621			5,534			5,216
Total	$	4,093		$	3,892		$	8,153		$	7,752
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 June 30,						Six Months Ended June 30,
	2015			2014			2015			2014
	(in thousands)
Contractual interest expense	$	2,482		$	—		$	4,634		$	—
Amortization of debt issuance costs	233			—			436			—
Amortization of debt discount	2,538			—			4,739			—
Total	$	5,253		$	—		$	9,809		$	—
Effective interest rate of the liability component	6.5		%	—		%	6.5		%	—		%