3.24.3 html 1140 560 1 true 184 0 false 9 false false R1.htm 000 - Document - Document And Entity Information Sheet http://www.spireenergy.com/20220930/role/statement-document-and-entity-information Document And Entity Information Cover 1 false false R2.htm 001 - Statement - Consolidated Statements of Income Sheet http://www.spireenergy.com/20220930/role/statement-consolidated-statements-of-income Consolidated Statements of Income Statements 2 false false R3.htm 002 - Statement - Consolidated Statements of Comprehensive Income Sheet http://www.spireenergy.com/20220930/role/statement-consolidated-statements-of-comprehensive-income Consolidated Statements of Comprehensive Income Statements 3 false false R4.htm 003 - Statement - Consolidated Balance Sheets Sheet http://www.spireenergy.com/20220930/role/statement-consolidated-balance-sheets Consolidated Balance Sheets Statements 4 false false R5.htm 004 - Statement - Consolidated Balance Sheets (Parentheticals) Sheet http://www.spireenergy.com/20220930/role/statement-consolidated-balance-sheets-parentheticals Consolidated Balance Sheets (Parentheticals) Statements 5 false false R6.htm 005 - Statement - Consolidated Statements of Shareholders' Equity Sheet http://www.spireenergy.com/20220930/role/statement-consolidated-statements-of-shareholders-equity Consolidated Statements of Shareholders' Equity Statements 6 false false R7.htm 006 - Statement - Consolidated Statements of Shareholders' Equity (Parentheticals) Sheet http://www.spireenergy.com/20220930/role/statement-consolidated-statements-of-shareholders-equity-parentheticals Consolidated Statements of Shareholders' Equity (Parentheticals) Statements 7 false false R8.htm 007 - Statement - Consolidated Statements of Cash Flows Sheet http://www.spireenergy.com/20220930/role/statement-consolidated-statements-of-cash-flows Consolidated Statements of Cash Flows Statements 8 false false R9.htm 008 - Disclosure - Note 1 - Summary of Significant Accounting Policies Sheet http://www.spireenergy.com/20220930/role/statement-note-1-summary-of-significant-accounting-policies Note 1 - Summary of Significant Accounting Policies Notes 9 false false R10.htm 009 - Disclosure - Note 2 - Revenue Sheet http://www.spireenergy.com/20220930/role/statement-note-2-revenue Note 2 - Revenue Notes 10 false false R11.htm 010 - Disclosure - Note 3 - Stock-based Compensation Sheet http://www.spireenergy.com/20220930/role/statement-note-3-stockbased-compensation Note 3 - Stock-based Compensation Notes 11 false false R12.htm 011 - Disclosure - Note 4 - Earnings Per Common Share Sheet http://www.spireenergy.com/20220930/role/statement-note-4-earnings-per-common-share Note 4 - Earnings Per Common Share Notes 12 false false R13.htm 012 - Disclosure - Note 5 - Shareholders' Equity Sheet http://www.spireenergy.com/20220930/role/statement-note-5-shareholders-equity Note 5 - Shareholders' Equity Notes 13 false false R14.htm 013 - Disclosure - Note 6 - Long-term Debt Sheet http://www.spireenergy.com/20220930/role/statement-note-6-longterm-debt Note 6 - Long-term Debt Notes 14 false false R15.htm 014 - Disclosure - Note 7 - Notes Payable and Credit Agreements Notes http://www.spireenergy.com/20220930/role/statement-note-7-notes-payable-and-credit-agreements Note 7 - Notes Payable and Credit Agreements Notes 15 false false R16.htm 015 - Disclosure - Note 8 - Fair Value of Financial Instruments Sheet http://www.spireenergy.com/20220930/role/statement-note-8-fair-value-of-financial-instruments Note 8 - Fair Value of Financial Instruments Notes 16 false false R17.htm 016 - Disclosure - Note 9 - Fair Value Measurements Sheet http://www.spireenergy.com/20220930/role/statement-note-9-fair-value-measurements Note 9 - Fair Value Measurements Notes 17 false false R18.htm 017 - Disclosure - Note 10 - Derivative Instruments and Hedging Activities Sheet http://www.spireenergy.com/20220930/role/statement-note-10-derivative-instruments-and-hedging-activities Note 10 - Derivative Instruments and Hedging Activities Notes 18 false false R19.htm 018 - Disclosure - Note 11 - Concentrations of Credit Risk Sheet http://www.spireenergy.com/20220930/role/statement-note-11-concentrations-of-credit-risk Note 11 - Concentrations of Credit Risk Notes 19 false false R20.htm 019 - Disclosure - Note 12 - Income Taxes Sheet