Proceeds from the sale of business, net of cash sold Proceeds from Divestiture of Businesses Revision of Prior Period [Axis] Revision of Prior Period [Axis] Total capitalization Total capitalization Capitalization, Long-Term Debt and Equity MountainWest sale Effective Income Tax Rate Reconciliation, Disposition of Business, Amount Expected return on plan assets Defined Benefit Plan, Expected Return (Loss) on Plan Assets AFUDC rate Public Utilities, Allowance for Funds Used During Construction, Rate Schedule of Expected Benefit Payments Schedule of Expected Benefit Payments [Table Text Block] Award Timing Predetermined Award Timing Predetermined [Flag] Defined Benefit Plan, Equity Securities And Fixed Income Investments Defined Benefit Plan, Equity Securities And Fixed Income Investments [Member] Defined Benefit Plan, Equity Securities And Fixed Income Investments Entity File Number Entity File Number Additional Paid-in Capital Additional Paid-in Capital [Member] Tax credits Effective 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Parent Insider Trading Policies and Procedures [Line Items] Common stock, authorized (in shares) Common Stock, Shares Authorized Nevada NEVADA Aggregate net proceeds from stock offering Sale Of Stock, Maximum Consideration To Be Received On Transaction Sale Of Stock, Maximum Consideration To Be Received On Transaction Common stock issuances (in shares) Stock Issued During Period, Shares, New Issues Medium-term notes, 6.76% series, due 2027 Debentures Medium Term Notes, 6.76% series, Due 2027 [Member] Debentures Medium Term Notes, 6.76% series, Due 2027 CAPITALIZATION AND LIABILITIES CAPITALIZATION AND LIABILITIES Liabilities and Equity [Abstract] Less: Carrying value of Centuri net assets prior to deconsolidation, including AOCI Discontinued Operation, Net Assets Prior To Deconsolidation, Carrying Value Discontinued Operation, Net Assets Prior To Deconsolidation, Carrying Value State: State and Local Jurisdiction [Member] Cover [Abstract] Money market fund investments Cash and Cash 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Compensation Amount Non-PEO NEO Average Total Compensation Amount Debt Instrument [Line Items] Debt Instrument [Line Items] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-Based Compensation Arrangements by Share-Based Payment Award [Table] Adjustment to Non-PEO NEO Compensation Footnote Adjustment to Non-PEO NEO Compensation Footnote [Text Block] Accounts payable Disposal Group, Including Discontinued Operation, Accounts Payable, Current Retirement Benefits [Abstract] Retirement Benefits [Abstract] Forgone Recovery due to Disqualification of Tax Benefits, Amount Forgone Recovery due to Disqualification of Tax Benefits, Amount Non-Rule 10b5-1 Arrangement Terminated Non-Rule 10b5-1 Arrangement Terminated [Flag] Income from continuing operations before income taxes Income (loss) before income taxes Income from continuing operations before income taxes Income before income taxes Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Noncurrent liabilities classified as discontinued operations Total noncurrent liabilities classified as discontinued operations Disposal Group, Including Discontinued Operation, Liabilities, Noncurrent Entity Shell Company Entity Shell Company Schedule of Long-term Debt Instruments [Table] Schedule of Long-Term Debt Instruments [Table] Proceeds from the sale of property Proceeds from Sale of Property, Plant, and Equipment Regulatory Assets [Line Items] Regulatory Asset [Line Items] Centuri deferred tax asset adjustment Discontinued Operation, Deferred Tax Asset Adjustment Discontinued Operation, Deferred Tax Asset Adjustment Statement of Stockholders' Equity [Abstract] Statement of Stockholders' Equity [Abstract] Operating Segments Operating Segments [Member] Schedule of Income Taxes Paid Schedule of Cash Flow, Supplemental Disclosures [Table Text Block] Employee benefits Deferred Tax Liabilities, Employee Benefits Deferred Tax Liabilities, Employee 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before Tax, Portion Attributable to Parent Weighted-average rate of compensation increase Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase Award Timing Method Award Timing Method [Text Block] Continuing operations (in USD per share) Income (Loss) from Continuing Operations, Per Basic Share Award Type [Axis] Award Type [Axis] Utility Plant [Domain] Utility Plant [Domain] Alternative revenue program revenues Alternative Revenue Program Revenues (Deferrals) Alternative revenue program revenues (deferrals). Investment, Name [Domain] Investment, Name [Domain] Trading Symbol Trading Symbol Changes in valuation allowance Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Percent Entity Address, City or Town Entity Address, City or Town Short-Term Debt, Type [Domain] Short-Term Debt, Type [Domain] Income Tax [Line Items] Income Tax [Line Items] Income Tax [Line Items] Total deferred tax assets Deferred Tax Assets, Net of Valuation Allowance Non-PEO NEO Average Compensation Actually Paid Amount Non-PEO NEO Average Compensation Actually Paid Amount Restricted Stock Units/Director Deferred Stock Units Restricted Stock Units (RSUs) [Member] Compensation Actually Paid vs. Other Measure Compensation Actually Paid vs. Other Measure [Text Block] Period of additional option to receive payment Deferred Compensation Plan, Additional Payment Option Period Additional Deferred Compensation Payment Options, period of payment, period Entity Emerging Growth Company Entity Emerging Growth Company 2028 Long-Term Debt, Maturity, Year