Agreements - Bayer (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended														6 Months Ended		12 Months Ended
	Jan. 31, 2016	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jun. 30, 2016	Dec. 31, 2008
Collaborative Agreements disclosures
Total revenues		$ 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
Bayer | Minimum
Collaborative Agreements disclosures
Percentage of royalty payments																						4.00%
Bayer | Maximum
Collaborative Agreements disclosures
Percentage of royalty payments																						7.00%
Bayer | Development milestones
Collaborative Agreements disclosures
Potential milestone payment		2,000																2,000				$ 16,000
Bayer | Regulatory milestones
Collaborative Agreements disclosures
Potential milestone payment		6,000																6,000				44,500
Bayer | Milestone payments
Collaborative Agreements disclosures
Potential milestone payment																						110,000
Upfront payment | Bayer
Collaborative Agreements disclosures
Total revenues																						4,000
License and milestone fees
Collaborative Agreements disclosures
Total revenues		$ 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 | Bayer
Collaborative Agreements disclosures
Total revenues																		$ 13,000
Potential milestone payment																						$ 170,500
License and milestone fees | Bayer | Phase 2 clinical trial
Collaborative Agreements disclosures
Total revenues	$ 10,000