Agreements - Novartis (Details)	1 Months Ended					3 Months Ended														6 Months Ended		12 Months Ended
	May 31, 2015 USD ($)	Jan. 31, 2015 USD ($)	Oct. 31, 2014 USD ($) item	Oct. 31, 2013 USD ($)	Mar. 31, 2013 USD ($) item	Dec. 31, 2017 USD ($)	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 ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Sep. 30, 2014 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2017 USD ($) item	Dec. 31, 2016 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2015 USD ($)	Dec. 31, 2010 USD ($) item
Collaborative Agreements disclosures
Amount of arrangement consideration included in license and milestone fees						$ 29,580,000	$ 79,000	$ 31,080,000	$ 18,730,000	$ 5,076,000	$ 76,000	$ 76,000	$ 10,077,000	$ 10,692,000	$ 6,070,000	$ 5,086,000	$ 5,078,000	$ 41,417,000	$ 6,234,000	$ 5,152,000	$ 16,762,000	$ 79,469,000	$ 15,305,000	$ 26,915,000	$ 57,815,000
Costs related to the research and development services						39,843,000	$ 31,689,000	$ 35,319,000	$ 32,888,000	$ 33,657,000	$ 32,909,000	$ 38,652,000	$ 36,094,000	$ 38,199,000	$ 35,132,000	$ 30,437,000	$ 25,666,000	$ 27,647,000	$ 28,018,000	66,566,000	$ 73,331,000	$ 139,739,000	$ 141,312,000	148,077,000	111,768,000
Novartis
Collaborative Agreements disclosures
Number of single-target licenses | item					1																	5				6
Number of related targets | item					2																	2
Payments received under collaboration agreement				$ 5,000,000																						$ 45,000,000
License exercise fee			$ 1,000,000		$ 1,000,000																					1,000,000
Potential milestone payments			$ 199,500,000		199,500,000																					$ 199,500,000
Term of agreement				1 year																						3 years
Potential milestone payments under second option					238,000,000
Number of remaining licenses | item			3
Costs related to the research and development services																				$ 17,000		$ 32,000		$ 67,000	141,000
Costs related to clinical materials sold																						0			$ 644,000
Payments received under collaboration agreement in connection with amended agreement					3,500,000
Novartis | Development milestones
Collaborative Agreements disclosures
Payments received under collaboration agreement	$ 5,000,000	$ 5,000,000
Potential milestone payments					22,500,000																					$ 22,500,000
Potential milestone payments under second option					22,500,000
Novartis | Phase 1 clinical trial
Collaborative Agreements disclosures
Payments received under collaboration agreement																						5,000,000
Potential milestone payments						5,000,000																5,000,000
Novartis | Phase 2 clinical trial
Collaborative Agreements disclosures
Potential milestone payments						$ 7,500,000																$ 7,500,000
Novartis | Regulatory milestones
Collaborative Agreements disclosures
Potential milestone payments					77,000,000																					77,000,000
Potential milestone payments under second option					115,500,000
Novartis | Sales milestones
Collaborative Agreements disclosures
Potential milestone payments					100,000,000																					$ 100,000,000
Potential milestone payments under second option					$ 100,000,000