| Document and Entity Information | Sep. 30, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Sep. 30, 2021 |
| Trading Symbol | IMPL |
| Entity Registrant Name | IMPEL NEUROPHARMA, INC. |
| Entity Central Index Key | 0001445499 |
| Entity Emerging Growth Company | true |
| Entity File Number | 001-40353 |
| Entity Incorporation, State or Country Code | DE |
| Entity Tax Identification Number | 26-3058238 |
| Entity Ex Transition Period | false |
| Entity Address, Address Line One | 201 Elliott Avenue West |
| Entity Address, Address Line Two | Suite 260 |
| Entity Address, City or Town | Seattle |
| Entity Address, State or Province | WA |
| Entity Address, Postal Zip Code | 98119 |
| City Area Code | 206 |
| Local Phone Number | 568-1466 |
| Entity Information, Former Legal or Registered Name | N/A |
| Title of 12(b) Security | Common Stock, $0.001 Par Value Per Share |
| Security Exchange Name | NASDAQ |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
