Convertible Senior Notes - Schedule of Convertible 2026 Notes (Details) - Convertible Senior Notes Due June 2026 - Convertible Debt - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Principal	$ 316,250	$ 316,250
Unamortized debt discount	(59,756)	(67,977)
Unamortized debt issuance costs	(4,489)	(5,114)
Carrying value	252,005	243,159
Net carrying amount
Debt Instrument [Line Items]
Net carrying amount	$ 81,550	$ 81,550

Debt Instrument, Convertible, Carrying Amount of Equity Component, Net

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Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of the respective bond issues. This does not include the amounts capitalized as part of the cost of the utility plant or asset.

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