Agreements - Bayer (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended														6 Months Ended		12 Months Ended
	Jan. 31, 2016	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	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2008
Collaborative Agreements disclosures
Amount of arrangement consideration included in license and milestone fees		$ 29,580	$ 79	$ 31,080	$ 18,730	$ 5,076	$ 76	$ 76	$ 10,077	$ 10,692	$ 6,070	$ 5,086	$ 5,078	$ 41,417	$ 6,234	$ 5,152	$ 16,762	$ 79,469	$ 15,305	$ 26,915	$ 57,815
Bayer
Collaborative Agreements disclosures
Payments received under collaboration agreement																						$ 4,000
Potential milestone payments																						$ 170,500
Cumulative earnings		13,000																13,000
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 payments		2,000																2,000				$ 16,000
Bayer | Phase 2 clinical trial
Collaborative Agreements disclosures
Amount of arrangement consideration included in license and milestone fees	$ 10,000
Bayer | Regulatory milestones
Collaborative Agreements disclosures
Potential milestone payments		$ 6,000																$ 6,000				44,500
Bayer | Sales milestones
Collaborative Agreements disclosures
Potential milestone payments																						$ 110,000