8. Debt Obligations

2017 Convertible Senior Notes

In November 2017, the Company issued $200.0 million aggregate principal amount of 1.75% convertible senior notes due 2022 in a private placement to qualified institutional buyers pursuant to Rule 144A under the Securities Act of 1933, as amended, (the “notes”). The notes are unsecured obligations of the Company and bear interest at a fixed rate of 1.75% per annum, payable semi-annually in arrears on June 1 and December 1 of each year, commencing on June 1, 2018. The total net proceeds from the debt offering, after deducting transaction costs, were approximately $193.8 million.

The conversion rate for the notes will initially be 57.6037 shares of the Company’s common stock per $1,000 principal amount of notes, which is equivalent to an initial conversion price of approximately $17.36 per share of common stock, subject to adjustment upon the occurrence of specified events.

Holders of the notes may convert their notes at their option at any time prior to the close of business on the business day immediately preceding September 1, 2022, only under the following circumstances: (1) during any calendar quarter commencing after the calendar quarter ending on March 31, 2018 (and only during such calendar quarter), if the last reported sale price of the Company’s common stock for at least 20 trading days (whether or not consecutive) during a period of 30 consecutive trading days ending on, and including, the last trading day of the immediately preceding calendar quarter is greater than or equal to 130% of the conversion price on each applicable trading day; (2) during the five-business day period after any five consecutive trading day period (the “measurement period”) in which the trading price per $1,000 principal amount of notes for each trading day of the measurement period was less than 98% of the product of the last reported sale price of the Company’s common stock and the conversion rate for the notes on each such trading day; (3) if the Company calls any or all of the notes for redemption, at any time prior to the close of business on the scheduled trading day immediately preceding the redemption date; or (4) upon the occurrence of specified corporate events. On or after September 1, 2022, holders may convert all or any portion of their notes at any time prior to the close of business on the scheduled trading day immediately preceding the maturity date regardless of the foregoing conditions. Upon conversion, the Company will pay or deliver, as the case may be, cash, shares of its common stock or a combination of cash and shares of its common stock, at its election. The Company intends to settle the principal amount of the notes with cash.

The Company may not redeem the notes prior to December 5, 2020. It may redeem for cash all or any portion of the notes, at its option, on or after December 5, 2020 if the last reported sale price of its common stock has been at least 130% of the conversion price then in effect for at least 20 trading days (whether or not consecutive) during any 30 consecutive trading day period (including the last trading day of such period) ending not more than three trading days preceding the date on which it provides notice of redemption at a redemption price equal to 100% of the principal amount of the notes to be redeemed, plus accrued and unpaid interest to, but excluding, the redemption date. No sinking fund is provided for the notes.

If the Company undergoes a fundamental change prior to the maturity date, holders may require the Company to repurchase for cash all or any portion of their notes at a fundamental change repurchase price equal to 100% of the principal amount of the notes to be repurchased, plus accrued and unpaid interest to, but excluding, the fundamental change repurchase date.

In accounting for the issuance of the notes, the Company separated the notes into liability and equity components. The carrying amount of the liability component of $149.3 million was calculated by measuring the fair value of a similar debt instrument that does not have an associated convertible feature. The carrying amount of the equity component of $50.7 million, representing the conversion option, was determined by deducting the fair value of the liability component from the par value of the notes. The excess of the principal amount of the liability component over its carrying amount (“debt discount”) is amortized to interest expense over the term of the notes at an effective interest rate of 5.8%.

The Company allocated the total debt issuance costs incurred of $6.2 million to the liability and equity components of the notes in proportion to the respective values. Issuance costs attributable to the liability component of $4.6 million are being amortized to interest expense using the effective interest method over the contractual terms of the notes. Issuance costs attributable to the equity component of $1.6 million were netted with the equity component in additional paid-in capital.

The net carrying amount of the liability component of the notes recorded in convertible senior notes, net on the condensed consolidated balance sheets was as follows (in thousands):

	March 31,
	2018
Principal	$	200,000
Unamortized debt discount		(47,435	)
Unamortized debt issuance costs		(4,319	)
Net carrying amount of the liability component	$	148,246

The net carrying amount of the equity component of the notes recorded in additional paid-in capital on the consolidated balance sheets was $49.1 million, net of debt issuance costs of $1.6 million as of March 31, 2018 and December 31, 2017.

The following table sets forth the interest expense related to the notes recognized in interest expense on the consolidated statements of operations (in thousands):

	Three Months Ended
	March 31,
	2018
Contractual interest expense	$	875
Amortization of debt discount		2,197
Amortization of debt issuance costs		229
Total interest expense related to the Notes	$	3,301