7. Debt

Our debt consists of:

	June 30,			December 31,
(In thousands)	2017			2016
Convertible subordinated notes due 2023	$	240,984		$	240,984
Non-recourse notes due 2029	422,758			487,189

Total debt	663,742			728,173
Unamortized debt issuance cost	(9,849		)	(12,080		)
Current portion of non-recourse notes due 2029	(15,181		)	(7,752		)

Net long-term debt	$	638,712		$	708,341

Convertible Subordinated Notes Due 2023

In January 2013, we completed an underwritten public offering of $287.5 million aggregate principal amount of our unsecured 2023 Notes, which will mature on January 15, 2023. The financing raised proceeds, net of issuance costs, of approximately $281.2 million, less $36.8 million to purchase two privately-negotiated capped call option transactions in connection with the issuance of the notes. The 2023 Notes bear interest at the rate of 2.125% per year that is payable semi-annually in arrears in cash on January 15 and July 15 of each year, beginning on July 15, 2013. The principal balance of the 2023 Notes was reduced to $241.0 million by the partial conversion of $32.4 million in 2014 and repurchase of $14.1 million in the open market in 2016. As of June 30, 2017, the capped call strike price and cap price are at $19.77 and $27.04, respectively.

Non-Recourse Notes Due 2029

In April 2014, we entered into certain note purchase agreements relating to the private placement of $450.0 million aggregate principal amount of the 2029 Notes issued by our wholly-owned subsidiary. The 2029 Notes bear an annual fixed interest rate of 9%, with interest and principal paid quarterly beginning November 15, 2014. The 2029 Notes may be redeemed at any time prior to maturity, in whole or in part, at specified redemption premiums. The redemption premium was 2.5% until April 17, 2017, and there is no redemption premium after such date.

Since the principal and interest payments on the 2029 Notes are based on royalties from product sales recorded by GSK, which will vary from quarter to quarter and are unknown to us, the 2029 Notes may be repaid prior to the final maturity date in 2029. Prior to June 30, 2017, the principal balance of the 2029 Notes was paid down by $71.3 million, of which $64.4 million was made during the six months ended June 30, 2017. The 2017 principal payments on the 2029 Notes consist of (1) $14.4 million based on our royalty revenues generated in the previous quarters ended December 31, 2016 and March 31, 2017, and (2) $50.0 million from our previously announced plan to prepay a portion of the outstanding principal of the 2029 Notes as part of the 2017 Capital Return Plan discussed below. In connection with the $50.0 million principal prepayment, we wrote off the corresponding pro-rata unamortized debt issuance cost of $0.8 million and these are presented as part of Other income (expense), net in our consolidated statements of operations for the three and six months ended June 30, 2017. As of June 30, 2017, the principal balance of the 2029 Notes was $422.8 million, which will be partially paid down by $15.2 million in the next quarterly payment expected to be made in August 2017. This payment is based on our royalty revenues of $61.8 million for the three months ended June 30, 2017.