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Convertible Senior Notes (Tables)
9 Months Ended
Sep. 30, 2021
Debt Disclosure [Abstract]  
Summary of Convertible Debt
The net carrying amount of the liability and equity components of the Notes was as follows (in thousands):
September 30, 2021December 31, 2020
Liability component:
Principal$345,000 $345,000 
Unamortized discount(43,255)(49,346)
Unamortized issuance costs(5,404)(6,164)
Net carrying amount$296,341 $289,490 
Equity component, net of purchase discounts and issuance costs$58,560 $58,560 

Interest expense related to the Notes is as follows (in thousands):
Three months ended September 30,Nine months ended September 30,
2021202020212020
Contractual interest expense$970 $970 $2,911 $2,910 
Amortization of debt discount2,045 1,983 6,091 5,903 
Amortization of issuance costs256 248 760 738 
Total interest expense$3,271 $3,201 $9,762 $9,551