Funding Arrangements (Details) - USD ($)	1 Months Ended		3 Months Ended		8 Months Ended	9 Months Ended
	Sep. 30, 2019	Dec. 31, 2016	Sep. 30, 2019	Sep. 30, 2018	Oct. 31, 2017	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
USAMRAA grant
Funding Arrangements
Maximum reimbursable research expenditures		$ 1,100,000
Grant income recognized			$ 0	$ 100,000		$ 37,000	$ 400,000
Funds received during the period						200,000	700,000
Grants receivable	$ 0		0			0		$ 200,000
CARB-X program
Funding Arrangements
Grant income recognized			600,000	$ 1,500,000		1,800,000	4,100,000
Funds received during the period						2,000,000	$ 1,900,000
Grants receivable	1,300,000		$ 1,300,000			$ 1,300,000		$ 1,500,000
Minimum | CARB-X program
Funding Arrangements
Reimbursable research expenditures					$ 16,400,000
Maximum | CARB-X program
Funding Arrangements
Reimbursable research expenditures	$ 16,800,000