http://www.spireenergy.com/20220930/role/statement-note-12-income-taxes Note 12 - Income Taxes Notes 20 false false R21.htm 020 - Disclosure - Note 13 - Pension Plans and Other Postretirement Benefits Sheet http://www.spireenergy.com/20220930/role/statement-note-13-pension-plans-and-other-postretirement-benefits Note 13 - Pension Plans and Other Postretirement Benefits Notes 21 false false R22.htm 021 - Disclosure - Note 14 - Information by Operating Segment Sheet http://www.spireenergy.com/20220930/role/statement-note-14-information-by-operating-segment Note 14 - Information by Operating Segment Notes 22 false false R23.htm 022 - Disclosure - Note 15 - Regulatory Matters Sheet http://www.spireenergy.com/20220930/role/statement-note-15-regulatory-matters Note 15 - Regulatory Matters Notes 23 false false R24.htm 023 - Disclosure - Note 16 - Commitments and Contingencies Sheet http://www.spireenergy.com/20220930/role/statement-note-16-commitments-and-contingencies Note 16 - Commitments and Contingencies Notes 24 false false R25.htm 024 - Disclosure - Note 17 - Leases Sheet http://www.spireenergy.com/20220930/role/statement-note-17-leases Note 17 - Leases Notes 25 false false R26.htm 025 - Disclosure - Significant Accounting Policies (Policies) Sheet http://www.spireenergy.com/20220930/role/statement-significant-accounting-policies-policies Significant Accounting Policies (Policies) Policies http://www.spireenergy.com/20220930/role/statement-note-1-summary-of-significant-accounting-policies 26 false false R27.htm 026 - Disclosure - Note 1 - Summary of Significant Accounting Policies (Tables) Sheet http://www.spireenergy.com/20220930/role/statement-note-1-summary-of-significant-accounting-policies-tables Note 1 - Summary of Significant Accounting Policies (Tables) Tables http://www.spireenergy.com/20220930/role/statement-note-1-summary-of-significant-accounting-policies 27 false false R28.htm 027 - Disclosure - Note 2 - Revenue (Tables) Sheet http://www.spireenergy.com/20220930/role/statement-note-2-revenue-tables Note 2 - Revenue (Tables) Tables http://www.spireenergy.com/20220930/role/statement-note-2-revenue 28 false false R29.htm 028 - Disclosure - Note 3 - Stock-based Compensation (Tables) Sheet http://www.spireenergy.com/20220930/role/statement-note-3-stockbased-compensation-tables Note 3 - Stock-based Compensation (Tables) Tables http://www.spireenergy.com/20220930/role/statement-note-3-stockbased-compensation 29 false false R30.htm 029 - Disclosure - Note 4 - Earnings Per Common Share (Tables) Sheet http://www.spireenergy.com/20220930/role/statement-note-4-earnings-per-common-share-tables Note 4 - Earnings Per Common Share (Tables) Tables http://www.spireenergy.com/20220930/role/statement-note-4-earnings-per-common-share 30 false false R31.htm 030 - Disclosure - Note 5 - Shareholders' Equity (Tables) Sheet http://www.spireenergy.com/20220930/role/statement-note-5-shareholders-equity-tables Note 5 - Shareholders' Equity (Tables) Tables http://www.spireenergy.com/20220930/role/statement-note-5-shareholders-equity 31 false false R32.htm 031 - Disclosure - Note 6 - Long-term Debt (Tables) Sheet http://www.spireenergy.com/20220930/role/statement-note-6-longterm-debt-tables Note 6 - Long-term Debt (Tables) Tables http://www.spireenergy.com/20220930/role/statement-note-6-longterm-debt 32 false false R33.htm 032 - Disclosure - Note 7 - Notes Payable and Credit Agreements (Tables) Notes http://www.spireenergy.com/20220930/role/statement-note-7-notes-payable-and-credit-agreements-tables Note 7 - Notes Payable and Credit Agreements (Tables) Tables http://www.spireenergy.com/20220930/role/statement-note-7-notes-payable-and-credit-agreements 33 false false R34.htm 033 - Disclosure - Note 8 - Fair Value of Financial Instruments (Tables) Sheet http://www.spireenergy.com/20220930/role/statement-note-8-fair-value-of-financial-instruments-tables Note 8 - Fair Value of Financial Instruments (Tables) Tables http://www.spireenergy.com/20220930/role/statement-note-8-fair-value-of-financial-instruments 34 false false R35.htm 034 - Disclosure - Note 9 - Fair Value Measurements (Tables) Sheet http://www.spireenergy.com/20220930/role/statement-note-9-fair-value-measurements-tables Note 9 - Fair Value Measurements (Tables) Tables http://www.spireenergy.com/20220930/role/statement-note-9-fair-value-measurements 