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Margin, interest - and property tax-tracking Margin, Interest - and Tax-Tracking [Member] Margin, Interest - and Tax-Tracking Receivables and Related Allowances Loans, Notes, Trade and Other Receivables Disclosure [Text Block] Amortization of net actuarial loss Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, after Tax Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Equity [Abstract] Equity [Abstract] Consolidation Items [Domain] Consolidation Items [Domain] Tax credits Effective Income Tax Rate Reconciliation, Tax Credit, Percent Commercial Paper Program Commercial Paper Program [Member] Commercial Paper Program [Member] Summary 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 [Table] Income Tax Disclosure [Table] Income Tax Disclosure [Table] Variable Rate [Axis] Variable Rate [Axis] Other income (deductions) Other Nonoperating Income (Expense) [Abstract] Segment Information Segment Reporting Disclosure [Text Block] Notes, 4.15%, due 2049 Debentures Notes Four Point Fifteen Percentage, Due Two Thousand And Forty Nine [Member] Debentures Notes Four Point Fifteen Percentage, Due Two Thousand And Forty Nine Finance lease, weighted average remaining lease term (in years) Finance Lease, Weighted Average Remaining Lease Term Number of types of services provided to customers Number Of Types Of Services Provided To Customers Number Of Types Of Services Provided To Customers Property, Plant and Equipment [Table] Property, Plant and Equipment [Table] Regulatory Asset [Axis] Regulatory Asset [Axis] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Document Fiscal Year Focus Document Fiscal Year Focus Customer contracts backlog Customer Contracts [Member] Variable Rate [Domain] Variable Rate [Domain] Additional paid-in capital Additional Paid-in Capital [Member] Regulatory assets Regulatory Assets 2027-2031 Defined Benefit Plan, Expected Future Benefit Payment, after Year Five for Next Five Years Regulated operations plant: Public Utilities, Property, Plant and Equipment, Net [Abstract] Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] Utility infrastructure services revenues Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual Entity Information [Line Items] Entity Information [Line Items] Other income (deductions) Total other income (deductions) Other Nonoperating Income (Expense) Qualified Retirement Plan Retirement plan Other Pension Plan [Member] Changes in other liabilities and deferred credits Increase (Decrease) in Other Operating Liabilities Construction work in progress Public Utilities, Property, Plant and Equipment, Construction Work in Progress Regulatory Assets [Line Items] Regulatory Assets [Line Items] Other Payments for (Proceeds from) Other Investing Activities Business Combinations [Abstract] Business Combinations [Abstract] Maximum Maximum [Member] Share-based Payment Arrangement [Abstract] Share-based Payment Arrangement [Abstract] Total noncurrent assets Assets, Noncurrent, Other than Noncurrent Investments and Property, Plant and Equipment Unamortized premium on reacquired debt Unamortized Premium On Reacquired Debt [Member] Unamortized Premium On Reacquired Debt [Member] 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 Award Type [Axis] Award Type [Axis] CASH FLOW FROM FINANCING ACTIVITIES: Net Cash Provided by (Used in) Financing Activities [Abstract] Global Global [Member] Global [Member] Schedule of Maturities of Operating Lease Liabilities Lessee, Operating Lease, Liability, Maturity [Table Text Block] Total Southwest Gas Holdings, Inc. equity Beginning balance, attributable to parent Ending balance, attributable to parent Stockholders' Equity Attributable to Parent Omnibus Incentive Plan Omnibus Incentive Plan [Member] Omnibus Incentive Plan City Area Code City Area Code Prepaid and other current assets Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Prepaid Expense and Other Assets Line of credit facility, maximum commitment amount Line Of Credit Facility, Maximum Commitment Amount Line Of Credit Facility, Maximum Commitment Amount Non-regulated property, equipment, and intangibles Property Plant Equipment And Intangible Assets Gross Property plant equipment and intangible assets gross. 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Allowance for doubtful accounts Contract with Customer, Asset, Allowance for Credit Loss Summary of Fair Values of Assets Acquired and Liabilities Assumed Schedule of Recognized Identified Assets Acquired and Liabilities Assumed [Table Text Block] Finance lease liabilities Finance lease liabilities Finance Lease, Liability Business Acquisition [Line Items] Business Acquisition [Line Items] Deferred tax liabilities, gross Deferred Tax Liabilities, Gross Lease remaining lease term (up to) Lessee, Operating Lease, Remaining Lease Term Equity Securities Defined Benefit Plan, Equity Securities [Member] Net Assets, Geographic Area Net Assets, Geographic Area [Member] Increments of change to the discount rate Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate, Increments Of Change Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate, Increments Of Change Vesting Tranche Two Share-based Payment Arrangement, Tranche Two [Member] 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] Deferred Tax Assets, Employee benefits Deferred Tax Assets (Liabilities), Employee benefits Deferred Tax Assets (Liabilities), Employee benefits Income Statement [Abstract] Income Statement [Abstract] Entity Registrant Name Entity Registrant Name Diluted earnings per share (in USD per Share) Business Acquisition, Pro Forma Earnings Per Share, Diluted Accounts receivable Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Receivables 2024 Finance Lease, Liability, to be Paid, Year Three 2025 Finance Lease, Liability, to be Paid, Year Four Income tax expense Income tax expense Total income tax expense Income Tax Expense (Benefit) Residential Residential [Member] Residential. 