Collaboration and Other Agreements, NIAID Contract (Details)		3 Months Ended								12 Months Ended
	Sep. 15, 2015 USD ($) Molecule	Dec. 31, 2018 USD ($)	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 ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Collaboration and Other Agreements [Line Items]
Revenues		$ 15,794,000	$ 20,798,000	$ 18,834,000	$ 4,695,000	$ 152,359,000	$ 1,663,000	$ 1,666,000	$ 2,055,000	$ 60,121,000	$ 157,742,000	$ 91,880,000
NIAID
Collaboration and Other Agreements [Line Items]
Commercialization of molecules | Molecule	2
Base period value	$ 7,500,000
Proceeds from additional development funding options under agreement										10,800,000
NIAID | Maximum
Collaboration and Other Agreements [Line Items]
Additional development funding options	17,000,000.0
Total potential value	$ 24,500,000
Revenues From License Agreements | NIAID
Collaboration and Other Agreements [Line Items]
Revenues										$ 1,300,000	$ 1,700,000	$ 5,100,000