Property and Equipment, Net - Summary of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Total cost	$ 8,163		$ 14,670
Less: Accumulated depreciation	(1,830)		(1,217)
Total property and equipment, net	6,333		13,453
Laboratory equipment
Property, Plant and Equipment [Line Items]
Total cost	2,195		1,731
Computer equipment
Property, Plant and Equipment [Line Items]
Total cost	2,950		465
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Total cost	1,941		201
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total cost	908		359
Construction in progress
Property, Plant and Equipment [Line Items]
Total cost	$ 169	$ 11,900	$ 11,914