Deferred Revenue - Additional Information (Details)										1 Months Ended	3 Months Ended		9 Months Ended		11 Months Ended
	Sep. 30, 2018 USD ($)	Sep. 19, 2018 USD ($)	May 28, 2016 USD ($)	Dec. 23, 2015 USD ($)	Oct. 02, 2015 USD ($)	Sep. 22, 2015 USD ($) shares	Jul. 20, 2015 USD ($) shares	Sep. 17, 2014 USD ($) shares	Dec. 17, 2013 USD ($) shares	Sep. 30, 2018 USD ($) shares	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) shares	Sep. 30, 2017 USD ($)	Mar. 31, 2019 USD ($)	Apr. 17, 2018 USD ($)	Dec. 31, 2017 USD ($)
Deferred Revenue Arrangement [Line Items]
Proceeds from funding agreement			$ 266,500	$ 715,500	$ 618,000	$ 1,600,000	$ 250,000	$ 500,000	$ 250,000
Interest in asset			0.35533%	0.954%	0.824%	2.1333%	0.50%	1.00%	0.50%
Number of shares issuable term						60 days	60 days	60 days	60 days
Number of shares issuable (in shares) | shares							25,000	62,500	31,250
Recognized as revenue													$ 333,000
Number of shares per dollar exchange rate (in shares) | shares						0.1
Grants receivable																$ 7,400,000
Grant revenue											$ 118,000	$ 0	163,000	$ 0
Increase to deferred revenue													500,000
Current portion	$ 660,000									$ 660,000	660,000		660,000				$ 379,000
Deferred revenue	402,000									$ 402,000	402,000		402,000				$ 2,116,000
BARDA
Deferred Revenue Arrangement [Line Items]
Proceeds from funding agreement	$ 611,000
Grant revenue													$ 0
Period of funding for remaining balance		2 years
Forecast
Deferred Revenue Arrangement [Line Items]
Grant revenue															$ 2,600,000
Plan | BARDA
Deferred Revenue Arrangement [Line Items]
Proceeds from funding agreement		$ 4,600,000
Common Stock
Deferred Revenue Arrangement [Line Items]
Stock newly-issued during the period (in shares) | shares													1,259,663
Common Stock | Valour
Deferred Revenue Arrangement [Line Items]
Stock newly-issued during the period (in shares) | shares										160,000
Within 2.5 Years
Deferred Revenue Arrangement [Line Items]
Buyback term on ownership percentage						2 years 6 months
Buyback rate						2
After 2.5 Years
Deferred Revenue Arrangement [Line Items]
Buyback term on ownership percentage						2 years 6 months
Buyback rate						3.5
Research and Development Arrangement December 17, 2013
Deferred Revenue Arrangement [Line Items]
Recognized as revenue											14,400	21,700	$ 43,400	54,300
Research and Development Arrangement September 17, 2014
Deferred Revenue Arrangement [Line Items]
Recognized as revenue											$ 39,200	$ 0	117,600	$ 0
Research and Development Arrangement July 20, 2015
Deferred Revenue Arrangement [Line Items]
Recognized as revenue													8,900
Research and Development Arrangement September 22, 2015
Deferred Revenue Arrangement [Line Items]
Recognized as revenue													$ 0