Three Change in Fair Value as of Vesting Date of Prior Year Equity Awards Vested in Covered Year Change in Fair Value as of Vesting Date of Prior Year Equity Awards Vested in Covered Year [Member] Other property Property, Plant and Equipment, Other, Net 2026 Defined Benefit Plan, Expected Future Benefit Payment, Year One Common stock, outstanding (in shares) Beginning balance (in shares) Ending balance (in shares) Common Stock, Shares, Outstanding Additions charged to expense Accounts Receivable, Credit Loss Expense (Reversal) Weighted-average assumptions (benefit obligation): Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract] Receivables and Related Allowances Loans, Notes, Trade and Other Receivables Disclosure [Text Block] Schedule of Revenue Disaggregated by Service Type and Contract Type Disaggregation of Revenue [Table Text Block] Current: Current Income Tax Expense (Benefit), Continuing Operations [Abstract] Common stock issued (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Shares Issued in Period Dividends or Other Earnings Paid on Equity Awards not Otherwise Reflected in Total Compensation for Covered Year Dividends or Other Earnings Paid on Equity Awards not Otherwise Reflected in Total Compensation for Covered Year [Member] Small commercial Small Commercial [Member] Small commercial. Change in benefit obligations: Defined Benefit Plan, Change in Benefit Obligation [Roll Forward] Income tax expense from deconsolidation Discontinued Operation, Tax Effect Of Deconsolidation From Disposal Of Discontinued Operation Discontinued Operation, Tax Effect Of Deconsolidation From Disposal Of Discontinued Operation Prepaid and other current assets Prepaid and other current assets Prepaid Expense and Other Assets, Current Restricted Stock/ Units Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Effective interest rates Debt Instrument, Interest Rate, Effective Percentage Entity Address, Postal Zip Code Entity Address, Postal Zip Code Restatement Determination Date Restatement Determination Date Income tax expense Income tax expense Income tax expense (benefit) Total income tax expense Income Tax Expense (Benefit) Debt, basis spread on variable rate Debt Instrument, Basis Spread on Variable Rate Discontinued operations (in USD per share) Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Basic Share Pension Adjustments Service Cost Pension Adjustments Service Cost [Member] Emerging markets Emerging Markets [Member] Emerging markets. 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Dividends, Common Stock Noncurrent assets classified as discontinued operations Total noncurrent assets classified as discontinued operations Disposal Group, Including Discontinued Operation, Assets, Noncurrent 2029 Defined Benefit Plan, Expected Future Benefit Payment, Year Four Total current liabilities Total current liabilities Liabilities, Current Effects of currency translation in discontinued operations Effect of Exchange Rate on Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Discontinued Operation Deferred purchased gas costs Deferred purchased gas costs Deferred Gas Purchases, Current Depreciation and Amortization Regulatory Depreciation and Amortization, Policy [Policy Text Block] Individual: Individual [Axis] Notes, 3.8%, due 2046 Debentures Notes, 3.8%, Due 2046 [Member] Debentures Notes, 3.8%, Due 2046 Income Tax Jurisdiction [Domain] Income Tax Jurisdiction [Domain] Gross decreases – current period tax positions Unrecognized Tax Benefits, Decrease Resulting from Current Period Tax Positions Accounting Changes and Error Corrections [Abstract] Dividends paid Dividends paid Payments of Ordinary Dividends, Common Stock Document Annual Report Document Annual Report Entities [Table] Entities [Table] Dividend Reinvestment and Stock Purchase Plan Dividend Reinvestment And Stock Purchase Plan [Member] Dividend Reinvestment And Stock Purchase Plan [Member] Forgone Recovery, Explanation of Impracticability Forgone Recovery, Explanation of Impracticability [Text Block] Other comprehensive income (loss) related to discontinued operations Other Comprehensive Income (Loss) From Discontinued Operations, Net Of Tax Other Comprehensive Income (Loss) From Discontinued Operations, Net Of Tax Entity Interactive Data Current Entity Interactive Data Current Number of customers Number Of Customers Number Of Customers Mutual funds Mutual Fund [Member] Condensed Income Statement [Table] Condensed Income Statement [Table] Funded status at year end Defined Benefit Plan, Funded (Unfunded) Status of Plan Revenue Revenue from Contract with Customer [Policy Text Block] Pooled funds and mutual funds Pooled Funds And Mutual Funds [Member] Pooled funds and mutual funds. Share-based compensation Adjustments To Additional Paid in Capital, Dividends In Excess of Retained Earnings, Netting Adjustments To Additional Paid in Capital, Dividends In Excess of Retained Earnings, Netting Disaggregation of Revenue [Table] Disaggregation of Revenue [Table] Net operating losses Deferred Tax Assets, Operating Loss Carryforwards Contributions from parent Proceeds from Contributions from Parent Property, Plant and Equipment, Type [Axis] Long-Lived Tangible Asset [Axis] Accrued utility revenue Accrued utility revenue Increase (Decrease) In Accrued Utility Revenue Increase (Decrease) In Accrued Utility Revenue Ownership [Domain] Ownership [Domain] Commercial Paper Program Commercial Paper Program [Member] Commercial Paper Program [Member] Schedule of Effective Interest Rates on Variable-Rate IDRBs Schedule Of Effective Interest Rates On