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Note 13 - Pension Plans and Other Postretirement Benefits - Fair Value Measurements of Pension Plan Assets (Details) - USD ($) $ in Millions | Sep. 30, 2022 | Sep. 30, 2021 | Sep. 30, 2020
--- | --- | --- | ---
Spire Missouri [Member] |  |  |
Defined Benefit Plan Assets |  | $ 364.0 | $ 336.2
Spire Alabama Inc [Member] |  |  |
Defined Benefit Plan Assets |  | 82.8 | 88.6
Pension Plan [Member] |  |  |
Defined Benefit Plan Assets | $ 332.7 | 498.9 | 473.1
Pension Plan [Member] | Spire Missouri [Member] |  |  |
Defined Benefit Plan Assets | 235.9 | 364.0 |
Pension Plan [Member] | Spire Alabama Inc [Member] |  |  |
Defined Benefit Plan Assets | 57.3 | 82.8 |
Pension Plan [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |
Defined Benefit Plan Assets | 89.9 | 129.1 |
Pension Plan [Member] | Fair Value, Inputs, Level 1 [Member] | Spire Missouri [Member] |  |  |
Defined Benefit Plan Assets | 59.7 | 92.3 |
Pension Plan [Member] | Fair Value, Inputs, Level 1 [Member] | Spire Alabama Inc [Member] |  |  |
Defined Benefit Plan Assets | 18.0 | 22.6 |
Pension Plan [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |
Defined Benefit Plan Assets | 242.8 | 369.8 |
Pension Plan [Member] | Fair Value, Inputs, Level 2 [Member] | Spire Missouri [Member] |  |  |
Defined Benefit Plan Assets | 176.2 | 271.7 |
Pension Plan [Member] | Fair Value, Inputs, Level 2 [Member] | Spire Alabama Inc [Member] |  |  |
Defined Benefit Plan Assets | 39.3 | 60.2 |
Pension Plan [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |
Defined Benefit Plan Assets | 0.0 | 0.0 |
Pension Plan [Member] | Fair Value, Inputs, Level 3 [Member] | Spire Missouri [Member] |  |  |
Defined Benefit Plan Assets | 0.0 | 0.0 |
Pension Plan [Member] | Fair Value, Inputs, Level 3 [Member] | Spire Alabama Inc [Member] |  |  |
Defined Benefit Plan Assets | 0.0 | 0.0 |
Pension Plan [Member] | Defined Benefit Plan, Cash and Cash Equivalents [Member] |  |  |
Defined Benefit Plan Assets | 11.5 | 10.6 |
Pension Plan [Member] | Defined Benefit Plan, Cash and Cash Equivalents [Member] | Spire Missouri [Member] |  |  |
Defined Benefit Plan Assets | 5.7 | 8.3 |
Pension Plan [Member] | Defined Benefit Plan, Cash and Cash Equivalents [Member] | Spire Alabama Inc [Member] |  |  |
Defined Benefit Plan Assets | 3.5 | 1.4 |
Pension Plan [Member] | Defined Benefit Plan, Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |
Defined Benefit Plan Assets | 11.5 | 10.6 |
Pension Plan [Member] | Defined Benefit Plan, Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 1 [Member] | Spire Missouri [Member] |  |  |
Defined Benefit Plan Assets | 5.7 | 8.3 |
Pension Plan [Member] | Defined Benefit Plan, Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 1 [Member] | Spire Alabama Inc [Member] |  |  |
Defined Benefit Plan Assets | 3.5 | 1.4 |
Pension Plan [Member] | Defined Benefit Plan, Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |
Defined Benefit Plan Assets | 0.0 | 0.0 |
Pension Plan [Member] | Defined Benefit Plan, Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 2 [Member] | Spire Missouri [Member] |  |  |
Defined Benefit Plan Assets | 0.0 | 0.0 |
Pension Plan [Member] | Defined Benefit Plan, Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 2 [Member] | Spire Alabama Inc [Member] |  |  |