35 false false R36.htm 035 - Disclosure - Note 10 - Derivative Instruments and Hedging Activities (Tables) Sheet http://www.spireenergy.com/20220930/role/statement-note-10-derivative-instruments-and-hedging-activities-tables Note 10 - Derivative Instruments and Hedging Activities (Tables) Tables http://www.spireenergy.com/20220930/role/statement-note-10-derivative-instruments-and-hedging-activities 36 false false R37.htm 036 - Disclosure - Note 12 - Income Taxes (Tables) Sheet http://www.spireenergy.com/20220930/role/statement-note-12-income-taxes-tables Note 12 - Income Taxes (Tables) Tables http://www.spireenergy.com/20220930/role/statement-note-12-income-taxes 37 false false R38.htm 037 - Disclosure - Note 13 - Pension Plans and Other Postretirement Benefits (Tables) Sheet http://www.spireenergy.com/20220930/role/statement-note-13-pension-plans-and-other-postretirement-benefits-tables Note 13 - Pension Plans and Other Postretirement Benefits (Tables) Tables http://www.spireenergy.com/20220930/role/statement-note-13-pension-plans-and-other-postretirement-benefits 38 false false R39.htm 038 - Disclosure - Note 14 - Information by Operating Segment (Tables) Sheet http://www.spireenergy.com/20220930/role/statement-note-14-information-by-operating-segment-tables Note 14 - Information by Operating Segment (Tables) Tables http://www.spireenergy.com/20220930/role/statement-note-14-information-by-operating-segment 39 false false R40.htm 039 - Disclosure - Note 15 - Regulatory Matters (Tables) Sheet http://www.spireenergy.com/20220930/role/statement-note-15-regulatory-matters-tables Note 15 - Regulatory Matters (Tables) Tables http://www.spireenergy.com/20220930/role/statement-note-15-regulatory-matters 40 false false R41.htm 040 - Disclosure - Note 17 - Leases (Tables) Sheet http://www.spireenergy.com/20220930/role/statement-note-17-leases-tables Note 17 - Leases (Tables) Tables http://www.spireenergy.com/20220930/role/statement-note-17-leases 41 false false R42.htm 041 - Disclosure - Note 1 - Summary of Significant Accounting Policies (Details Textual) Sheet http://www.spireenergy.com/20220930/role/statement-note-1-summary-of-significant-accounting-policies-details-textual Note 1 - Summary of Significant Accounting Policies (Details Textual) Details http://www.spireenergy.com/20220930/role/statement-note-1-summary-of-significant-accounting-policies-tables 42 false false R43.htm 042 - Disclosure - Note 1 - Summary of Significant Accounting Policies - Accrued Capital Expenditures Excluded From Capital Expenditures in the Statements of Cash Flows (Details) Sheet http://www.spireenergy.com/20220930/role/statement-note-1-summary-of-significant-accounting-policies-accrued-capital-expenditures-excluded-from-capital-expenditures-in-the-statements-of-cash-flows-details Note 1 - Summary of Significant Accounting Policies - Accrued Capital Expenditures Excluded From Capital Expenditures in the Statements of Cash Flows (Details) Details 43 false false R44.htm 043 - Disclosure - Note 1 - Summary of Significant Accounting Policies - Schedule of Asset Retirement Obligations (Details) Sheet http://www.spireenergy.com/20220930/role/statement-note-1-summary-of-significant-accounting-policies-schedule-of-asset-retirement-obligations-details Note 1 - Summary of Significant Accounting Policies - Schedule of Asset Retirement Obligations (Details) Details 44 false false R45.htm 044 - Disclosure - Note 1 - Summary of Significant Accounting Policies - Transactions With Affiliates (Details) Sheet http://www.spireenergy.com/20220930/role/statement-note-1-summary-of-significant-accounting-policies-transactions-with-affiliates-details Note 1 - Summary of Significant Accounting Policies - Transactions With Affiliates (Details) Details 45 false false R46.htm 045 - Disclosure - Note 1 - Summary of Significant Accounting Policies - Activity in the Allowance for Credit Losses (Details) Sheet http://www.spireenergy.com/20220930/role/statement-note-1-summary-of-significant-accounting-policies-activity-in-the-allowance-for-credit-losses-details Note 1 - Summary of Significant Accounting Policies - Activity in the Allowance for Credit Losses (Details) Details 46 false false R47.htm 046 - Disclosure - Note 2 - Revenue - Disaggregated of Revenue (Details) Sheet http://www.spireenergy.com/20220930/role/statement-note-2-revenue-disaggregated-of-revenue-details