(in thousands)	June 30, 2020			December 31, 2019
2.25% Senior Convertible Notes due 2021:
Principal amount	$	650,000		$	650,000
Unamortized debt discount		(13,344	)		(22,501	)
Unamortized debt issuance costs		(2,514	)		(4,201	)
		634,142			623,298
1.00% Senior Convertible Notes due 2023:
Principal amount		450,000			—
Unamortized debt discount		(55,761	)		—
Unamortized debt issuance costs		(13,512	)		—
		380,727			—
0.375% Senior Convertible Notes due 2025:
Principal amount		450,000			—
Unamortized debt discount		(73,549	)		—
Unamortized debt issuance costs		(10,459	)		—
		365,992			—
Total Senior Convertible Notes	$	1,380,861		$	623,298

Less: Current portion		(634,142	)		—
Long-term Senior Convertible Notes	$	746,719		$	623,298

In March 2016, the Company issued $650.0 million principal amount of unsecured Senior Convertible Notes with a stated interest rate of 2.25% and a maturity date of March 15, 2021 (the “2021 Notes”). The net proceeds from the offering, after deducting initial purchasers' discounts and costs directly related to the offering, were approximately $634.1 million. The 2021 Notes may be settled in cash, stock, or a combination thereof, solely at the Company's discretion. It is the Company's current intent and policy to settle all conversions through combination settlement, which involves satisfying the principal amount outstanding with cash and any note conversion value over the principal amount in shares of the Company's common stock. The initial conversion rate of the 2021 Notes is 16.7158 shares per $1,000 principal amount, which is equivalent to a conversion price of approximately $59.82 per share, subject to adjustments. The Company uses the treasury share method for assumed conversion of the 2021 Notes to compute the weighted average shares of common stock outstanding for diluted earnings per share. The Company also entered into transactions for a convertible notes hedge (the “2021 Hedge”) and warrants (the “2021 Warrants”) concurrently with the issuance of the 2021 Notes.

The cash conversion feature of the 2021 Notes required bifurcation from the notes and was initially accounted for as an equity instrument classified to stockholders’ equity, which resulted in recognizing $84.8 million in additional paid-in-capital during 2016.

The interest expense recognized on the 2021 Notes during the three months ended June 30, 2020 includes $3.7 million, $4.6 million and $0.9 million for the contractual coupon interest, the accretion of the debt discount and the amortization of the debt issuance costs, respectively. The interest expense recognized on the 2021 Notes during the six months ended June 30, 2020 includes $7.3 million, $9.2 million and $1.7 million for the contractual coupon interest, the accretion of the debt discount and the amortization of the debt issuance costs, respectively. The interest expense recognized on the 2021 Notes during the three months ended June 30, 2019 includes $3.7 million, $4.4 million and $0.8 million for the contractual coupon interest, the accretion of the debt discount and the amortization of the debt issuance costs, respectively. The interest expense recognized on the 2021 Notes during the six months ended June 30, 2019 includes $7.3 million, $8.7 million and $1.5 million for the contractual coupon interest, the accretion of the debt discount and the amortization of the debt issuance costs, respectively. The effective interest rate on the 2021 Notes is 5.8%, which includes the interest on the notes, amortization of the debt discount and debt issuance costs. Interest on the 2021 Notes began accruing upon issuance and is payable semi-annually.

