Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Property and Equipment
Property and equipment, gross	$ 62,230	$ 60,212
Less: accumulated depreciation	(45,808)	(47,568)
Property and equipment, net	16,422	12,644
Depreciation expense	3,300	3,300	$ 3,000
Computer equipment
Property and Equipment
Property and equipment, gross	2,314	2,119
Software
Property and Equipment
Property and equipment, gross	2,076	1,718
Furniture and fixtures
Property and Equipment
Property and equipment, gross	3,812	3,665
Laboratory equipment
Property and Equipment
Property and equipment, gross	29,753	30,546
Leasehold improvements
Property and Equipment
Property and equipment, gross	$ 24,275	$ 22,164

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