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v3.25.3

Segment Information - Schedule of Information about Segment Revenue, Segment Expenses and Adjusted Earnings (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Sep. 30, 2025 | Sep. 30, 2024 | Sep. 30, 2023
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from external customers |  | $ 2,476.4 | $ 2,593.0 | $ 2,666.3
Intersegment revenues |  | 0.0 | 0.0 | 0.0
Total Operating Revenues |  | 2,476.4 | 2,593.0 | 2,666.3
Cost of gas sold, incl. gross receipts taxes |  | 1,021.2 | 1,231.5 | 1,392.6
Operation and maintenance expense |  | 542.1 | 507.4 | 517.6
Depreciation and amortization expense |  | 298.2 | 278.4 | 254.8
Interest Expense |  | 204.1 | 201.1 | 185.7
Income tax expense (benefit) |  | 59.7 | 58.7 | 38.8
Other segment items | [1] | 75.6 | 68.5 | 48.7
Adjusted Earnings (Loss) |  | 275.5 | 247.4 | 228.1
Capital expenditures |  | 922.4 | 861.3 | 662.5
Operating Segments [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from external customers |  | 2,473.9 | 2,592.3 | 2,665.6
Intersegment revenues |  | 46.4 | 45.5 | 36.5
Total Operating Revenues |  | 2,520.3 | 2,637.8 | 2,702.1
Cost of gas sold, incl. gross receipts taxes |  | 1,067.6 | 1,276.9 | 1,429.1
Operation and maintenance expense |  | 531.8 | 505.7 | 511.7
Depreciation and amortization expense |  | 297.8 | 277.9 | 254.3
Interest Expense |  | 148.7 | 154.3 | 148.5
Income tax expense (benefit) |  | 74.2 | 68.4 | 49.3
Other segment items | [1] | 86.6 | 76.9 | 47.0
Adjusted Earnings (Loss) |  | 313.6 | 277.7 | 262.2
Capital expenditures |  | 923.7 | 862.5 | 662.6
Intersegment Eliminations [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from external customers |  | 0.0 | 0.0 | 0.0
Intersegment revenues |  | (46.4) | (45.5) | (36.5)
Total Operating Revenues |  | (46.4) | (45.5) | (36.5)
Cost of gas sold, incl. gross receipts taxes |  | (46.4) | (45.5) | (36.5)
Operation and maintenance expense |  | 0.0 | 0.0 | 0.0
Depreciation and amortization expense |  | 0.0 | 0.0 | 0.0
Interest Expense |  | 0.0 | 0.0 | 0.0
Income tax expense (benefit) |  | 0.0 | 0.0 | 0.0
Other segment items | [1] | 0.0 | 0.0 | 0.0
Adjusted Earnings (Loss) |  | 0.0 | 0.0 | 0.0
Capital expenditures |  | 0.0 | 0.0 | 0.0
Gas Utility [Member] | Operating Segments [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from external customers |  | 2,207.5 | 2,436.2 | 2,456.6
Intersegment revenues |  | 0.1 | 1.7 | 0.3
Total Operating Revenues |  | 2,207.6 | 2,437.9 | 2,456.9
Cost of gas sold, incl. gross receipts taxes |  | 970.9 | 1,238.7 | 1,321.1
Operation and maintenance expense |  | 467.1 | 452.8 | 461.8
Depreciation and amortization expense |  | 277.6 | 263.6 | 244.4
Interest Expense |  | 137.1 | 147.3 | 139.9
Income tax expense (benefit) |  | 47.4 | 48.0 | 32.7
Other segment items | [1] | 76.1 | 66.7 | 56.5
Adjusted Earnings (Loss) |  | 231.4 | 220.8 | 200.5
Capital expenditures |  | 816.8 | 691.1 | 588.6
Gas Marketing [Member] | Operating Segments [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from external customers |  | 157.2 | 99.2 | 179.1
Intersegment revenues |  | 0.0 | 0.0 | 0.0
Total Operating Revenues |  | 157.2 | 99.2 | 179.1
Cost of gas sold, incl. gross receipts taxes |  | 93.7 | 37.1 | 108.0
Operation and maintenance expense |  | 19.4 | 18.2 | 19.4
Depreciation and amortization expense |  | 1.0 | 1.5 | 1.5
Interest Expense |  | 0.0 | 0.0 | 0.0
Income tax expense (benefit) |  | 11.1 | 10.8 | 12.8
Other segment items | [1] | 6.1 | 8.2 | (10.2)
Adjusted Earnings (Loss) |  | 25.9 | 23.4 | 47.6
Capital expenditures |  | 0.1 | 0.1 | 0.4
Midstream [Member] | Operating Segments [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from external customers |  | 109.2 | 56.9 | 29.9
Intersegment revenues |  | 46.3 | 43.8 | 36.2
Total Operating Revenues |  | 155.5 | 100.7 | 66.1
Cost of gas sold, incl. gross receipts taxes |  | 3.0 | 1.1 | 0.0
Operation and maintenance expense |  | 45.3 | 34.7 | 30.5
Depreciation and amortization expense |  | 19.2 | 12.8 | 8.4
Interest Expense |  | 11.6 | 7.0 | 8.6
Income tax expense (benefit) |  | 15.7 | 9.6 | 3.8
Other segment items | [1] | 4.4 | 2.0 | 0.7
Adjusted Earnings (Loss) |  | 56.3 | 33.5 | 14.1
Capital expenditures |  | 106.8 | 171.3 | 73.6
Other [Member] |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from external customers | [2] | 2.5 | 0.7 | 0.7
Intersegment revenues | [2] | 0.0 | 0.0 | 0.0
Total Operating Revenues | [2] | 2.5 | 0.7 | 0.7
Cost of gas sold, incl. gross receipts taxes | [2] | 0.0 | 0.1 | 0.0
Operation and maintenance expense | [2] | 10.3 | 1.7 | 5.9
Depreciation and amortization expense | [2] | 0.4 | 0.5 | 0.5
Interest Expense | [2] | 55.4 | 46.8 | 37.2
Income tax expense (benefit) | [2] | (14.5) | (9.7) | (10.5)
Other segment items | [1],[2] | (11.0) | (8.4) | 1.7
Adjusted Earnings (Loss) | [2] | (38.1) | (30.3) | (34.1)
Capital expenditures | [2] | $ (1.3) | $ (1.2) | $ (0.1)
[1] | Other segment items for each reportable segment include fair value and timing adjustments, acquisition and restructuring activities, taxes other than income and gross receipt taxes, and miscellaneous income and deductions.
[2] | 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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