Income Taxes - Additional Information (Details) $ in Millions	3 Months Ended
Dec. 31, 2018 USD ($)
Spire Missouri
Income Taxes [Line Items]
Excess accumulated deferred taxes returned	$ 2.1

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