Defined Benefit Plan Assets | 0.0 | 0.0 |
Pension Plan [Member] | Defined Benefit Plan, Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |
Defined Benefit Plan Assets | 0.0 | 0.0 |
Pension Plan [Member] | Defined Benefit Plan, Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 3 [Member] | Spire Missouri [Member] |  |  |
Defined Benefit Plan Assets | 0.0 | 0.0 |
Pension Plan [Member] | Defined Benefit Plan, Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 3 [Member] | Spire Alabama Inc [Member] |  |  |
Defined Benefit Plan Assets | 0.0 | 0.0 |
Pension Plan [Member] | Equity Funds [Member] |  |  |
Defined Benefit Plan Assets | 122.2 | 201.2 |
Pension Plan [Member] | Equity Funds [Member] | Spire Missouri [Member] |  |  |
Defined Benefit Plan Assets | 85.7 | 148.6 |
Pension Plan [Member] | Equity Funds [Member] | Spire Alabama Inc [Member] |  |  |
Defined Benefit Plan Assets | 21.6 | 32.3 |
Pension Plan [Member] | Equity Funds [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |
Defined Benefit Plan Assets | 0.0 | 0.0 |
Pension Plan [Member] | Equity Funds [Member] | Fair Value, Inputs, Level 1 [Member] | Spire Missouri [Member] |  |  |
Defined Benefit Plan Assets | 0.0 | 0.0 |
Pension Plan [Member] | Equity Funds [Member] | Fair Value, Inputs, Level 1 [Member] | Spire Alabama Inc [Member] |  |  |
Defined Benefit Plan Assets | 0.0 | 0.0 |
Pension Plan [Member] | Equity Funds [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |
Defined Benefit Plan Assets | 122.2 | 201.2 |
Pension Plan [Member] | Equity Funds [Member] | Fair Value, Inputs, Level 2 [Member] | Spire Missouri [Member] |  |  |
Defined Benefit Plan Assets | 85.7 | 148.6 |
Pension Plan [Member] | Equity Funds [Member] | Fair Value, Inputs, Level 2 [Member] | Spire Alabama Inc [Member] |  |  |
Defined Benefit Plan Assets | 21.6 | 32.3 |
Pension Plan [Member] | Equity Funds [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |
Defined Benefit Plan Assets | 0.0 | 0.0 |
Pension Plan [Member] | Equity Funds [Member] | Fair Value, Inputs, Level 3 [Member] | Spire Missouri [Member] |  |  |
Defined Benefit Plan Assets | 0.0 | 0.0 |
Pension Plan [Member] | Equity Funds [Member] | Fair Value, Inputs, Level 3 [Member] | Spire Alabama Inc [Member] |  |  |
Defined Benefit Plan Assets | 0.0 | 0.0 |
Pension Plan [Member] | Real Asset Funds [Member] |  |  |
Defined Benefit Plan Assets | 61.0 | 87.7 |
Pension Plan [Member] | Real Asset Funds [Member] | Spire Missouri [Member] |  |  |
Defined Benefit Plan Assets | 47.2 | 59.2 |
Pension Plan [Member] | Real Asset Funds [Member] | Spire Alabama Inc [Member] |  |  |
Defined Benefit Plan Assets | 8.1 | 14.6 |
Pension Plan [Member] | Real Asset Funds [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |
Defined Benefit Plan Assets | 0.0 | 0.0 |
Pension Plan [Member] | Real Asset Funds [Member] | Fair Value, Inputs, Level 1 [Member] | Spire Missouri [Member] |  |  |
Defined Benefit Plan Assets | 0.0 | 0.0 |
Pension Plan [Member] | Real Asset Funds [Member] | Fair Value, Inputs, Level 1 [Member] | Spire Alabama Inc [Member] |  |  |
Defined Benefit Plan Assets | 0.0 | 0.0 |
Pension Plan [Member] | Real Asset Funds [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |
