| Document and Entity Information | Oct. 05, 2023 |
| Cover [Abstract] | |
| Document Type | 8-K/A |
| Amendment Flag | true |
| Document Period End Date | Oct. 05, 2023 |
| Entity Registrant Name | SPERO THERAPEUTICS, INC. |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 001-38266 |
| Entity Tax Identification Number | 46-4590683 |
| Entity Address Address Line 1 | 675 Massachusetts Avenue, 14th Floor |
| Entity Address City Or Town | Cambridge |
| Entity Address State Or Province | MA |
| Entity Address Postal Zip Code | 02140 |
| City Area Code | 857 |
| Local Phone Number | 242-1600 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common Stock, $0.001 par value |
| Trading Symbol | SPRO |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
| Amendment Description | Spero Therapeutics, Inc. (the “Company”) is filing this Amendment No. 1 to Current Report on Form 8-K/A (this “Amendment”) to amend the Current Report on Form 8-K, originally filed by the Company with the U.S. Securities and Exchange Commission (the “SEC”) on October 10, 2023 (the “Original Report”). The Original Report was filed, among other things, to disclose (i) the voting results of the Company’s Annual Meeting of Stockholders held on October 5, 2023 (the “Annual Meeting”) and (ii) the filing on October 6, 2023 of a certificate of amendment (the “Charter Amendment”) to the Company’s Amended and Restated Certificate of Incorporation, as amended (the “Charter”), with the Secretary of State of the State of Delaware (the “Delaware Secretary”) to reflect new Delaware law provisions regarding officer exculpation and to add a federal forum selection clause.This Amendment amends the Original Report solely to correct the disclosure regarding the previously reported voting results with respect to the Charter Amendment Proposals (as defined below) and to disclose that the Company has filed a Certificate of Correction (the “Certificate of Correction”) with the Delaware Secretary to undo the Charter Amendment. |
| Current Fiscal Year End Date | --12-31 |
| Entity Central Index Key | 0001701108 |