Long Term Debt [Table Text Block] Schedule Of Effective Interest Rates On Long-Term Debt [Table Text Block] Income Tax Disclosure 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Block] Error Correction [Table] Error Correction [Table] Prior Year End Fair Value of Equity Awards Granted in Any Prior Year that Fail to Meet Applicable Vesting Conditions During Covered Year Prior Year End Fair Value of Equity Awards Granted in Any Prior Year that Fail to Meet Applicable Vesting Conditions During Covered Year [Member] Regulatory Liabilities [Line Items] Regulatory Liability [Line Items] Outstanding Aggregate Erroneous Compensation Amount Outstanding Aggregate Erroneous Compensation Amount Tax-exempt Series A, due 2028 Variable Rate Bonds Tax Exempt Series A- Due 2028 [Member] Variable Rate Bonds Tax Exempt Series Due 2028 Schedule of Defined Benefit Plans Disclosures [Table] Defined Benefit Plan [Table] Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Vesting Tranche One Share-Based Payment Arrangement, Tranche One [Member] Regulatory assets (liability), no return on investment, recovery period Regulatory Assets (Liability), No Return On Investment, Recovery Period Regulatory Assets (Liability), No Return On Investment, Recovery Period Customer deposits Customer deposits Contract with Customer, Liability, Current Exercise Price Award Exercise Price Entity Filer Category Entity Filer Category Capitalization: Capitalization: Capitalization, Long-Term Debt and Equity [Abstract] Number of officers received special performance stock unit Number Of Officers Received Special Performance Stock Unit Number Of Officers Received Special Performance Stock Unit Benefits paid Defined Benefit Plan, Benefit Obligation, Benefits Paid U.S. federal statutory income tax Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent Discontinued operation, consideration Disposal Group, Including Discontinued Operation, Consideration Gain on deconsolidation of Centuri before income tax Gain on deconsolidation Discontinued Operation, Gain (Loss) from Disposal of 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Address, Address Line One Entity Address, Address Line One Global Global [Member] Global [Member] AOCI AOCI Attributable to Parent [Member] Omnibus Incentive Plan Omnibus Incentive Plan [Member] Omnibus Incentive Plan Redeemable noncontrolling interest Redeemable Noncontrolling Interest, Equity, Carrying Amount Ownership [Axis] Ownership [Axis] Amortization of prior service cost Defined Benefit Plan, Amortization of Prior Service Cost (Credit) Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] Fair Value as of Grant Date Award Grant Date Fair Value Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Table] Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Table] Disposal Group, Held-for-sale, Not Discontinued Operations Disposal Group, Held-for-Sale, Not Discontinued Operations [Member] U.S. equity securities Defined Benefit Plan, Equity Securities, US [Member] Operating loss carryforward Operating Loss Carryforwards Changes in unrecognized tax benefits Effective Income Tax Rate Reconciliation, Tax Contingency, Amount Schedule of Carrying Amounts and Estimated Fair Values of Long-Term Debt Schedule of Long-Term Debt Instruments [Table Text Block] Granted (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period 8% Series, due 2026 Debentures 8% Series Due 2026 [Member] Debentures 8% Series Due 2026 Receivables And Related Allowances [Line Items] Receivables And Related Allowances [Line Items] Receivables And Related Allowances [Line Items] Total operating expenses Total operating expenses Costs and Expenses Forfeited or expired (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Forfeited in Period Compensation cost related to nonvested shares not yet recognized Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount Changed Peer Group, Footnote Changed Peer Group, Footnote [Text Block] Counterparty Name [Domain] Counterparty Name [Domain] Adjustment To PEO Compensation, Footnote Adjustment To PEO Compensation, Footnote [Text Block] Title Trading Arrangement, Individual Title Peer Group Total Shareholder Return Amount Peer Group Total Shareholder Return Amount 2028 Defined Benefit Plan, Expected Future Benefit Payment, Year Three Margin, interest - and property tax-tracking Margin, Interest - and Property Tax-Tracking [Member] Margin, Interest - and Property Tax-Tracking Other current liabilities Disposal Group, Including Discontinued Operation, Other Liabilities, Current Debt covenant, equity cushion relating to minimum net worth requirement Equity Cushion Relating To Minimum Net Worth Requirement Equity cushion relating to 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Deferred compensation plan, payment term, option two Deferred Compensation Plan, Payment Term, Option Two Deferred Compensation Plan, Payment Term, Option Two Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Recovery of Erroneously Awarded Compensation Disclosure [Line Items] Fair Value Estimate of Fair Value Measurement [Member] Other Other Miscellaneous Regulatory Asset [Member] Other Miscellaneous Regulatory Asset [Member] Retirement Plan Type [Domain] Retirement Plan Type [Domain] Schedule of Allowance for Uncollectibles Accounts Receivable, Allowance for Credit Loss [Table Text Block] MNPI Disclosure Timed for Compensation Value MNPI Disclosure Timed for Compensation Value [Flag] Regulatory adjustment, net of tax benefit of $(12,844), $(2,360) and $(319), respectively Regulatory adjustment, net of tax benefit of $(12,844), $(2,360) and $(319), respectively Other Comprehensive Income Defined Benefit Plans Regulatory Adjustment Net of Tax The portion of the pension, PBOP, and SERP liability that is recoverable in rates net-of-tax. 