In August 2019, the Company issued $1,150.0 million in par value of convertible senior notes due 2027 (the "2027 Notes"). The 2027 Notes are senior unsecured obligations of the Company, bear regular interest of 0.375%, payable semi-annually in arrears on March 1 and September 1 of each year, and mature on September 1, 2027, unless repurchased or converted in accordance with their terms prior to maturity.

•during any calendar quarter commencing after the calendar quarter ended December 31, 2019 (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 the 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;

•during the five business day period after any five consecutive trading day period in which the trading price per $1,000 principal amount of 2027 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 on each such trading day; or

In December 2021, the Company made an irrevocable election to settle the principal amount of the 2027 Notes only in cash. Accordingly, upon conversion, the Company will pay the principal amount in cash and will pay, or deliver, as the case may be, any amount in excess of the principal amount in cash, shares of common stock or a combination of cash and shares of the Company stock, at the Company's election. Prior to this election, upon conversion, the Company, could have elected to deliver to holders cash, shares of the Company's common stock or a combination of cash and shares of the Company's common stock for the principal amount.

The initial conversion rate is 8.6073 shares of the Company's common stock per $1,000 principal amount, which is equivalent to an initial conversion price of approximately $116.18 per share, subject to adjustments in certain events, and represents a potential conversion into 9.9 million shares.

In accounting for the issuance of the 2027 Notes, the Company separated the 2027 Notes into liability and equity components. The carrying cost of the liability component was calculated by measuring the fair value of a similar debt obligation 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 2027 Notes. The difference between the principal amount of the 2027 Notes and the proceeds allocated to the liability component (“debt discount”) is amortized to interest expense using the effective interest method over the term of the 2027 Notes. The equity component is recorded in additional paid-in capital in the consolidated balance sheet and will not be 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 2027 Notes, the Company allocated the total transaction costs incurred to the liability and equity components based on their relative values. Transaction costs attributable to the liability component are being amortized to interest expense over the term of the 2027 Notes, and transaction costs attributable to the equity component are netted against the equity component of the 2027 Notes in stockholders’ equity.


	December 31, 2021		December 31, 2020
Liability component:
Principal	$	1,150,000	$	1,150,000
Less: debt discount and issuance costs, net of amortization	(169,030)		(196,359)
Net carrying amount	$	980,970	$	953,641

Equity component:	$	220,529	$	220,529

The estimated fair value of the 2027 Notes at December 31, 2021 and 2020 was $1,359.3 million and $1,277.8 million, respectively. The fair value was determined based on the quoted price of the 2027 Notes in an inactive market on the last trading day of the reporting period and has been classified as Level 2 within the fair value hierarchy. Based on the closing price of the Company's common stock of $117.04 on December 31, 2021, the value of the 2027 Notes if converted to common stock was more than the principal amount of $1,150.0 million.

The Company used $100.0 million of the proceeds from the offering to repurchase shares of its common stock, concurrent with the issuance of the 2027 Notes. The repurchase was made in accordance with a share repurchase program previously approved by the board of directors. Additionally, $127.1 million of the proceeds was used for the net cost of the convertible note hedge and warrant transactions. The remaining net proceeds are intended to be used for share repurchases, working capital and general corporate purposes, including potential acquisitions and other strategic transactions.

To minimize the impact of potential dilution upon conversion of the 2027 Notes, the Company entered into convertible note hedge transactions with respect to its common stock in August 2019. The Company paid $312.2 million for the note hedge transactions. The note hedge transactions cover approximately 9.9 million shares of the Company’s common stock at a strike price that corresponds to the initial conversion price of the 2027 Notes, also subject to adjustment, and are exercisable upon conversion of the 2027 Notes. The Company determined that the note hedge meets the definition of a derivative and is classified in stockholders’ equity, as the note hedge is indexed to the Company's common stock, and the Company, at its election, may pay or deliver to holders cash, shares of the Company's common stock or a combination of cash and shares of the Company's common stock. The Company recorded the purchase of the hedge as a decrease to additional paid-in capital. The Company does not recognize subsequent changes in fair value of the note hedge in its consolidated financial statements.

