| Document and Entity Information | Oct. 27, 2020 |
| Cover [Abstract] | |
| Amendment Flag | false |
| Entity Central Index Key | 0001590750 |
| Current Fiscal Year End Date | --12-31 |
| Document Type | 8-K |
| Document Period End Date | Oct. 27, 2020 |
| Entity Registrant Name | MIRAGEN THERAPEUTICS, INC. |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 001-36483 |
| Entity Tax Identification Number | 47-1187261 |
| Entity Address, Address Line One | 6200 Lookout Road |
| Entity Address, City or Town | Boulder |
| Entity Address, State or Province | CO |
| Entity Address, Postal Zip Code | 80301 |
| City Area Code | (720) |
| Local Phone Number | 643-5200 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common stock, $0.01 Par Value |
| Trading Symbol | MGEN |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
