Agreements - Novartis (Details)	1 Months Ended			3 Months Ended												12 Months Ended
	Oct. 31, 2014 USD ($) item	Oct. 31, 2013 USD ($)	Mar. 31, 2013 USD ($) item	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	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 ($)	Dec. 31, 2019 USD ($) item	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2010 USD ($) item	May 31, 2015 USD ($)	Jan. 31, 2015 USD ($)
Collaborative Agreements disclosures
Revenue from contract with customer				$ 44,864,000	$ 13,281,000	$ 15,542,000	$ 8,584,000	$ 13,416,000	$ 10,928,000	$ 9,287,000	$ 19,815,000	$ 39,448,000	$ 8,480,000	$ 39,020,000	$ 28,499,000	$ 82,271,000	$ 53,446,000	$ 115,447,000
Contract with Customer, Liability				127,432,000				80,802,000				89,967,000				$ 127,432,000	80,802,000	89,967,000
Novartis
Collaborative Agreements disclosures
Number of single-target licenses | item			1													5			6
Number of related targets | item			2
Number of remaining licenses | item	3
Novartis | Right-to-test agreement
Collaborative Agreements disclosures
Revenue from contract with customer		$ 5,000,000
Term of agreement																			3 years
Term of extension of the agreement		1 year
Novartis | License amendments
Collaborative Agreements disclosures
Revenue from contract with customer			$ 3,500,000
Novartis | Development milestones
Collaborative Agreements disclosures
Potential milestone payment				22,500,000												$ 22,500,000				$ 5,000,000	$ 5,000,000
Novartis | Phase 1 clinical trial
Collaborative Agreements disclosures
Revenue from contract with customer																4,700,000		5,000,000
Potential milestone payment				5,000,000.0												5,000,000.0
Contract with Customer, Liability				300,000												300,000
Novartis | Phase 2 clinical trial
Collaborative Agreements disclosures
Potential milestone payment				7,500,000												7,500,000
Novartis | Regulatory milestones
Collaborative Agreements disclosures
Potential milestone payment																			$ 77,000,000
Novartis | Milestone payments
Collaborative Agreements disclosures
Potential milestone payment	$ 199,500,000			100,000,000												100,000,000
Upfront payment | Novartis
Collaborative Agreements disclosures
Revenue from contract with customer	$ 1,000,000		$ 1,000,000																45,000,000
License and milestone fees
Collaborative Agreements disclosures
Revenue from contract with customer				$ 29,551,000	$ 79,000	5,079,000	79,000	1,747,000	672,000	1,321,000	11,540,000	29,580,000	79,000	31,080,000	18,730,000	34,788,000	15,280,000	79,469,000
License and milestone fees | Novartis
Collaborative Agreements disclosures
Revenue from contract with customer																	978,000
Potential milestone payment																			199,500,000
Exercise fee | Novartis
Collaborative Agreements disclosures
Revenue from contract with customer																			$ 1,000,000
Research and development support
Collaborative Agreements disclosures
Revenue from contract with customer						$ 51,000	$ 17,000	$ 218,000	$ 388,000	$ 388,000	$ 383,000	$ 452,000	$ 650,000	$ 902,000	$ 1,478,000	$ 68,000	$ 1,377,000	$ 3,482,000