Long-term Debt	9 Months Ended
Sep. 30, 2020
Debt Disclosure [Abstract]
Long-term Debt	5. Long-term Debt Convertible Senior Notes On September 16, 2019, the Company completed a private offering of the 2019 Convertible Notes with an aggregate principal amount of $220.0 million which were issued pursuant to the Indenture with U.S. Bank National Association, as trustee. The net proceeds from the sale of the 2019 Convertible Notes were approximately $212.9 million after deducting the initial purchasers’ discounts and commissions of $6.6 million and offering expenses of $0.5 million by the Company. The Company used $28.4 million of the net proceeds from the sale to pay the cost of the capped call transactions in September 2019 described below. On May 12,2020, the Company issued the 2020 Convertible Notes with an aggregate principal amount of $300.0 million. The net proceeds from the sale of the 2020 Convertible Notes were approximately $322.9 million after deducting the purchasers’ discounts and commission of $5.7 million and offering expenses of $0.3 million. The Company used $43.1 million of the net proceeds from the sale to pay the cost of the additional capped call transactions in May 2020 described below. The Convertible Notes are senior unsecured obligations of the Company and bear interest at a rate of 3.5% per year payable semiannually in arrears on March 15 and September 15 of each year, beginning on March 15, 2020. The Convertible Notes will mature on September 15, 2026, unless converted earlier, redeemed or repurchased in accordance with their terms. The Convertible Notes are convertible into shares of the Company’s common stock at an initial conversion rate of 25.3405 shares per $1,000 principal amount of Convertible Notes (equivalent to an initial conversion price of approximately $39.46 per share of common stock). The conversion rate is subject to customary anti-dilution adjustments. In addition, following certain events that occur prior to the maturity date or if the Company deliver a notice of redemption, the Company will increase the conversion rate for a holder who elects to convert its Convertible Notes in connection with such corporate event or a notice of redemption, as the case may be, in certain circumstances as provided in the indenture. Prior to March 15, 2026, the Convertible Notes are convertible only upon the occurrence of certain events. On or after March 15, 2026 until the close of business on the second scheduled trading day immediately preceding the maturity date of the Convertible Notes, holders may convert the Convertible Notes at any time. Upon conversion of the Convertible Notes, the Company will pay or deliver, as the case may be, cash, shares of the Company’s common stock or a combination of cash and shares of common stock, at the Company’s election. Prior to September 20, 2023, the Company may not redeem the Convertible Notes. The Company may redeem for cash all or a portion of the Convertible Notes, at its option, on or after September 20, 2023 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 (whether or not consecutive), including the trading day immediately preceding the date on which the Company provides a notice of redemption, during any 30 consecutive trading day period ending on, and including, the trading day immediately preceding the date on which the Company provides notice of redemption. The redemption price will be equal to 100% of the principal amount of the Convertible Notes to be redeemed, plus accrued and unpaid interest to, but excluding, the redemption date. If the Company undergoes a “fundamental change,” as defined in the Indenture, prior to maturity, subject to certain conditions, holders may require the Company to repurchase for cash all or any portion of their Convertible Notes at a fundamental change repurchase price equal to 100% of the principal amount of the notes to be repurchased, plus any accrued and unpaid interest to, but excluding, the fundamental change repurchase date. The Company used an effective interest rate of 10.5% to determine the liability component of the 2019 and 2020 Convertible Notes. This resulted in the recognition of $145.1 million and $204.5 million as the liability component of the 2019 and 2020 Convertible Notes, respectively and the recognition of the residual amount of $74.9 million and $95.5 million as the debt discount with a corresponding increase to additional paid in capital for the equity component of the 2019 and 2020 Convertible Notes, respectively. The 2020 Convertible Notes aggregate debt issuance costs of $6.0 million were allocated to the liability and equity components in the amounts of $3.7 and $2.3 million, respectively. The 2019 Convertible Notes aggregate debt issuance costs of $7.1 million were allocated to the liability and equity components in the amounts of $4.7 million and $2.4 million, respectively. Interest expense for the Convertible Notes was $9.5 million and $20.3 million and for the three and nine months ended September 30, 2020, respectively. For the three months ended September 30, 2020, interest expense included the amortization of the discount on the Convertible Notes of $4.8 million, accrued semi-annual coupon payable of $4.6 million and amortization of debt issuance costs of $0.1 million. For the nine months ended September 30, 2020 interest expense included the amortization of the discount on the Convertible Notes of $10.1 million, accrued semi-annual coupon payable of $9.8 million and amortization of debt issuance costs of $0.4 million. As of September 30, 