Agreements - Takeda (Details)	1 Months Ended	3 Months Ended														6 Months Ended		12 Months Ended
	Mar. 31, 2015 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 ($)
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
Remaining arrangement consideration to be recognized as license revenue		6,800,000				7,100,000										7,100,000		6,800,000	7,100,000
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
Takeda
Collaborative Agreements disclosures
Term of agreement	3 years
Number of single-target licenses | item	2																	1
Term of extension of the agreement	1 year
Potential payments to extend the agreement term	$ 4,000,000
Potential payment to expand agreement scope	8,000,000
Payments received under collaboration agreement	20,000,000
Potential milestone payments	$ 210,000,000												210,000,000
Additional term of extension of the agreement	2 years
Estimated utilization period after commercialization	10 years
Discount rate (as a percent)	13.00%
Amount of arrangement consideration included in license and milestone fees																				8,600,000
Cumulative earnings		31,400,000																$ 31,400,000
Estimated term of development and commercialization license	25 years
Remaining arrangement consideration to be recognized as license revenue		17,300,000																17,300,000
Costs related to the research and development services																678,000		913,000		469,000	113,000
Costs related to clinical materials sold																$ 0		2,100,000		$ 0	$ 0
Takeda | Development milestones
Collaborative Agreements disclosures
Potential milestone payments	$ 30,000,000												30,000,000
Cumulative earnings		25,900,000																25,900,000
Takeda | Phase 1 clinical trial
Collaborative Agreements disclosures
Potential milestone payments		5,000,000																5,000,000
Takeda | Regulatory milestones
Collaborative Agreements disclosures
Potential milestone payments	85,000,000												85,000,000
Takeda | Sales milestones
Collaborative Agreements disclosures
Potential milestone payments	$ 95,000,000												$ 95,000,000
Takeda | Future Technological Improvements
Collaborative Agreements disclosures
Cumulative earnings		2,100,000																2,100,000
Takeda | Research Services
Collaborative Agreements disclosures
Cumulative earnings		$ 3,400,000																$ 3,400,000