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

Upon conversion of the 2022 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 upon settlement. We settled the principal amount of our 2018 Notes with cash and currently intend to settle the principal amount of the 2022 Notes with cash.



	Convertible Date	Initial Conversion Price per Share		Initial Conversion Rate per $1,000 Par Value	Initial Number of Shares
					(in thousands)
2022 Notes	February 1, 2022	$	134.75	7.42 shares	5,807
2018 Notes	July 1, 2018	$	73.88	13.54 shares	7,783

Conversion of the 2022 Notes prior to the Convertible Date. At any time prior to the close of business on the business day immediately preceding February 1, 2022 (Convertible Date), holders of the 2022 Notes may convert their Notes at their option, only if one of the following conditions are met:

Conversion of the 2022 Notes on or after the Convertible Date. On or after the 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, and such conversions will settle upon the Maturity Date. Upon settlement, 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.

The conversion price of the 2022 Notes will be subject to adjustment in some events. Holders of the 2022 Notes who convert their 2022 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 2022 Notes may require us to purchase with cash all or a portion of the 2022 Notes upon the occurrence of a fundamental change, at a purchase price equal to 100% of the principal amount of the 2022 Notes plus any accrued and unpaid special interest, if any.

The Conversion Condition for the 2022 Notes was met for all quarters ended June 30, 2018 through December 31, 2019, except for the quarter ended December 31, 2018. Therefore, our 2022 Notes became convertible at the holders’ option beginning on July 1, 2018 and continue to be convertible through March 31, 2020, except for the quarter ended March 31, 2019 because the Conversion Condition for the 2022 Notes was not met for the quarter ended December 31, 2018. During the year ended December 31, 2019, we paid cash to settle an immaterial principal amount of the 2022 Notes. Based on additional conversion requests we have received through the filing date, we expect to settle in cash an aggregate of approximately $2.5 million and $5.2 million in principal amount of the 2022 Notes during the first and second quarter of 2020, respectively. We may receive additional conversion requests that require settlement in the second quarter of 2020.

The Conversion Condition for the 2018 Notes was met for all quarters ended June 30, 2017 through March 31, 2018. Therefore, our 2018 Notes became convertible at the holders’ option beginning on July 1, 2017 and continued to be convertible at the holders’ option through June 30, 2018. Conversion requests received subsequent to June 30, 2018 were settled on the maturity date. We settled $413.2 million principal amount of the 2018 Notes in early conversions and the remaining principal amount of $161.8 million was settled on November 1, 2018, the maturity date of our 2018 Notes.

The conversion value over the principal amount for the early 2018 Note conversions was settled in cash from the exercise of the 2018 Note Hedges (as defined below). The conversion value over the principal amount for the principal amount settled on November 1, 2018 was satisfied with approximately 1.3 million shares of our common stock, which was entirely offset by shares of our common stock delivered to us by the 2018 Note Hedge counterparties under the 2018 Note Hedge, and cash in lieu of fractional shares. The shares delivered to us by the 2018 Note Hedge counterparties were immediately retired. As a result of the early note conversions, we recorded a loss of $4.1 million for the year ended December 31, 2018. As a result of the settlement of the 2018 Notes and the 2018 Note Hedges, we recorded an aggregate $6.4 million net reduction to additional paid-in capital, reflecting $773.3 million of fair value adjustments to the conversion option settled, offset by a $766.9 million benefit from the exercise of the 2018 Note Hedges.

For statement of cash flow presentation, we bifurcated the principal amount of the 2018 Notes paid during the year ended December 31, 2018 into two components: the portion of the repayment attributable to debt discount is classified as cash outflows from operating activities, and the portion of the repayment attributable to the principal is classified as cash outflows from financing activities.

We consider the fair value of the 2022 Notes at December 31, 2019 to be a Level 2 measurement. The estimated fair value of the 2022 Notes at December 31, 2019 and 2018 based on the closing trading price per $100 of the Notes was as follows (in thousands):



	Year Ended December 31,
	2019		2018		2017
Amortization of debt issuance cost
2022 Notes	$	1,606	$	1,531	$	860
2018 Notes	—		1,131		1,911
Amortization of debt discount
2022 Notes	31,677		30,159		16,921
2018 Notes	—		19,912		33,702
Total	$	33,283	$	52,733	$	53,394
Effective interest rate of the liability component
2022 Notes	4.75%
2018 Notes	6.50%

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 2018 Note Hedge offset the dilution and cash payments in excess of the principal amount of the converted 2018 Notes and expired upon the maturity date of the 2018 Notes, which was November 1, 2018.

The 2022 Note Hedge covers shares of our common stock at a strike price per share that corresponds to the initial conversion price of the 2022 Notes, subject to adjustment, and are exercisable upon conversion of the 2022 Notes. If exercised, we may elect to receive cash, shares of our common stock, or a combination of cash and shares. The 2022 Note Hedge will expire upon the maturity of the 2022 Notes. The 2022 Note Hedge is intended to reduce the potential economic dilution upon conversion of the 2022 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 2022 Notes. The 2022 Note Hedge is a separate transaction and is not part of the terms of the 2022 Notes. Holders of the 2022 Notes will not have any rights with respect to the 2022 Note Hedge. The 2022 Note Hedge does not impact earnings per share, as it was entered into to offset any dilution from the 2022 Notes.



	Proceeds		Shares	Strike Price		First Expiration Date	Shares as of December 31, 2019
	(in thousands)		(in thousands)				(in thousands)
2022 Warrants	$	54,071	5,807	$	203.40	September 1, 2022	5,807
2018 Warrants	$	84,525	7,783	$	107.46	February 1, 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 2018 Warrants were automatically exercised and the 2022 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.

As the 2022 Warrants will be net share settled, the total number of shares of our common stock we will issue depends on the daily volume-weighted average stock prices over a 60 trading day period beginning on the first expiration date of the 2022 Warrants, which will be September 1, 2022. During the year end December 31, 2019, we issued approximately 4.3 million shares of our common stock upon the automatic exercise of the 2018 Warrants. The 2018 Warrants were no longer outstanding as of the second quarter of 2019. We expect to issue additional shares of our common stock in the second half of 2022 upon the automatic exercise of the 2022 Warrants. The 2022 Warrants could have a dilutive effect to the extent that the daily volume-weighted average stock prices over a 60 trading day period beginning on September 1, 2022 exceeds the strike price of the 2022 Warrants. Based on the volume-weighted average stock price on December 31, 2019, the total number of shares of our common stock to be issued upon the automatic exercise of the 2022 Warrants would be approximately 1.6 million. The actual number of shares of our common stock issuable upon the automatic exercise of the 2022 Warrants, if any, is unknown at this time.