Agreements - Sanofi (Details) $ in Thousands		3 Months Ended		9 Months Ended
	May 30, 2017 USD ($) item	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)
Collaborative Agreements disclosures
License and milestone fees		$ 79	$ 76	$ 49,889	$ 10,229
Sanofi
Collaborative Agreements disclosures
Number of compounds | item	4
Payments received under collaboration agreement	$ 30,000
License and milestone fees				$ 30,000