Agreements - Sanofi (Details) $ in Thousands		3 Months Ended		6 Months Ended
	May 30, 2017 USD ($) item	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)
Collaborative Agreements disclosures
License and milestone fees		$ 31,080	$ 76	$ 49,810	$ 10,153
Sanofi
Collaborative Agreements disclosures
Number of compounds | item	4
Payments received under collaboration agreement	$ 30,000
License and milestone fees		$ 30,000		$ 30,000