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Equity Component [Domain] Equity Component [Domain] 2022 Lessee, Operating Lease, Liability, to be Paid, Year One Notes, 4.875%, due 2043 Debentures Notes Four Point Eight Seven Five Percentage Due Two Thousand And Forty Three [Member] Debentures Notes Four Point Eight Seven Five Percentage Due Two Thousand And Forty Three [Member] Defined Benefit Plan, Plan Assets, Category [Axis] Defined Benefit Plan, Plan Assets, Category [Axis] Accrued taxes Increase (Decrease) in Accrued Taxes Payable Schedule of Other Income (Deductions) Schedule of Other Nonoperating Income, by Component [Table Text Block] Total operating revenues Revenues Regulated and Unregulated Operating Revenue Revenue, expected to be recognized on multi-year contracts Revenue, Remaining Performance Obligation, Amount Short-term Debt, Type [Axis] Short-term Debt, Type [Axis] All other deferred All Other Deferred [Member] All Other Deferred [Member] Schedule of Fair Value of Plan Assets Schedule of Allocation of Plan Assets [Table Text Block] Notes 3.18%, due 2051 Senior Notes 3.18% Due 2051 [Member] Senior Notes 3.18% Due 2051 Storage Storage [Member] Storage [Member] 2025 Lessee, Operating Lease, Liability, to be Paid, Year Four Time and materials contracts Time-and-materials Contract [Member] Miscellaneous income and (expense) Miscellaneous Income Expense Miscellaneous income (expense). Finance lease liabilities, current Finance Lease, Liability, Current Income before income taxes Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Level 2 – Significant other observable inputs Fair Value, Inputs, Level 2 [Member] Total assets acquired Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Assets Acquired Including Goodwill Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Assets Acquired Including Goodwill Auditor Location Auditor Location Deferred ITC, net Deferred Investment Tax Credit, Net Deferred Investment Tax Credit, Net Segment Reporting [Abstract] Segment Reporting [Abstract] Employee benefits Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits Notes, 3.875%, due 2022 Debentures Notes Three Point Eight Seven Five Percentage Due Two Thousand And Twenty Two [Member] Debentures Notes Three Point Eight Seven Five Percentage Due Two Thousand And Twenty Two [Member] Interest on lease liabilities Finance Lease, Interest Expense Schedule of Earnings Per Share, Basic and Diluted Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Right of use assets under operating leases Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Right Of Use Assets Under Operating Leases Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Right Of Use Assets Under Operating Leases Finance Leases Finance Lease, Liability, Payment, Due [Abstract] International International [Member] International. Title of 12(b) Security Title of 12(b) Security Restricted Stock/Unit Plan Restricted Stock/Unit Plan [Member] Restricted Stock/Unit Plan [Member] Investment, Name [Domain] Investment, Name [Domain] Common stock, authorized (in shares) Common Stock, Shares Authorized Gross proceeds Proceeds From Issuance Of Common Stock, Gross Proceeds From Issuance Of Common Stock, Gross Changes in customer advances Changes In Customer Advances, Investing Activities Changes In Customer Advances, Investing Activities Document Type Document Type Deferred compensation plan, payment term, option three Deferred Compensation Plan, Payment Term, Option Three Deferred Compensation Plan, Payment Term, Option Three Product and Service [Domain] Product and Service [Domain] Medium-term notes, 7.78% series, due 2022 Debentures Medium Term Notes Seven Point Seven Eight Percentage Series Due Two Thousand And Twenty Two [Member] Debentures Medium Term Notes Seven Point Seven Eight Percentage Series Due Two Thousand and Twenty Two [Member] Debt instrument, stated interest rate Debt Instrument, Interest Rate, Stated Percentage Lease renewal term (up to) Lessee, Operating Lease, Renewal Term Net income attributable to noncontrolling interests Net Income (Loss) Attributable to Noncontrolling Interest Redeemable Noncontrolling Interests Noncontrolling Interest Disclosure [Text Block] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Revolving Credit Facility Revolving Credit Facility [Member] 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 Medium-term notes, 6.76% series, due 2027 Debentures Medium Term Notes Six Point Seven Six Percentage Series Due Two Thousand And Twenty Seven [Member] Debentures Medium Term Notes Six Point Seven Six Percentage Series Due Two Thousand and Twenty Seven [Member] Schedule of Components of Lease Expense, and Supplemental Cash Flow Information Related to Leases Lease, Cost [Table Text Block] Preferred stock purchase price, exercisable term, beneficial ownership percentage benchmark Preferred Stock Purchase Price, Exercisable Term, Beneficial Ownership Percentage Benchmark Preferred Stock Purchase Price, Exercisable Term, Beneficial Ownership Percentage Benchmark Deferred charges and other assets Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed, Deferred Charges And Other Assets Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed, Deferred Charges And Other Assets Geographical [Axis] Geographical [Axis] Environmental compliance programs Environmental Compliance Programs [Member] Environmental compliance programs. State State and Local Jurisdiction [Member] Vesting [Domain] Vesting [Domain] Increase in weighted-average rate of compensation Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Weighted-Average Rate Of Compensation, Increase (Decrease) Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Weighted-Average Rate Of Compensation, Increase (Decrease) Amortization of prior service cost Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, before Tax Goodwill tax-deductible amount Business Acquisition, Goodwill, Expected Tax Deductible Amount Amortization of prior service cost Accumulated Defined Benefit Plans Adjustment, Net Prior Service Attributable to Parent [Member] Change in COLI policies Life Insurance, Corporate or Bank Owned, Change in Value Net cash provided by financing activities Net Cash Provided by (Used in) Financing Activities MountainWest unsecured senior notes, 4.875%, due in 2041 Senior Notes, 4.875% Due In 2041 [Member] Senior Notes, 4.875% Due In 2041 Equity in earnings of unconsolidated investment – Western Income (Loss) from Equity Method Investments Schedule of Maturities of Finance Lease Liabilities Finance Lease, Liability, Fiscal Year Maturity [Table Text Block] Other property Property, Plant and Equipment, Other, Net Concentration Risk Type [Axis] Concentration Risk Type [Axis] Equity AFUDC Equity AFUDC Increase (Decrease) in Allowance for Equity Funds Used During Construction Change in 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 2024 Finite-Lived Intangible Asset, Expected Amortization, Year Three Foreign Foreign Tax Authority [Member] Transportation Transportation [Member] Transportation. Trade and other payables Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Accounts Payable Schedule of Accounts Receivable for Services Accounts Receivable For Services [Table Text Block] Accounts Receivable For Services Table Text Block. Operating revenues: Revenues [Abstract] Deferred tax liabilities: Deferred Tax Liabilities, Net [Abstract] Goodwill Goodwill and Intangible Assets, Goodwill, Policy [Policy Text Block] Software and software-related intangibles Computer Software, Intangible Asset [Member] Document Period End Date Document Period End Date Percentage of interest retained by noncontrolling party subject to election Noncontrolling Interest, Percentage Of Interest Retained By Noncontrolling Party Subject To Election Noncontrolling Interest, Percentage Of Interest Retained By Noncontrolling Party Subject To Election Regulatory Assets And Liabilities [Line Items] Regulatory Assets And Liabilities [Line Items] Regulatory Assets And Liabilities [Line Items] Concentration Risk Benchmark [Domain] Concentration Risk Benchmark [Domain] Fair Value, Inputs, Level 1 and 2 Fair Value, Inputs, Level 1, 2 and 3 [Member] Net state taxes Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent State Deferred State and Local Income Tax Expense (Benefit) Debt Instrument, term Debt Instrument, Term Deferred compensation, percentage of multiple interest rate Floating Interest Rate Index Floating Interest Rate Index Deferred purchased gas costs Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Deferred Purchased Gas Costs Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Deferred Purchased Gas Costs Incurred and expensed acquisition costs Business Acquisition, Transaction Costs Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward] Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward] 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. AOCI Including Portion Attributable to Noncontrolling Interest AOCI Including Portion Attributable to Noncontrolling Interest [Member] Regulatory balancing accounts Deferred Tax Liabilities, Regulatory Assets and Liabilities Schedule of Estimated Future Amortization of Intangible Assets Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block] Retirement of long-term debt Retirement of long-term debt Repayments of Long-term Debt Earnings per share: Earnings Per Share [Abstract] Electric power infrastructure services Electric Power Infrastructure Services [Member] Electric Power Infrastructure Services [Member] Operating lease obligations Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Operating Lease Obligations Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Operating Lease Obligations Industrial/other Industrial/other [Member] Industrial/other. Noncontrolling Interest [Table] Noncontrolling Interest [Table] Beginning Balance Ending Balance Accounts Receivable, Allowance for Credit Loss Notes, 6.1%, due 2041 Debentures Notes 6.1% Due 2041 [Member] Debentures Notes Six Point One Percentage Due Two Thousand And Forty One [Member] Revenues Revenues 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. Reclassification from AOCI, net of tax Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax Operating expenses: Costs and Expenses [Abstract] Accrued pension and other postretirement benefit costs Accrued Pension And Other Postretirement Benefit Costs [Member] Accrued Pension And Other Postretirement Benefit Costs [Member] AFUDC rate Public Utilities, Allowance for Funds Used During Construction, Rate Beginning balance, attributable to parent, before tax Ending balance, attributable to parent, before tax Stockholders' Equity Attributable To Parent, Before Tax Stockholders' Equity Attributable To Parent, Before Tax Working capital adjustments, period post-acquisition Business Combination, Provisional Information, Initial Accounting Incomplete, Working Capital Adjustments Period Post Acquisition Business Combination, Provisional Information, Initial Accounting Incomplete, Working Capital Adjustments Period Post Acquisition Entity Current Reporting Status Entity Current Reporting Status Market value of plan assets at beginning of year Market value of plan assets at end of year Defined benefit plan, plan assets, amount Defined Benefit Plan, Plan Assets, Amount Weighted- average grant date fair value Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract] Prior service cost Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Tax Effective income tax rate Consolidated effective income tax rate Effective Income Tax Rate Reconciliation, Percent Other debt obligations Other Debt Obligations [Member] General Business Tax Credit Carryforward General Business Tax Credit Carryforward [Member] Short-term lease total future lease payments Short-term Lease Commitment, Amount Other Current Liabilities Other Current Liabilities [Policy Text Block] Other Current Liabilities [Policy Text Block] Gains on sale of equipment Gain (Loss) on Disposition of Property Plant Equipment Tax Credit Carryforward, Name [Domain] Tax Credit Carryforward, Name [Domain] Gas plant Natural Gas Processing Plant [Member] United States UNITED STATES Deferred compensation plan, matching percentage Deferred Compensation Arrangement With Individual, Matching Percentage Deferred Compensation Arrangement With Individual, Matching Percentage Shares registered and available for issuance (in shares) Common Stock, Capital Shares Reserved for Future Issuance Income Tax [Table] Income Tax [Table] Income Tax [Table] Forward-starting interest rate swaps (“FSIRS”): Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax [Abstract] Gross-up related to contributions in aid of construction Gross-Up Related To Contributions In Aid Of Construction [Member] Gross-Up Related To Contributions In Aid Of Construction [Member] Income Taxes Income Tax, Policy [Policy Text Block] LIBOR London Interbank Offered Rate (LIBOR) [Member] Acquired gross contractual receivable Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Gross Contractual Receivable Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Gross Contractual Receivable Accumulated Other Comprehensive Income (Loss) [Line Items] Accumulated Other Comprehensive Income (Loss) [Line Items] EIP, percent of compensation deferred with match Employees' Investment Plan, Percent Of Compensation Deferred With Match Employees' Investment Plan, Percent Of Compensation Deferred With Match Entity Address, Postal Zip Code Entity Address, Postal Zip Code Gas Operating Revenues Revenue from Contract with Customer [Policy Text Block] Diluted (in shares) Average diluted shares (in shares) Weighted Average Number of Shares Outstanding, Diluted U.S. Income (Loss) from Continuing Operations before Income Taxes, Domestic Income Taxes Income Tax Disclosure [Text Block] Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Debt, basis spread on variable rate Debt Instrument, Basis Spread on Variable Rate Regulatory Liabilities [Line Items] Regulatory Liabilities [Line Items] Unit price contracts Unit Priced Contracts [Member] Unit priced contracts. Schedule of Net Benefit Cost Schedule of Net Benefit Costs [Table Text Block] Questar Pipelines Dominion Energy Questar Pipeline, LLC [Member] Dominion Energy Questar Pipeline, LLC Regulated Operations Plant and Leases Regulated Operations Plant And Leases Disclosure [Text Block] Regulated Operations Plant And Leases Disclosure Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Maximum loss exposure amount Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount Gas operating revenues Total Gas operating revenues Regulated Operating Revenue, Gas Class of Stock [Line Items] Class of Stock [Line Items] Credit Facility [Axis] Credit Facility [Axis] Finite-Lived Intangible Assets, Major Class Name [Domain] Finite-Lived Intangible Assets, Major Class Name [Domain] Entity Address, Address Line One Entity Address, Address