Revenue - Additional Information (Details) $ in Millions	3 Months Ended
Dec. 31, 2020 USD ($)
Spire Alabama
Disaggregation Of Revenue [Line Items]
Public utilities requested rate increase decrease amount	$ 3.4

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

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