Prior to September 15, 2020, holders may convert their 2021 Notes only under the following conditions: (a) during any calendar quarter beginning June 30, 2016, if the reported sale price of the Company's common stock for at least 20 days out of 30 consecutive trading days ending on the last trading day of the immediately preceding calendar quarter is greater than 130% of the conversion price on each applicable trading day; (b) during the five business day period in which the trading price of the 2021 Notes falls below 98% of the product of (i) the last reported sale price of the Company's common stock and (ii) the conversion rate on that date; and (c) upon the occurrence of specified corporate events, as defined in the 2021 Notes. From September 15, 2020 and until the close of business on the second scheduled trading day immediately preceding March 15, 2021, holders may convert their 2021 Notes at any time (regardless of the foregoing circumstances). Prior to March 20, 2019, the Company could not redeem the 2021 Notes. The Company may redeem the 2021 Notes, at its option, in whole or in part on or after March 20, 2019 until the close of business on the business day immediately preceding September 15, 2020 if the last reported sale price of the Company’s common stock has been at least 130% of the conversion price then in effect for at least 20 trading days during any 30 consecutive trading day period ending on, and including, the trading day immediately preceding the date on which the Company delivers written notice of a redemption. The redemption price will be equal to 100% of the principal amount of such 2021 Notes to be redeemed plus accrued and unpaid interest to, but excluding, the redemption date. No principal payments are due on the 2021 Notes prior to maturity. Other than restrictions relating to certain fundamental changes and consolidations, mergers or asset sales and customary anti-dilution adjustments, the 2021 Notes do not contain any financial covenants and do not restrict the Company from paying dividends or issuing or repurchasing any of its other securities. As of June 30, 2020, the Company is unaware of any current events or market conditions that would allow holders to convert the 2021 Notes.

In connection with the offering of the 2021 Notes, the Company entered into the hedge transaction with the initial purchasers of the 2021 Notes and/or their affiliates (the “2021 Counterparties”) entitling the Company to purchase up to 10,865,270 shares of the Company's common stock at an initial stock price of $59.82 per share, each of which is subject to adjustment. The cost of the 2021 Hedge was $111.2 million and accounted for as an equity instrument by recognizing $111.2 million in additional paid-in-capital during 2016. The 2021 Hedge will expire on March 15, 2021. The 2021 Hedge is expected to reduce the potential equity dilution upon conversion of the 2021 Notes if the daily volume-weighted average price per share of the Company's common stock exceeds the strike price of the 2021 Hedge. An assumed exercise of the 2021 Hedge by the Company is considered anti-dilutive since the effect of the inclusion would always be anti-dilutive with respect to the calculation of diluted earnings per share.

The Company sold warrants to the 2021 Counterparties to acquire up to 10,865,270 shares of the Company’s common stock. The 2021 Warrants will expire on various dates from June 2021 through December 2021 and may be settled in cash or net shares. It is the Company's current intent and policy to settle all conversions in shares of the Company’s common stock. The Company received $44.9 million in cash proceeds from the sale of the 2021 Warrants, which was recorded in additional paid-in-capital. The 2021 Warrants could have a dilutive effect on the Company's earnings per share to the extent that the price of the Company's common stock during a given measurement period exceeds the strike price of the 2021 Warrants, which is $80.00 per share. The Company uses the treasury share method for assumed conversion of its 2021 Warrants to compute the weighted average common shares outstanding for diluted earnings per share.

In June 2020, the Company issued $450.0 million principal amount of unsecured Senior Convertible Notes with a stated interest rate of 1.00% and a maturity date of June 1, 2023. The net proceeds from the offering, after deducting initial purchasers’ discounts and costs directly related to the offering, were approximately $436.2 million. The 2023 Notes will initially be settled in cash, or, if the Company has sufficient reserved shares, the Company may settle conversions in cash, stock, or a combination thereof, solely at the Company’s discretion. As of June 30, 2020, the Company did not have sufficient reserved shares with respect to the 2023 Notes. To the extent the Company in the future has sufficient reserved shares, it is the Company’s current intent and policy to settle all conversions through combination settlement, which involves satisfying the principal amount outstanding with cash and any note conversion value over the principal amount in shares of the Company’s common stock. The initial conversion rate of the 2023 Notes is 11.8778 shares per $1,000 principal amount, which is equivalent to a conversion price of approximately $84.19 per share, subject to adjustments. In addition, following certain corporate events that occur prior to the maturity date, the Company will increase the conversion rate for a holder who elects to convert its 2023 Notes in connection with such a corporate event in certain circumstances. The Company also entered into transactions for a convertible notes hedge and warrants concurrently with the issuance of the 2023 Notes.

As discussed in Note 3, the Embedded Conversion Derivative requires bifurcation from the 2023 Notes and is accounted for as a liability, which is included in long-term liabilities in the Company’s Unaudited Consolidated Balance Sheet. The fair value of the 2023 Notes Embedded Conversion Derivative at the time of issuance of the 2023 Notes was $57.2 million, and was recorded as the original debt discount for purposes of accounting for the debt component of the 2023 Notes. This discount will be recognized as interest expense using the effective interest method over the term of the 2023 Notes.

