Convertible note obligations included in the condensed consolidated balance sheets consisted of the following:

(1)

As each of the convertible instruments may be settled in cash upon conversion, for accounting purposes, they were bifurcated into a liability component and an equity component, which are both initially recorded at fair value. The amount allocated to the equity component is the difference between the principal value of the instrument and the fair value of the liability component at issuance. The resulting debt discount is being amortized to interest expense at the respective effective interest rate over the contractual term of the debt. In March 2019 a portion of the 2025 Convertible Notes were extinguished. The fair value of the liability component at issuance reflected above represents the liability value at issuance for the applicable portion of the 2025 Notes which remain outstanding at June 30, 2019. The fair value of the liability component of the 2025 Notes at December 31, 2018 was $654.8 million with the equity component being $269.7 million including a $14.2 million premium.

(2)	The unamortized discount consists of the following:


(In thousands)	June 30, 2019		December 31, 2018
2027 Convertible notes	$	266,952	$	—
2025 Convertible notes		96,651		227,403
Total unamortized discount	$	363,603	$	227,403

(3)	Debt issuance costs consists of the following:


(In thousands)	June 30, 2019		December 31, 2018
2027 Convertible notes	$	10,954	$	—
2025 Convertible notes		6,854		16,348
Total debt issuance costs	$	17,808	$	16,348

(4)

As of June 30, 2019, the 2025 Convertible Notes were convertible and included within convertible notes, net, current portion on the condensed consolidated balance sheet. As of December 31, 2018, the 2025 Convertible Notes were not convertible and included within long-term convertible notes, net on the condensed consolidated balance sheet.

Issuances and Settlements

In January 2018, the Company issued and sold $690.0 million in aggregate principal amount of 1.0% Convertible Notes (the “January 2018 Notes”) with a maturity date of January 15, 2025 (the “Maturity Date”). The January 2018 Notes accrue interest at a fixed rate of 1.0% per year, payable semi-annually in arrears on January 15 and July 15 of each year, beginning on July 15, 2018. The net proceeds from the issuance of the January 2018 Notes were approximately $671.1 million, after deducting underwriting discounts and commissions and the offering expenses payable by the Company.

In June 2018, the Company issued and sold an additional $218.5 million in aggregate principal amount of 1.0% Convertible Notes (the “June 2018 Notes”). The June 2018 Notes were issued under the same indenture pursuant to which the Company previously issued the January 2018 Notes (the “Indenture”). The January 2018 Notes and the June 2018 Notes (collectively, the “2025 Notes”) have identical terms and will be treated as a single series of securities. The net proceeds from the issuance of the June 2018 Notes were approximately $225.3 million, after deducting underwriting discounts and commissions and the offering expenses payable by the Company.

In March 2019, the Company issued and sold $747.5 million in aggregate principal amount of 0.375% Convertible Notes (the “2027 Notes” and, collectively with the 2025 Notes, the “Notes”) with a maturity date of March 15, 2027 (the “Maturity Date”). The 2027 Notes accrue interest at a fixed rate of 0.375% per year, payable semi-annually in arrears on March 15 and September 15 of each year, beginning on September 15, 2019. The net proceeds from the issuance of the 2027 Notes were approximately $729.5 million, after deducting underwriting discounts and commissions and the offering expenses payable by the Company.

The Company utilized a portion of the proceeds from the issuance of the 2027 Notes to settle a portion of the 2025 Notes in privately negotiated transactions. In March 2019, the Company used cash of $494.0 million and an aggregate of 2.2 million shares of the Company’s common stock valued at $182.4 million for total consideration of $676.5 million to settle $493.4 million of the 2025 Notes, of which $375.1 million was allocated to the liability component, $300.8 million was allocated to the equity component, and $0.6 million was used to pay off interest accrued on the 2025 Notes. The consideration transferred was allocated to the liability and equity components of the 2025 Notes using the equivalent rate that reflected the borrowing rate for a similar non-convertible debt instrument immediately prior to settlement. The transaction resulted in a loss on settlement of convertible notes of $10.6 million, which is recorded in interest income (expense) in the Company’s condensed consolidated statement of operations. The loss represents the difference between (i) the fair value of the liability component and (ii) the sum of the carrying value of the debt component and any unamortized debt issuance costs at the time of repurchase.

Summary of Conversion Features

Until the six-months immediately preceding the maturity date of the applicable series of Notes, each series of Notes is convertible only upon the occurrence of certain events and during certain periods, as set forth in the Indenture. The Notes will be convertible into cash, shares of the Company’s common stock (plus, if applicable, cash in lieu of any fractional share), or a combination of cash and shares of the Company’s common stock, at the Company’s election. On or after the date that is six-months immediately preceding the maturity date of the applicable series of Notes until the close of business on the second scheduled trading day immediately preceding the maturity date, holders may convert such Notes at any time.

