Leases - Narrative (Details) $ in Thousands		3 Months Ended
	Sep. 28, 2016 USD ($) renewal_option	Mar. 31, 2020 USD ($)	Mar. 31, 2019 USD ($)	Jan. 01, 2019
Property, Plant and Equipment [Line Items]
Weighted average remaining lease term in years		4 years 4 months 24 days
Variable lease expenses		$ 246	$ 243
Amortization of operating lease right-of-use assets		314	287
Office and Laboratory Space
Property, Plant and Equipment [Line Items]
Number lease renewal options | renewal_option	1
Term of lease contract	5 years
Operating lease discount rate				10.00%
Weighted average remaining lease term in years				5 years 8 months 12 days
Variable lease expenses		200	200
Amortization of operating lease right-of-use assets		$ 300	$ 300
Office and Laboratory Space | Restricted Cash Noncurrent
Property, Plant and Equipment [Line Items]
Letters of credit issued to the landlord in connection with lease agreement	$ 500