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v3.23.3

Note 6 - Long-term Debt (Details Textual) - USD ($) $ in Millions |  | 12 Months Ended | 19 Months Ended
--- | --- | --- | ---
Dec. 07, 2021 | Sep. 30, 2023 | Sep. 30, 2022 | Sep. 30, 2021 | Sep. 30, 2023
Long-Term Debt, Gross |  | $ 3,732.7 | $ 3,258.9 |  | $ 3,732.7
Interest Paid, Capitalized, Investing Activities |  | 8.6 | 4.5 | $ 4.4 |
Stock Issued During Period, Value, New Issues |  | 40.5 | 50.3 |  |
Subsidiaries [Member] |  |  |  |  |
Long-Term Debt, Gross |  | 229.7 |  |  | 229.7
Spire Missouri [Member] |  |  |  |  |
Long-Term Debt, Gross |  | 1,798.0 | 1,648.0 |  | 1,798.0
Interest Paid, Capitalized, Investing Activities |  | 3.1 | 0.6 | 0.2 |
Regulatory Preferred Stock and Debt Securities Issuance Amount Authorized |  | 800.0 |  |  | 800.0
Stock Issued During Period, Value, New Issues |  | 38.7 | 51.1 |  |
Spire Missouri [Member] | Universal Shelf Registration [Member] |  |  |  |  |
Stock Issued During Period, Value, New Issues |  | 79.1 |  |  | 79.1
Spire Missouri [Member] | First Mortgage Bonds Due December Two Two Thousand Twenty Four [Member] |  |  |  |  |
Long-Term Debt, Gross | $ 300.0 |  |  |  |
Debt Instrument, Interest Rate, Stated Percentage | 8.00% |  |  |  |
Spire Missouri [Member] | First Mortgage Bonds Due December Two Two Thousand Twenty Four [Member] | Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate [Member] |  |  |  |  |
Debt Instrument, Basis Spread on Variable Rate | 0.50% |  |  |  |
Spire Missouri [Member] | Floating Rate Series Due December 2, 2024 [Member] |  |  |  |  |
Long-Term Debt, Gross |  | 300.0 |  |  | 300.0
Spire Missouri [Member] | First Mortgage Bond [Member] |  |  |  |  |
Debt Instrument, Face Amount |  | 400.0 |  |  | 400.0
Spire Alabama Inc [Member] |  |  |  |  |
Long-Term Debt, Gross |  | 750.0 | 575.0 |  | $ 750.0
Interest Paid, Capitalized, Investing Activities |  | $ 2.3 | $ 3.2 | $ 3.2 |

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