Property, Plant and Equipment - Summary of property, plant, and equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 68,183	$ 43,203
Less: accumulated depreciation and amortization	20,709	12,676
Property, plant and equipment, net	47,474	30,527
Manufacturing equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	37,939	25,314
Research and development equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	8,933	6,088
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	7,620	7,080
Capital leases
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	1,108	882
Software
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	274	60
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	433	195
Vehicles
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	210	210
Assets not yet placed in service
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 11,666	$ 3,374