The interest expense recognized on the 2023 Notes during both the three and six months ended June 30, 2020 includes $0.4 million, $1.5 million and $0.3 million for the contractual coupon interest, the accretion of the debt discount and the amortization of the debt issuance costs, respectively. The effective interest rate on the 2023 Notes is 6.8%, which includes the interest on the notes, amortization of the debt discount and debt issuance costs. Interest on the 2023 Notes began accruing upon issuance and is payable semi-annually.

Prior to February 1, 2023, holders may convert their 2023 Notes only under the following conditions: (a) during any calendar quarter commencing after the calendar quarter ending on September 30, 2020 (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; (b) during the five business day period after any five consecutive trading day period (the “measurement period”) in which the trading price of the 2023 Notes 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 on such trading day; or (c) upon the occurrence of specified corporate events, as defined in the 2023 Notes. On or after February 1, 2023, until the close of business on the second scheduled trading day immediately preceding June 1, 2023, holders may convert their 2023 Notes at any time, regardless of the foregoing conditions.

The Company may not redeem the 2023 Notes prior to the maturity date and no principal payments are due on the 2023 Notes prior to maturity. Other than restrictions relating to certain fundamental changes and consolidations, mergers or asset sales and customary anti-dilution adjustments, the 2023 Notes do not contain any financial covenants and do not restrict the Company from conducting significant restructuring transactions, paying dividends or issuing or repurchasing any of its other securities. As of June 30, 2020, the Company is unaware of any current events or market conditions that would allow holders to convert the 2023 Notes.

In connection with the sale of the 2023 Notes, the Company entered into privately negotiated call option transactions with certain dealers, which included affiliates of certain of the initial purchasers of the 2023 Notes and other financial institutions (the “2023 Counterparties”), entitling the Company to purchase up to 5,345,010 shares of the Company’s common stock at an initial stock price of $84.19 per share, each of which is subject to adjustment. The 2023 Hedge will initially be settled in cash, or, if the Company has sufficient reserved shares with respect to the 2023 Notes, the 2023 Hedge may be settled in cash, stock, or a combination thereof. As discussed in Note 3, the 2023 Hedge is accounted for as a derivative asset as of June 30, 2020, and the Convertible Note Hedge Derivative is included in long-term assets in the Company’s Unaudited Consolidated Balance Sheet. The cost of the 2023 Hedge was $69.5 million. The 2023 Hedge will expire on the second scheduled trading day immediately preceding June 1, 2023. The 2023 Hedge is expected to reduce the potential equity dilution upon conversion of the 2023 Notes if the daily volume-weighted average price per share of the Company’s common stock exceeds the strike price of the 2023 Hedge.

The Company sold warrants to the 2023 Counterparties to acquire up to 3,093,500 shares of the Company’s common stock. The 2023 Warrants will expire on various dates from September 2023 through November 2023 and may be settled in net shares or cash, subject to certain conditions. It is the Company’s current intent and policy to settle all conversions in shares of the Company’s common stock. The Company received $46.8 million in cash proceeds from the sale of the 2023 Warrants, which was recorded in additional paid-in-capital. The 2023 Warrants could have a dilutive effect on the Company’s earnings per share to the extent that the price of the Company's common stock during a given measurement period exceeds the strike price of the 2023 Warrants, which is $104.84 per share. The Company uses the treasury share method for assumed conversion of its 2023 Warrants to compute the weighted average common shares outstanding for diluted earnings per share.

