Notes Payable and Convertible Notes - Summary of Classification of Notes Payable and Convertible Notes (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Long-term debt	$ 56,217	$ 67,015	$ 87,989
Less current portion	(6,817)	(5,024)
Long term portion	49,400	61,991
Gotham Green Partners LLC
Debt Instrument [Line Items]
Long-term debt			35,607
LI Lending, LLC
Debt Instrument [Line Items]
Long-term debt	47,588	45,362	44,289
Long term portion	47,588	45,362
May 2020 Convertible Notes
Debt Instrument [Line Items]
Long-term debt		2,855
Long term portion		2,855
May 2020 Convertible Notes (Swap)
Debt Instrument [Line Items]
Long-term debt		11,867
Long term portion		11,867
Other Loans
Debt Instrument [Line Items]
Long-term debt	8,629	6,931	$ 8,093
Less current portion	(6,817)	(5,024)
Long term portion	$ 1,812	$ 1,907

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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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