Income Taxes - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Jun. 30, 2019	Jun. 30, 2019
Spire Missouri
Income Taxes [Line Items]
Excess accumulated deferred taxes returned	$ 2.1	$ 6.3

Regulatory Order, Excess Deferred Income Tax Returned To Customers

No definition available.

Name:	sr_RegulatoryOrderExcessDeferredIncomeTaxReturnedToCustomers
Namespace Prefix:	sr_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration