Property and Equipment, Net - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 44,358	$ 37,745
Less: accumulated depreciation and amortization	(3,374)	(2,108)
Property and equipment, net	40,984	35,637
Laboratory Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	10,051	9,309
Manufacturing Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	1,113
Computers and Purchased Software
Property Plant And Equipment [Line Items]
Property and equipment, gross	487	248
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Property and equipment, gross	1,236	1,066
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property and equipment, gross	29,160	24,520
Assets Not Yet in Service
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 2,311	$ 2,602

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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