Separately, in August 2019, the Company entered into warrant transactions, whereby the Company sold warrants to acquire, subject to anti-dilution adjustments, up to 9.9 million shares of the Company’s common stock at a strike price of approximately $178.74 per share. The Company received aggregate proceeds of $185.2 million from the sale of the warrants. The convertible note hedge and warrant transactions will generally have the effect of increasing the conversion price of the 2027 Notes to approximately $178.74 per share. The Company determined that the warrants meet the definition of a derivative and are classified in stockholders’ equity, as the warrants are indexed to the Company's common stock, and the Company, at its election, may pay or deliver to holders cash, shares of the Company's common stock or a combination of cash and shares of the Company's common stock. The Company recorded the proceeds from issuance of the warrants as an increase to additional paid-in capital. The Company does not recognize subsequent changes in fair value of the warrants in its consolidated financial statements.

In May 2018, the Company issued $1,150.0 million in par value of convertible senior notes due 2025 (the "2025 Notes"). The 2025 Notes are senior unsecured obligations of the Company, bear regular interest of 0.125%, payable semi-annually on May 1 and November 1 of each year, and mature on May 1, 2025, unless repurchased or converted prior to maturity.

•during any calendar quarter commencing after the calendar quarter ended June 30, 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 the 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;

•during the five business day period after any five consecutive trading day period in which the trading price per $1,000 principal amount of 2025 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 on each such trading day; or

On or after January 1, 2025, holders may convert all or any portion of their 2025 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 circumstances.

In December 2021, the Company made an irrevocable election to settle the principal amount of the 2025 Notes only in cash. Accordingly, upon conversion, the Company will pay the principal amount in cash and will pay, or deliver, as the case may be, any amount in excess of the principal amount in cash, shares of common stock or a combination of cash and shares of the Company stock, at the Company's election. Prior to this election, upon conversion, the Company, could have elected to deliver to holders cash, shares of the Company's common stock or a combination of cash and shares of the Company's common stock for the principal amount.

The initial conversion rate is 10.5150 shares of the Company's common stock per $1,000 principal amount, which is equivalent to an initial conversion price of approximately $95.10 per share, subject to adjustments in certain events, and represents a potential conversion into 12.1 million shares.

In accounting for the issuance of the 2025 Notes, the Company separated the 2025 Notes into liability and equity components. The carrying cost of the liability component was calculated by measuring the fair value of a similar debt obligation 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 2025 Notes. The difference between the principal amount of the 2025 Notes and the proceeds allocated to the liability component (“debt discount”) is amortized to interest expense using the effective interest method over the term of the 2025 Notes. The equity component is recorded in additional paid-in capital in the consolidated balance sheet and will not be 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 2025 Notes, the Company allocated the total transaction costs incurred to the liability and equity components based on their relative values. Transaction costs attributable to the liability component are being amortized to interest expense over the term of the 2025 Notes, and transaction costs attributable to the equity component are netted against the equity component of the 2025 Notes in stockholders’ equity.


	December 31, 2021		December 31, 2020
Liability component:
Principal	$	1,150,000	$	1,150,000
Less: debt discount and issuance costs, net of amortization	(154,803)		(196,934)
Net carrying amount	$	995,197	$	953,066

Equity component:	$	285,225	$	285,225

The estimated fair value of the 2025 Notes at December 31, 2021 and 2020 was $1,510.4 million and $1,422.8 million, respectively. The fair value was determined based on the quoted price of the 2025 Notes in an inactive market on the last trading day of the reporting period and has been classified as Level 2 within the fair value hierarchy. Based on the closing price of the Company's common stock of $117.04 on December 31, 2021, the value of the 2025 Notes if converted to common stock was more than the principal amount of $1,150.0 million.

The Company used $46.2 million of the proceeds from the offering to repurchase shares of its common stock, concurrent with the issuance of the 2025 Notes. The repurchase was made in accordance with a share repurchase program previously approved by the board of directors. Additionally, $141.8 million of the proceeds was used for the net cost of convertible note hedge and warrant transactions. The Company also used a portion of the net proceeds to repay at maturity the $690.0 million in par value of convertible senior notes due in 2019. The remaining net proceeds are intended to be used for share repurchases, working capital and general corporate purposes, including potential acquisitions and other strategic transactions.

