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Non-current regulatory assets Schedule of Regulatory Assets and Liabilities [Table Text Block] Tabular disclosure of assets that are created when regulatory agencies permit public utilities to defer certain costs included in rate-setting to the balance sheet and regulatory liabilities. Detailed information about liabilities that result from rate actions of a regulator. Rate actions of a regulator can impose a liability on a regulated enterprise resulting in a regulatory liability. Schedule of Regulatory Assets and Liabilities Related Party Transaction Sales From Related Party Related party transaction sales from related party Sales of natural gas to Spire Marketing Nature of Operations [Text Block] Nature of Operations Financial Support to Nonconsolidated Legal Entity [Domain] Preferred Stock [Member] Spire [Member] Spire. Spire [Member] Schedule Of Capital Expenditure Excluded From Statement Of Cash Flow [Table Text Block] Tabular disclosure of capital expenditure excluded from statement of cash flow. Schedule of Capital Expenditure Excluded From Statement Of Cash Flow Reconciliation Of Consolidated Net Economic Earnings To Consolidated Net Income [Table Text Block] A tabular disclosure regarding the reconciliation of consolidated net economic earnings to consolidated net income. Reconciliation of Consolidated Net Economic Earnings to Consolidated Net Income Highest borrowings outstanding Highest borrowings outstanding Payments of Dividends Payments of Dividends, Total Dividends paid Dividends paid Business Combinations and Goodwill Disclosure of accounting policy for business combination and goodwill. 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Current regulatory assets Fair Value Hierarchy and NAV [Axis] Earnings Per Share [Abstract] Temporary equity Supplemental disclosure of cash paid for: Derivative Asset Derivative Assets Regulatory assets and liabilities us-gaap_IncreaseDecreaseInRegulatoryAssetsAndLiabilities Accounts Receivable Allowance For Credit Loss Acquisition Accounts receivable allowance for credit loss acquisition. Acquisition Disposal Group, Including Discontinued Operation, Revenue Operating Revenues Master Note Purchase Agreement [Member] Master Note Purchase Agreement [Member] Business Combination, Recognized Asset Acquired, Other Asset, Current Other current assets Document Type Series 2026 Senior Notes [Member] Series Two Thousand Twenty Six Senior Notes [Member] Series two thousand twenty six senior notes. 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PGA Assets Not Earning a Return [Member] Transactions With Affiliates [Policy Text Block] Disclosure of accounting policy for transactions with affiliates. Transaction with Affiliates Disposal Group Classification [Domain] Common stock, par value (in dollars per share) Infrastructure System Replacement Surcharge [Member] Infrastructure System Replacement Surcharge. Infrastructure System Replacement Surcharge [Member] Other Comprehensive Income, Net of Tax Other comprehensive income (loss), net of tax Other comprehensive income, net of tax Other Comprehensive Income (Loss), Net of Tax Gas Marketing [Member] Gas Marketing. Gas Marketing [Member] Adjusted SOFR [Member[ Related to adjusted SOFR. Adjusted SOFR [Member[ Share-Based Payment Arrangement, Tranche One [Member] Public Utilities, Policy [Policy Text Block] Regulated Operations Base Rate [Member] Base Rate [Member] Piedmont Tennessee Transaction [Member] Piedmont Tennessee Transaction. Disposal Group, Including Discontinued Operation Public Utilities Property Plant and Equipment Accumulated Depreciation Disposal group, including discontinued operation public utilities property plant and equipment accumulated depreciation Less - Accumulated depreciation and amortization Debt Disclosure [Abstract] Consolidation, Eliminations [Member] Eliminations [Member] Spire Marketing. Spire Marketing [Member] Fair Value Measurement and Measurement Inputs, Recurring and Nonrecurring [Text Block] Fair Value Measurements Estimate of Fair Value Measurement [Member] Proceeds from (Repayments of) Related Party Debt (Repayments to) Borrowings from Spire, net Income Tax Expense Related to Items of Other Comprehensive Income Income Tax Benefit Related to Items of Other Comprehensive Income Natural Gas Commodity Contracts [Member] Natural Gas Commodity Contracts. 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