In March 2020, the Company issued $450.0 million principal amount of unsecured Senior Convertible Notes with a stated interest rate of 0.375% and a maturity date of March 15, 2025 (the “2025 Notes”). The net proceeds from the offering, after deducting initial purchasers’ discounts and costs directly related to the offering, were approximately $437.0 million. The 2025 Notes may be settled in cash, stock, or a combination thereof, solely at the Company’s discretion. It is the Company's current intent and policy to settle all conversions through combination settlement, which involves satisfying the principal amount outstanding with cash and any note conversion value over the principal amount in shares of the Company’s common stock. The initial conversion rate of the 2025 Notes is 10.7198 shares per $1,000 principal amount, which is equivalent to a conversion price of approximately $93.29 per share, subject to adjustments. In addition, following certain corporate events that occur prior to the maturity date or if the Company issues a notice of redemption, the Company will increase the conversion rate for a holder who elects to convert its 2025 Notes in connection with such a corporate event or in connection with such redemption in certain circumstances. The Company uses the treasury share method for assumed conversion of the 2025 Notes to compute the weighted average shares of common stock outstanding for diluted earnings per share. The Company also entered into transactions for a convertible notes hedge (the “2025 Hedge”) and warrants (the “2025 Warrants”) concurrently with the issuance of the 2025 Notes.

The cash conversion feature of the 2025 Notes required bifurcation from the notes and was initially accounted for as an equity instrument classified to stockholders’ equity, which resulted in recognizing $78.3 million in additional paid-in-capital during the six months ended June 30, 2020.

The interest expense recognized on the 2025 Notes during the three months ended June 30, 2020 includes $0.4 million, $3.5 million and $0.4 million for the contractual coupon interest, the accretion of the debt discount and the amortization of the debt issuance costs, respectively. The interest expense recognized on the 2025 Notes during the six months ended June 30, 2020 includes $0.6 million, $4.7 million and $0.6 million for the contractual coupon interest, the accretion of the debt discount and the amortization of the debt issuance costs, respectively. The effective interest rate on the 2025 Notes is 4.9%, which includes the interest on the notes, amortization of the debt discount and debt issuance costs. Interest on the 2025 Notes began accruing upon issuance and is payable semi-annually.

Prior to September 15, 2024, holders may convert their 2025 Notes only under the following conditions: (a) during any calendar quarter commencing after the calendar quarter ending on June 30, 2020 (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; (b) during the five business day period after any five consecutive trading day period (the “measurement period”) in which the trading price of the 2025 Notes 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 on such trading day; (c) if the Company calls any or all of the 2025 Notes for redemption, at any time prior to the close of business on the second scheduled trading day preceding the redemption date; or (d) upon the occurrence of specified corporate events, as defined in the 2025 Notes. On or after September 15, 2024, until the close of business on the second scheduled trading day immediately preceding March 15, 2025, holders may convert their 2025 Notes at any time, regardless of the foregoing conditions.

The Company may not redeem the 2025 Notes prior to March 20, 2023. The Company may redeem the 2025 Notes, at its option, in whole or in part, on or after March 20, 2023 until the close of business on the business day immediately preceding September 15, 2024, if the last reported sale price of the Company’s common stock has been at least 130% of the conversion price then in effect for at least 20 trading days during any 30 consecutive trading day period ending on, and including, the trading day immediately preceding the date on which the Company delivers written notice of a redemption. The redemption price will be equal to 100% of the principal amount of such 2025 Notes to be redeemed plus accrued and unpaid interest to, but excluding, the redemption date. No principal payments are due on the 2025 Notes prior to maturity. Other than restrictions relating to certain fundamental changes and consolidations, mergers or asset sales and customary anti-dilution adjustments, the 2025 Notes do not contain any financial covenants and do not restrict the Company from conducting significant restructuring transactions, paying dividends or issuing or repurchasing any of its other securities. As of June 30, 2020, the Company is unaware of any current events or market conditions that would allow holders to convert the 2025 Notes.

In connection with the sale of the 2025 Notes, the Company entered into privately negotiated call option transactions with certain dealers, which included affiliates of certain of the initial purchasers of the 2025 Notes and other financial institutions (the “2025 Counterparties”), entitling the Company to purchase up to 4,823,910 shares of the Company’s common stock at an initial stock price of $93.29 per share, each of which is subject to adjustment. The cost of the 2025 Hedge was $78.3 million and accounted for as an equity instrument by recognizing $78.3 million in additional paid-in-capital during the six months ended June 30, 2020. The 2025 Hedge will expire on the second scheduled trading day immediately preceding March 15, 2025. The 2025 Hedge is expected to reduce the potential equity dilution upon conversion of the 2025 Notes if the daily volume-weighted average price per share of the Company’s common stock exceeds the strike price of the 2025 Hedge. An assumed exercise of the 2025 Hedge by the Company is considered anti-dilutive since the effect of the inclusion would always be anti-dilutive with respect to the calculation of diluted earnings per share.

