Deferred Revenue - Narrative (Details) - USD ($)					3 Months Ended		9 Months Ended		12 Months Ended	17 Months Ended
	Sep. 19, 2018	Jul. 20, 2015	Sep. 17, 2014	Dec. 17, 2013	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2019	Apr. 17, 2018
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Proceeds from funding agreement		$ 250,000	$ 500,000	$ 250,000
Interest in asset		0.50%	1.00%	0.50%
Number of shares issuable term			60 days	60 days
Number of shares issuable (in shares)			62,500	31,250
Recognized as revenue					$ 20,641,000	$ 4,366,000	$ 32,851,000	$ 9,220,000
Grants receivable											$ 7,400,000
BARDA
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Proceeds from funding agreement									$ 600,000
Period of funding for remaining balance	2 years
Plan | BARDA
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Proceeds from funding agreement	$ 4,600,000
Grants
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue from contract with customer							1,600,000			$ 5,600,000
Research and Development Arrangement December 17, 2013
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Recognized as revenue							115,900	43,400
Research and Development Arrangement September 17, 2014
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Recognized as revenue							313,700	117,600
Research and Development Arrangement July 20, 2015
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Recognized as revenue							214,300	$ 0
Research and Development Arrangement September 19, 2018
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Recognized as revenue							$ 225,000