Note 2 - Revenue - Disaggregated of Revenue (Details) Details 47 false false R48.htm 047 - Disclosure - Note 2 - Revenue - Taxes Associated With Natural Gas Utility Services (Details) Sheet http://www.spireenergy.com/20220930/role/statement-note-2-revenue-taxes-associated-with-natural-gas-utility-services-details Note 2 - Revenue - Taxes Associated With Natural Gas Utility Services (Details) Details 48 false false R49.htm 048 - Disclosure - Note 3 - Stock-based Compensation (Details Textual) Sheet http://www.spireenergy.com/20220930/role/statement-note-3-stockbased-compensation-details-textual Note 3 - Stock-based Compensation (Details Textual) Details http://www.spireenergy.com/20220930/role/statement-note-3-stockbased-compensation-tables 49 false false R50.htm 049 - Disclosure - Note 3 - Stock-based Compensation - Activity of Restricted Stock Units (Details) Sheet http://www.spireenergy.com/20220930/role/statement-note-3-stockbased-compensation-activity-of-restricted-stock-units-details Note 3 - Stock-based Compensation - Activity of Restricted Stock Units (Details) Details 50 false false R51.htm 050 - Disclosure - Note 3 - Stock-based Compensation - Schedule of Significant Assumptions (Details) Sheet http://www.spireenergy.com/20220930/role/statement-note-3-stockbased-compensation-schedule-of-significant-assumptions-details Note 3 - Stock-based Compensation - Schedule of Significant Assumptions (Details) Details 51 false false R52.htm 051 - Disclosure - Note 3 - Stock-based Compensation - Compensation Cost of Share-based Compensation Arrangements (Details) Sheet http://www.spireenergy.com/20220930/role/statement-note-3-stockbased-compensation-compensation-cost-of-sharebased-compensation-arrangements-details Note 3 - Stock-based Compensation - Compensation Cost of Share-based Compensation Arrangements (Details) Details 52 false false R53.htm 052 - Disclosure - Note 4 - Earnings Per Common Share - Earnings Per Common Share (Details) Sheet http://www.spireenergy.com/20220930/role/statement-note-4-earnings-per-common-share-earnings-per-common-share-details Note 4 - Earnings Per Common Share - Earnings Per Common Share (Details) Details 53 false false R54.htm 053 - Disclosure - Note 5 - Shareholders' Equity (Details Textual) Sheet http://www.spireenergy.com/20220930/role/statement-note-5-shareholders-equity-details-textual Note 5 - Shareholders' Equity (Details Textual) Details http://www.spireenergy.com/20220930/role/statement-note-5-shareholders-equity-tables 54 false false R55.htm 054 - Disclosure - Note 5 - Shareholders' Equity - Number of Shares to be Purchased Per Stock Purchase Contract (Details) Sheet http://www.spireenergy.com/20220930/role/statement-note-5-shareholders-equity-number-of-shares-to-be-purchased-per-stock-purchase-contract-details Note 5 - Shareholders' Equity - Number of Shares to be Purchased Per Stock Purchase Contract (Details) Details 55 false false R56.htm 055 - Disclosure - Note 5 - Shareholders' Equity - Components of Accumulated Other Comprehensive Income (Details) Sheet http://www.spireenergy.com/20220930/role/statement-note-5-shareholders-equity-components-of-accumulated-other-comprehensive-income-details Note 5 - Shareholders' Equity - Components of Accumulated Other Comprehensive Income (Details) Details 56 false false R57.htm 056 - Disclosure - Note 6 - Long-term Debt (Details Textual) Sheet http://www.spireenergy.com/20220930/role/statement-note-6-longterm-debt-details-textual Note 6 - Long-term Debt (Details Textual) Details http://www.spireenergy.com/20220930/role/statement-note-6-longterm-debt-tables 57 false false R58.htm 057 - Disclosure - Note 6 - Long-term Debt - Composition of Long-term Debt (Details) Sheet http://www.spireenergy.com/20220930/role/statement-note-6-longterm-debt-composition-of-longterm-debt-details Note 6 - Long-term Debt - Composition of Long-term Debt (Details) Details 58 false false R59.htm 058 - Disclosure - Note 6 - Long-term Debt - Composition of Long-term Debt (Details) (Parentheticals) Sheet http://www.spireenergy.com/20220930/role/statement-note-6-longterm-debt-composition-of-longterm-debt-details-parentheticals Note 6 - Long-term Debt - Composition of Long-term Debt (Details) (Parentheticals) Details 59 false false R60.htm 059 - Disclosure - Note 6 - Long-term