Leases - Narrative (Details) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019 USD ($) lease	Jun. 30, 2019 USD ($) lease
Lessee, Lease, Description [Line Items]
Number of noncancellable operating leases | lease	2	2
Short-term lease cost	$ 220	$ 548
Cash paid for amounts included in measurement of lease liabilities		$ 600
Weighted average remaining lease term	7 years 6 months	7 years 6 months
Weighted-average discount rate (percent)	6.00%	6.00%
Emeryville lease
Lessee, Lease, Description [Line Items]
Length of each lease renewal	5 years	5 years
Short-term Lease Terminated in March 2019
Lessee, Lease, Description [Line Items]
Short-term lease cost	$ 200	$ 200