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v3.25.3

Regulatory Matters (Tables) | 12 Months Ended
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Sep. 30, 2025
Regulated Operations [Abstract] |
Schedule of Regulatory Assets and Liabilities | The following regulatory assets and regulatory liabilities were reflected in the balance sheets of the Company, Spire Missouri and Spire Alabama as of September 30, 2025 and 2024.
|  | Spire |  |  | Spire Missouri |  |  | Spire Alabama |
September 30 |  | 2025 |  |  | 2024 |  |  | 2025 |  |  | 2024 |  |  | 2025 |  |  | 2024 |
Regulatory Assets: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Current: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Unamortized purchased gas adjustments |  | $ | 16.5 |  |  | $ | 28.9 |  |  | $ | 14.9 |  |  | $ | 28.1 |  |  | $ | — |  |  | $ | — |
Other |  |  | 61.8 |  |  |  | 86.5 |  |  |  | 34.0 |  |  |  | 55.9 |  |  |  | 16.1 |  |  |  | 19.2 |
Total Current Regulatory Assets |  |  | 78.3 |  |  |  | 115.4 |  |  |  | 48.9 |  |  |  | 84.0 |  |  |  | 16.1 |  |  |  | 19.2 |
Noncurrent: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Future income taxes due from customers |  |  | 154.2 |  |  |  | 150.7 |  |  |  | 146.6 |  |  |  | 142.7 |  |  |  | 1.6 |  |  |  | 1.8 |
Pension and postretirement benefit costs |  |  | 217.8 |  |  |  | 237.5 |  |  |  | 157.0 |  |  |  | 166.5 |  |  |  | 59.1 |  |  |  | 68.2 |
Cost of removal |  |  | 688.3 |  |  |  | 668.2 |  |  |  | 98.8 |  |  |  | 97.0 |  |  |  | 589.6 |  |  |  | 571.2 |
Unamortized purchased gas adjustments |  |  | 9.0 |  |  |  | 1.2 |  |  |  | 9.0 |  |  |  | 1.2 |  |  |  | — |  |  |  | — |
Energy efficiency |  |  | 65.0 |  |  |  | 61.0 |  |  |  | 65.0 |  |  |  | 61.0 |  |  |  | — |  |  |  | — |
Other |  |  | 189.2 |  |  |  | 133.2 |  |  |  | 176.8 |  |  |  | 119.6 |  |  |  | 0.3 |  |  |  | 0.8 |
Total Noncurrent Regulatory Assets |  |  | 1,323.5 |  |  |  | 1,251.8 |  |  |  | 653.2 |  |  |  | 588.0 |  |  |  | 650.6 |  |  |  | 642.0 |
Total Regulatory Assets |  | $ | 1,401.8 |  |  | $ | 1,367.2 |  |  | $ | 702.1 |  |  | $ | 672.0 |  |  | $ | 666.7 |  |  | $ | 661.2 |
Regulatory Liabilities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Current: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Unamortized purchased gas adjustments |  | $ | 34.9 |  |  | $ | 42.3 |  |  | $ | 13.9 |  |  | $ | 10.2 |  |  | $ | 20.2 |  |  | $ | 30.9 |
Other |  |  | 4.5 |  |  |  | 7.2 |  |  |  | — |  |  |  | — |  |  |  | 0.1 |  |  |  | 2.9 |
Total Current Regulatory Liabilities |  |  | 39.4 |  |  |  | 49.5 |  |  |  | 13.9 |  |  |  | 10.2 |  |  |  | 20.3 |  |  |  | 33.8 |
Noncurrent: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Deferred taxes due to customers |  |  | 100.3 |  |  |  | 114.2 |  |  |  | 88.8 |  |  |  | 101.8 |  |  |  | — |  |  |  | — |
Pension and postretirement benefit costs |  |  | 300.1 |  |  |  | 232.9 |  |  |  | 261.2 |  |  |  | 196.6 |  |  |  | 26.5 |  |  |  | 25.1 |
Accrued cost of removal |  |  | 138.2 |  |  |  | 133.6 |  |  |  | 96.0 |  |  |  | 94.5 |  |  |  | — |  |  |  | — |
Unamortized purchased gas adjustments |  |  | 6.5 |  |  |  | 17.2 |  |  |  | 6.5 |  |  |  | 17.2 |  |  |  | — |  |  |  | — |
Other |  |  | 32.9 |  |  |  | 37.6 |  |  |  | 28.8 |  |  |  | 33.2 |  |  |  | 2.7 |  |  |  | 3.2 |
Total Noncurrent Regulatory Liabilities |  |  | 578.0 |  |  |  | 535.5 |  |  |  | 481.3 |  |  |  | 443.3 |  |  |  | 29.2 |  |  |  | 28.3 |
Total Regulatory Liabilities |  | $ | 617.4 |  |  | $ | 585.0 |  |  | $ | 495.2 |  |  | $ | 453.5 |  |  | $ | 49.5 |  |  | $ | 62.1 |
Schedule of Regulatory Assets Not Earning Return | A portion of the Company’s and Spire Missouri's regulatory assets are not earning a return, as shown in the table below:
|  | Spire |  |  | Spire Missouri |
September 30 |  | 2025 |  |  | 2024 |  |  | 2025 |  |  | 2024 |
Pension and postretirement benefit costs |  | $ | 119.1 |  |  | $ | 129.7 |  |  | $ | 119.1 |  |  | $ | 129.7 |
Future income taxes due from customers |  |  | 152.7 |  |  |  | 148.9 |  |  |  | 146.6 |  |  |  | 142.7 |
Unamortized purchase gas adjustments |  |  | 23.9 |  |  |  | 29.3 |  |  |  | 23.9 |  |  |  | 29.3 |
Other |  |  | 177.0 |  |  |  | 132.5 |  |  |  | 177.0 |  |  |  | 132.5 |
Total Regulatory Assets Not Earning a Return |  | $ | 472.7 |  |  | $ | 440.4 |  |  | $ | 466.6 |  |  | $ | 434.2 |

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- Definition Tabular disclosure of assets that are created when regulatory agencies permit public utilities to defer certain costs included in rate-setting to the balance sheet and regulatory liabilities. Detailed information about liabilities that result from rate actions of a regulator. Rate actions of a regulator can impose a liability on a regulated enterprise resulting in a regulatory liability. + References No definition available. + Details
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- Definition Tabular disclosure of regulatory assets not earning return. + References No definition available. + Details
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