Defined Benefit Plan Assets | 61.0 | 87.7 |
Pension Plan [Member] | Real Asset Funds [Member] | Fair Value, Inputs, Level 2 [Member] | Spire Missouri [Member] |  |  |
Defined Benefit Plan Assets | 47.2 | 59.2 |
Pension Plan [Member] | Real Asset Funds [Member] | Fair Value, Inputs, Level 2 [Member] | Spire Alabama Inc [Member] |  |  |
Defined Benefit Plan Assets | 8.1 | 14.6 |
Pension Plan [Member] | Real Asset Funds [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |
Defined Benefit Plan Assets | 0.0 | 0.0 |
Pension Plan [Member] | Real Asset Funds [Member] | Fair Value, Inputs, Level 3 [Member] | Spire Missouri [Member] |  |  |
Defined Benefit Plan Assets | 0.0 | 0.0 |
Pension Plan [Member] | Real Asset Funds [Member] | Fair Value, Inputs, Level 3 [Member] | Spire Alabama Inc [Member] |  |  |
Defined Benefit Plan Assets | 0.0 | 0.0 |
Pension Plan [Member] | U S Bond Funds [Member] |  |  |
Defined Benefit Plan Assets | 42.3 | 58.4 |
Pension Plan [Member] | U S Bond Funds [Member] | Spire Missouri [Member] |  |  |
Defined Benefit Plan Assets | 29.4 | 38.4 |
Pension Plan [Member] | U S Bond Funds [Member] | Spire Alabama Inc [Member] |  |  |
Defined Benefit Plan Assets | 7.7 | 12.3 |
Pension Plan [Member] | U S Bond Funds [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |
Defined Benefit Plan Assets | 42.3 | 58.4 |
Pension Plan [Member] | U S Bond Funds [Member] | Fair Value, Inputs, Level 1 [Member] | Spire Missouri [Member] |  |  |
Defined Benefit Plan Assets | 29.4 | 38.4 |
Pension Plan [Member] | U S Bond Funds [Member] | Fair Value, Inputs, Level 1 [Member] | Spire Alabama Inc [Member] |  |  |
Defined Benefit Plan Assets | 7.7 | 12.3 |
Pension Plan [Member] | U S Bond Funds [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |
Defined Benefit Plan Assets | 0.0 | 0.0 |
Pension Plan [Member] | U S Bond Funds [Member] | Fair Value, Inputs, Level 2 [Member] | Spire Missouri [Member] |  |  |
Defined Benefit Plan Assets | 0.0 | 0.0 |
Pension Plan [Member] | U S Bond Funds [Member] | Fair Value, Inputs, Level 2 [Member] | Spire Alabama Inc [Member] |  |  |
Defined Benefit Plan Assets | 0.0 | 0.0 |
Pension Plan [Member] | U S Bond Funds [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |
Defined Benefit Plan Assets | 0.0 | 0.0 |
Pension Plan [Member] | U S Bond Funds [Member] | Fair Value, Inputs, Level 3 [Member] | Spire Missouri [Member] |  |  |
Defined Benefit Plan Assets | 0.0 | 0.0 |
Pension Plan [Member] | U S Bond Funds [Member] | Fair Value, Inputs, Level 3 [Member] | Spire Alabama Inc [Member] |  |  |
Defined Benefit Plan Assets | 0.0 | 0.0 |
Pension Plan [Member] | U S Government Index Funds [Member] |  |  |
Defined Benefit Plan Assets | 36.1 | 60.1 |
Pension Plan [Member] | U S Government Index Funds [Member] | Spire Missouri [Member] |  |  |
Defined Benefit Plan Assets | 24.6 | 45.6 |
Pension Plan [Member] | U S Government Index Funds [Member] | Spire Alabama Inc [Member] |  |  |
Defined Benefit Plan Assets | 6.8 | 8.9 |
Pension Plan [Member] | U S Government Index Funds [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |
Defined Benefit Plan Assets | 36.1 | 60.1 |
Pension Plan [Member] | U S Government Index Funds [Member] | Fair Value, Inputs, Level 1 [Member] | Spire Missouri [Member] |  |  |
