License Agreements (Details) $ in Thousands, € in Millions		1 Months Ended								3 Months Ended	12 Months Ended					15 Months Ended	25 Months Ended	127 Months Ended
	Feb. 27, 2018	Oct. 31, 2018 USD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)	Apr. 30, 2017 USD ($)	Apr. 30, 2017 EUR (€)	Sep. 30, 2015 USD ($)	Sep. 30, 2015 EUR (€)	Jun. 30, 2009	Jun. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2019 EUR (€)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)
Research Agreements
Collaborative arrangement, milestone payments											$ 0		$ 0	$ 8,712
License agreements, upfront payment received				$ 10,000
License agreements, first commercial sale anniversary											10 years	10 years
Eisai | License Agreement
Research Agreements
Period after the date of the first commercial sale of the product for license expiration			10 years
Initial license fee paid			$ 500												$ 400
Additional payments to be made upon achievement of certain clinical and regulatory milestones			22,300
Duke University | License Agreement
Research Agreements
Nonrefundable, non-creditable payment				1,300													$ 500
Additional payments to be made upon achievement of certain milestones				$ 3,800
Collaborative arrangement, termination period				60 days
Collaborative Arrangement | 3M Company and 3M Innovative Properties Company
Research Agreements
Supply agreement, term	5 years
Supply agreement, termination period	24 months								90 days
Funding to purchase capital equipment		$ 9,600
Nonrefundable, non-creditable payment																$ 14,400		$ 28,900
Collaborative Arrangement | Ipsen
Research Agreements
Nonrefundable, non-creditable payment							$ 13,000
Additional payments to be made upon achievement of certain milestones							$ 28,700	€ 24.0
Collaborative arrangement, milestone payments					$ 8,700	€ 8.0					$ 8,700	€ 8.0
Royalty rate (as a percent)							5.00%	5.00%
Period after the date of the first commercial sale of the product for license expiration							10 years	10 years
Royalty expense											$ 8,700		$ 5,000
Collaborative Arrangement | Ipsen | Sublicense Agreement
Research Agreements
Period after the date of the first commercial sale of the product for license expiration							10 years	10 years
Agreement expiration period, period after date of first commercial sale of product							10 years	10 years
Collaborative Arrangement | Ipsen | License Agreement
Research Agreements
Amount awarded to other party			10,000
Settlement interest			800
License agreement, obligation to pay			5,000
Settlement expense										$ 10,800
Upfront payment received			10,000
Aggregate upfront payment received			40,000
Collaborative Arrangement | Eisai
Research Agreements
Nonrefundable, non-creditable payment			$ 1,000
Collaborative Arrangement | Teijin Agreement
Research Agreements
Additional payments to be made upon achievement of certain milestones				$ 40,000
License agreements, upfront payment received				$ 10,000