Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Number of options
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding at the beginning of the year (in shares)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number
Exercised during the year (in shares)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period
Forfeited or expired during the year (in shares)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures and Expirations in Period
Outstanding and exercisable at year end (in shares)
Weighted- average exercise price
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Outstanding at the beginning of the year (in USD per share)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price
Exercised during the year (in USD per share)
Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price
Forfeited or expired during the year (in USD per share)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures and Expirations in Period, Weighted Average Exercise Price
Outstanding and exercisable at year end (in USD per share)
Outstanding and exercisable
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value
Exercised
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value
Document And Entity Information [Abstract]
Document and entity information.
Document Information [Table]
Document Information [Table]
Legal Entity [Axis]
Legal Entity [Axis]
Entity [Domain]
Entity [Domain]
Southwest Gas Corporation
Southwest Gas Corporation [Member]
Southwest gas corporation.
Document Information [Line Items]
Document Information [Line Items]
Document Type
Document Type
Amendment Flag
Amendment Flag
Document Period End Date
Document Period End Date
Document Fiscal Year Focus
Document Fiscal Year Focus
Document Fiscal Period Focus
Document Fiscal Period Focus
Trading Symbol
Trading Symbol
Entity Registrant Name
Entity Registrant Name
Entity Central Index Key
Entity Central Index Key
Current Fiscal Year End Date
Current Fiscal Year End Date
Entity Well-known Seasoned Issuer
Entity Well-known Seasoned Issuer
Entity Current Reporting Status
Entity Current Reporting Status
Entity Voluntary Filers
Entity Voluntary Filers
Entity Filer Category
Entity Filer Category
Entity Emerging Growth Company
Entity Emerging Growth Company
Entity Small Business
Entity Small Business
Entity Common Stock, Shares Outstanding
Entity Common Stock, Shares Outstanding
Entity Shell Company
Entity Shell Company
Entity Public Float
Entity Public Float
Share-based compensation plan expense, net of related tax benefits
Allocated Share-based Compensation Expense, Net of Tax
Share-based compensation plan related tax benefits
Employee Service Share-based Compensation, Tax Benefit from Compensation Expense
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Notional Amounts under Swaps Contracts
Schedule of Notional Amounts of Outstanding Derivative Positions [Table Text Block]
Amount of Gain or Losses Recognized in Income on Derivatives
Derivative Instruments, Gain (Loss) [Table Text Block]
Fair Values of Swaps in Consolidated Balance Sheets
Schedule of Derivative Instruments in Statement of Financial Position, Fair Value [Table Text Block]
Paid to and Received from Counterparties for Settlements of Matured Swaps
Paid And Received From Counterparties For Settlements Of Matured Swaps [Table Text Block]
Paid and Received From Counterparties for Settlements of Matured Swaps [Table Text Block]
Regulatory Assets/Liabilities Offsetting Derivatives at Fair Value in Condensed Consolidated Balance Sheets
Regulatory Assets Or Liabilities Offsetting Amounts In Financial Position [Table Text Block]
Regulatory Assets or Liabilities Offsetting Amounts In Financial Position [Table Text Block]
Summary of Financial Assets and Liabilities at Fair Value
Fair Value Measurements, Recurring and Nonrecurring [Table Text Block]
Noncontrolling Interest [Abstract]
Utility Infrastructure Services Noncontrolling Interests
Noncontrolling Interest Disclosure [Text Block]
Receivables [Abstract]
Receivables And Related Allowances [Table]
Receivables And Related Allowances [Table]
Receivables And Related Allowances [Table]
Geographical [Axis]
Geographical [Axis]
Geographical [Domain]
Geographical [Domain]
Arizona
ARIZONA
Nevada
NEVADA
California
CALIFORNIA
Receivables And Related Allowances [Line Items]
Receivables And Related Allowances [Line Items]
Receivables And Related Allowances [Line Items]
Percent of customers by state
Percent Of Customers By State
Percent Of Customers By State
Equity [Abstract]
Accumulated Other Comprehensive Income (Loss) [Table]
Accumulated Other Comprehensive Income (Loss) [Table]
Equity Components [Axis]
Equity Components [Axis]
Equity Component [Domain]
