Long-Term Debt (Tables)

6 Months Ended

Jun. 30, 2018

Debt Disclosure [Abstract]

Notes Payable

Total convertible notes payable consisted of the following at (in thousands):

	June 30, 2018			December 31,  2017
Principal amount of the Notes	$	325,000		$	325,000
Unamortized debt issuance costs		(6,525	)		(7,237	)
Total convertible notes payable	$	318,475		$	317,763

Interest Expense

Interest expense incurred in connection with the Notes consisted of the following (in thousands):

	Three Months Ended June 30,				Six Months Ended June 30,
	2018		2017		2018		2017
Coupon interest	$	3,047	$	3,047	$	6,094	$	6,094
Amortization of debt issuance costs		356		356		712		712
Total interest expense on the Notes	$	3,403	$	3,403	$	6,806	$	6,806