Document And Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Mar. 17, 2021	Jun. 30, 2020
Document And Entity Information [Abstract]
Document Type	10-K
Document Period End Date	Dec. 31, 2020
Entity Registrant Name	ARMATA PHARMACEUTICALS, INC.
Entity Current Reporting Status	Yes
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Filer Category	Non-accelerated Filer
Entity Interactive Data Current	Yes
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		24,940,442
Entity Public Float			$ 37.7
Entity Central Index Key	0000921114
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Amendment Flag	false