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Underlying Securities Award Underlying Securities Amount Equity Component [Domain] Equity Component [Domain] Document Period End Date Document Period End Date Cash and Cash Equivalents [Domain] Cash and Cash Equivalents [Domain] Changes in customer advances Changes in customer advances Changes In Customer Advances, Investing Activities Changes In Customer Advances, Investing Activities Subsequent Events Subsequent Events, Policy [Policy Text Block] Income Taxes Income Tax Disclosure [Text Block] Deferred compensation plan, payment term, option three Deferred Compensation Plan, Payment Term, Option Three Deferred Compensation Plan, Payment Term, Option Three Beginning Balance Ending Balance Accounts Receivable, Allowance for Credit Loss Awards Close in Time to MNPI Disclosures, Table Awards Close in Time to MNPI Disclosures [Table Text Block] Total equity Beginning balance Ending balance Total equity Equity, Including Portion Attributable to Noncontrolling Interest Regulatory assets, margin, interest and property tax-tracking, recovery period Regulatory Assets, Margin, Interest And Property Tax-Tracking, Recovery Period Regulatory Assets, Margin, Interest And Property Tax-Tracking, Recovery Period Document Type Document Type Name Outstanding Recovery, Individual Name Loss Contingencies [Table] Loss Contingencies [Table] Public Offering And Private Placement Public Offering And Private Placement [Member] Public Offering And Private Placement Schedule of Defined Benefit Plans Disclosures Schedule of Defined Benefit Plans Disclosures [Table Text Block] Impairment of assets and other charges Impairment Of Assets And Other Charges Impairment Of Assets And Other Charges Revenue from contracts with customers Revenues from external customers Revenue from Contract with Customer, Excluding Assessed Tax Gas pipe materials and operating supplies Gas Pipe Materials And Operating Supplies Gas Pipe Materials And Operating Supplies Income tax benefit related to final disposition, release of valuation allowance and other separation costs Discontinued Operation, Tax Effect Of Final Disposition, Release Of Valuation Allowance And Other Separation Costs From Disposal Of Discontinued Operation Discontinued Operation, Tax Effect Of Final Disposition, Release Of Valuation Allowance And Other Separation Costs From Disposal Of Discontinued Operation Less: accumulated depreciation Less: accumulated depreciation and amortization Public Utilities, Property, Plant and Equipment, Accumulated Depreciation Environmental compliance programs Environmental Compliance Programs [Member] Environmental compliance programs. Total current assets Total current assets Assets, Current Statistical Measurement [Axis] Statistical Measurement [Axis] Realized gain (loss) on disposal of equity method investment Equity Method Investment, Realized Gain (Loss) on Disposal Commitment fee, unfunded portion Line of Credit Facility, Unused Capacity, Commitment Fee Percentage Regulatory Asset [Domain] Regulatory Asset [Domain] Depreciation and amortization Disposal Group, Including Discontinued Operation, Depreciation and Amortization Aggregate Erroneous Compensation Amount Aggregate Erroneous Compensation Amount Disposal Group Name [Axis] Disposal Group Name [Axis] Withholding remittance – share-based compensation Withholding remittance – share-based compensation Payment, Tax Withholding, Share-Based Payment Arrangement Peer Group Issuers, Footnote Peer Group Issuers, Footnote [Text Block] Entity Information [Line Items] Entity Information [Line Items] Income (loss) from discontinued operations before income taxes Discontinued Operation, Income (Loss) from Discontinued Operation, before Income Tax Current liabilities: Current liabilities: Liabilities, Current [Abstract] Debt-related costs Deferred Tax Liabilities, Debt-Related Costs Deferred Tax Liabilities, Debt-Related Costs Net earnings per share - diluted (in USD per share) Net earnings per share - diluted (in USD per share) Earnings Per Share, Diluted Medium-term notes, 7.92% series, due 2027 Debentures Medium Term Notes, 7.92% series, Due 2027 [Member] Debentures Medium Term Notes, 7.92% series, Due 2027 Accounts receivable, net of allowances Accounts Receivable, after Allowance for Credit Loss, Current Change in long-term credit facility and commercial paper Change in long-term credit facility and commercial paper Proceeds From Repayments Of Lines Of Credit And Commercial Paper The net cash inflow or cash outflow from a contractual arrangement with the lender, including letter of credit, standby letter of credit and revolving credit arrangements, under which borrowings can be made up to a specific amount at any point in time with either short term or long term maturity that is collateralized (backed by pledge, mortgage or other lien in the entity's assets) and issuing (borrowing) and repaying commercial paper Schedule of Asset Return Assumption Defined Benefit Plan, Assumptions [Table Text Block] Utility infrastructure services expenses Disposal Group, Including Discontinued Operation, Utility Infrastructure Services Expenses Disposal Group, Including Discontinued Operation, Utility Infrastructure Services Expenses Sale of stock, number of shares (in shares) Sale of Stock, Number of Shares Issued in Transaction Transportation Transportation [Member] Transportation. State: Income Tax Paid, State and Local, after Refund Received Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items] Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items] Consolidation Items [Domain] Consolidation Items [Domain] Income (loss) from discontinued operations, net of income tax Less: Income (loss) from discontinued operations, net of income tax Net income (loss) from discontinued operations Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest Auditor Location Auditor Location Regulatory Assets And Liabilities [Line Items] Regulatory Assets And Liabilities [Line Items] Regulatory Assets And Liabilities [Line Items] Actuarial loss (gain) Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss) Federal Domestic Tax Jurisdiction [Member] Regulatory Liability [Domain] Regulatory Liability [Domain] Regulated operations plant: Regulated operations plant: Public Utilities, Property, Plant and Equipment, Net [Abstract] Deferred compensation, percentage of multiple interest rate Floating Interest Rate Index Floating Interest Rate Index Income taxes paid, net Income Taxes Paid, Net Other Effective Income Tax Rate Reconciliation, Nondeductible Expense, Other, Percent Current assets classified as discontinued operations Total current assets classified as discontinued operations Disposal Group, Including Discontinued Operation, Assets, Current Long-term debt, gross Long-Term Debt, Gross Self-insured retention amount associated with general liability claims Self Insured Retention Amount Associated With General Liability Claims Amount of risk retained by the entity per incident before the insurance arrangement begins to provide coverage. Entity Well-known Seasoned Issuer Entity Well-known Seasoned Issuer Deferred charges and other assets Disposal Group, Including Discontinued Operation, Deferred Charges And Other Assets, Noncurrent Disposal Group, Including Discontinued Operation, Deferred Charges And Other Assets, Noncurrent Equity AFUDC Equity AFUDC Increase (Decrease) in Allowance for Equity Funds Used During Construction Expiration Date Trading Arrangement Expiration Date Centuri Holdings, Inc. Centuri Holdings, Inc. [Member] Centuri Holdings, Inc. Changes in other liabilities and deferred credits Changes in other liabilities and deferred credits Increase (Decrease) in Other Operating Liabilities Large commercial Large Commercial [Member] Large commercial. Number of performance share units granted (in shares) Number Of Performance Share Units Granted Number Of Performance Share Units Granted. Compensation Actually Paid vs. Net Income Compensation Actually Paid vs. Net Income [Text Block] Accounts receivable, net of allowances Accounts receivable, net of allowances Increase (Decrease) in Accounts Receivable Interest period Debt Instrument, Interest Period Debt Instrument, Interest Period Entity Current Reporting Status Entity Current Reporting Status Receivables [Abstract] Receivables [Abstract] Awards Close in Time to MNPI Disclosures Awards Close in Time to MNPI Disclosures [Table] Accrued pension and other postretirement benefit costs Accrued Pension And Other Postretirement Benefit Costs [Member] Accrued Pension And Other Postretirement Benefit Costs [Member] U.S. federal statutory income tax Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate, Amount Gains on sale of property and equipment Gain on sale of property Gain (Loss) on Disposition of Property Plant Equipment Corporate and administrative Corporate And Administrative Income (Expense) Corporate And Administrative Income (Expense) Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] Executive Category: Executive Category [Axis] State and local income tax, net of deferred benefit Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent Other comprehensive income (loss), net of tax Other comprehensive income (loss), net of tax Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest [Abstract] Accumulated benefit obligation Defined Benefit Plan, Accumulated Benefit Obligation Issuance of long-term debt, net Issuance of long-term debt, net Proceeds from Issuance of Long-Term Debt Current Fiscal Year End Date Current Fiscal Year End Date Per capita cost of covered health care benefits medical rate trend assumption Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Next Fiscal Year Net interest deductions Disposal Group, Including Discontinued Operation, Interest 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With Individual, Matching Percentage Deferred Compensation Arrangement With Individual, Matching Percentage Amortization of prior service cost Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, before Tax Income Tax [Table] Income Tax [Table] Income Tax [Table] Employees' investment plan, percent of compensation deferred with match Employees' Investment Plan, Percent Of Compensation Deferred With Match Employees' Investment Plan, Percent Of Compensation Deferred With Match Unrecognized tax benefits at beginning of year Unrecognized tax benefits at end of year Unrecognized Tax Benefits Antidilutive securities (in shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Allowance for Funds Used During Construction ("AFUDC") Allowance for Funds Used During Construction, Policy [Policy Text Block] 2027 Long-Term Debt, Maturity, Year Two Other Other Plant in Service [Member] Net cash used in financing activities Cash Provided by (Used in) Financing Activity, Including Discontinued Operation Measure: Measure [Axis] Defined benefit pension plans: Defined benefit pension