Grants (Details)	1 Months Ended				3 Months Ended								12 Months Ended
	Mar. 31, 2019 USD ($)	Sep. 30, 2016 USD ($)	Jan. 31, 2016 USD ($)	Oct. 31, 2013 USD ($)	Dec. 31, 2019 USD ($) contract_option	Sep. 30, 2019 USD ($)	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, 2019 USD ($) contract_option	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Disaggregation of Revenue [Line Items]
Total revenue					$ 14,055,000	$ 17,046,000	$ 13,083,000	$ 16,025,000	$ 35,421,000	$ 41,757,000	$ 28,851,000	$ 29,039,000	$ 60,209,000	$ 135,068,000	$ 205,825,000
Deferred revenue					199,528,000				240,924,000				199,528,000	240,924,000
Grant revenue
Disaggregation of Revenue [Line Items]
Total revenue													12,173,000	12,556,000	28,851,000
BARDA
Disaggregation of Revenue [Line Items]
Award amount		$ 125,800,000
Amount committed for funding					117,300,000								117,300,000
Available funding					$ 8,500,000								$ 8,500,000
BARDA | Initial base award
Disaggregation of Revenue [Line Items]
Award amount		8,200,000
BARDA | Contract options
Disaggregation of Revenue [Line Items]
Award amount		$ 117,600,000
Number of contract options exercised | contract_option					3								3
Number of contract options | contract_option					4								4
BARDA | Grant revenue
Disaggregation of Revenue [Line Items]
Total revenue													$ 7,600,000	6,800,000	20,100,000
The Bill & Melinda Gates Foundation
Disaggregation of Revenue [Line Items]
Award amount			$ 100,000,000.0
Available funding					$ 80,000,000								80,000,000
Deferred revenue					1,500,000				800,000				1,500,000	800,000
The Bill & Melinda Gates Foundation | Initial project
Disaggregation of Revenue [Line Items]
Award amount	$ 1,100,000.0		$ 20,000,000.0
Amount committed for funding					21,100,000								21,100,000
The Bill & Melinda Gates Foundation | Grant revenue
Disaggregation of Revenue [Line Items]
Total revenue													3,400,000	1,400,000	1,100,000
DARPA
Disaggregation of Revenue [Line Items]
Award amount				$ 24,600,000									19,700,000
Amount committed for funding					$ 19,700,000				$ 19,700,000.0				19,700,000	19,700,000.0
DARPA | Grant revenue
Disaggregation of Revenue [Line Items]
Total revenue													$ 500,000	$ 3,500,000	$ 7,700,000