| Summary of Convertible Notes |
The outstanding 2023 Notes consist of the following: | | | | | | | | | | | | | | | | | As of September 30, 2021 | | As of December 31, 2020 | | Liability component: | | | | | | Principal | | $ | 10,909 | | | $ | 48,035 | | | Unamortized debt discount | | (765) | | | (4,915) | | | Unamortized debt issuance costs | | (76) | | | (501) | | | Net carrying amount | | 10,068 | | | 42,619 | | | | | | | | Equity component: | | | | | | | | | | | | | | | | Net carrying amount | | $ | 2,321 | | | $ | 10,217 | |
The outstanding 2026 Notes consist of the following: | | | | | | | | | | | | | | | | | As of September 30, 2021 | | As of December 31, 2020 | | Liability component: | | | | | | Principal | | $ | 316,250 | | | $ | 316,250 | | | Unamortized debt discount | | (59,756) | | | (67,977) | | | Unamortized debt issuance costs | | (4,489) | | | (5,114) | | | Net carrying amount | | 252,005 | | | 243,159 | | | | | | | Equity component: | | | | | | | | | | | | | | | | Net carrying amount | | $ | 81,550 | | | $ | 81,550 | |
The outstanding 2025 Notes consist of the following: | | | | | | | | | | | | | | | | | As of September 30, 2021 | | As of December 31, 2020 | | Liability component: | | | | | | Principal | | $ | 350,000 | | | $ | 350,000 | | | Unamortized debt discount | | (62,894) | | | (73,075) | | | Unamortized debt issuance costs | | (4,476) | | | (5,235) | | | Net carrying amount | | 282,630 | | | 271,690 | | | | | | | Equity component: | | | | | | | | | | | | | | | | Net carrying amount | | $ | 73,109 | | | $ | 73,097 | |
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| Summary of Interest Expense |
The following table sets forth total interest expense recognized related to the 2023 Notes: | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Three Months Ended September 30, | | Nine Months Ended September 30, | | | 2021 | | 2020 | | 2021 | | 2020 | | Contractual interest expense | | $ | 20 | | | $ | 431 | | | $ | 172 | | | $ | 1,294 | | | Amortization of debt issuance costs | | 45 | | | 276 | | | 197 | | | 819 | | | Amortization of debt discount | | 127 | | | 2,506 | | | 1,088 | | | 7,422 | | | Total | | $ | 192 | | | $ | 3,213 | | | $ | 1,457 | | | $ | 9,535 | |
The following table sets forth total interest expense recognized related to the 2026 Notes: | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Three Months Ended September 30, | | Nine Months Ended September 30, | | | 2021 | | 2020 | | 2021 | | 2020 | | Contractual interest expense | | $ | 593 | | | $ | 593 | | | 1,779 | | | $ | 1,772 | | | Amortization of debt issuance costs | | 219 | | | 206 | | | 636 | | | 608 | | | Amortization of debt discount | | 2,801 | | | 2,698 | | | 8,188 | | | 7,959 | | | Total | | $ | 3,613 | | | $ | 3,497 | | | $ | 10,603 | | | $ | 10,339 | |
The following table sets forth total interest expense recognized related to the 2025 Notes: | | | | | | | | | | | | | | | | | | | | | Three Months Ended | | Nine Months Ended | | | | | September 30, 2021 | | September 30, 2021 | | | | | | Contractual interest expense | | $ | 109 | | | $ | 327 | | | | | | | Amortization of debt issuance costs | | 241 | | | 717 | | | | | | | Amortization of debt discount | | 3,416 | | | 10,122 | | | | | | | Total | | $ | 3,766 | | | $ | 11,166 | | | | | |
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