Convertible Senior Notes

In May and June 2017, we issued $782.5 million of 0% convertible senior notes (the 2022 Notes), due June 1, 2022 unless earlier converted or repurchased in accordance with their terms. In November 2013, we issued $575.0 million of 0% convertible senior notes (the 2018 Notes, and together with the 2022 Notes, the Notes), due November 1, 2018 unless earlier converted or repurchased in accordance with their terms. The Notes do not bear interest, and we cannot redeem the Notes prior to maturity.

The Notes are unsecured obligations and do not contain any financial covenants or restrictions on the payments of dividends, the incurrence of indebtedness or the issuance or repurchase of securities by us or any of our subsidiaries.

Upon conversion of the Notes, we may choose to pay or deliver, as the case may be, cash, shares of our common stock or a combination of cash and shares of our common stock. We currently intend to settle the principal amount of the Notes with cash.



	Convertible Date	Initial Conversion Price per Share		Initial Conversion Rate per $1,000 Par Value	Initial Number of Shares
2022 Notes	February 1, 2022	$	134.75	7.42 shares	5,806,936
2018 Notes	July 1, 2018	$	73.88	13.54 shares	7,783,023

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 February 1, 2022 and July 1, 2018, for the 2022 Notes and 2018 Notes, respectively (each, a Convertible Date), only under the following circumstances:

•

during any calendar quarter (and only during such calendar quarter) if the last reported sale price of our common stock for at least 20 trading days (whether or not consecutive) during the period of 30 consecutive trading days ending on the last trading day of the immediately preceding calendar quarter is greater than or equal to 130% of the applicable conversion price on each applicable trading day; or


•	during the five-business day period after any five-consecutive trading day period, or the measurement period, in which the trading price per $1,000 principal amount of the Notes for each trading day of the measurement period was less than 98% of the product of the last reported sale price of our common stock and the applicable conversion rate on each such trading day; or


•	upon the occurrence of specified corporate events.

On or after the applicable Convertible Date, a holder may convert all or any portion of its Notes at any time prior to the close of business on the second scheduled trading day immediately preceding the maturity date regardless of the foregoing conditions. Upon conversion, we will pay or deliver, as the case may be, cash, shares of our common stock or a combination of cash and shares of our common stock, at our election. As noted above, we currently intend to settle the principal amount of the Notes with cash.

The conversion price will be subject to adjustment in some events. Holders of the Notes who convert their Notes in connection with certain corporate events that constitute a “make-whole fundamental change” are, under certain circumstances, entitled to an increase in the conversion rate. Additionally, in the event of a corporate event that constitutes a “fundamental change,” holders of the Notes may require us to purchase with cash all or a portion of the Notes upon the occurrence of a fundamental change, at a purchase price equal to 100% of the principal amount of the respective Notes plus any accrued and unpaid special interest, if any.

In accounting for the issuance of the Notes, we separated the Notes into liability and equity components. The carrying cost of the liability component was calculated by measuring the fair value of a similar liability that does not have an associated convertible feature. The carrying amount of the equity component representing the conversion option was determined by deducting the fair value of the liability component from the par value of the Notes. The difference between the principal amount of the Notes and the proceeds allocated to the liability component, or the debt discount, is amortized to interest expense using the effective interest method over the term of the respective Notes. The equity component is not remeasured as long as it continues to meet the conditions for equity classification.

In accounting for the transaction costs related to the issuance of the Notes, we allocated the total amount incurred to the liability and equity components based on their relative fair values. Transaction costs attributable to the liability component are being amortized to interest expense over the respective terms of the Notes, and transaction costs attributable to the equity component were netted with the equity component of the Notes in stockholders’ equity. The Notes consisted of the following (in thousands):



	December 31, 2017			December 31, 2016
Liability component:
Principal:
2022 Notes	$	782,500		$	—
2018 Notes	574,994			575,000
Less: debt issuance cost and debt discount, net of amortization
2022 Notes	(152,482		)	—
2018 Notes	(31,576		)	(67,188		)
Net carrying amount	$	1,173,436		$	507,812



	2022 Notes			2018 Notes
Equity component recorded at issuance:
Note	$	162,039		$	155,319
Issuance cost	(2,148		)	(3,257		)
Net amount recorded in equity	$	159,891		$	152,062

