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v3.25.3

Revenue - Schedule of Revenue Disaggregated by Source and Customer Type (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Sep. 30, 2025 | Sep. 30, 2024 | Sep. 30, 2023
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues |  | $ 2,476.4 | $ 2,593.0 | $ 2,666.3
Operating Segments [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues |  | 2,520.3 | 2,637.8 | 2,702.1
Gas Utility [Member] | Operating Segments [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues |  | 2,207.6 | 2,437.9 | 2,456.9
Gas Marketing [Member] | Operating Segments [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues |  | 157.2 | 99.2 | 179.1
Midstream [Member] | Operating Segments [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues |  | 155.5 | 100.7 | 66.1
Other [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | [1] | 2.5 | 0.7 | 0.7
Spire [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues |  | 2,476.4 | 2,593.0 | 2,666.3
Spire [Member] | Operating Segments [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues |  | 2,540.8 | 2,655.4 | 2,718.8
Spire [Member] | Intercompany Eliminations [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues |  | (64.4) | (62.4) | (52.5)
Spire [Member] | Gas Utility [Member] | Operating Segments [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue |  | 2,187.2 | 2,386.6 | 2,422.2
Changes in accrued revenue under alternative revenue programs |  | 20.3 | 51.3 | 34.7
Total Gas Utility operating revenues |  | 2,207.5 | 2,437.9 | 2,456.9
Spire [Member] | Gas Utility [Member] | Operating Segments [Member] | Residential [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue |  | 1,462.6 | 1,617.4 | 1,648.5
Spire [Member] | Gas Utility [Member] | Operating Segments [Member] | Commercial and Industrial [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue |  | 501.3 | 581.0 | 606.0
Spire [Member] | Gas Utility [Member] | Operating Segments [Member] | Transportation [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue |  | 133.6 | 130.0 | 121.6
Spire [Member] | Gas Utility [Member] | Operating Segments [Member] | Off-system and Other Incentive [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue |  | 65.3 | 37.0 | 30.0
Spire [Member] | Gas Utility [Member] | Operating Segments [Member] | Other Customer Revenue [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue |  | 24.4 | 21.2 | 16.1
Spire [Member] | Gas Marketing [Member] | Operating Segments [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Unregulated Operating Revenue |  | 157.2 | 99.2 | 179.1
Spire [Member] | Midstream [Member] | Operating Segments [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Unregulated Operating Revenue |  | 155.5 | 100.7 | 66.1
Spire [Member] | Other [Member] | Operating Segments [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Unregulated Operating Revenue |  | 20.6 | 17.6 | 16.7
Spire Missouri [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Changes in accrued revenue under alternative revenue programs |  | 24.2 | 51.0 | 23.9
Operating Revenues |  | 1,544.1 | 1,737.4 | 1,762.9
Spire Missouri [Member] | Gas Utility [Member] | Operating Segments [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue |  | 1,519.9 | 1,686.4 | 1,739.0
Spire Missouri [Member] | Gas Utility [Member] | Operating Segments [Member] | Residential [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue |  | 1,092.1 | 1,217.7 | 1,261.3
Spire Missouri [Member] | Gas Utility [Member] | Operating Segments [Member] | Commercial and Industrial [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue |  | 326.0 | 390.9 | 411.9
Spire Missouri [Member] | Gas Utility [Member] | Operating Segments [Member] | Transportation [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue |  | 35.9 | 34.1 | 33.2
Spire Missouri [Member] | Gas Utility [Member] | Operating Segments [Member] | Off-system and Other Incentive [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue |  | 51.9 | 28.8 | 20.1
Spire Missouri [Member] | Gas Utility [Member] | Operating Segments [Member] | Other Customer Revenue [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue |  | 14.0 | 14.9 | 12.5
Spire Alabama Inc [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Changes in accrued revenue under alternative revenue programs |  | (3.8) | 0.2 | 6.7
Operating Revenues |  | 545.2 | 578.9 | 571.1
Spire Alabama Inc [Member] | Gas Utility [Member] | Operating Segments [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue |  | 549.0 | 578.7 | 564.4
Spire Alabama Inc [Member] | Gas Utility [Member] | Operating Segments [Member] | Residential [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue |  | 307.5 | 336.4 | 322.9
Spire Alabama Inc [Member] | Gas Utility [Member] | Operating Segments [Member] | Commercial and Industrial [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue |  | 134.5 | 149.5 | 150.4
Spire Alabama Inc [Member] | Gas Utility [Member] | Operating Segments [Member] | Transportation [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue |  | 87.3 | 85.1 | 77.6
Spire Alabama Inc [Member] | Gas Utility [Member] | Operating Segments [Member] | Off-system and Other Incentive [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue |  | 13.4 | 8.1 | 9.9
Spire Alabama Inc [Member] | Gas Utility [Member] | Operating Segments [Member] | Other Customer Revenue [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenue |  | $ 6.3 | $ (0.4) | $ 3.6
[1] | All other components of the Company's consolidated information include Spire's subsidiaries engaged in the operation of a propane pipeline and risk management, among other activities, and unallocated corporate items, including certain debt and associated interest costs.

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