2020, $8.0 million of debt issuance costs was recorded on the consolidated balance sheet as a reduction to the carrying amount of the Convertible Notes. The aggregate balance of the Convertible Notes, net of unamortized debt issuance costs, as of September 30, 2020 and December 31, 2019 was $353.8 million and $142.6 million respectively. Capped Call Transactions On September 11, 2019, and May 6, 2020 concurrently with the pricing of the 2019 Convertible Notes and the 2020 Convertible Notes, respectively, the Company entered into capped call transactions with two counterparties. The capped call transactions are expected generally to reduce the potential dilution to the Company’s common stock upon any conversion of Convertible Notes and/or offset any cash payments the Company is required to make in excess of the principal amount of converted Convertible Notes, as the case may be, in the event that the market price per share of the Company’s common stock, as measured under the terms of the capped call transactions, is greater than the strike price of the capped call transactions, which is initially $39.4625 (the conversion price of the Convertible Notes) and is subject to anti-dilution adjustments substantially similar to those applicable to the conversion rate of such Convertible Notes. If, however, the market price per share of the Company’s common stock, as measured under the terms of the capped call transactions, exceeds the cap price of the capped call transactions, which is initially $63.14 per share, there would nevertheless be dilution and/or there would not be an offset of such potential cash payments, in each case, to the extent that such market price exceeds the cap price of the capped call transactions. Pursuant to ASC 815-40 Derivatives and Hedging, the Company determined that the capped call transactions should be classified as equity instruments and the capped call premium paid in the amount of $28.4 million and $43.1 million were recorded as reductions to additional paid-in capital as September 30, 2020 for the 2019 and 2020 Convertible Notes, respectively. Term Loan Facility On October 20, 2017, the Company entered into a loan and security agreement with Silicon Valley Bank (“SVB”) to provide for a $20.0 million term loan facility (the “term loan facility”). Borrowings under the term loan facility accrued interest at a floating rate per annum equal to the WSJ prime rate plus 1.50%. Under the agreement, the Company was required to make monthly interest-only payments through November 1, 2019 and was required to make 24 equal monthly payments of principal, plus accrued interest, from November 1, 2019 through October 1, 2021, when all unpaid principal and interest became due and payable. On March 26, 2019, the Company voluntarily repaid all outstanding amounts due and owed, including applicable termination fees, under the term loan facility. The final payment of $21.8 million totaled per diem interest of $0.1 million and $21.7 million for the outstanding balance of the term loan which included (i) a final payment equal to 8% of the original principal amount of the term loan of $1.6 million, and (ii) a prepayment fee contractually owed of $0.1 million plus other fees which resulted in a total loss on extinguishment of debt of $1.2 million. In connection with the Company’s entry into the term loan facility, the Company issued to SVB a warrant to purchase 14,064 shares of the Company’s common stock with an exercise price per share of $5.484. The warrant has a ten-year term and included a put option pursuant to which, in the event of an acquisition, change in control or dissolution or winding up of the Company, or the expiration of the warrant, SVB could have required the Company to repurchase the warrant for a total aggregate purchase price of $250 thousand. The warrants were exercised in November 2019. Promissory Note On October 19, 2017, the Company issued and sold an unsecured promissory note in the principal amount of $7.0 million to Golda Darty Partners S.A. (“GDP”). The promissory note accrued interest at a rate per annum of 8.0%, and was due and payable quarterly in arrears on the 19th day of each April, July, October and January. The promissory note had a maturity date of October 19, 2022 when the $7.0 million would be due and payable in its entirety. The promissory note was contractually subordinated to the Company’s obligations to SFJ under the SFJ Agreement. On September 16, 2019, the Company voluntarily repaid all outstanding amounts due and owed under the promissory note, except for a small amount of interest subsequently repaid. The payment of $7.1 million totaled per diem interest of $0.1 million and $7.0 million for the outstanding principal balance of the promissory note. In connection with the issuance and sale of the above promissory note, the Company issued to GDP a warrant to purchase 93,764 shares of the Company’s common stock at a price per share of $5.484, which was exercised in whole in October 2017. The Company recorded the fair value of the warrant in the aggregate amount of $0.4 million as a discount to the promissory note. This amount was being accreted as additional interest expense over the term of the promissory note. Upon the repayment of the promissory note, the Company recorded a loss on extinguishment of debt of $0.3 million due to the remaining discount. The contractual maturities of the Company’s long-term debt obligations due subsequent to September 30, 2020 consist of the $353.8 million Convertible Senior Notes which mature in September 2026.

