Agreements - Sanofi (Details) $ in Thousands	1 Months Ended	3 Months Ended														6 Months Ended		12 Months Ended
	May 31, 2017 item	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Jun. 30, 2016 USD ($)
Collaborative Agreements disclosures
Revenue from contract with customer		$ 13,416	$ 10,928	$ 9,287	$ 19,815	$ 39,448	$ 8,480	$ 39,020	$ 28,499	$ 13,846	$ 7,660	$ 7,408	$ 19,714	$ 18,029	$ 14,851	$ 21,506	$ 32,880	$ 53,446	$ 115,447	$ 48,628	$ 60,002
Sanofi
Collaborative Agreements disclosures
Number of compounds | item	4
Sanofi | Development milestones
Collaborative Agreements disclosures
Revenue from contract with customer																		26,500
License and milestone fees
Collaborative Agreements disclosures
Revenue from contract with customer		$ 1,747	$ 672	$ 1,321	$ 11,540	$ 29,580	$ 79	$ 31,080	$ 18,730	$ 5,076	$ 76	$ 76	$ 10,077	$ 10,692	$ 6,070	$ 5,152	$ 16,762	$ 15,280	79,469	$ 15,305	$ 26,915
License and milestone fees | Sanofi
Collaborative Agreements disclosures
Revenue from contract with customer																			30,000
License and milestone fees | Sanofi | Development milestones
Collaborative Agreements disclosures
Revenue from contract with customer																			6,000
License amendments | Sanofi
Collaborative Agreements disclosures
Revenue from contract with customer																			$ 30,000