Note 1 - Summary of Significant Accounting Policies - Accrued Capital Expenditures Excluded from Capital Expenditures in the Statements of Cash Flows (Details) - USD ($) $ in Millions |
9 Months Ended | 12 Months Ended | |
---|---|---|---|
Jun. 30, 2024 |
Jun. 30, 2023 |
Sep. 30, 2023 |
|
Accrued capital expenditures | $ 81.6 | $ 62.2 | $ 104.3 |
Spire Missouri [Member] | |||
Accrued capital expenditures | 43.5 | 33.4 | 56.5 |
Spire Alabama Inc [Member] | |||
Accrued capital expenditures | $ 5.5 | $ 4.5 | $ 4.6 |