Long-term Debt

9 Months Ended

Sep. 30, 2020

5. Long-term Debt

Convertible Senior Notes

On September 16, 2019, the Company completed a private offering of the 2019 Convertible Notes with an aggregate principal amount of $220.0 million which were issued pursuant to the Indenture with U.S. Bank National Association, as trustee.

The net proceeds from the sale of the 2019 Convertible Notes were approximately $212.9 million after deducting the initial purchasers’ discounts and commissions of $6.6 million and offering expenses of $0.5 million by the Company. The Company used $28.4 million of the net proceeds from the sale to pay the cost of the capped call transactions in September 2019 described below.

On May 12,2020, the Company issued the 2020 Convertible Notes with an aggregate principal amount of $300.0 million. The net proceeds from the sale of the 2020 Convertible Notes were approximately $322.9 million after deducting the purchasers’ discounts and commission of $5.7 million and offering expenses of $0.3 million. The Company used $43.1 million of the net proceeds from the sale to pay the cost of the additional capped call transactions in May 2020 described below.

The Convertible Notes are senior unsecured obligations of the Company and bear interest at a rate of 3.5% per year payable semiannually in arrears on March 15 and September 15 of each year, beginning on March 15, 2020. The Convertible Notes will mature on September 15, 2026, unless converted earlier, redeemed or repurchased in accordance with their terms.

The Convertible Notes are convertible into shares of the Company’s common stock at an initial conversion rate of 25.3405 shares per $1,000 principal amount of Convertible Notes (equivalent to an initial conversion price of approximately $39.46 per share of common stock). The conversion rate is subject to customary anti-dilution adjustments. In addition, following certain events that occur prior to the maturity date or if the Company deliver a notice of redemption, the Company will increase the conversion rate for a holder who elects to convert its Convertible Notes in connection with such corporate event or a notice of redemption, as the case may be, in certain circumstances as provided in the indenture.

Prior to March 15, 2026, the Convertible Notes are convertible only upon the occurrence of certain events. On or after March 15, 2026 until the close of business on the second scheduled trading day immediately preceding the maturity date of the Convertible Notes, holders may convert the Convertible Notes at any time. Upon conversion of the Convertible Notes, the Company will pay or deliver, as the case may be, cash, shares of the Company’s common stock or a combination of cash and shares of common stock, at the Company’s election.

Prior to September 20, 2023, the Company may not redeem the Convertible Notes. The Company may redeem for cash all or a portion of the Convertible Notes, at its option, on or after September 20, 2023 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 (whether or not consecutive), including the trading day immediately preceding the date on which the Company provides a notice of redemption, during any 30 consecutive trading day period ending on, and including, the trading day immediately preceding the date on which the Company provides notice of redemption. The redemption price will be equal to 100% of the principal amount of the Convertible Notes to be redeemed, plus accrued and unpaid interest to, but excluding, the redemption date.

If the Company undergoes a “fundamental change,” as defined in the Indenture, prior to maturity, subject to certain conditions, holders may require the Company to repurchase for cash all or any portion of their Convertible Notes at a fundamental change repurchase price equal to 100% of the principal amount of the notes to be repurchased, plus any accrued and unpaid interest to, but excluding, the fundamental change repurchase date.

The Company used an effective interest rate of 10.5% to determine the liability component of the 2019 and 2020 Convertible Notes. This resulted in the recognition of $145.1 million and $204.5 million as the liability component of the 2019 and 2020 Convertible Notes, respectively and the recognition of the residual amount of $74.9 million and $95.5 million as the debt discount with a corresponding increase to additional paid in capital for the equity component of the 2019 and 2020 Convertible Notes, respectively. The 2020 Convertible Notes aggregate debt issuance costs of $6.0 million were allocated to the liability and equity components in the amounts of $3.7 and $2.3 million, respectively. The 2019 Convertible Notes aggregate debt issuance costs of $7.1 million were allocated to the liability and equity components in the amounts of $4.7 million and $2.4 million, respectively.

Interest expense for the Convertible Notes was $9.5 million and $20.3 million and for the three and nine months ended September 30, 2020, respectively. For the three months ended September 30, 2020, interest expense included the amortization of the discount on the Convertible Notes of $4.8 million, accrued semi-annual coupon payable of $4.6 million and amortization of debt issuance costs of $0.1 million. For the nine months ended September 30, 2020 interest expense included the amortization of the discount on the Convertible Notes of $10.1 million, accrued semi-annual coupon payable of $9.8 million and amortization of debt issuance costs of $0.4 million. As of September 30, 2020, $8.0 million of debt issuance costs was recorded on the consolidated balance sheet as a reduction to the carrying amount of the Convertible Notes.