Line One Entity Address, Address Line Two Entity Address, Address Line Two Non-regulated accumulated provision for depreciation and amortization Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Other deferred credits and other long-term liabilities Other deferred credits and other long-term liabilities Deferred Credits and Other Liabilities, Noncurrent Multiemployer plan, special surcharges Multiemployer Plan, Special Surcharges Multiemployer Plan, Special Surcharges CASH FLOW FROM OPERATING ACTIVITIES: Net Cash Provided by (Used in) Operating Activities [Abstract] 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 Consolidation Consolidation, Policy [Policy Text Block] Entity Shell Company Entity Shell Company Total current liabilities Liabilities, Current Withholding remittance – share-based compensation Withholding remittance – share-based compensation Payment, Tax Withholding, Share-based Payment Arrangement Money Market Funds Money Market Funds [Member] Cash and cash equivalents Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents Loss Contingencies [Table] Loss Contingencies [Table] Current Fiscal Year End Date Current Fiscal Year End Date Unamortized discount and debt issuance costs Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net 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 Income Taxes [Line Items] Income Taxes [Line Items] Income Taxes [Line Items] Revenue earned on contracts in progress in excess of billings Contract with Customer, Asset, Reclassified to Receivable Income taxes receivable, net Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Income Taxes Receivable, Net Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Income Taxes Receivable, Net Net income (loss) Net income Net Income (Loss), Including Portion Attributable to Nonredeemable Noncontrolling Interest Mutual funds Mutual Fund [Member] Statement [Table] Statement [Table] Schedule of Other Property and Investments Investment [Table Text Block] Recently Accounting Standards Updates New Accounting Pronouncements, Policy [Policy Text Block] Other Deferred Tax Assets, Other 2026 Defined Benefit Plan, Expected Future Benefit Payment, Year Five Compensation cost related to nonvested management incentive plan shares, performance shares, and restricted stock/units not yet recognized Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount Natural Gas Distribution Natural Gas Distribution Segment [Member] Natural Gas Distribution Segment Schedule of Amount Recognized Before Income Tax in Accumulated Other Comprehensive Income Schedule of Amounts Recognized in Other Comprehensive Income Schedule of Amounts Recognized in Other Comprehensive Income (Loss) [Table Text Block] Statistical Measurement [Axis] Statistical Measurement [Axis] Receivables and Related Allowances Accounts Receivable [Policy Text Block] Subsequent Event Subsequent Event [Member] Finance lease liabilities, noncurrent Finance Lease, Liability, Noncurrent Net Carrying Amount Finite-Lived Intangible Assets, Net Goodwill Goodwill Goodwill, beginning balance Goodwill, ending balance Goodwill Linetec Linetec Services, LLC [Member] Linetec Services, LLC [Member] FSIRS AOCI, Derivative Qualifying as Hedge, Excluded Component, Parent [Member] Insurance company general account contracts Fair Value Measured at Net Asset Value Per Share [Member] Scenario [Domain] Scenario [Domain] Schedule of Goodwill Schedule of Goodwill [Table Text Block] Adjustments to reconcile net income to net cash provided by operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Subsequent Event Type [Axis] Subsequent Event Type [Axis] Operating lease cost Operating Lease, Cost Property-related items Property Related Items [Member] Property-Related Items [Member] Cash and Cash Equivalents [Axis] Cash and Cash Equivalents [Axis] Defined Benefit Plans Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member] White River Hub, LLC White River Hub, LLC [Member] White River Hub, LLC Total deferred income tax expense Deferred Income Tax Expense (Benefit) Notes, 3.7%, due 2028 Debentures Notes Three Point Seven Percentage Due Two Thousand And Twenty Eight [Member] Debentures notes three point seven percentage due two thousand and twenty eight. Deferred income taxes Business Combination Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Assets Foreign transaction gain (loss) Foreign Currency Transaction Gain (Loss), Realized U.S. federal statutory income tax rate Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent Earnings Per Share Earnings Per Share, Policy [Policy Text Block] Purchased gas cost adjustments Purchased Gas Cost Adjustments [Member] Purchased Gas Cost Adjustments [Member] Significant Components of Deferred Income Tax Expense (Benefit) Schedule Of Deferred Income Tax Expense Benefit [Table Text Block] Schedule Of Deferred Income Tax Expense (Benefit) [Table Text Block] Trade name and trademarks Trademarks and Trade Names [Member] Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Net income attributable to Southwest Gas Holdings, Inc. Segment net income Net Income (Loss) Attributable to Parent Significant Components Of Deferred Income Tax Expense [Table] Significant Components Of Deferred Income Tax Expense [Table] Significant Components Of Deferred Income Tax Expense [Table] Operating lease ROU assets Operating Lease, Right-of-Use Asset Deferred charges and other assets Deferred Charges And Other Assets [Member] Deferred Charges And Other Assets [Member] Federal net operating losses Deferred Tax Assets, Operating Loss Carryforwards Employee benefits Employee Benefits [Member] Employee Benefits [Member] Interest cost Defined Benefit Plan, Interest Cost MountainWest unsecured senior notes, 3.53%, due in 2028 Senior Notes, 3.53% Due In 2028 [Member] Senior Notes, 3.53% Due In 2028 Accumulated Amortization Finite-Lived Intangible Assets, Accumulated Amortization Statistical Measurement [Domain] Statistical Measurement [Domain] Estimated Maturities of Long-Term Debt Schedule of Maturities of Long-term Debt [Table Text Block] Future estimated funding amount Future Estimated Funding Amount In Next Fiscal Year Future estimated funding amount in next fiscal year Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Revenue from Contract with Customer [Abstract] Revenue from Contract with Customer [Abstract] Additional paid-in capital Additional Paid in Capital, Common Stock Previous Owner Of Linetec Previous Owner Of Linetec [Member] Previous Owner Of Linetec Significant Accounting Policies [Table] Significant Accounting Policies [Table] Significant Accounting Policies [Table] Deferred charges and other assets Deferred charges and other assets Other Assets, Noncurrent Expected return on plan assets Defined Benefit Plan, Expected Return (Loss) on Plan Assets Segments [Axis] Segments [Axis] Retirement Benefits [Abstract] Retirement Benefits [Abstract] Entity File Number Entity File Number Debt instrument discount rate Debt