Defined Benefit Plan Assets | 24.6 | 45.6 |
Pension Plan [Member] | U S Government Index Funds [Member] | Fair Value, Inputs, Level 1 [Member] | Spire Alabama Inc [Member] |  |  |
Defined Benefit Plan Assets | 6.8 | 8.9 |
Pension Plan [Member] | U S Government Index Funds [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |
Defined Benefit Plan Assets | 0.0 | 0.0 |
Pension Plan [Member] | U S Government Index Funds [Member] | Fair Value, Inputs, Level 2 [Member] | Spire Missouri [Member] |  |  |
Defined Benefit Plan Assets | 0.0 | 0.0 |
Pension Plan [Member] | U S Government Index Funds [Member] | Fair Value, Inputs, Level 2 [Member] | Spire Alabama Inc [Member] |  |  |
Defined Benefit Plan Assets | 0.0 | 0.0 |
Pension Plan [Member] | U S Government Index Funds [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |
Defined Benefit Plan Assets | 0.0 | 0.0 |
Pension Plan [Member] | U S Government Index Funds [Member] | Fair Value, Inputs, Level 3 [Member] | Spire Missouri [Member] |  |  |
Defined Benefit Plan Assets | 0.0 | 0.0 |
Pension Plan [Member] | U S Government Index Funds [Member] | Fair Value, Inputs, Level 3 [Member] | Spire Alabama Inc [Member] |  |  |
Defined Benefit Plan Assets | 0.0 | 0.0 |
Pension Plan [Member] | Global Funds Including U S [Member] |  |  |
Defined Benefit Plan Assets | 59.6 | 80.9 |
Pension Plan [Member] | Global Funds Including U S [Member] | Spire Missouri [Member] |  |  |
Defined Benefit Plan Assets | 43.3 | 63.9 |
Pension Plan [Member] | Global Funds Including U S [Member] | Spire Alabama Inc [Member] |  |  |
Defined Benefit Plan Assets | 9.6 | 13.3 |
Pension Plan [Member] | Global Funds Including U S [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |
Defined Benefit Plan Assets | 0.0 | 0.0 |
Pension Plan [Member] | Global Funds Including U S [Member] | Fair Value, Inputs, Level 1 [Member] | Spire Missouri [Member] |  |  |
Defined Benefit Plan Assets | 0.0 | 0.0 |
Pension Plan [Member] | Global Funds Including U S [Member] | Fair Value, Inputs, Level 1 [Member] | Spire Alabama Inc [Member] |  |  |
Defined Benefit Plan Assets | 0.0 | 0.0 |
Pension Plan [Member] | Global Funds Including U S [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |
Defined Benefit Plan Assets | 59.6 | 80.9 |
Pension Plan [Member] | Global Funds Including U S [Member] | Fair Value, Inputs, Level 2 [Member] | Spire Missouri [Member] |  |  |
Defined Benefit Plan Assets | 43.3 | 63.9 |
Pension Plan [Member] | Global Funds Including U S [Member] | Fair Value, Inputs, Level 2 [Member] | Spire Alabama Inc [Member] |  |  |
Defined Benefit Plan Assets | 9.6 | 13.3 |
Pension Plan [Member] | Global Funds Including U S [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |
Defined Benefit Plan Assets | 0.0 | 0.0 |
Pension Plan [Member] | Global Funds Including U S [Member] | Fair Value, Inputs, Level 3 [Member] | Spire Missouri [Member] |  |  |
Defined Benefit Plan Assets | 0.0 | 0.0 |
Pension Plan [Member] | Global Funds Including U S [Member] | Fair Value, Inputs, Level 3 [Member] | Spire Alabama Inc [Member] |  |  |
Defined Benefit Plan Assets | 0.0 | 0.0 |
Other Postretirement Benefits Plan [Member] |  |  |
Defined Benefit Plan Assets | 264.7 | 326.9 | 291.0
