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Other Current Liabilities Policy Allowance for doubtful accounts Contract with Customer, Asset, Allowance for Credit Loss Southwest Gas Holdings, Inc. 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Amortization of prior service costs Defined Benefit Plan, Amortization of Prior Service Cost (Credit) Corporate and administrative Corporate, Non-Segment [Member] Regulatory Liability [Domain] Regulatory Liability [Domain] Centuri distribution to redeemable noncontrolling interest Distribution To Redeemable Noncontrolling Interest Distribution To Redeemable Noncontrolling Interest Interest adjustment rate Debt Instrument, Interest Adjustment Rate Debt Instrument, Interest Adjustment Rate Debt instrument interest rate Debt Instrument, Interest Rate, Stated Percentage Award Timing, How MNPI Considered Award Timing, How MNPI Considered [Text Block] Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] Entity Information [Line Items] Entity Information [Line Items] Qualified Retirement Plan Other Pension Plan [Member] Total equity Beginning balance, attributable to parent Ending balance, attributable to parent Equity, Attributable to Parent Current assets held for sale Current assets held for sale adjustment Disposal Group, Including Discontinued Operation, Assets, Current Consolidation Items [Axis] Consolidation Items [Axis] Utility Infrastructure Services Utility Infrastructure Services Segment [Member] Utility Infrastructure Services Segment [Member] Goodwill impairment loss Goodwill, Impairment Loss Deferred Purchased Gas Costs Deferred Purchased Costs [Policy Text Block] Deferred Purchased Costs Foreign currency translation adjustments Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax Schedule of Stock by Class [Table] Schedule of Stock by Class [Table] Revision of Prior Period [Domain] Revision of Prior Period [Domain] Income (loss) before income taxes Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest FSIRS AOCI, Derivative Qualifying as Hedge, Excluded Component, Parent [Member] Common Stock Common Stock Disclosure [Text Block] Common Stock Disclosure [Text Block] Depreciation and amortization Depreciation, Depletion and Amortization, Nonproduction Schedule of Amount Recognized Before Income Tax in Accumulated Other Comprehensive Income Schedule of Amounts Recognized in Other Comprehensive Income (Loss) [Table Text Block] Entity Emerging Growth Company Entity Emerging Growth Company Disposal Group Classification [Domain] Disposal Group Classification [Domain] Tax-exempt Series A, due 2028 Variable Rate Bonds Tax Exempt Series A- Due Two Thousand And Twenty Eight [Member] Variable Rate Bonds Tax Exempt Series Due Two Thousand and Twenty Eight [Member] Condensed Income Statement [Table] Condensed Income Statement [Table] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Named Executive Officers, Footnote Named Executive Officers, Footnote [Text Block] Large commercial Large Commercial [Member] Large commercial. 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Exercise Price Award Exercise Price Significant Accounting Policies [Table] Significant Accounting Policies [Table] Significant Accounting Policies [Table] Total other comprehensive income, net of tax Other Comprehensive Income (Loss), Net of Tax Disposal Group Classification [Axis] Disposal Group Classification [Axis] Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Foreign Currency Items Accumulated Foreign Currency Adjustment Including Portion Attributable to Noncontrolling Interest [Member] Accrued general taxes Accrual for Taxes Other than Income Taxes, Current ASSETS Assets [Abstract] Award Timing MNPI Disclosure Award Timing MNPI Disclosure [Text Block] Issuance of long-term debt, net Proceeds from Issuance of Long-Term Debt Nonrelated Party Nonrelated Party [Member] Contract with Customer, Basis of Pricing [Domain] Contract with Customer, Basis of Pricing [Domain] Withholding remittance - share-based compensation Withholding remittance - share-based compensation Payment, Tax Withholding, Share-Based Payment Arrangement Net income (loss) Net income Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Income taxes paid, net Income taxes paid (received), net Income Taxes Paid, Net Net cash provided by (used in) financing activities Net Cash Provided by (Used in) Financing Activities Deferred income taxes Deferred