Long-Term Debt (Tables)

12 Months Ended

Dec. 31, 2017

Debt Disclosure [Abstract]

Notes Payable

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

	December 31, 2017		December 31, 2016
Principal amount of Notes	$	325,000	$	325,000
Unamortized debt issuance costs		(7,237)		(8,661)
Total convertible notes payable	$	317,763	$	316,339

Interest Expense

Interest expense incurred in connection with the Notes consisted of the following for the years ended December 31 (in thousands):

	2017		2016
Coupon interest	$	12,188	$	11,240
Amortization of debt issuance costs		1,424		1,305
Total interest expense on Notes	$	13,612	$	12,545