Equity Component [Domain]
Defined Benefit Plans
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
Amortization of prior service cost
Accumulated Defined Benefit Plans Adjustment, Net Prior Service Attributable to Parent [Member]
Amortization of net actuarial loss
Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent [Member]
Regulatory adjustment
Accumulated Defined Benefit Plans Adjustment, Regulartory Adjustment, Attributable to Parent [Member]
Accumulated Defined Benefit Plans Adjustment, Regulartory Adjustment, Attributable to Parent [Member]
FSIRS
AOCI, Derivative Qualifying as Hedge, Excluded Component, Parent [Member]
Foreign Currency Items
Accumulated Foreign Currency Adjustment Including Portion Attributable to Noncontrolling Interest [Member]
AOCI Including Portion Attributable to Noncontrolling Interest
AOCI Including Portion Attributable to Noncontrolling Interest [Member]
AOCI Attributable to Parent
AOCI Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Stockholders' Equity, Including Portion Attributable To Noncontrolling Interest, Other
Stockholders' Equity, Including Portion Attributable To Noncontrolling Interest, Other
Stockholders' Equity, Including Portion Attributable To Noncontrolling Interest, Other
AOCI Attributable to Parent, Net of Tax [Roll Forward]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance, before tax
Stockholders' Equity, Including Portion Attributable To Noncontrolling Interest, Before Tax
Stockholders' Equity, Including Portion Attributable To Noncontrolling Interest, Before Tax
Beginning balance, tax
Stockholders' Equity, Including Portion Attributable To Noncontrolling Interest, Tax
Stockholders' Equity, Including Portion Attributable To Noncontrolling Interest, Tax
Beginning balance
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest
Beginning balance, attributable to parent, before tax
Stockholders' Equity Attributable To Parent, Before Tax
Stockholders' Equity Attributable To Parent, Before Tax
Beginning balance, attributable to parent, tax
Stockholders' Equity Attributable To Parent, Tax
Stockholders' Equity Attributable To Parent, Tax
Beginning balance, attributable to parent
Stockholders' Equity Attributable to Parent
Other comprehensive income (loss) before reclassifications, before tax
Other Comprehensive Income (Loss), before Reclassifications, before Tax
Other comprehensive income (loss) before reclassifications, tax
Other Comprehensive Income (Loss) before Reclassifications, Tax
Other comprehensive income (loss) before reclassifications, net of tax
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax
Reclassification from AOCI, before Tax
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax
Reclassification from AOCI, tax
Reclassification from AOCI, Current Period, Tax
Reclassification from AOCI, net of tax
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax
Other comprehensive income (loss), before tax
Other Comprehensive Income (Loss), before Tax
Other comprehensive income (loss), tax
Other Comprehensive Income (Loss), Tax
Total other comprehensive income, net of tax
Other Comprehensive Income (Loss), Net of Tax
Accumulated Other Comprehensive Income, Reclassification Of Excess Deferred Taxes
Accumulated Other Comprehensive Income, Reclassification Of Excess Deferred Taxes
Accumulated Other Comprehensive Income, Reclassification Of Excess Deferred Taxes
Ending balance, attributable to parent, before tax
Ending balance, attributable to parent, tax
Ending balance, attributable to parent
Ending balance, before tax
Ending balance, tax
Ending balance
Effective income tax rate
Effective Income Tax Rate Reconciliation, Percent
Business Combinations [Abstract]
Schedule of Business Acquisitions, by Acquisition [Table]
Schedule of Business Acquisitions, by Acquisition [Table]
Business Acquisition [Axis]
Business Acquisition [Axis]
Business Acquisition, Acquiree [Domain]
Business Acquisition, Acquiree [Domain]
Neuco
Neuco [Member]
Neuco.
Linetec
Linetec Services, LLC [Member]
Linetec Services, LLC [Member]
Business Acquisition [Line Items]
Business Acquisition [Line Items]
Cash and cash equivalents
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents
Accounts receivable
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Receivables
Other receivables
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Receivables
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Receivables
Revenue earned on contracts in progress in excess of billings
Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Current Assets Other Receivables
Business combination recognized identifiable assets acquired and liabilities assumed current assets other receivables.