Debt - Maturities of Long-term Debt (Details) Sheet http://www.spireenergy.com/20220930/role/statement-note-6-longterm-debt-maturities-of-longterm-debt-details Note 6 - Long-term Debt - Maturities of Long-term Debt (Details) Details 60 false false R61.htm 060 - Disclosure - Note 7 - Notes Payable and Credit Agreements (Details Textual) Notes http://www.spireenergy.com/20220930/role/statement-note-7-notes-payable-and-credit-agreements-details-textual Note 7 - Notes Payable and Credit Agreements (Details Textual) Details http://www.spireenergy.com/20220930/role/statement-note-7-notes-payable-and-credit-agreements-tables 61 false false R62.htm 061 - Disclosure - Note 7 - Notes Payable and Credit Agreements - Short-term Borrowings (Details) Notes http://www.spireenergy.com/20220930/role/statement-note-7-notes-payable-and-credit-agreements-shortterm-borrowings-details Note 7 - Notes Payable and Credit Agreements - Short-term Borrowings (Details) Details 62 false false R63.htm 062 - Disclosure - Note 8 - Fair Value of Financial Instruments - Estimated Fair Value of Financial Instruments Not Measured at Fair Value on Recurring Basis (Details) Sheet http://www.spireenergy.com/20220930/role/statement-note-8-fair-value-of-financial-instruments-estimated-fair-value-of-financial-instruments-not-measured-at-fair-value-on-recurring-basis-details Note 8 - Fair Value of Financial Instruments - Estimated Fair Value of Financial Instruments Not Measured at Fair Value on Recurring Basis (Details) Details 63 false false R64.htm 063 - Disclosure - Note 9 - Fair Value Measurements (Details Textual) Sheet http://www.spireenergy.com/20220930/role/statement-note-9-fair-value-measurements-details-textual Note 9 - Fair Value Measurements (Details Textual) Details http://www.spireenergy.com/20220930/role/statement-note-9-fair-value-measurements-tables 64 false false R65.htm 064 - Disclosure - Note 9 - Fair Value Measurements - Schedule of Derivative Assets and Liabilities, Including Receivables and Payables (Details) Sheet http://www.spireenergy.com/20220930/role/statement-note-9-fair-value-measurements-schedule-of-derivative-assets-and-liabilities-including-receivables-and-payables-details Note 9 - Fair Value Measurements - Schedule of Derivative Assets and Liabilities, Including Receivables and Payables (Details) Details 65 false false R66.htm 065 - Disclosure - Note 10 - Derivative Instruments and Hedging Activities (Details Textual) Sheet http://www.spireenergy.com/20220930/role/statement-note-10-derivative-instruments-and-hedging-activities-details-textual Note 10 - Derivative Instruments and Hedging Activities (Details Textual) Details http://www.spireenergy.com/20220930/role/statement-note-10-derivative-instruments-and-hedging-activities-tables 66 false false R67.htm 066 - Disclosure - Note 10 - Derivative Instruments and Hedging Activities - Summary of NYMEX and ICE Natural Gas Futures and Swap Positions (Details) Sheet http://www.spireenergy.com/20220930/role/statement-note-10-derivative-instruments-and-hedging-activities-summary-of-nymex-and-ice-natural-gas-futures-and-swap-positions-details Note 10 - Derivative Instruments and Hedging Activities - Summary of NYMEX and ICE Natural Gas Futures and Swap Positions (Details) Details 67 false false R68.htm 067 - Disclosure - Note 10 - Derivative Instruments and Hedging Activities - Effect of Derivative Instruments on the Consolidated Statements of Income and Comprehensive Income (Details) Sheet http://www.spireenergy.com/20220930/role/statement-note-10-derivative-instruments-and-hedging-activities-effect-of-derivative-instruments-on-the-consolidated-statements-of-income-and-comprehensive-income-details Note 10 - Derivative Instruments and Hedging Activities - Effect of Derivative Instruments on the Consolidated Statements of Income and Comprehensive Income (Details) Details 68 false false R69.htm 068 - Disclosure - Note 10 - Derivative Instruments and Hedging Activities - Fair Value of Derivative Instruments in the Consolidated Balance Sheets (Details) Sheet http://www.spireenergy.com/20220930/role/statement-note-10-derivative-instruments-and-hedging-activities-fair-value-of-derivative-instruments-in-the-consolidated-balance-sheets-details Note 10 - Derivative Instruments and Hedging Activities - Fair Value of Derivative Instruments in