Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property and equipment
Property and equipment, gross	$ 15,314	$ 14,470
Less accumulated depreciation and amortization	(11,219)	(9,346)
Property and equipment, net	4,095	5,124
Depreciation and amortization expense	1,900	1,200	$ 1,100
Lab equipment and furniture
Property and equipment
Property and equipment, gross	8,995	8,331
Leasehold improvements
Property and equipment
Property and equipment, gross	2,731	2,731
Software
Property and equipment
Property and equipment, gross	2,181	2,004
Computer equipment
Property and equipment
Property and equipment, gross	1,313	1,226
Construction-in-progress
Property and equipment
Property and equipment, gross	$ 94	$ 178

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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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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