Convertible Senior Notes (Tables)

3 Months Ended

Mar. 31, 2016

Debt Disclosure [Abstract]

Schedule of Debt

The 2017 Notes consist of the following:

Liability component	March 31, 2016			December 31, 2015
	(in thousands)
Principal	$	275,000		$	275,000
Less: Debt discount, net(1)	(16,200		)	(19,527		)
Net carrying amount	$	258,800		$	255,473

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⁽¹⁾  Included in the accompanying condensed 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.

The 2022 Notes consist of the following:

Liability component	March 31, 2016			December 31, 2015
	(in thousands)
Principal	$	400,000		$	400,000
Less: Debt discount, net(1)	(84,920		)	(87,893		)
Net carrying amount	$	315,080		$	312,107

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⁽¹⁾  Included in the accompanying condensed 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.

Schedule of Interest Expense

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

	Three Months Ended March 31,
	2016			2015
	(in thousands)
Contractual interest expense	$	2,500		$	2,152
Amortization of debt discount	2,974			2,403
Total	$	5,474		$	4,555
Effective interest rate of the liability component	6.5		%	6.5		%

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

	Three Months Ended March 31,
	2016			2015
	(in thousands)
Contractual interest expense	$	945		$	945
Amortization of debt discount	3,327			3,113
Total	$	4,272		$	4,058
Effective interest rate of the liability component	6.02		%	6.02		%