Subsequent Events - Narrative (Details) - Dermelix License Agreement - Collaborative Arrangement - Subsequent Event	Feb. 17, 2019 USD ($) target
Subsequent Event [Line Items]
Number of additional collaboration targets | target	5
Term of license agreement	6 years
Non-refundable upfront payment received for research agreement	$ 1,000,000
Option exercise fee	$ 1,000,000
Period to exercise upon commencement of SNA technology development	30 days
Aggregate regulatory milestone revenue	$ 13,500,000
Potential milestone revenue	$ 152,500,000
Exercise termination period upon change of control	90 days