| Document And Entity Information | Jan. 03, 2025 |
| Document Information [Line Items] | |
| Entity, Registrant Name | Spire Inc. |
| Document, Type | 8-K |
| Document, Period End Date | Jan. 03, 2025 |
| Entity, File Number | 1-16681 |
| Entity, Address, Address Line One | 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 or 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 Flag | false |
| Entity, Central Index Key | 0001126956 |
| CommonStock Custom [Member] | |
| Document Information [Line Items] | |
| Title of 12(b) Security | Common Stock |
| Trading Symbol | SR |
| Security Exchange Name | NYSE |
| DepositaryShares Custom [Member] | |
| Document Information [Line Items] | |
| Title of 12(b) Security | Depositary Shares |
| Trading Symbol | SR.PRA |
| Security Exchange Name | NYSE |
| Spire Missouri Inc [Member] | |
| Document Information [Line Items] | |
| Entity, Registrant Name | Spire Missouri Inc. |
| Entity, File Number | 1-1822 |
| Entity, Address, Address Line One | 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 or Country Code | MO |
| Entity, Tax Identification Number | 43-0368139 |
| Spire Alabama Inc [Member] | |
| Document Information [Line Items] | |
| Entity, Registrant Name | Spire Alabama Inc. |
| Entity, File Number | 2-38960 |
| Entity, Address, Address Line One | 605 Richard Arrington Blvd N |
| Entity, Address, City or Town | Birmingham |
| Entity, Address, State or Province | AL |
| Entity, Address, Postal Zip Code | 35203 |
| City Area Code | 205 |
| Local Phone Number | 326-8100 |
| Entity, Incorporation, State or Country Code | AL |
| Entity, Tax Identification Number | 63-0022000 |