Other Postretirement Benefits Plan [Member] | Spire Missouri [Member] |  |  |
Defined Benefit Plan Assets | 176.7 | 221.7 | 199.2
Other Postretirement Benefits Plan [Member] | Spire Alabama Inc [Member] |  |  |
Defined Benefit Plan Assets | 83.3 | 99.4 | $ 87.0
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |
Defined Benefit Plan Assets | 181.4 | 227.5 |
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 1 [Member] | Spire Missouri [Member] |  |  |
Defined Benefit Plan Assets | 176.7 | 221.7 |
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 1 [Member] | Spire Alabama Inc [Member] |  |  |
Defined Benefit Plan Assets | 0.0 | 0.0 |
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |
Defined Benefit Plan Assets | 83.3 | 99.4 |
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 2 [Member] | Spire Missouri [Member] |  |  |
Defined Benefit Plan Assets | 0.0 | 0.0 |
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 2 [Member] | Spire Alabama Inc [Member] |  |  |
Defined Benefit Plan Assets | 83.3 | 99.4 |
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |
Defined Benefit Plan Assets | 0.0 | 0.0 |
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 3 [Member] | Spire Missouri [Member] |  |  |
Defined Benefit Plan Assets | 0.0 | 0.0 |
Other Postretirement Benefits Plan [Member] | Fair Value, Inputs, Level 3 [Member] | Spire Alabama Inc [Member] |  |  |
Defined Benefit Plan Assets | 0.0 | 0.0 |
Other Postretirement Benefits Plan [Member] | Defined Benefit Plan, Cash and Cash Equivalents [Member] |  |  |
Defined Benefit Plan Assets | 3.5 | 3.1 |
Other Postretirement Benefits Plan [Member] | Defined Benefit Plan, Cash and Cash Equivalents [Member] | Spire Missouri [Member] |  |  |
Defined Benefit Plan Assets | 2.7 | 2.4 |
Other Postretirement Benefits Plan [Member] | Defined Benefit Plan, Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |
Defined Benefit Plan Assets | 3.5 | 3.1 |
Other Postretirement Benefits Plan [Member] | Defined Benefit Plan, Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 1 [Member] | Spire Missouri [Member] |  |  |
Defined Benefit Plan Assets | 2.7 | 2.4 |
Other Postretirement Benefits Plan [Member] | Defined Benefit Plan, Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |
Defined Benefit Plan Assets | 0.0 | 0.0 |
Other Postretirement Benefits Plan [Member] | Defined Benefit Plan, Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 2 [Member] | Spire Missouri [Member] |  |  |
Defined Benefit Plan Assets | 0.0 | 0.0 |
Other Postretirement Benefits Plan [Member] | Defined Benefit Plan, Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |
Defined Benefit Plan Assets | 0.0 | 0.0 |
Other Postretirement Benefits Plan [Member] | Defined Benefit Plan, Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 3 [Member] | Spire Missouri [Member] |  |  |
Defined Benefit Plan Assets | 0.0 | 0.0 |
Other Postretirement Benefits Plan [Member] | U S Stock Bond Mutual Fund [Member] |  |  |
Defined Benefit Plan Assets | 246.5 | 305.7 |
Other Postretirement Benefits Plan [Member] | U S Stock Bond Mutual Fund [Member] | Spire Missouri [Member] |  |  |
Defined Benefit Plan Assets | 174.0 | 219.3 |
Other Postretirement Benefits Plan [Member] | U S Stock Bond Mutual Fund [Member] | Spire Alabama Inc [Member] |  |  |