the Consolidated Balance Sheets (Details) Details 69 false false R70.htm 069 - Disclosure - Note 10 - Derivative Instruments and Hedging Activities - Reconciliation of Amounts in the Consolidated Balance Sheet (Details) Sheet http://www.spireenergy.com/20220930/role/statement-note-10-derivative-instruments-and-hedging-activities-reconciliation-of-amounts-in-the-consolidated-balance-sheet-details Note 10 - Derivative Instruments and Hedging Activities - Reconciliation of Amounts in the Consolidated Balance Sheet (Details) Details 70 false false R71.htm 070 - Disclosure - Note 11 - Concentrations of Credit Risk (Details Textual) Sheet http://www.spireenergy.com/20220930/role/statement-note-11-concentrations-of-credit-risk-details-textual Note 11 - Concentrations of Credit Risk (Details Textual) Details http://www.spireenergy.com/20220930/role/statement-note-11-concentrations-of-credit-risk 71 false false R72.htm 071 - Disclosure - Note 12 - Income Taxes (Details Textual) Sheet http://www.spireenergy.com/20220930/role/statement-note-12-income-taxes-details-textual Note 12 - Income Taxes (Details Textual) Details http://www.spireenergy.com/20220930/role/statement-note-12-income-taxes-tables 72 false false R73.htm 072 - Disclosure - Note 12 - Income Taxes - Provision (Benefit) for Income Taxes (Details) Sheet http://www.spireenergy.com/20220930/role/statement-note-12-income-taxes-provision-benefit-for-income-taxes-details Note 12 - Income Taxes - Provision (Benefit) for Income Taxes (Details) Details 73 false false R74.htm 073 - Disclosure - Note 12 - Income Taxes - Effective Income Tax Rate (Details) Sheet http://www.spireenergy.com/20220930/role/statement-note-12-income-taxes-effective-income-tax-rate-details Note 12 - Income Taxes - Effective Income Tax Rate (Details) Details 74 false false R75.htm 074 - Disclosure - Note 12 - Income Taxes - Significant Items Comprising the Net Deferred Tax Liability or Asset (Details) Sheet http://www.spireenergy.com/20220930/role/statement-note-12-income-taxes-significant-items-comprising-the-net-deferred-tax-liability-or-asset-details Note 12 - Income Taxes - Significant Items Comprising the Net Deferred Tax Liability or Asset (Details) Details 75 false false R76.htm 075 - Disclosure - Note 12 - Income Taxes - Summary of Federal and State Loss and Contribution and Tax Credit Carryforwards (Details) Sheet http://www.spireenergy.com/20220930/role/statement-note-12-income-taxes-summary-of-federal-and-state-loss-and-contribution-and-tax-credit-carryforwards-details Note 12 - Income Taxes - Summary of Federal and State Loss and Contribution and Tax Credit Carryforwards (Details) Details 76 false false R77.htm 076 - Disclosure - Note 12 - Income Taxes - Reconciliation of Unrecognized Tax Benefits (Details) Sheet http://www.spireenergy.com/20220930/role/statement-note-12-income-taxes-reconciliation-of-unrecognized-tax-benefits-details Note 12 - Income Taxes - Reconciliation of Unrecognized Tax Benefits (Details) Details 77 false false R78.htm 077 - Disclosure - Note 13 - Pension Plans and Other Postretirement Benefits (Details Textual) Sheet http://www.spireenergy.com/20220930/role/statement-note-13-pension-plans-and-other-postretirement-benefits-details-textual Note 13 - Pension Plans and Other Postretirement Benefits (Details Textual) Details http://www.spireenergy.com/20220930/role/statement-note-13-pension-plans-and-other-postretirement-benefits-tables 78 false false R79.htm 078 - Disclosure - Note 13 - Pension Plans and Other Postretirement Benefits - Net Pension Costs (Details) Sheet http://www.spireenergy.com/20220930/role/statement-note-13-pension-plans-and-other-postretirement-benefits-net-pension-costs-details Note 13 - Pension Plans and Other Postretirement Benefits - Net Pension Costs (Details) Details 79 false false R80.htm 079 - Disclosure - Note 13 - Pension Plans and Other Postretirement Benefits - Other Changes in Plan Assets and Pension Benefit Obligations (Details) Sheet http://www.spireenergy.com/20220930/role/statement-note-13-pension-plans-and-other-postretirement-benefits-other-changes-in-plan-assets-and-pension-benefit-obligations-details Note 13 - Pension Plans and Other Postretirement Benefits - Other Changes in Plan Assets and Pension Benefit Obligations (Details) Details 80 false false R81.htm 080 - Disclosure - Note 