Instrument, Discount Rate Debt Instrument, Discount Rate Public Utility, Property, Plant and Equipment [Table] Public Utility, Property, Plant and Equipment [Table] W.S. Nicholls Western Construction LTD WS Nicholls Western Construction Ltd [Member] WS Nicholls Western Construction Ltd. Deferred Income Tax Expense (Benefit Components [Axis] Deferred Income Tax Expense (Benefit Components [Axis] Deferred Income Tax Expense (Benefit Components Organization, Consolidation and Presentation of Financial Statements [Abstract] Organization, Consolidation and Presentation of Financial Statements [Abstract] Net operating loss Net Operating Loss [Member] Net Operating Loss Debentures Debentures [Member] Debentures [Member] Net actuarial gain (loss) Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, after Tax Other property and investments Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Other Property And Investments Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Other Property And Investments Debt covenant, additional debt amount could be issued Debt Instrument, Covenant, Compliance Credit Risk Exposure Amount Debt instrument covenant compliance credit risk exposure amount. Net income attributable to Southwest Gas Holdings, Inc. Business Combination, Pro Forma Information, Earnings or Loss of Acquiree since Acquisition Date, Actual Weighted average grant date fair value (in USD per share) Granted (in USD per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value Commitment fee percentage Line of Credit Facility, Commitment Fee Percentage Actual return on plan assets Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss) Finance lease obligations Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finance Lease Obligations Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finance Lease Obligations SOFR Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate [Member] Credit Facility [Domain] Credit Facility [Domain] ASSETS Assets [Abstract] Unamortized gain on reacquired debt Unamortized Gain On Reacquired Debt [Member] Unamortized Gain On Reacquired Debt [Member] Redemption value adjustment Noncontrolling Interest, Change in Redemption Value 2024 Long-Term Debt, Maturity, Year Three Finance leases Right-of-Use Asset Obtained in Exchange for Finance Lease Liability Segment Reconciling Items Segment Reconciling Items [Member] Number of shares, granted (in shares) Granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Long-lived assets Concentration Risk, Percentage Net Utility Plant Property, Plant and Equipment, Policy [Policy Text Block] Trade Names Trade Names [Member] Discount rate Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate Debt Instrument [Axis] Debt Instrument [Axis] Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Net regulated operations plant Public Utilities, Property, Plant and Equipment, Net Bid contract Bid Contract [Member] Bid contract. Amortization of prior service cost Defined Benefit Plan, Amortization of Prior Service Cost (Credit) Secured Debt Secured Debt [Member] Measurement period adjustments Measurement Period Adjustments Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Consideration Transferred Operating leases Right-of-Use Asset Obtained in Exchange for Operating Lease Liability Business Acquisition, Pro Forma Information Business Acquisition, Pro Forma Information [Table Text Block] Deferred Tax Assets and Liabilities Schedule of Deferred Tax Assets and Liabilities [Table Text Block] Award vesting percentage Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Abstract] Defined benefit plan, plan assets, target allocation, percentage Defined Benefit Plan, Plan Assets, Target Allocation, Percentage Number of contracts with original duration more than one year Revenue Recognition, Number Of Contracts With Original Duration More Than One Year Revenue Recognition, Number Of Contracts With Original Duration More Than One Year Net actuarial loss (gain) Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, before Tax Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Prime Rate Prime Rate [Member] Deferred compensation plan, percentage of contributions with matching Deferred Compensation Arrangement With Individual, Percentage Of Contributions With Matching Deferred Compensation Arrangement With Individual, Percentage Of Contributions With Matching Amount of FSIRS existing AOCI losses expected to be reclassified into interest expense Interest Rate Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months, Net Arizona ARIZONA Other comprehensive income (loss), before tax Other Comprehensive Income (Loss), before Tax Business acquisition, pro forma adjustment, transaction costs, incremental interest expense Business Acquisition, Pro Forma Adjustment, Incremental Interest Expense Business Acquisition, Pro Forma Adjustment, Incremental Interest Expense Net defined benefit pension plans Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax 2024 Lessee, Operating Lease, Liability, to be Paid, Year Three 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. Public Utility [Axis] Public Utility [Axis] Thereafter Finite-Lived Intangible Asset, Expected Amortization, after Year Five Depreciation and Amortization Regulatory Depreciation and Amortization, Policy [Policy Text Block] Summary of Revenue Disaggregated by Service Type and Contract Type Disaggregation of Revenue [Table Text Block] 2026 Long-Term Debt, Maturity, Year Five Restricted Stock/ Units Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Schedule of Nonvested Performance and Restricted Stock Unit Plans Schedule of Nonvested Share Activity [Table Text Block] Deferred income taxes for future amortization of ITC and excess deferred taxes Deferred Tax Assets, Tax Credit Carryforwards Business acquisition, pro forma adjustment, transaction costs Business Acquisition, Pro Forma Adjustment, Transaction Costs Business Acquisition, Pro Forma Adjustment, Transaction Costs Operating cash flows from operating leases Operating Lease, Payments Change in short-term portion of credit facilities Proceeds from (Repayments of) Short-term Debt Regulatory Assets and Liabilities Schedule of Regulatory Assets and Liabilities [Text Block] Schedule of Capitalized and Debt Portion of AFUDC Schedule of Capitalization [Table Text Block] Business combination consideration Business Combination, Consideration Transferred Additions charged to expense Accounts Receivable, Credit Loss Expense (Reversal) Foreign currency exchange translation adjustment Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, before Tax, Portion Attributable to Parent Long-term debt, gross Long-term Debt, Gross Goodwill [Roll Forward] Goodwill [Roll Forward] Finance lease ROU assets Finance Lease, Right-of-Use Asset, after Accumulated Amortization Proceeds from issuance of bonds Proceeds From Issuance Of Bonds Proceeds From Issuance Of Bonds Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward] Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward] Management