It is the Company’s intent and policy to settle all conversions through combination settlement. The initial conversion rate is 13.2569 and 8.9554 shares of common stock per $1,000 principal amount for the 2025 Notes and 2027 Notes, respectively, which is equivalent to an initial conversion price of approximately $75.43 and $111.66 per share of the Company’s common stock for the 2025 Notes and 2027 Notes, respectively. The conversion rate is subject to adjustment upon the occurrence of certain specified events but will not be adjusted for accrued and unpaid interest. In addition, holders of the Notes who convert their Notes in connection with a “make-whole fundamental change” (as defined in the Indenture), will, under certain circumstances, be entitled to an increase in the conversion rate.

If the Company undergoes a “fundamental change” (as defined in the Indenture), holders of the Notes may require the Company to repurchase for cash all or part of their Notes at a repurchase price equal to 100% of the principal amount of the Notes to be repurchased, plus accrued and unpaid interest.

As of June 30, 2019, the 2027 Notes were not convertible. The holders of the 2025 Notes have the right to convert their debentures between July 1, 2019 and September 30, 2019, because the closing price of the Company’s common stock exceeded the Conversion Price by 130% for at least 20 trading days (whether or not consecutive) in the period of the 30 consecutive trading days ending on June 30, 2019.

Based on the closing price of our common stock of $118.04 on June 28, 2019, the if-converted values on our 2025 Notes and 2027 Notes exceed the principal amount by $234.5 million and $42.7 million, respectively.

Ranking of Convertible Notes

The Notes are the Company’s senior unsecured obligations and (i) rank senior in right of payment to all of its future indebtedness that is expressly subordinated in right of payment to the Notes; equal in right of payment to all of the Company’s future liabilities that are not so subordinated, unsecured indebtedness; (ii) are effectively junior to all of our existing and future secured indebtedness and other secured obligations, to the extent of the value of the assets securing that indebtedness and other secured obligations; and (iii) are structurally subordinated to all indebtedness and other liabilities of the Company’s subsidiaries.

The 2025 Notes are classified as current on the Company’s condensed consolidated balance sheets at June 30, 2019, while the 2027 Notes are classified on the Company’s condensed consolidated balance sheets at June 30, 2019 as long-term. The future convertibility and resulting balance sheet classification of the Notes will be monitored at each quarterly reporting date and will be analyzed dependent upon market prices of the Company’s common stock during the prescribed measurement periods. In the event that the holders of the Notes have the election to convert the Notes at any time during the prescribed measurement period, the Notes would then be considered a current obligation and classified as such.

The Company allocated the total transaction costs of approximately $18.8 million related to the issuance of the January 2018 Notes to the liability and equity components of the January 2018 Notes based on their relative values, with $13.6 million being allocated to the liability component of the January 2018 Notes. Transaction costs attributable to the liability component are amortized to interest expense over the seven-year term of the January 2018 Notes, and transaction costs attributable to the equity component are netted with the equity component in stockholders’ equity.

The Company allocated the total transaction costs of approximately $7.4 million related to the issuance of the June 2018 Notes to the liability and equity components of the June 2018 Notes based on their relative values, with $5.1 million being allocated to the liability component of the June 2018 Notes. Transaction costs attributable to the liability component are amortized to interest expense over the remaining six-and-a-half-year term of the June 2018 Notes, and transaction costs attributable to the equity component are netted with the equity component in stockholders’ equity.

The Company allocated the total transaction costs of approximately $18.0 million related to the issuance of the 2027 Notes to the liability and equity components of the 2027 Notes based on their relative values, with $11.4 million being allocated to the liability component of the 2027 Notes. Transaction costs attributable to the liability component are amortized to interest expense over the eight-year term of the 2027 Notes, and transaction costs attributable to the equity component are netted with the equity component in stockholders’ equity.

The Notes do not contain any financial or operating covenants or any restrictions on the payment of dividends, the issuance of other indebtedness or the issuance or repurchase of securities by the Company.

Interest expense includes the following:


	Three Months Ended				Six Months Ended
	June 30,				June 30,
(In thousands)	2019		2018		2019		2018
Debt issuance costs amortization	$	645	$	517	$	1,330	$	920
Debt discount amortization		10,075		6,171		18,468		10,822
Loss on settlement of convertible notes		—		—		10,558		—
Coupon interest expense		1,739		1,866		3,846		3,271
Total interest expense on convertible notes		12,459		8,554		34,202		15,013
Other interest expense		253		49		500		100
Total interest expense	$	12,712	$	8,603	$	34,702	$	15,113

The remaining period over which the unamortized debt discount will be recognized as non-cash interest expense is 7.71 years and 5.55 years for the 2027 Notes and 2025 Notes, respectively.