Notes Payable and Convertible Notes - Summary of Future Minimum Payments of Notes and Convertible Notes (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
Debt Disclosure [Abstract]
2021	$ 6,034
2022	1,730
2024	52,915
Total minimum payments	60,679
Effect of discounting	(4,462)
Long-term debt	56,217	$ 67,015	$ 87,989
Less current portion	(6,817)	(5,024)
Long term portion	$ 49,400	$ 61,991

Long term debt before discount maturities repayments of principal in next twelve months.

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- Definition

Long term debt before discount maturities repayments of principal in remainder of fiscal year.

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- Definition

Long term debt before discount maturities repayments of principal in year three.

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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 of unamortized debt discount (premium) and debt issuance costs.

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

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