13 - Pension Plans and Other Postretirement Benefits - Reconciliation of Pension Benefit Obligation (Details) Sheet http://www.spireenergy.com/20220930/role/statement-note-13-pension-plans-and-other-postretirement-benefits-reconciliation-of-pension-benefit-obligation-details Note 13 - Pension Plans and Other Postretirement Benefits - Reconciliation of Pension Benefit Obligation (Details) Details 81 false false R82.htm 081 - Disclosure - Note 13 - Pension Plans and Other Postretirement Benefits - Reconciliation of Fair Value of Plan Assets (Details) Sheet http://www.spireenergy.com/20220930/role/statement-note-13-pension-plans-and-other-postretirement-benefits-reconciliation-of-fair-value-of-plan-assets-details Note 13 - Pension Plans and Other Postretirement Benefits - Reconciliation of Fair Value of Plan Assets (Details) Details 82 false false R83.htm 082 - Disclosure - Note 13 - Pension Plans and Other Postretirement Benefits - Amounts Recognized in the Balance Sheets (Details) Sheet http://www.spireenergy.com/20220930/role/statement-note-13-pension-plans-and-other-postretirement-benefits-amounts-recognized-in-the-balance-sheets-details Note 13 - Pension Plans and Other Postretirement Benefits - Amounts Recognized in the Balance Sheets (Details) Details 83 false false R84.htm 083 - Disclosure - Note 13 - Pension Plans and Other Postretirement Benefits - Amounts Recognized in AOCI Not Yet Recognized As Components of Net Periodic Pension Costs (Details) Sheet http://www.spireenergy.com/20220930/role/statement-note-13-pension-plans-and-other-postretirement-benefits-amounts-recognized-in-aoci-not-yet-recognized-as-components-of-net-periodic-pension-costs-details Note 13 - Pension Plans and Other Postretirement Benefits - Amounts Recognized in AOCI Not Yet Recognized As Components of Net Periodic Pension Costs (Details) Details 84 false false R85.htm 084 - Disclosure - Note 13 - Pension Plans and Other Postretirement Benefits - Assumption Used (Details) Sheet http://www.spireenergy.com/20220930/role/statement-note-13-pension-plans-and-other-postretirement-benefits-assumption-used-details Note 13 - Pension Plans and Other Postretirement Benefits - Assumption Used (Details) Details 85 false false R86.htm 085 - Disclosure - Note 13 - Pension Plans and Other Postretirement Benefits - PBO, ABO, and Fair Value of Plan Assets for Plans in Excess of Plan Assets (Details) Sheet http://www.spireenergy.com/20220930/role/statement-note-13-pension-plans-and-other-postretirement-benefits-pbo-abo-and-fair-value-of-plan-assets-for-plans-in-excess-of-plan-assets-details Note 13 - Pension Plans and Other Postretirement Benefits - PBO, ABO, and Fair Value of Plan Assets for Plans in Excess of Plan Assets (Details) Details 86 false false R87.htm 086 - Disclosure - Note 13 - Pension Plans and Other Postretirement Benefits - Targeted and Actual Plan Assets by Category (Details) Sheet http://www.spireenergy.com/20220930/role/statement-note-13-pension-plans-and-other-postretirement-benefits-targeted-and-actual-plan-assets-by-category-details Note 13 - Pension Plans and Other Postretirement Benefits - Targeted and Actual Plan Assets by Category (Details) Details 87 false false R88.htm 087 - Disclosure - Note 13 - Pension Plans and Other Postretirement Benefits - Expected Pension Benefit Payments for Succeeding Fiscal Years (Details) Sheet http://www.spireenergy.com/20220930/role/statement-note-13-pension-plans-and-other-postretirement-benefits-expected-pension-benefit-payments-for-succeeding-fiscal-years-details Note 13 - Pension Plans and Other Postretirement Benefits - Expected Pension Benefit Payments for Succeeding Fiscal Years (Details) Details 88 false false R89.htm 088 - Disclosure - Note 13 - Pension Plans and Other Postretirement Benefits - Assumed Medical Cost Trend Rates (Details) Sheet http://www.spireenergy.com/20220930/role/statement-note-13-pension-plans-and-other-postretirement-benefits-assumed-medical-cost-trend-rates-details Note 13 - Pension Plans and Other Postretirement Benefits - Assumed Medical Cost Trend Rates (Details) Details 89 false false R90.htm 089 - Disclosure - Note 13 - Pension Plans and Other Postretirement Benefits - Fair Value Measurements of Pension Plan Assets (Details) Sheet http://www.spireenergy.com/20220930/role/statement-note-13-pension-plans-and-other-postretirement-benefits-fair-value-measurements-of-pension-plan-assets-details