0.25% Convertible Senior Notes, Convertible Note Hedge and Warrant (Tables)

3 Months Ended

Mar. 31, 2019

Debt Instrument [Line Items]

Schedule of Interest Expense

Interest expense related to the 2022 Notes is as follows:

	Three Months Ended March 31,
	2019		2018
	(in thousands)
Contractual interest expense	$	250	$	250
Amortization of debt discount		4,894		4,567
Amortization of issuance costs		366		341
Total interest expense	$	5,510	$	5,158

0.25% Convertible Senior Notes Due 2022 as Liability Component [Member]

Debt Instrument [Line Items]

Schedule of Net Carrying Amount of Notes

The net carrying amount of the liability component of the 2022 Notes is as follows:

	As of March 31, 2019			As of December 31, 2018
	(in thousands)
Principal	$	400,000		$	400,000
Unamortized debt discount		(70,681	)		(75,575	)
Unamortized issuance costs		(5,277	)		(5,643	)
Net carrying amount	$	324,042		$	318,782