The price of our common stock was greater than or equal to 130% of the conversion price of the 2018 Notes for at least 20 trading days during the 30 consecutive trading days ending on the last trading day of the quarter ended June 30, 2017. Therefore, the 2018 Notes first became convertible at the holders’ option beginning on July 1, 2017 and continue to be convertible at the holders' option through March 31, 2018. During the year ended December 31, 2017, we paid cash to settle an immaterial principal amount of the 2018 Notes. Based on additional conversion requests we have received through the filing date, we expect to settle in cash an aggregate of $37.3 million in principal amount of the 2018 Notes during the first quarter of 2018 and $7.3 million in principal amount of the 2018 Notes during the second quarter of 2018. We may receive additional conversion requests that require settlement in the second quarter or the remainder of the year 2018.

As we have the option to settle the principal amount in shares and we are less than 12 months away from the maturity date, we have classified the net carrying amount of our 2018 Notes as a current liability and the equity component of our 2018 Notes continues to remain in permanent equity. Our 2018 Notes were not convertible as of December 31, 2016. Our 2022 Notes were not convertible as of December 31, 2017.

We consider the fair value of the Notes at December 31, 2017 to be a Level 2 measurement. The estimated fair values of the Notes at December 31, 2017 and December 31, 2016 based on the closing trading price per $100 of the Notes were as follows (in thousands):



	December 31, 2017		December 31, 2016
2022 Notes	$	897,778	N/A
2018 Notes	$	1,015,554	$	681,375

As of December 31, 2017, the remaining life of the 2022 Notes and 2018 Notes are 53 months and 10 months, respectively. The following table sets forth total interest expense recognized related to the Notes (in thousands):



	Year Ended December 31,
	2017		2016		2015
Amortization of debt issuance cost
2022 Notes	$	860	$	—	$	—
2018 Notes	1,911		1,785		1,668
Amortization of debt discount
2022 Notes	16,921		—		—
2018 Notes	33,702		31,493		29,429
Total	$	53,394	$	33,278	$	31,097
Effective interest rate of the liability component
2022 Notes	4.75%
2018 Notes	6.50%

Note Hedges

To minimize the impact of potential economic dilution upon conversion of the Notes, we entered into convertible note hedge transactions (the 2022 Note Hedge and 2018 Note Hedge, respectively, and collectively, the Note Hedges) with certain investment banks, with respect to our common stock concurrently with the issuance of the 2022 Notes and 2018 Notes.

The Note Hedges cover shares of our common stock at a strike price per share that corresponds to the initial conversion price of the respective Notes, subject to adjustment, and are exercisable upon conversion of the Notes. If exercised, we may elect to receive cash, shares of our common stock, or a combination of cash and shares. We have accounted for the aggregate amount of purchase price for the Note Hedges as a reduction to additional paid-in capital. The Note Hedges will expire upon the maturity of the Notes. The Note Hedges are intended to reduce the potential economic dilution upon conversion of the Notes in the event that the fair value per share of our common stock at the time of exercise is greater than the conversion price of the Notes. The Note Hedges are separate transactions and are not part of the terms of the Notes. Holders of the Notes will not have any rights with respect to the Note Hedges. The Note Hedges do not impact earnings per share, as they were entered into to offset any dilution from the Notes. As of December 31, 2017, 7,782,946 shares remain subject to the 2018 Note Hedge due to early conversions that have occurred during the year ended December 31, 2017.

Warrants



	Proceeds		Shares	Strike Price		First Expiration Date
	(in thousands)
2022 Warrants	$	54,071	5,806,936	$	203.40	September 2022
2018 Warrants	$	84,525	7,783,023	$	107.46	February 2019

Separately, we entered into warrant transactions with certain investment banks, whereby we sold warrants to acquire, subject to adjustment, the number of shares of our common stock shown in the table above (the 2022 Warrants and 2018 Warrants, respectively, and collectively, the Warrants). If the average market value per share of our common stock for the reporting period, as measured under the Warrants, exceeds the strike price of the respective Warrants, such Warrants would have a dilutive effect on our earnings per share to the extent we report net income. According to the terms of each of the Warrants, the Warrants will be automatically exercised over a 60 trading day period beginning on the first expiration date of the respective Warrants as set forth above. The Warrants are separate transactions and are not remeasured through earnings each reporting period. The Warrants are not part of the Notes or Note Hedges, and have been accounted for as part of additional paid-in capital.

(in thousands)

2022 Note Hedge

2018 Note Hedge