Pension Plans and Other Postretirement Benefits - Additional Information (Details)	3 Months Ended
Dec. 31, 2018 USD ($)
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Anticipated Contributions to pension plans for qualified trust	$ 1,400,000
Anticipated contributions to pension plans for non-qualified plans	$ 0
Medical insurance available until age is reached after early retirement	65 years
Pension Plans \| Spire Missouri
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Anticipated Contributions to pension plans for qualified trust	$ 25,300,000
Postretirement Plans \| Spire Alabama
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Anticipated Contributions to pension plans for qualified trust	0
Employer contributions	0
Postretirement Plans \| Spire Missouri
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Anticipated Contributions to pension plans for qualified trust	0
Employer contributions	$ 0

Anticipated contributions to the pension plans for fiscal year 2012 for non-qualified plans.

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- Definition

Anticipated contributions to the pension plans for the next fiscal year for qualified trusts.

+ References

No definition available.

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- Definition

Reflects the upper limit on age eligibility, post early retirement, when medical insurance is available to retiree.

+ References

No definition available.

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- Definition

Amount of contribution received by defined benefit plan from employer which increases plan assets.

+ References

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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.

+ References

No definition available.

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