Document And Entity Information - shares	9 Months Ended
	Sep. 30, 2021	Nov. 05, 2021
Document And Entity Information [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Transition Report	false
Document Period End Date	Sep. 30, 2021
Entity File Number	001-37544
Entity Registrant Name	Armata Pharmaceuticals, Inc.
Entity Incorporation, State or Country Code	WA
Entity Tax Identification Number	91-1549568
Entity Address, Address Line One	4503 Glencoe Avenue
Entity Address, City or Town	Marina del Rey
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	90292
City Area Code	310
Local Phone Number	665-2928
Title of 12(b) Security	Common Stock
Trading Symbol	ARMP
Security Exchange Name	NYSEAMER
Entity Current Reporting Status	Yes
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		27,086,299
Entity Central Index Key	0000921114
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q3
Amendment Flag	false