Incentive Plan shares (in shares) Incremental Common Shares Attributable to Dilutive Effect of Equity Forward Agreements Significant Accounting Policies [Line Items] Significant Accounting Policies [Line Items] Significant Accounting Policies [Line Items] Revolving credit facility and commercial paper Revolving Credit Facility And Commercial Paper [Member] Revolving Credit Facility And Commercial Paper [Member] Total capitalization and liabilities Liabilities and Equity All other differences Effective Income Tax Rate Reconciliation, Other Adjustments, Percent Debt term, percentage of committed amount under specific acquisition financings Debt Instrument, Percentage Of Committed Amount Under Specific Acquisition Financings Debt Instrument, Percentage Of Committed Amount Under Specific Acquisition Financings Less: accumulated depreciation Less: accumulated depreciation Public Utilities, Property, Plant and Equipment, Accumulated Depreciation Net forward-starting interest rate swaps Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax Vesting Tranche One Share-based Payment Arrangement, Tranche One [Member] Customer deposits Contract with Customer, Liability, Current 2026 Lessee, Operating Lease, Liability, to be Paid, Year Five Benefits paid Defined Benefit Plan, Plan Assets, Benefits Paid Receivables And Related Allowances [Table] Receivables And Related Allowances [Table] Receivables And Related Allowances [Table] 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 Lessee, Lease, Description [Table] Lessee, Lease, Description [Table] Total deferred federal and state Deferred Income Tax Expense (Benefit), Gross Deferred Income Tax Expense (Benefit), Gross Short-term Debt, Type [Domain] Short-term Debt, Type [Domain] Reclassification from AOCI, tax Reclassification from AOCI, Current Period, Tax General General [Member] General [Member] Cash and Cash Equivalents [Domain] Cash and Cash Equivalents [Domain] 2023 Defined Benefit Plan, Expected Future Benefit Payment, Year Two Regulatory liabilities Regulatory Liabilities Minimum Minimum [Member] Net regulatory liabilities Net Regulatory Liabilities Net Regulatory Liabilities Pipeline and Storage Pipeline And Storage Segment [Member] Pipeline And Storage Segment Accrued purchased gas costs Accrued Purchased Gas Costs [Member] Accrued Purchased Gas Costs [Member] Borrowings outstanding under facility Long-term Line of Credit 2023 Lessee, Operating Lease, Liability, to be Paid, Year Two Effects of currency translation on cash and cash equivalents Effect of Exchange Rate on Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table] Contributions from Southwest Gas Holdings, Inc. Adjustments To Additional Paid In Capital Contributions From Parent Adjustments to additional paid in capital contributions from parent. 2009 Series A, due 2039 Variable Rate Bonds Two Thousand And Nine Series A- Due Two Thousand And Thirty Nine [Member] Variable Rate Bonds Two Thousand and Nine Series A Due Two Thousand and Thirty Nine [Member] Income taxes payable, net Income Taxes Payable Net Income taxes payable net. 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Commitments and contingencies (Note 10) Commitments and Contingencies Contract liabilities Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Contract Liabilities Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Contract Liabilities Equity portion Equity AFUDC Public Utilities, Allowance for Funds Used During Construction, Capitalized Cost of Equity Summary of Redeemable Noncontrolling Interest Redeemable Noncontrolling Interest [Table Text Block] Accumulated other comprehensive loss, net Accumulated Other Comprehensive Income (Loss), Net of Tax Acquired contractual receivable deemed uncollectible Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Gross Contractual Receivable Uncollectible Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Gross Contractual Receivable Uncollectible Entity Emerging Growth Company Entity Emerging Growth Company Short-term lease, terms less than one month, cost Short-Term Lease, Terms Less Than One Month, Cost Short-Term Lease, Terms Less Than One Month, Cost Receivables [Abstract] Receivables [Abstract] Proceeds from debt Proceeds from Issuance of Debt Master services agreement Master Services Agreement [Member] Master Services Agreement [Member] Auditor Name Auditor Name Cover [Abstract] Industrial development revenue bonds Industrial Development Revenue Bonds [Member] Industrial Development Revenue Bonds [Member] Receivable from parent Accounts receivable for Centuri services Due from Related Parties, Current Promissory Note Promissory Note [Member] Promissory Note Net actuarial gain (loss) arising during period, less amortization of unamortized benefit plan cost, net of tax Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax Other Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax Other Total operating expenses Costs and Expenses Other comprehensive income (loss) before reclassifications, net of tax Other Comprehensive Income (Loss), before Reclassifications, Net of Tax Accrued utility revenue Accrued Utility Revenue Accrued utility revenue. Deferred purchased gas costs Deferred Gas Purchases, Current Cash and Cash Equivalents Cash and Cash Equivalents, Policy [Policy Text Block] Less imputed interest Lessee, Operating Lease, Liability, Undiscounted Excess Amount Weighted-average rate of compensation increase Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Rate of Compensation Increase California CALIFORNIA Preferred stock purchase price, exercisable term, beneficial ownership percentage benchmark with passive institutional investor Preferred Stock Purchase Price, Exercisable Term, Beneficial Ownership Percentage Benchmark With Passive Institutional Investor Preferred Stock Purchase Price, Exercisable Term, Beneficial Ownership Percentage Benchmark With Passive Institutional Investor Centuri Centuri Group, Inc. [Member] Centuri Group, Inc. [Member] Alternative minimum tax Alternative Minimum Tax [Member] Alternative Minimum Tax Less imputed interest Finance Lease, Liability, Undiscounted Excess Amount Current: Current Income Tax Expense (Benefit), Continuing Operations [Abstract] Carrying Amount Reported Value Measurement [Member] Auditor [Table] Auditor [Table] Riggs Distler Riggs Distler [Member] Riggs Distler Contract assets Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Contract Assets Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Contract Assets 2026 Finance Lease, Liability, to be Paid, Year Five Common Stock Common Stock [Member] Foreign Income (Loss) from Continuing Operations before Income Taxes, Foreign Operating income Operating Income (Loss) Defined contribution plans, employer contribution amount Defined Contribution Plan, Employer Discretionary Contribution Amount Operating lease liabilities, current Operating Lease, Liability, Current Background, Organization, and