Income Tax Assets, Net Small commercial Small Commercial [Member] Small commercial. Retirement Plan Type [Axis] Retirement Plan Type [Axis] Other Payments for (Proceeds from) Other Investing Activities Retained earnings Retained Earnings [Member] Current maturities of long-term debt Less: current maturities Long-Term Debt, Current Maturities Forward-starting interest rate swaps (“FSIRS”): Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax [Abstract] Adjustment to Non-PEO NEO Compensation Footnote Adjustment to Non-PEO NEO Compensation Footnote [Text Block] Total capitalization and liabilities Liabilities and Equity Equity AFUDC Public Utilities, Allowance for Funds Used During Construction, Capitalized Cost of Equity Other income and (expenses): Nonoperating Income (Expense) [Abstract] Deferred charges and other assets Deferred charges and other assets Other Assets, Noncurrent Peer Group Total Shareholder Return Amount Peer Group Total Shareholder Return Amount Ownership [Domain] Ownership [Domain] Net forward-starting interest rate swaps Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax Basic (in USD per share) Earnings Per Share, Basic Schedule of Long-term Debt Instruments [Table] Schedule of Long-Term Debt Instruments [Table] Construction work in progress Public Utilities, Property, Plant and Equipment, Construction Work in Progress Equity Valuation Assumption Difference, Footnote Equity Valuation Assumption Difference, Footnote [Text Block] Sale of Stock [Domain] Sale of Stock [Domain] Erroneous Compensation Analysis Erroneous Compensation Analysis [Text Block] Notes, 5.8%, due 2027 Debentures Notes Five Point Eight Percentage, Due Two Thousand And Twenty Seven [Member] Debentures Notes Five Point Eight Percentage, Due Two Thousand And Twenty Seven Other components of net periodic benefit cost Defined Benefit Plan, Actuarial Gain (Loss), Immediate Recognition as Component in Net Periodic Benefit (Cost) Credit Arrangement Duration Trading Arrangement Duration Regulatory Liability [Axis] Regulatory Liability [Axis] Entity Address, City or Town Entity Address, City or Town Award Timing MNPI Considered Award Timing MNPI Considered [Flag] $550 Million Term Loan Credit Agreement Due October 2024 $550 Million Term Loan Credit Agreement Due October 2024 [Member] $550 Million Term Loan Credit Agreement Due October 2024 Schedule of Segment Reporting Information Schedule of Segment Reporting Information, by Segment [Table Text Block] Related Party Related Party [Member] Centuri secured revolving credit facility Centuri Secured Revolving Credit Facility [Member] Centuri secured revolving credit facility. Revision of Prior Period, Error Correction, Adjustment Revision of Prior Period, Error Correction, Adjustment [Member] Discontinued Operations, Disposed of by Sale Discontinued Operations, Disposed of by Sale [Member] Southwest Gas Corporation Southwest Gas Corporation [Member] Southwest gas corporation. Document Transition Report Document Transition Report Award Timing Predetermined Award Timing Predetermined [Flag] Centuri secured term loan facility Centuri Term Loan Facility [Member] Centuri term loan facility. Redemption of equity interest from noncontrolling party Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests Termination Date Trading Arrangement Termination Date Accounts payable Increase (Decrease) in Accounts Payable Common stock, authorized (in shares) Common Stock, Shares Authorized Short-term debt Short-term debt Short-Term Debt Long-term debt, gross Long-Term Debt, Gross Adjustments to reconcile net income (loss) to net cash provided by operating activities: 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] All Trading Arrangements All Trading Arrangements [Member] Centuri And Southwest Gas Holdings, Inc. Centuri And Southwest Gas Holdings, Inc. [Member] Centuri And Southwest Gas Holdings, Inc. [Member] Loss on disposal adjustment Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal All Adjustments to Compensation All Adjustments to Compensation [Member] Reclassification from AOCI, tax Reclassification from AOCI, Current Period, Tax Alternative revenue program revenues (deferrals) Alternative Revenue Program Revenues (Deferrals) Alternative revenue program revenues (deferrals). Award Timing Disclosures [Line Items] Compensation Amount Outstanding Recovery Compensation Amount $450 Million Term Loan $450 Million