Commitments and Contingencies - Additional Information (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019 USD ($) ft² LeaseFacility	Mar. 31, 2018 USD ($)	Dec. 31, 2016 USD ($)
Operating Leased Assets [Line Items]
Operating lease, remaining lease term	10 years 6 months 18 days
Security deposit	$ 0.5
Operating leases rent expense	1.2	$ 1.3
Operating Leases variable lease payments	$ 0.3
Bank Of America Merrill Lynch
Operating Leased Assets [Line Items]
Letter of credit outstanding			$ 0.5
Berkeley, California
Operating Leased Assets [Line Items]
Operating lease, remaining lease term	11 years
Number of lease facility | LeaseFacility	1
Berkeley, California | Sublease
Operating Leased Assets [Line Items]
Total square footage of leased property | ft²	30,885
Lease expiration date	Dec. 31, 2020
Sublease Income	$ 0.4
Oss, Netherlands
Operating Leased Assets [Line Items]
Operating leases term of expiration	2020-12
Number of lease facility | LeaseFacility	1