Prepaid expenses and other current assets
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Prepaid Expense and Other Assets
Property and equipment
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment
Intangible assets
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill
Goodwill
Goodwill
Total assets acquired
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets
Accounts payable
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Accounts Payable
Accrued liabilities
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Accrued Liabilities
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Accrued Liabilities
Deferred compensation and related accrued taxes
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Compensation And Related Accrued Taxes
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Compensation And Related Accrued Taxes
Redeemable noncontrolling interest
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Other
Current liabilities
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities
Other long-term liabilities
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities
Total liabilities assumed and noncontrolling interest
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities
Net assets acquired
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net
Derivative [Table]
Derivative [Table]
Hedging Relationship [Axis]
Hedging Relationship [Axis]
Hedging Relationship [Domain]
Hedging Relationship [Domain]
Cash Flow Hedging
Cash Flow Hedging [Member]
Derivative [Line Items]
Derivative [Line Items]
Natural gas portfolios, maximum % rate
Natural Gas Portfolios Percentage Rate Range Maximum
The maximum percentage of the natural gas portfolio that is fixed
Gains (losses) recognized in income or other comprehensive income for derivative designated cash flow hedges
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax
Derivative instrument loss at settlement amortization period
Derivative Instruments, Gain (Loss) Reclassification from Accumulated OCI to Income, Estimate of Time to Transfer
Gas utility customer accounts receivable balance (in thousands)
Gas Utility Customer Accounts Receivable
Gas Utility Customer Accounts Receivable
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Other Property and Investments
Investment [Table Text Block]
Summary of Intangible Assets
Schedule of Finite-Lived Intangible Assets [Table Text Block]
Schedule of Estimated Future Amortization of Intangible Assets
Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block]
Schedule of Goodwill
Schedule of Goodwill [Table Text Block]
Schedule of Capitalized and Debt Portion of AFUDC
Schedule of Capitalization [Table Text Block]
Schedule of Other Income (Deductions)
Schedule of Other Nonoperating Income, by Component [Table Text Block]
Schedule of Earnings Per Share, Basic and Diluted
Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]
Revenue from Contract with Customer [Abstract]
Billed on completed contracts and contracts in progress
Billed on completed contracts and contracts in progress
Billed on completed contracts and contracts in progress.
Other receivables
Other Receivables
Contracts receivable, gross
Accounts Receivable, Gross
Allowance for doubtful accounts
Allowance for Doubtful Accounts Receivable
Contracts receivable, net
Accounts Receivable, Net
Debt Disclosure [Abstract]
Schedule of Carrying Amounts and Estimated Fair Values of Long-Term Debt
Schedule of Long-term Debt Instruments [Table Text Block]
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]
Estimated Maturities of Long-Term Debt
Schedule of Maturities of Long-term Debt [Table Text Block]
Long-Term Debt
Long-term Debt [Text Block]
Schedule of Defined Benefit Plans Disclosures [Table]
Schedule of Defined Benefit Plans Disclosures [Table]
Retirement Plan Type [Axis]
Retirement Plan Type [Axis]
Retirement Plan Type [Domain]
Retirement Plan Type [Domain]
Retirement Plan
Pension Plan [Member]
SERP
Supplemental Employee Retirement Plan [Member]
PBOP
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Disclosure [Line Items]
Retirement plan net actuarial loss
Defined Benefit Plan, Expected Amortization of Gain (Loss), Next Fiscal Year
PBOP prior service cost
Defined Benefit Plan, Expected Amortization of Prior Service Cost (Credit), Next Fiscal Year
Income Tax Disclosure [Abstract]
Income Tax [Table]
Income Tax [Table]
Income Tax [Table]
Income Tax [Line Items]
Income Tax [Line Items]
Income Tax [Line Items]
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]
Unrecognized tax benefits at beginning of year
Unrecognized Tax Benefits