Term Loan [Member] $450 Million Term Loan Comprehensive income attributable to noncontrolling interests Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest Variable Rate Debt Agreements With Reference To LIBOR Variable Rate Debt Agreements With Reference To LIBOR [Member] Variable Rate Debt Agreements With Reference To LIBOR Other Other Infrastructure Services [Member] Other Infrastructure Services Deferred income taxes and other credits: Other Liabilities, Noncurrent [Abstract] Net income (loss) Net income (loss) Net Income (Loss), Including Portion Attributable to Nonredeemable Noncontrolling Interest Net cost of gas sold Decrease of net cost of gas sold Utilities Operating Expense, Gas and Petroleum Purchased Total noncurrent assets Assets, Noncurrent, Other than Noncurrent Investments and Property, Plant and Equipment Subsequent Event Type [Axis] Subsequent Event Type [Axis] Statement of Comprehensive Income [Abstract] Statement of Comprehensive Income [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] Contributions from parent Proceeds from Contributions from Parent Certain Members Of Riggs Distler Management Certain Members Of Riggs Distler Management [Member] Certain Members Of Riggs Distler Management $300 Million Credit Facility $300 Million Credit Facility [Member] $300 Million Credit Facility Prepaid and other current assets Prepaid and other current assets Prepaid Expense and Other Assets, Current Other current assets and liabilities Other current assets and liabilities Increase (Decrease) in Other Current Assets and Liabilities, Net Insider Trading Arrangements [Line Items] AOCI Attributable to Parent, Net of Tax [Roll Forward] AOCI Attributable to Parent, Net of Tax [Roll Forward] Related Party [Axis] Related Party, Type [Axis] Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Accrued purchased gas cost Unrecovered Costs for Purchased Gas Amount MountainWest MountainWest [Member] MountainWest Natural Gas Distribution Natural Gas Distribution Segment [Member] Natural Gas Distribution Segment Regulatory adjustment Regulatory adjustment 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. Entity Registrant Name Entity Registrant Name Material Terms of Trading Arrangement Material Terms of Trading Arrangement [Text Block] Award Timing Method Award Timing Method [Text Block] Changes in deferred charges and other assets Changes in deferred charges and other assets Increase (Decrease) in Other Operating Assets Debt secured by assets Debt Instrument, Collateral Amount Taxes other than income taxes Taxes, Miscellaneous 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. Adjustment to Compensation, Amount Adjustment to Compensation Amount Document Period End Date Document Period End Date Compensation Actually Paid vs. Net Income Compensation Actually Paid vs. Net Income [Text Block] Adoption Date Trading Arrangement Adoption Date Peer Group Issuers, Footnote Peer Group Issuers, Footnote [Text Block] Non-regulated accumulated provision for depreciation and amortization Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Disposal Group Name [Axis] Disposal Group Name [Axis] Bid contract Bid Contract [Member] Bid contract. Retirement of long-term debt Retirement of long-term debt Repayments of Long-Term Debt Entity Central Index Key Entity Central Index Key Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Equity Shelf Program Equity Shelf Program [Member] Equity Shelf Program [Member] Gains on sale of property and equipment Gain on sale of property Gain (Loss) on Disposition of Property Plant Equipment Non-Rule 10b5-1 Arrangement Terminated Non-Rule 10b5-1 Arrangement Terminated [Flag] Effect of dilutive securities: Dilutive Securities, Effect on Basic Earnings Per Share [Abstract] Income tax expense (benefit) Income tax expense (benefit) Income Tax Expense (Benefit) Notes, 4.05%, due 2032 Debentures Notes Four Point Zero Five Percentage Due Two Thousand And Thirty Two [Member] Debentures Notes Four Point Zero Five Percentage Due Two Thousand And Thirty Two Name Trading Arrangement, Individual Name Reclassification from AOCI, net of tax Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax Impairment of asset held for sale adjustment Impairment of Long-Lived Assets to be Disposed of Debt issuance costs written off Deferred Debt Issuance Cost, Writeoff Schedule of Revenue Disaggregated by Service Type and Contract Type