Convertible Senior Notes (Tables)

12 Months Ended

Dec. 31, 2014

Debt Disclosure [Abstract]

Schedule of Debt Liability Component

The Notes consisted of the following:

Liability component	December 31, 2014			December 31, 2013
	(in thousands)
Principal	$	275,000		$	275,000
Less: Debt discount, net(1)	(28,324		)	(38,912		)
Net carrying amount	$	246,676		$	236,088

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

Schedule of Debt Interest Expense

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

	Years Ended December 31,
	2014			2013			2012
	(in thousands)
Contractual interest expense	$	3,781		$	3,781		$	2,101
Amortization of debt issuance costs	1,332			1,179			598
Amortization of debt discount	10,588			9,978			5,306
	$	15,701		$	14,938		$	8,005
Effective interest rate of the liability component	6.02		%	6.02		%	6.02		%