Commitments and Contingencies - Additional Information (Details) $ in Thousands	1 Months Ended			3 Months Ended
	Oct. 31, 2018	May 31, 2018 ft²	Feb. 28, 2018	Mar. 31, 2019 USD ($)	Mar. 31, 2018 USD ($)
Loss Contingencies [Line Items]
Operating lease right-of-use asset				$ 2,645
Operating lease liability				1,916
Operating lease liability				2,793
Rent expense				300	$ 100
Fremont, California
Loss Contingencies [Line Items]
Lease term expiration date	Jun. 30, 2019		Sep. 30, 2019
Operating lease right-of-use asset				100
Operating lease liability				$ 100
Operating lease, remaining lease term				6 months
Santa Clara, California
Loss Contingencies [Line Items]
Lease term expiration date		Aug. 31, 2022
Operating lease right-of-use asset				$ 2,400
Operating lease, remaining lease term				3 years 4 months
Lease commencement date		2018-09
Area of office and laboratory space | ft²		35,000
Letter of credit secured by restricted cash				$ 500
Operating lease liability				2,600
Germany
Loss Contingencies [Line Items]
Operating lease right-of-use asset				100
Operating lease liability				$ 100
Operating lease, weighted average remaining lease term				14 months
Operating lease liability, weighted average incremental borrowing rate				6.93%