| Document and Entity Information | Feb. 05, 2024 |
| Cover [Abstract] | |
| Document Type | 8-K/A |
| Amendment Flag | true |
| Document Period End Date | Feb. 05, 2024 |
| Entity File Number | 1-16681 |
| Entity Registrant Name | Spire Inc. |
| Entity Address Address Line 1 | 700 Market Street |
| Entity Address City Or Town | St. Louis |
| Entity Address State Or Province | MO |
| Entity Address Postal Zip Code | 63101 |
| City Area Code | 314 |
| Local Phone Number | 342-0500 |
| Entity Incorporation State Country Code | MO |
| Entity Tax Identification Number | 74-2976504 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Amendment Description | Spire Inc. (“Spire”) is filing this amendment to its Current Report on Form 8-K filed on February 9, 2024 (the “Original Filing”). |
| Entity Central Index Key | 0001126956 |
