Collaborative Research and License Agreements (Details) $ in Thousands			3 Months Ended		6 Months Ended
	Nov. 13, 2019 USD ($) agreements	Feb. 17, 2019 USD ($) target	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaboration revenue			$ 4,847	$ 434	$ 14,030	$ 459
Current portion of deferred revenue							$ 21,873
Allergan Collaboration | Collaboration Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of collaboration programs | agreements	2
Non-refundable upfront payment received for research agreement	$ 25,000
Collaboration option exercise fee	10,000
Collaboration option exercise fee	$ 10,000
Termination period upon written notice	90 days
Collaboration revenue			4,833		13,949
Current portion of deferred revenue			10,880		10,880
Dermelix License Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Aggregate regulatory milestone revenue		$ 13,500
Potential milestone revenue		152,500
Dermelix License Agreement | Collaboration Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Non-refundable upfront payment received for research agreement		1,000
Collaboration option exercise fee		$ 1,000
Collaboration revenue			$ 14	$ 434	$ 81	$ 459
Number of additional collaboration targets | target		5
Collaboration agreement term		6 years
Collaboration development expenses		$ 1,000
Collaboration option rights usage term		30 days
Development and Commercialization License | Allergan Collaboration | Collaboration Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaboration option exercise fee	$ 15,000
Maximum | Allergan Collaboration | Collaboration Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Development milestone payment	55,000
Product approval and launch milestone payment	132,500
Sales milestone payment	$ 175,000