Note 13 - Pension Plans and Other Postretirement Benefits - Fair Value Measurements of Pension Plan Assets (Details) Details 90 false false R91.htm 090 - Disclosure - Note 14 - Information by Operating Segment (Details Textual) Sheet http://www.spireenergy.com/20220930/role/statement-note-14-information-by-operating-segment-details-textual Note 14 - Information by Operating Segment (Details Textual) Details http://www.spireenergy.com/20220930/role/statement-note-14-information-by-operating-segment-tables 91 false false R92.htm 091 - Disclosure - Note 14 - Information by Operating Segment - Segment Information by Segment (Details) Sheet http://www.spireenergy.com/20220930/role/statement-note-14-information-by-operating-segment-segment-information-by-segment-details Note 14 - Information by Operating Segment - Segment Information by Segment (Details) Details 92 false false R93.htm 092 - Disclosure - Note 14 - Information by Operating Segment - Total Assets by Segment (Details) Sheet http://www.spireenergy.com/20220930/role/statement-note-14-information-by-operating-segment-total-assets-by-segment-details Note 14 - Information by Operating Segment - Total Assets by Segment (Details) Details 93 false false R94.htm 093 - Disclosure - Note 14 - Information by Operating Segment - Net Economic Earnings to Net Income (Details) Sheet http://www.spireenergy.com/20220930/role/statement-note-14-information-by-operating-segment-net-economic-earnings-to-net-income-details Note 14 - Information by Operating Segment - Net Economic Earnings to Net Income (Details) Details 94 false false R95.htm 094 - Disclosure - Note 15 - Regulatory Matters (Details Textual) Sheet http://www.spireenergy.com/20220930/role/statement-note-15-regulatory-matters-details-textual Note 15 - Regulatory Matters (Details Textual) Details http://www.spireenergy.com/20220930/role/statement-note-15-regulatory-matters-tables 95 false false R96.htm 095 - Disclosure - Note 15 - Regulatory Matters - Regulatory Assets and Liabilities (Details) Sheet http://www.spireenergy.com/20220930/role/statement-note-15-regulatory-matters-regulatory-assets-and-liabilities-details Note 15 - Regulatory Matters - Regulatory Assets and Liabilities (Details) Details 96 false false R97.htm 096 - Disclosure - Note 15 - Regulatory Matters - Regulatory Assets Not Earning a Return (Details) Sheet http://www.spireenergy.com/20220930/role/statement-note-15-regulatory-matters-regulatory-assets-not-earning-a-return-details Note 15 - Regulatory Matters - Regulatory Assets Not Earning a Return (Details) Details 97 false false R98.htm 097 - Disclosure - Note 16 - Commitments and Contingencies (Details Textual) Sheet http://www.spireenergy.com/20220930/role/statement-note-16-commitments-and-contingencies-details-textual Note 16 - Commitments and Contingencies (Details Textual) Details http://www.spireenergy.com/20220930/role/statement-note-16-commitments-and-contingencies 98 false false R99.htm 098 - Disclosure - Note 17 - Leases - Operating Lease Cost, Cash Flow and Noncash Information (Details) Sheet http://www.spireenergy.com/20220930/role/statement-note-17-leases-operating-lease-cost-cash-flow-and-noncash-information-details Note 17 - Leases - Operating Lease Cost, Cash Flow and Noncash Information (Details) Details 99 false false R100.htm 099 - Disclosure - Note 17 - Leases - Year-end Balance Sheet and Weighted-average Information About Operating Lease (Details) Sheet http://www.spireenergy.com/20220930/role/statement-note-17-leases-yearend-balance-sheet-and-weightedaverage-information-about-operating-lease-details Note 17 - Leases - Year-end Balance Sheet and Weighted-average Information About Operating Lease (Details) Details 100 false false R101.htm 100 - Disclosure - Note 17 - Leases - Maturity of Operating Lease Liabilities (Details) Sheet http://www.spireenergy.com/20220930/role/statement-note-17-leases-maturity-of-operating-lease-liabilities-details Note 17 - Leases - Maturity of Operating Lease Liabilities (Details) Details 101 false false All Reports Book All Reports spre20230315_8k.htm ex_489314.htm sr-20220930.xsd sr-20220930_cal.xml sr-20220930_def.xml sr-20220930_lab.xml sr-20220930_pre.xml http://fasb.org/us-gaap/2023 http://xbrl.sec.gov/dei/2023 true true