Convertible 3.75% Senior Notes (Tables)

12 Months Ended

Dec. 31, 2017

Debt Disclosure [Abstract]

Convertible debt

At December 31, 2017 and December 31, 2016, the net carrying amount of the liability component and the remaining unamortized debt discount were as follows:  

	December 31, 2017		December 31, 2016
	(in thousands)		(in thousands)
Face amount of the Notes	$	143,750	$	143,750
Unamortized discount	20,517		29,160
Debt issuance costs	2,256		3,199
Carrying amount of the Notes	$	120,977	$	111,391

Expenses for convertible notes

For the years ended December 31, 2017, December 31, 2016 and December 31, 2015, the Company recorded the following expenses in relation to the Notes:

	December 31, 2017			December 31, 2016			December 31, 2015
	(in thousands)			(in thousands)			(in thousands)
Interest Expense at 3.75% coupon rate	$	5,391		$	5,391		$	5,391
Debt discount amortization	8,643			7,599			6,680
Amortization of deferred financing costs	942			828			728
Less: capitalized interest and other	(3,778		)	(514		)	559
Total interest expense	$	11,198		$	13,304		$	13,358