Disaggregation of Revenue [Table Text Block] Common stock issuances Common stock issued, amount Stock Issued During Period, Value, New Issues Equity [Abstract] Equity [Abstract] Regulated operations revenues Total Regulated operations revenues Regulated Operating Revenue, Gas Revenue from contracts with customers Revenue from Contract with Customer, Excluding Assessed Tax Entity [Domain] Entity [Domain] Compensation Actually Paid vs. Company Selected Measure Compensation Actually Paid vs. Company Selected Measure [Text Block] Long-term Debt, Type [Axis] Long-Term Debt, Type [Axis] Amendment Flag Amendment Flag Schedule of Redeemable Noncontrolling Interest Redeemable Noncontrolling Interest [Table Text Block] 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] Legal Entity [Axis] Legal Entity [Axis] Money Market Funds Money Market Funds [Member] Amortization of net actuarial loss Defined Benefit Plan, Amortization of Gain (Loss) Other comprehensive income (loss), net of tax Other comprehensive income, net of tax Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest [Abstract] Cash and Cash Equivalents [Axis] Cash and Cash Equivalents [Axis] Floor interest rate Debt Instrument, Floor Interest Rate Debt Instrument, Floor Interest Rate Deferred income taxes Deferred income taxes Increase (Decrease) in Deferred Income Taxes Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Acquisition of businesses, net of cash acquired Payments to Acquire Businesses, Net of Cash Acquired 2003 Series A, due 2038 Variable Rate Bonds Two Thousand And Three Series A- Due Two Thousand And Thirty Eight [Member] Variable Rate Bonds Two Thousand and Three Series A Due Two Thousand and Thirty Eight [Member] Interest paid, net of amounts capitalized Interest paid, net of amounts capitalized Interest Paid, Excluding Capitalized Interest, Operating Activities Comprehensive income (loss) Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Beginning balance, tax (expense) benefit Ending balance, tax (expense) benefit Stockholders' Equity, Including Portion Attributable To Noncontrolling Interest, Tax Stockholders' Equity, Including Portion Attributable To Noncontrolling Interest, Tax Common stock issued (in shares) Share-Based Compensation Arrangement by Share-Based Payment Award, Shares Issued in Period 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. Credit Facility [Domain] Credit Facility [Domain] Accrued post-closing payment Disposal Group, Not Discontinued Operation, Accrued Post-Closing Payment Disposal Group, Not Discontinued Operation, Accrued Post-Closing Payment Current liabilities held for sale Disposal Group, Including Discontinued Operation, Liabilities, Current Debt, basis spread on variable rate Debt Instrument, Basis Spread on Variable Rate Compensation Actually Paid vs. Other Measure Compensation Actually Paid vs. Other Measure [Text Block] Loss contingency, damages sought value (up to) Loss Contingency, Damages Sought, Value Long-term debt, less current maturities Long-term debt, less current maturities Long-Term Debt, Excluding Current Maturities Diluted (in shares) Weighted average diluted shares (in shares) Weighted Average Number of Shares Outstanding, Diluted Pipeline and Storage Pipeline And Storage Segment [Member] Pipeline And Storage Segment Number of performance share units granted (in shares) Number Of Performance Share Units Granted Number Of Performance Share Units Granted. Forgone Recovery, Explanation of Impracticability Forgone Recovery, Explanation of Impracticability [Text Block] Payment for repurchase of redeemable noncontrolling interest Payments for Repurchase of Redeemable Noncontrolling Interest Schedule of Utility Infrastructure Services Contracts Receivable Contract with Customer, Contract Asset, Contract Liability, and Receivable [Table Text Block] Electric power infrastructure services Electric Power Infrastructure Services [Member] Electric Power Infrastructure Services Revenue Revenue from Contract with Customer [Text Block] Construction expenditures and property additions Construction expenditures and property additions Payments to Acquire Property, Plant, and Equipment Company Selected Measure Amount Company Selected Measure Amount Additional paid-in capital Additional Paid in Capital, Common Stock Additional paid-in capital Additional Paid-in Capital [Member] 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 Total