Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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The amount of expense recognized in the current period that reflects the allocation of the cost of tangible assets over the assets' useful lives. Includes production and non-production related depreciation.

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Amount before accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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Property and Equipment, Net - Schedule of Property Plant And Equipment (Details) - USD ($) $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property and equipment gross	$ 7,367		$ 6,987	$ 6,606
Less accumulated depreciation and amortization	(3,026)		(2,173)	(984)
Property and equipment, net	4,341		4,814	5,622
Depreciation	869	$ 895	1,188	784	$ 429
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment gross	1,110		1,073	1,076
Computer equipment
Property, Plant and Equipment [Line Items]
Property and equipment gross	1,430		1,051	869
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment gross	$ 4,827		$ 4,863	$ 4,661