Defined Benefit Plan Assets | 69.4 | 82.5 |
Other Postretirement Benefits Plan [Member] | U S Stock Bond Mutual Fund [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |
Defined Benefit Plan Assets | 177.1 | 223.2 |
Other Postretirement Benefits Plan [Member] | U S Stock Bond Mutual Fund [Member] | Fair Value, Inputs, Level 1 [Member] | Spire Missouri [Member] |  |  |
Defined Benefit Plan Assets | 174.0 | 219.3 |
Other Postretirement Benefits Plan [Member] | U S Stock Bond Mutual Fund [Member] | Fair Value, Inputs, Level 1 [Member] | Spire Alabama Inc [Member] |  |  |
Defined Benefit Plan Assets | 0.0 | 0.0 |
Other Postretirement Benefits Plan [Member] | U S Stock Bond Mutual Fund [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |
Defined Benefit Plan Assets | 69.4 | 82.5 |
Other Postretirement Benefits Plan [Member] | U S Stock Bond Mutual Fund [Member] | Fair Value, Inputs, Level 2 [Member] | Spire Missouri [Member] |  |  |
Defined Benefit Plan Assets | 0.0 | 0.0 |
Other Postretirement Benefits Plan [Member] | U S Stock Bond Mutual Fund [Member] | Fair Value, Inputs, Level 2 [Member] | Spire Alabama Inc [Member] |  |  |
Defined Benefit Plan Assets | 69.4 | 82.5 |
Other Postretirement Benefits Plan [Member] | U S Stock Bond Mutual Fund [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |
Defined Benefit Plan Assets | 0.0 | 0.0 |
Other Postretirement Benefits Plan [Member] | U S Stock Bond Mutual Fund [Member] | Fair Value, Inputs, Level 3 [Member] | Spire Missouri [Member] |  |  |
Defined Benefit Plan Assets | 0.0 | 0.0 |
Other Postretirement Benefits Plan [Member] | U S Stock Bond Mutual Fund [Member] | Fair Value, Inputs, Level 3 [Member] | Spire Alabama Inc [Member] |  |  |
Defined Benefit Plan Assets | 0.0 | 0.0 |
Other Postretirement Benefits Plan [Member] | Debt Security, Corporate, Non-US [Member] |  |  |
Defined Benefit Plan Assets | 14.7 | 18.1 |
Other Postretirement Benefits Plan [Member] | Debt Security, Corporate, Non-US [Member] | Spire Alabama Inc [Member] |  |  |
Defined Benefit Plan Assets | 13.9 | 16.9 |
Other Postretirement Benefits Plan [Member] | Debt Security, Corporate, Non-US [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |
Defined Benefit Plan Assets | 0.8 | 1.2 |
Other Postretirement Benefits Plan [Member] | Debt Security, Corporate, Non-US [Member] | Fair Value, Inputs, Level 1 [Member] | Spire Alabama Inc [Member] |  |  |
Defined Benefit Plan Assets | 0.0 | 0.0 |
Other Postretirement Benefits Plan [Member] | Debt Security, Corporate, Non-US [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |
Defined Benefit Plan Assets | 13.9 | 16.9 |
Other Postretirement Benefits Plan [Member] | Debt Security, Corporate, Non-US [Member] | Fair Value, Inputs, Level 2 [Member] | Spire Alabama Inc [Member] |  |  |
Defined Benefit Plan Assets | 13.9 | 16.9 |
Other Postretirement Benefits Plan [Member] | Debt Security, Corporate, Non-US [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |
Defined Benefit Plan Assets | 0.0 | 0.0 |
Other Postretirement Benefits Plan [Member] | Debt Security, Corporate, Non-US [Member] | Fair Value, Inputs, Level 3 [Member] | Spire Alabama Inc [Member] |  |  |
Defined Benefit Plan Assets | $ 0.0 | $ 0.0 |

X
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