Summary of Significant Accounting Policies Organization, Consolidation and Presentation of Financial Statements Disclosure and Significant Accounting Policies [Text Block] 2023 Finite-Lived Intangible Asset, Expected Amortization, Year Two Schedule of Common Stock Activity Schedule Of Common Stock Activity [Table Text Block] Schedule Of Common Stock Activity [Table Text Block] Distribution Gas Distribution [Member] 8% Series, due 2026 Debentures Eight Percentage Series Due Two Thousand And Twenty Six [Member] Debentures Eight Percentage Series Due Two Thousand And Twenty Six [Member] Changes in undistributed stock compensation Compensation expense Share-based Payment Arrangement, Noncash Expense AOCI Attributable to Parent, Net of Tax [Roll Forward] AOCI Attributable to Parent, Net of Tax [Roll Forward] Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Number of types of agreements with customers Number Of Types Of Agreements With Customers Number Of Types Of Agreements With Customers Deferred income taxes Deferred income taxes Increase (Decrease) in Deferred Income Taxes Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis] Net actuarial gain/(loss) Amortization of net actuarial loss Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent [Member] Regulatory adjustments Regulatory Adjustments [Member] Regulatory Adjustments [Member] Operations and Maintenance Expense Operations And Maintenance Expense [Policy Text Block] Operations And Maintenance Expense Policy Text Block Term Loan Facility due December 30, 2022 Term Loan Facility Due December 30, 2022 [Member] Term Loan Facility Due December 30, 2022 Line of credit designated for working capital purposes Line Of Credit Facility Working Capital Purposes Line Of Credit Facility, Working Capital Purposes Benefits paid Defined Benefit Plan, Benefit Obligation, Benefits Paid Accrued general taxes Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Accrued General Taxes Business Combination, Recognized Identifiable Assets Acquired And Liabilities Assumed, Accrued General Taxes Construction expenditures and property additions Payments to Acquire Property, Plant, and Equipment Capital expenditures Payments to Acquire Property, Plant, and Equipment Other current liabilities Other current liabilities Other Liabilities, Current Other deferred credits and other long-term liabilities Other Deferred Credits And Other Long-term Liabilities [Member] Other Deferred Credits And Other Long-term Liabilities [Member] Accumulated benefit obligation Defined Benefit Plan, Accumulated Benefit Obligation Employer contributions Defined Benefit Plan, Plan Assets, Contributions by Employer Deferred tax assets: Deferred Tax Assets, Net [Abstract] 2022 Finite-Lived Intangible Asset, Expected Amortization, Year One Schedule of Regulatory Liabilities [Table] Schedule of Regulatory Liabilities [Table] Consolidation Items [Axis] Consolidation Items [Axis] Operating loss carryforward Operating Loss Carryforwards Accounts receivable, extending period Accounts Receivable, Extending Period Accounts Receivable, Extending Period Common stock, issued (in shares) Common Stock, Shares, Issued Gas utility customer accounts receivable balance Gas Utility Customer Accounts Receivable Gas Utility Customer Accounts Receivable Recognized in AOCI Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, before Tax Accumulated Removal Costs Accumulated Removal Costs [Policy Text Block] Accumulated Removal Costs Policy Text Block. 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Comprehensive income attributable to Southwest Gas Holdings, Inc. 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Lease, Cost Amortization of excess deferred taxes Effective Income Tax Rate Reconciliation, Amortization Of Excess Deferred Taxes, Percent Effective Income Tax Rate Reconciliation, Amortization Of Excess Deferred Taxes, Percent Gross decreases – tax positions in prior period Unrecognized Tax Benefits, Decrease Resulting from Prior Period Tax Positions Customer relationships Customer Relationships [Member] Loss Contingencies [Line Items] Loss Contingencies [Line Items] Long-term debt Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Long-term Debt Total deferred income taxes and other credits Other Liabilities, Noncurrent Benefit obligation for service rendered to date at beginning of year (PBO/PBO/APBO) Benefit obligation at end of year (PBO/PBO/APBO) Defined Benefit Plan, Benefit Obligation Schedule of Carrying Amounts and Estimated Fair Values of Long-Term Debt Schedule of Long-term Debt Instruments [Table Text Block] Deferred Purchased Gas Costs Deferred Purchased Costs [Policy Text Block] Deferred Purchased Costs Policy Text Block. 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Condensed Income Statements, Captions [Line Items] Condensed Income Statements, Captions [Line Items] Operations and maintenance Utilities Operating Expense, Maintenance and Operations Other current liabilities Other Current Liabilities [Member] Utility Infrastructure Services Utility Infrastructure Services Utility Infrastructure Services Segment [Member] Utility Infrastructure Services Segment [Member] Vesting Tranche Three Share-based Payment Arrangement, Tranche Three [Member] Amortization of net actuarial loss Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax Nature of Operations Nature Of Operations [Policy Text Block] Nature Of Operations [Policy Text Block] Weighted-average assumptions (benefit obligation): Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract] Capital Loss Carryforward Capital Loss Carryforward [Member] Long-term debt, less current maturities Long-term debt, less current maturities Long-term Debt, Excluding Current Maturities Deferred Income Tax Expense (Benefit Components [Domain] Deferred Income Tax Expense (Benefit Components [Domain] Deferred Income Tax Expense (Benefit Components [Domain] Schedule of Goodwill [Table] Schedule of Goodwill [Table] Schedule of Regulatory Assets Schedule of Regulatory Assets [Table Text Block] Debt portion Public Utilities, Allowance for Funds Used During Construction, Capitalized, Debt Portion Public Utilities, Allowance for Funds Used During Construction, Capitalized, Debt Portion Lease-related item Deferred Tax Assets, Lease-Related Item Deferred Tax Assets, Lease-Related Item Ownership percentage by noncontrolling owners Ownership percentage by noncontrolling owners Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners Change in short-term portion of credit facilities Proceeds From (Repayments Of) Short-term Portion Of Credit Facilities Proceeds From (Repayments Of) Short-term Portion Of Credit Facilities Beginning balance, tax Ending balance, tax Stockholders' Equity, Including Portion Attributable To Noncontrolling Interest, Tax Stockholders' Equity, Including Portion Attributable To Noncontrolling Interest, Tax Entities [Table] Entities [Table] Centuri Secured Term Loan Facility and Revolving