To minimize the impact of potential dilution upon conversion of the 2025 Notes, the Company entered into convertible note hedge transactions with respect to its common stock in May 2018. The Company paid $261.7 million for the note hedge transactions. The note hedge transactions cover approximately 12.1 million shares of the Company’s common stock at a strike price that corresponds to the initial conversion price of the 2025 Notes, also subject to adjustment, and are exercisable upon conversion of the 2025 Notes. The Company determined that the note hedge meets the definition of a derivative and is classified in stockholders’ equity, as the note hedge is indexed to the Company's common stock, and the Company, at its election, may pay or deliver to holders cash, shares of the Company's common stock or a combination of cash and shares of the Company's common stock. The Company recorded the purchase of the hedge as a decrease to additional paid-in capital. The Company does not recognize subsequent changes in fair value of the note hedge in its consolidated financial statements.

Separately, in May 2018, the Company entered into warrant transactions, whereby the Company sold warrants to acquire, subject to anti-dilution adjustments, up to 12.1 million shares of the Company’s common stock at a strike price of approximately $149.18 per share. The Company received aggregate proceeds of $119.9 million from the sale of the warrants. The convertible note hedge and warrant transactions will generally have the effect of increasing the conversion price of the 2025 Notes to approximately $149.18 per share. The Company determined that the warrants meet the definition of a derivative and are classified in stockholders’ equity, as the warrants are indexed to the Company's common stock, and the Company, at its election, may pay or deliver to holders cash, shares of the Company's common stock or a combination of cash and shares of the Company's common stock. The Company recorded the proceeds from issuance of the warrants as an increase to additional paid-in capital. The Company does not recognize subsequent changes in fair value of the warrants in its consolidated financial statements.

In February 2014, the Company issued $690.0 million in par value of convertible senior notes due 2019 (the "2019 Notes"). The 2019 Notes were senior unsecured obligations of the Company and did not bear regular interest. The 2019 Notes matured and were repaid in full on February 15, 2019 as no repurchases or conversions occurred prior to maturity.

In May 2018, the Company entered into a $500.0 million five-year, revolving credit agreement (the “Credit Agreement”). Borrowings under the Credit Agreement may be used to finance working capital needs and for general corporate purposes. The Credit Agreement provides for an initial $500.0 million in revolving loans. Under specified circumstances, the facility can be increased to up to $1.0 billion in aggregate principal amount. The Credit Agreement expires in May 2023.

Borrowings under the Credit Agreement bear interest, at the Company's option, at a base rate plus a spread of 0.00% to 0.25% or an adjusted LIBOR rate plus a spread of 0.875% to 1.25%, in each case with such spread being determined based on the Company's consolidated leverage ratio specified in the Credit Agreement. Regardless of what amounts, if any, are outstanding under the Credit Agreement, the Company is also obligated to pay an ongoing commitment fee on undrawn amounts at a rate of 0.075% to 0.15%, with such rate being based on the Company's consolidated leverage ratio specified in the Credit Agreement.

The Credit Agreement contains customary representations and warranties, affirmative and negative covenants and events of default. Principal covenants include a maximum consolidated leverage ratio and a minimum consolidated interest coverage ratio. There were no outstanding borrowings under the Credit Agreement as of December 31, 2021.

The 2027 Notes bear interest at a fixed rate of 0.375%. The interest is payable semi-annually on March 1 and September 1 of each year. The 2027 Notes have an effective interest rate of 3.1% attributable to the conversion feature. The 2025 Notes bear interest at a fixed rate of 0.125%. The interest is payable semi-annually on May 1 and November 1 of each year. The 2025 Notes have an effective interest rate of 4.26% attributable to the conversion feature. The 2019 Notes did not bear regular interest, but had an effective interest rate of 3.2% attributable to the conversion feature. The Company is also obligated to pay ongoing commitment fees under the terms of the Credit Agreement. The following table sets forth total interest expense included in the consolidated statements of income for the years ended December 31, 2021, 2020 and 2019 (in thousands):


	2021		2020		2019
Amortization of debt discount and issuance costs	$	69,697	$	67,153	$	52,059
Coupon interest payable on 2025 Notes	1,437		1,437		1,436
Coupon interest payable on 2027 Notes	4,313		4,312		1,557
Revolving credit facility contractual interest expense	557		548		513
Capitalization of interest expense	(3,672)		(4,330)		(6,201)
Total interest expense	$	72,332	$	69,120	$	49,364