The aggregate balance of the Convertible Notes, net of unamortized debt issuance costs, as of September 30, 2020 and December 31, 2019 was $353.8 million and $142.6 million respectively.

Capped Call Transactions

On September 11, 2019, and May 6, 2020 concurrently with the pricing of the 2019 Convertible Notes and the 2020 Convertible Notes, respectively, the Company entered into capped call transactions with two counterparties. The capped call transactions are expected generally to reduce the potential dilution to the Company’s common stock upon any conversion of Convertible Notes and/or offset any cash payments the Company is required to make in excess of the principal amount of converted Convertible Notes, as the case may be, in the event that the market price per share of the Company’s common stock, as measured under the terms of the capped call transactions, is greater than the strike price of the capped call transactions, which is initially $39.4625 (the conversion price of the Convertible Notes) and is subject to anti-dilution adjustments substantially similar to those applicable to the conversion rate of such Convertible Notes. If, however, the market price per share of the Company’s common stock, as measured under the terms of the capped call transactions, exceeds the cap price of the capped call transactions, which is initially $63.14 per share, there would nevertheless be dilution and/or there would not be an offset of such potential cash payments, in each case, to the extent that such market price exceeds the cap price of the capped call transactions.

Pursuant to ASC 815-40 Derivatives and Hedging, the Company determined that the capped call transactions should be classified as equity instruments and the capped call premium paid in the amount of $28.4 million and $43.1 million were recorded as reductions to additional paid-in capital as September 30, 2020 for the 2019 and 2020 Convertible Notes, respectively.

Term Loan Facility

On October 20, 2017, the Company entered into a loan and security agreement with Silicon Valley Bank (“SVB”) to provide for a $20.0 million term loan facility (the “term loan facility”). Borrowings under the term loan facility accrued interest at a floating rate per annum equal to the WSJ prime rate plus 1.50%. Under the agreement, the Company was required to make monthly interest-only payments through November 1, 2019 and was required to make 24 equal monthly payments of principal, plus accrued interest, from November 1, 2019 through October 1, 2021, when all unpaid principal and interest became due and payable.

On March 26, 2019, the Company voluntarily repaid all outstanding amounts due and owed, including applicable termination fees, under the term loan facility. The final payment of $21.8 million totaled per diem interest of $0.1 million and $21.7 million for the outstanding balance of the term loan which included (i) a final payment equal to 8% of the original principal amount of the term loan of $1.6 million, and (ii) a prepayment fee contractually owed of $0.1 million plus other fees which resulted in a total loss on extinguishment of debt of $1.2 million.

In connection with the Company’s entry into the term loan facility, the Company issued to SVB a warrant to purchase 14,064 shares of the Company’s common stock with an exercise price per share of $5.484. The warrant has a ten-year term and included a put option pursuant to which, in the event of an acquisition, change in control or dissolution or winding up of the Company, or the expiration of the warrant, SVB could have required the Company to repurchase the warrant for a total aggregate purchase price of $250 thousand. The warrants were exercised in November 2019.

Promissory Note

On October 19, 2017, the Company issued and sold an unsecured promissory note in the principal amount of $7.0 million to Golda Darty Partners S.A. (“GDP”). The promissory note accrued interest at a rate per annum of 8.0%, and was due and payable quarterly in arrears on the 19th day of each April, July, October and January. The promissory note had a maturity date of October 19, 2022 when the $7.0 million would be due and payable in its entirety. The promissory note was contractually subordinated to the Company’s obligations to SFJ under the SFJ Agreement.

On September 16, 2019, the Company voluntarily repaid all outstanding amounts due and owed under the promissory note, except for a small amount of interest subsequently repaid. The payment of $7.1 million totaled per diem interest of $0.1 million and $7.0 million for the outstanding principal balance of the promissory note.

In connection with the issuance and sale of the above promissory note, the Company issued to GDP a warrant to purchase 93,764 shares of the Company’s common stock at a price per share of $5.484, which was exercised in whole in October 2017. The Company recorded the fair value of the warrant in the aggregate amount of $0.4 million as a discount to the promissory note. This amount was being accreted as additional interest expense over the term of the promissory note. Upon the repayment of the promissory note, the Company recorded a loss on extinguishment of debt of $0.3 million due to the remaining discount.

The contractual maturities of the Company’s long-term debt obligations due subsequent to September 30, 2020 consist of the $353.8 million Convertible Senior Notes which mature in September 2026.