Credit Facility Centuri Secured Term Loan Facility And Revolving Credit Facility [Member] Centuri Secured Term Loan Facility And Revolving Credit Facility Net income Net income Net income Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Total liabilities assumed and noncontrolling interest Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities Summary of Income Before Taxes and Noncontrolling Interest for Domestic and Foreign Operations Schedule of Income before Income Tax, Domestic and Foreign [Table Text Block] Employee investment plan cost Employees' Investment Plan, Cost Employees' Investment Plan, Cost Cash and cash equivalents at beginning of period Cash and cash equivalents at end of period Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Common stock, par (in USD per share) Common Stock, Par or Stated Value Per Share Defined Benefit Plan Disclosure [Line Items] Defined Benefit Plan Disclosure [Line Items] Statement of Comprehensive Income [Abstract] Statement of Comprehensive Income [Abstract] Current assets: Assets, Current [Abstract] Other Proceeds from (Payments for) Other Financing Activities Gross Carrying Amount Finite-Lived Intangible Assets, Gross Gas plant Public Utilities, Property, Plant and Equipment, Gas Plant Public Utilities, Property, Plant and Equipment, Gas Plant Summary of Intangible Assets Schedule of Finite-Lived Intangible Assets [Table Text Block] Cash and cash equivalents Cash and Cash Equivalents, Fair Value Disclosure Weighted average price per share (USD per share) Common Stock Weighted Average Issue Price Per Share Common stock weighted average issue price per share. Drum Drum [Member] Drum Gas plant Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Gas Plant, Net Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Gas Plant, Net Total other comprehensive income (loss), net of tax Other Comprehensive Income (Loss), Net of Tax Accrued interest Interest Payable, Current Deferred Compensation Plan, percent of amount deferred with match Deferred Compensation Plan, Percent Of Amount Deferred With Match Deferred Compensation Plan, Percent Of Amount Deferred With Match Other Comprehensive Income and Accumulated Other Comprehensive Income ("AOCI") Stockholders' Equity Note Disclosure [Text Block] Lapse in statute of limitations Unrecognized Tax Benefits, Reduction Resulting from Lapse of Applicable Statute of Limitations Measurement Basis [Axis] Measurement Basis [Axis] 2026 Finite-Lived Intangible Asset, Expected Amortization, Year Five Number of private placement unsecured senior notes Debt Instrument, Number Of Private Placement Unsecured Senior Notes Debt Instrument, Number Of Private Placement Unsecured Senior Notes Deferred income taxes and other credits: Other Liabilities, Noncurrent [Abstract] Other income and (expenses): Nonoperating Income (Expense) [Abstract] Auditor Firm ID Auditor Firm ID Deferred purchased gas costs Deferred purchased gas costs Increase (Decrease) in Deferred Gas Cost Net cash used in investing activities Net Cash Provided by (Used in) Investing Activities Change in benefit obligations: Defined Benefit Plan, Change in Benefit Obligation [Roll Forward] Portion at Fair Value Measurement Portion at Fair Value Measurement [Member] Changes in current assets and liabilities: Increase (Decrease) in Operating Capital [Abstract] Medium-term notes, 7.92% series, due 2027 Debentures Medium Term Notes Seven Point Nine Two Percentage Series Due Two Thousand And Twenty Seven [Member] Debentures Medium Term Notes Seven Point Nine Two Percentage Series Due Two Thousand and Twenty Seven [Member] 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 Reconciliation of Unrecognized Tax Benefits Summary of Positions for which Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Table Text Block] Payments to acquire business Payments to Acquire Businesses, Gross Deferred payroll taxes Deferred Payroll Taxes [Member] Deferred Payroll Taxes Schedule of Accumulated Benefit Obligation Schedule of Accumulated and Projected Benefit Obligations [Table Text Block] Credit facility maximum borrowing capacity Line of Credit Facility, Maximum Borrowing Capacity Operating cash flows from finance leases Finance Lease, Interest Payment on Liability Foreign currency translation adjustment Goodwill, Foreign Currency Translation Gain (Loss) Schedule of Finite-Lived Intangible Assets Acquired as Part of Business Combination Schedule of Finite-Lived Intangible Assets Acquired as Part of Business Combination [Table Text Block] Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Ownership [Domain] Ownership [Domain] Taxes other than income taxes Taxes, Miscellaneous Gas pipe materials and operating supplies Materials, Supplies, and Other Discount rate Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Weighted-average rate of compensation increase Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase Government fixed income and mortgage backed securities Asset-backed Securities [Member] Prepaids and other current assets Prepaid Expenses and Other Current Assets [Member] Effect of dilutive securities: Dilutive Securities, Effect on Basic Earnings Per Share [Abstract] Unrecognized other postretirement benefit cost Unrecognized Other Postretierment Benefit Cost [Member] Unrecognized Other Postretierment Benefit Cost Accrued pension and other postretirement benefit costs, recovery period Regulatory Assets, Accrued Pension And Other Postretirement Benefit Costs, Recovery Period Regulatory Assets, Accrued Pension And Other Postretirement Benefit Costs, Recovery Period Infrastructure replacement programs and similar Infrastructure Replacement Programs and Similar [Member] Infrastructure replacement programs and similar. Foreign Current Foreign Tax Expense (Benefit) Pension Pension Plan [Member] Regulated Operations [Abstract] Regulated Operations [Abstract] Concentration Risk Benchmark [Axis] Concentration Risk Benchmark [Axis] Other liabilities Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Liabilities Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Liabilities Measurement Period Adjustments, Deferred tax liabilities Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Deferred Tax Liabilities Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Deferred Tax Liabilities Number of preferred stock purchase right, per share of common stock dividend (in shares) Dividends, Common Stock, Paid-in-kind, Number Of Preferred Stock Purchase Right Dividends, Common Stock, Paid-in-kind, Number Of Preferred Stock Purchase Right Schedule of Allowance for Uncollectibles Accounts Receivable, Allowance for Credit Loss [Table Text Block] Schedule of Finite-Lived Intangible Assets [Table] Schedule of Finite-Lived Intangible Assets [Table] Accrued absence time Accrued Absence Time [Member] Accrued absence time. Certain Members Of Riggs Distler Management Certain Members Of Riggs Distler Management [Member] Certain Members Of Riggs Distler Management