plans: Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax [Abstract] Regulated Operations Plant Regulated Operations Plant And Leases Disclosure [Text Block] Regulated Operations Plant And Leases Disclosure Total of amount recognized in net periodic benefit cost and other comprehensive (income) loss Defined Benefit Plan, Amount Recognized in Net Periodic Benefit Cost (Credit) and Other Comprehensive (Income) Loss, before Tax Property, Plant and Equipment, Type [Domain] Long-Lived Tangible Asset [Domain] Disposal Group Classification [Domain] Disposal Group Classification [Domain] Number of customers party to contracts with rate components subject to negotiation (less than) Number Of Customers Party To Contracts With Rate Components Subject To Negotiation Number Of Customers Party To Contracts With Rate Components Subject To Negotiation Pay vs Performance Disclosure, Table Pay vs Performance [Table Text Block] Forgone Recovery due to Violation of Home Country Law, Amount Forgone Recovery due to Violation of Home Country Law, Amount Entity Tax Identification Number Entity Tax Identification Number Tax credits Effective Income Tax Rate Reconciliation, Tax Credit, Percent Non-service components of net periodic benefit cost Defined Benefit Plan, Actuarial Gain (Loss), Immediate Recognition as Component in Net Periodic Benefit (Cost) Credit Loss on final disposition of retained interest Disposal Group, Including Discontinued Operation, Gain (Loss) On Final Disposal Of Equity Method Investment Disposal Group, Including Discontinued Operation, Gain (Loss) On Final Disposal Of Equity Method Investment Common stock, issued (in shares) Common Stock, Shares, Issued 2029 Long-Term Debt, Maturity, Year Four Total regulatory liabilities Regulatory liabilities Regulatory Liability Performance measurement period Share-based Compensation Arrangement by Share-based Payment Award, Performance Measurement Period Share-based Compensation Arrangement by Share-based Payment Award, Performance Measurement Period Effect of dilutive securities: Dilutive Securities, Effect on Basic Earnings Per Share [Abstract] Regulatory adjustment, tax benefit Other Comprehensive Income Defined Benefit Plans Regulatory Adjustment, Tax Other Comprehensive Income Defined Benefit Plans Regulatory Adjustment, Tax Dividends declared Dividends Payable, Current Entity Public Float Entity Public Float Interest expense Interest Expense, Nonoperating Trading Arrangement: Trading Arrangement [Axis] Income tax benefit resulting from operations through deconsolidation Discontinued Operation, Tax Effect Of Operations From Disposal Of Discontinued Operation Discontinued Operation, Tax Effect Of Operations From Disposal Of Discontinued Operation Total Shareholder Return Amount Total Shareholder Return Amount Goodwill Disposal Group, Including Discontinued Operation, Goodwill, Noncurrent Loss Contingencies [Line Items] Loss Contingencies [Line Items] Natural Gas Distribution Natural Gas Distribution Segment [Member] Natural Gas Distribution Segment Security Exchange Name Security Exchange Name Canada Income Tax Paid, Foreign, after Refund Received Regulated operations revenues Total Regulated operations revenues Regulated Operating Revenue, Gas QRP QRP Other Pension Plan [Member] Credit facility maximum borrowing capacity Line of Credit Facility, Maximum Borrowing Capacity Defined Benefit Plan, Plan Assets, Category [Domain] Defined Benefit Plan, Plan Assets, Category [Domain] Other current liabilities Other current liabilities Other Liabilities, Current Discount rate Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate Statement [Line Items] Statement [Line Items] Rule 10b5-1 Arrangement Adopted Rule 10b5-1 Arrangement Adopted [Flag] Cash and cash equivalents Cash and cash equivalents Cash and Cash Equivalent Common stock shares Common Stock [Member] Deferred income taxes Deferred income taxes Increase (Decrease) in Deferred Income Taxes Vested and issued (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period Change in cash and cash equivalents, including discontinued operations Change in cash and cash equivalent Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Period Increase (Decrease), Including Exchange Rate Effect and Discontinued Operation Summary of Significant Accounting Policies Significant Accounting Policies [Text Block] Statistical Measurement [Domain] Statistical Measurement [Domain] Schedule of Other Income (Deductions) Schedule of Other Nonoperating Income, by Component [Table Text Block] Amortization of prior service cost, net of tax expense of $42, $42 and $42, respectively Amortization of prior service cost, net of tax expense of $42, $42 and $42, respectively Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, after Tax Other property and investments, net Disposal Group, Including Discontinued Operation, Property, Plant and Equipment Defined benefit plan, funded percentage Defined Benefit Plan, Funded Percentage Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis] Deferred charges and other assets Deferred Charges And Other Assets [Member] Deferred Charges And Other Assets [Member] Equity in earnings of unconsolidated investments Income (Loss) from Equity Method Investments Gross increases – tax positions in prior period Unrecognized Tax Benefits, Increase Resulting from Prior Period Tax Positions Future estimated funding amount Future Estimated Funding Amount In Next Fiscal Year Future estimated funding amount in next fiscal year Earnings (loss) per share attributable to Southwest Gas Holdings, Inc.: Earnings Per Share, Basic [Abstract] Operating