assets Assets Name Awards Close in Time to MNPI Disclosures, Individual Name Equity in earnings of unconsolidated investments Income (Loss) from Equity Method Investments Revision of Prior Period [Axis] Revision of Prior Period [Axis] Cover [Abstract] Cover [Abstract] Line of credit designated as long term debt Line Of Credit Facility Amount Classified As Long Term Debt Line Of Credit Facility, Amount Classified As Long-Term Debt Other Segment Reconciling Items [Member] Debentures Debentures [Member] Debentures [Member] Total deferred income taxes and other credits Other Liabilities, Noncurrent Equity AFUDC Increase (Decrease) in Allowance for Equity Funds Used During Construction Non-NEOs Non-NEOs [Member] Transaction price allocated to unsatisfied performance obligations of contracts Revenue, Remaining Performance Obligation, Amount Components of Net Periodic Benefit Cost Compensation and Employee Benefit Plans [Text Block] Defined benefit pension plans: Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax [Abstract] Gas cost balancing account recovery period Deferred Purchased Gas Costs, Balancing Account Recovery Period Deferred Purchased Gas Costs, Balancing Account Recovery Period Segment Information Segment Reporting Disclosure [Text Block] Change in cash and cash equivalents Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect CASH FLOW FROM FINANCING ACTIVITIES: Net Cash Provided by (Used in) Financing Activities [Abstract] Secured Debt Secured Debt [Member] Industrial development revenue bonds Industrial Development Revenue Bonds [Member] Industrial Development Revenue Bonds [Member] Non-PEO NEO Non-PEO NEO [Member] Time and materials contracts Time-and-Materials Contract [Member] Equity Component [Domain] Equity Component [Domain] Adjustment to Compensation: Adjustment to Compensation [Axis] Notes, 3.8%, due 2046 Debentures Notes Three Point Eight Percentage Due Two Thousand And Forty Six [Member] Debentures notes three point eight percentage due two thousand and forty six. 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] Non-GAAP Measure Description Non-GAAP Measure Description [Text Block] Debt Instrument [Line Items] Debt Instrument [Line Items] Certain Funds Affiliated With Carl C. Icahn Certain Funds Affiliated With Carl C. Icahn [Member] Certain Funds Affiliated With Carl C. Icahn Contracts receivable, net Contracts receivable, net Contract with Customer, Asset, after Allowance for Credit Loss Net actuarial gain Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, after Tax Basic (in shares) Weighted average basic shares (in shares) Weighted Average Number of Shares Outstanding, Basic Entity Current Reporting Status Entity Current Reporting Status Fixed price contracts Fixed-Price Contract [Member] Operating income (loss) Operating Income (Loss) Other revenues Other Revenue Other Revenue Goodwill impairment and loss on sale Goodwill Impairment And Loss On Sale Goodwill Impairment And Loss On Sale Prepaid and other current assets Prepaid And Other Current Assets Policy [Policy Text Block] Prepaid And Other Current Assets Policy AOCI Including Portion Attributable to Noncontrolling Interest AOCI Including Portion Attributable to Noncontrolling Interest [Member] Operating revenues: Revenues [Abstract] Other property and investments Property, Plant and Equipment, Other, Net Income taxes payable, net Income Taxes Payable, Net Income Taxes Payable, Net Schedule of Accounts Receivable Not Eliminated During Consolidation Schedule Of Accounts Receivable Not Eliminated During Consolidation [Table Text Block] Schedule Of Accounts Receivable Not Eliminated During Consolidation Pay vs Performance Disclosure Pay vs Performance Disclosure [Table] Segments [Axis] Segments [Axis] Statement [Line Items] Statement [Line Items] Fair Value Estimate of Fair Value Measurement [Member] Amortization of net actuarial loss Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, after Tax Forgone Recovery due to Disqualification of Tax Benefits, Amount Forgone Recovery due to Disqualification of Tax Benefits, Amount Awards Close in Time to MNPI Disclosures Awards Close in Time to MNPI Disclosures [Table] Borrowings outstanding under facility Long-Term Line of Credit Contributions from Southwest Gas Holdings, Inc. Adjustments To Additional Paid In Capital Contributions From Parent Adjustments to additional paid in capital contributions from parent.