| Cover | Oct. 28, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Oct. 28, 2021 |
| Entity File Number | 001-37544 |
| Entity Registrant Name | ARMATA PHARMACEUTICALS, INC. |
| Entity Central Index Key | 0000921114 |
| Entity Tax Identification Number | 91-1549568 |
| Entity Incorporation, State or Country Code | WA |
| 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 | 655-2928 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock, par value $0.01 per share |
| Trading Symbol | ARMP |
| Security Exchange Name | NYSEAMER |
| Entity Emerging Growth Company | false |