Activities [Axis] Operating Activities [Axis] Accounts payable Accounts payable Increase (Decrease) in Accounts Payable Schedule of Disposal Groups, Including Discontinued Operations Disposal Groups, Including Discontinued Operations [Table Text Block] Net interest deductions Interest Income (Expense), Nonoperating Significant Accounting Policies [Table] Significant Accounting Policies [Table] Significant Accounting Policies [Table] Trading Arrangements, by Individual Trading Arrangements, by Individual [Table] Net earnings per share - basic (in USD per share) Net earnings per share - basic (in USD per share) Earnings Per Share, Basic Commercial Paper Commercial Paper [Member] Net cash used in financing activities of continuing operations Cash Provided by (Used in) Financing Activity, Continuing Operation Shares registered and available for issuance (in shares) Common Stock, Capital Shares Reserved for Future Issuance Changes in unrecognized tax benefits Effective Income Tax Rate Reconciliation, Tax Contingency, Percent Discount rate Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate Total other comprehensive income (loss), net of tax Other Comprehensive Income (Loss), Net of Tax Schedule of Segment Reporting Information Schedule of Segment Reporting Information, by Segment [Table Text Block] Discontinued operations (in USD per share) Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Diluted Share Short-term debt Short-Term Debt Revenue, backlog performance obligations Revenue, Remaining Performance Obligation, Amount Award Timing MNPI Disclosure Award Timing MNPI Disclosure [Text Block] Debentures Debentures [Member] Debentures [Member] Total share-based compensation expense Share-Based Payment Arrangement, Expense Debt covenant, additional debt amount could be issued Debt Instrument, Covenant, Compliance Credit Risk Exposure Amount Debt instrument covenant compliance credit risk exposure amount. Current assets: Current assets: Assets, Current [Abstract] Schedule of Net Utility Plant Public Utility Property, Plant, and Equipment [Table Text Block] Total capitalization and liabilities Total capitalization and liabilities Liabilities and Equity Cash and cash equivalents, including discontinued operations, at beginning of period Cash and cash equivalents, including discontinued operations, at end of period Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Including Discontinued Operation Long-term debt, less current maturities Disposal Group, Including Discontinued Operation, Long-Term Debt, Excluding Current Maturities Disposal Group, Including Discontinued Operation, Long-Term Debt, Excluding Current Maturities Other income (deductions) Other Nonoperating Income (Expense) [Abstract] Other Deferred Tax Assets, Other Unamortized gain on reacquired debt Unamortized Gain On Reacquired Debt [Member] Unamortized Gain On Reacquired Debt [Member] Capital expenditures Segment, Expenditure, Addition to Long-Lived Assets Accounting Policies [Abstract] Public Utility [Axis] Public Utility [Axis] Income from continuing operations Income from continuing operations, net of income tax Income (loss) from continuing operations Income (loss) from continuing operations, net of income tax Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest Pay vs Performance Disclosure [Line Items] Notes, 3.18%, due 2051 Debentures Notes, 3.18%, Due 2051 [Member] Debentures Notes, 3.18%, Due 2051 Depreciation and amortization Depreciation and amortization expense Depreciation, Depletion and Amortization, Nonproduction Total deferred income taxes and other credits Total deferred income taxes and other credits Other Liabilities, Noncurrent Auditor [Line Items] Auditor [Line Items] Accrued general taxes Accrued general taxes Accrual for Taxes Other than Income Taxes, Current Schedule of Other Property and Investments Investment [Table Text Block] Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Current maturities of long-term debt Less: current maturities Long-Term Debt, Current Maturities Company Selected Measure Amount Company Selected Measure Amount Employer contributions Defined Benefit Plan, Plan Assets, Contributions by Employer Comprehensive income attributable to Southwest Gas Holdings, Inc. Comprehensive income (loss) attributable to Southwest Gas Holdings, Inc. Comprehensive Income (Loss), Net of Tax, Attributable to Parent Disposal Group Name [Domain] Disposal Group Name [Domain] Name Measure Name Secured Debt Secured Debt [Member] Class of Stock [Line Items] Class of Stock [Line Items] Decoupling Mechanism Decoupling Mechanism [Member] Decoupling Mechanism Asset return assumption Expected return on plan assets Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-Term Rate of Return on Plan Assets Net income (loss) from discontinued operations attributable to Southwest Gas Holdings, Inc. Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent Revision of Previously Issued Financial Statements Previously Issued Condensed Consolidated Financial Statements (Unaudited) Error Correction [Text Block] Accrued taxes Accrued taxes Increase (Decrease) in Accrued Taxes Payable Deferred income taxes and investment tax credits, net Deferred income taxes and investment tax credits, net Deferred Income Taxes And Unamortized Investment Tax Credits Represents deferred tax liabilities, which result from applying the applicable tax rate to net taxable temporary differences pertaining to each jurisdiction to which the entity is obligated to pay income tax. Additionally, this element includes the future effects on income taxes attributable to investment tax credits. Adjustments Revision of Prior Period, Adjustment [Member] Total Long-term debt outstanding Long-Term Debt Legal Entity [Axis] Legal Entity [Axis] Total assets Total assets Segment assets Assets Total noncurrent assets Assets, Noncurrent, Other than Noncurrent Investments and Property, Plant and Equipment Vested and issued (in USD per share) Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value Geographical [Domain] Geographical [Domain] Regulatory Liability [Axis] Regulatory Liability [Axis] Income Taxes Income Tax, Policy [Policy Text Block] CASH FLOW FROM OPERATING ACTIVITIES: CASH FLOW FROM OPERATING ACTIVITIES: Cash Provided by (Used in) Operating Activity, Including Discontinued Operation [Abstract] Background and Organization Organization, Consolidation and Presentation of Financial Statements Disclosure and Significant Accounting Policies [Text Block] Other segment items Segment Reporting, Other Segment Item, Amount Centuri deconsolidation Noncontrolling Interest, Decrease from Deconsolidation MountainWest Pipelines Holding Company MountainWest Pipelines Holding Company [Member] MountainWest Pipelines Holding Company Dividends declared per common share (in USD per share) Common Stock, Dividends, Per Share, Declared Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Level 2 – Significant other observable inputs Fair Value, Inputs, Level 2 [Member] Document Financial Statement Error Correction Document Financial Statement Error Correction [Flag] State and local income tax, net of deferred benefit Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Amount Schedule of Regulatory Assets Schedule of Regulatory Assets [Table Text Block] Industrial and other Industrial and Other [Member] Industrial/other. Insider Trading Policies and Procedures Not Adopted Insider Trading Policies and Procedures Not Adopted [Text Block] Related Party Related Party [Member] Regulatory Assets and Liabilities Schedule of Regulatory Assets and Liabilities [Text Block] Change in plan assets: Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] Notes, 3.7%, due 2028 Debentures Notes, 3.7%, Due 2028 [Member] Debentures Notes, 3.7%, Due 2028 Significant Accounting Policies [Line Items] Significant Accounting Policies [Line Items] Significant Accounting Policies [Line Items] Schedule of Income Tax Expense (Benefit) Schedule of Components of Income Tax Expense (Benefit) [Table Text Block] Plan Name [Axis] Plan Name [Axis] Net Regulated Operations Plant Property, Plant and Equipment, Policy [Policy Text Block] PEO PEO [Member] Changes in current assets and liabilities: Changes in current assets and liabilities: Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity, Increase (Decrease) in Operating Capital [Abstract] Changes in valuation allowance Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount Property-related items, including accelerated depreciation Deferred Tax Liabilities, Property, Plant and Equipment Receivables And Related Allowances [Table] Receivables And Related Allowances [Table] Receivables And Related Allowances [Table] Retained Earnings Retained Earnings [Member] Dividends (in shares) Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Dividends Share based compensation arrangement by share based payment award equity instruments other than options dividends Income Tax Jurisdiction [Axis] Income Tax Jurisdiction [Axis] Share-based Payment Arrangement [Abstract] Share-Based Payment Arrangement [Abstract] Cash and cash equivalents, including discontinued operations, at beginning of period Cash and cash equivalents, including discontinued operations, at end of period Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Continuing Operation Income Statement [Abstract] Income Statement [Abstract] Sale of Stock [Domain] Sale of Stock [Domain] Deferred income taxes Disposal Group, Including Discontinued Operation, Deferred Tax Assets General General [Member] General [Member] Revolving Credit Agreement Due December 2026 Revolving Credit Agreement Due December 2026 [Member] Revolving Credit Agreement Due December 2026 Continuing operations (in USD per share) Income (Loss) from Continuing Operations, Per Diluted Share Southwest Gas Holdings, Inc. Parent [Member] Net income Net income Net income Net income (loss) Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Restatement does not require Recovery Restatement Does Not Require Recovery [Text Block] Pipeline And Storage Pipeline And Storage Segment [Member] Pipeline And Storage Segment Organization, Consolidation and Presentation of Financial Statements [Abstract] Organization, Consolidation and Presentation of Financial Statements [Abstract] Net actuarial gain (loss), net of tax expense (benefit) of $13,114, $1,162 and $(765), respectively Net actuarial gain (loss), net of tax expense (benefit) of $13,114, $1,162 and $(765), respectively Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, after Tax Nontaxable and nondeductible items Effective Income Tax Rate Reconciliation, Tax Exempt Income, Amount Equity AFUDC capitalized in regulated operations plant Equity portion Equity AFUDC Public Utilities, Allowance for Funds Used During Construction, Capitalized Cost of Equity City Area Code City Area Code Award Timing, How MNPI Considered Award Timing, How MNPI Considered [Text Block] Contributions from Southwest Gas Holdings, Inc. Adjustments To Additional Paid In Capital, Contributions From Parent Adjustments to additional paid in capital contributions from parent. 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