The Company sold warrants to the 2025 Counterparties to acquire up to 4,823,910 shares of the Company’s common stock. The 2025 Warrants will expire on various dates from June 2025 through October 2025 and may be settled in net shares or cash, subject to certain conditions. It is the Company’s current intent and policy to settle all conversions in shares of the Company’s common stock. The Company received $47.1 million in cash proceeds from the sale of the 2025 Warrants, which was recorded in additional paid-in-capital. The 2025 Warrants could have a dilutive effect on the Company’s earnings per share to the extent that the price of the Company's common stock during a given measurement period exceeds the strike price of the 2025 Warrants, which is $127.84 per share. The Company uses the treasury share method for assumed conversion of its 2025 Warrants to compute the weighted average common shares outstanding for diluted earnings per share.

In February 2020, the Company entered into a Second Amended and Restated Credit Agreement (the “2020 Credit Agreement”) for a revolving senior credit facility (the “2020 Facility”), which replaced the previous Amended and Restated Credit Agreement the Company had entered into in April 2017. The 2020 Credit Agreement was further amended in May 2020 to, among other things, provide additional flexibility in determining the financial covenant leverage ratios for the second and third fiscal quarters of 2020 and to adjust certain margin and benchmark rates used to determine interest under the 2020 Facility. The 2020 Credit Agreement provides for secured revolving loans, multicurrency loan options and letters of credit in an aggregate amount of up to $550.0 million. The 2020 Credit Agreement also contains an expansion feature, which allows the Company to increase the aggregate principal amount of the 2020 Facility provided the Company remains in compliance with the underlying financial covenants on a pro forma basis, including but not limited to, compliance with the consolidated interest coverage ratio and certain consolidated leverage ratios.

The 2020 Facility matures in February 2025 (subject to an earlier springing maturity date), and includes a sublimit of $50.0 million for standby letters of credit, a sublimit of $250.0 million for multicurrency borrowings, and a sublimit of $5.0 million for swingline loans. All assets of the Company and its material domestic subsidiaries continue to be pledged as collateral under the 2020 Facility (subject to customary exceptions) pursuant to the terms set forth in the Second Amended and Restated Security and Pledge Agreement executed in favor of the administrative agent by the Company. Each of the Company’s material domestic subsidiaries guarantee the 2020 Facility. In connection with the 2020 Facility, the Company incurred issuance costs which will be amortized over the term of the 2020 Facility. The Company did not carry any outstanding revolving loans under the 2020 Facility as of June 30, 2020 and December 31, 2019.

Any borrowings under the 2020 Facility are intended to be used by the Company to provide financing for working capital and other general corporate purposes, including potential mergers and acquisitions and to refinance indebtedness. Borrowings under the 2020 Facility bear interest, at the Company’s option, at a rate equal to an applicable margin plus: (a) the applicable Eurocurrency Rate (as defined in the 2020 Credit Agreement), or (b) a base rate determined by reference to the highest of (1) the federal funds effective rate plus 0.50%, (2) the Bank of America prime rate, and (3) the Eurocurrency Rate for an interest period of one month plus 1.00%. The margin for the 2020 Facility ranges, based on the Company’s consolidated total net leverage ratio, from 0.50% to 1.25% in the case of base rate loans and from 1.50% to 2.25% in the case of Eurocurrency Rate loans. The 2020 Facility includes an unused line fee ranging, based on the Company’s consolidated total net leverage ratio, from 0.35% to 0.50% per annum on the revolving commitment.

The 2020 Credit Agreement contains affirmative, negative, permitted acquisition and financial covenants, and events of default customary for financings of this type. The financial covenants require the Company to maintain a consolidated interest coverage ratio and certain consolidated leverage ratios, which are measured on a quarterly basis. The 2020 Facility grants the lenders preferred first priority liens and security interests in capital stock, intercompany debt and all of the present and future property and assets of the Company and each guarantor. The Company is currently in compliance with the 2020 Credit Agreement covenants.