Gross increases – tax positions in prior period
Unrecognized Tax Benefits, Increase Resulting from Prior Period Tax Positions
Gross decreases – tax positions in prior period
Unrecognized Tax Benefits, Decrease Resulting from Prior Period Tax Positions
Gross increases – current period tax positions
Unrecognized Tax Benefits, Increase Resulting from Current Period Tax Positions
Gross decreases – current period tax positions
Unrecognized Tax Benefits, Decrease Resulting from Current Period Tax Positions
Settlements
Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities
Lapse in statute of limitations
Unrecognized Tax Benefits, Reduction Resulting from Lapse of Applicable Statute of Limitations
Unrecognized tax benefits at end of year
Regulated Operations [Abstract]
Schedule of Regulatory Assets
Schedule of Regulatory Assets [Table Text Block]
Schedule of Regulatory Liabilities
Schedule of Regulatory Liabilities [Table Text Block]
Background, Organization and Summary of Significant Accounting Policies
Organization, Consolidation and Presentation of Financial Statements Disclosure and Significant Accounting Policies [Text Block]
Schedule of Long-term Debt Instruments [Table]
Schedule of Long-term Debt Instruments [Table]
Long-term Debt, Type [Axis]
Long-term Debt, Type [Axis]
Long-term Debt, Type [Domain]
Long-term Debt, Type [Domain]
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]
2008 Series A, due 2038
Variable Rate Bonds Two Thousand And Eight Series A- Due Two Thousand And Thirty Eight [Member]
Variable Rate Bonds Two Thousand and Eight Series A Due Two Thousand and Thirty Eight [Member]
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]
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]
Debt Instrument [Line Items]
Debt Instrument [Line Items]
Effective interest rates
Debt Instrument, Interest Rate, Effective Percentage
Income Taxes [Table]
Income Taxes [Table]
Income Taxes [Table]
Income Taxes [Line Items]
Income Taxes [Line Items]
Income Taxes [Line Items]
U.S. federal statutory income tax rate
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent
Net state taxes
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent
Tax credits
Effective Income Tax Rate Reconciliation, Tax Credit, Percent
Company owned life insurance
Effective Income Tax Rate Reconciliation Company Owned Life Insurance
Effective income tax rate reconciliation, company owned life insurance.
Change in U.S. Federal Income Tax Rate
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Percent
All other differences
Effective Income Tax Rate Reconciliation, Other Adjustments, Percent
Consolidated effective income tax rate
Commitments and Contingencies Disclosure [Abstract]
Loss Contingencies [Table]
Loss Contingencies [Table]
Centuri
Centuri Construction Group [Member]
Centuri Construction Group [Member]
Loss Contingencies [Line Items]
Loss Contingencies [Line Items]
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.
Additional self-insured retention amount of general liability
Additional Self Insured Retention Amount Of General Liability
Additional self-insured retention amount of general liability
Significant Accounting Policies [Table]
Significant Accounting Policies [Table]
Significant Accounting Policies [Table]
Ownership [Axis]
Ownership [Axis]
Ownership [Domain]
Ownership [Domain]
IntelliChoice Energy LLC
Intellichoice Energy Llc [Member]
Intellichoice Energy Llc [Member]
Inventory [Axis]
Inventory [Axis]
Inventory [Domain]
Inventory [Domain]
Gas Pipe Materials and Supplies
Gas Pipe Inventory And Operating Supplies [Member]
Gas pipe inventory and operating supplies.
Cash and Cash Equivalents [Axis]
Cash and Cash Equivalents [Axis]
Cash and Cash Equivalents [Domain]
Cash and Cash Equivalents [Domain]
Money Market Funds
Money Market Funds [Member]
Investment, Name [Axis]
Investment, Name [Axis]
Investment, Name [Domain]
Investment, Name [Domain]
W.S. Nicholls Western Construction LTD
WS Nicholls Western Construction Ltd [Member]
WS Nicholls Western Construction Ltd.
Balance Sheet Location [Axis]
Balance Sheet Location [Axis]
Balance Sheet Location [Domain]
Balance Sheet Location [Domain]
Prepaids and other current assets
Prepaid Expenses and Other Current Assets [Member]
Significant Accounting Policies [Line Items]
Significant Accounting Policies [Line Items]
Significant Accounting Policies [Line Items]
Ownership percentage by parent
Noncontrolling Interest, Ownership Percentage by Parent
Proceeds from contributed capital
Proceeds from Contributed Capital
Percentage of equity interest acquired
Percentage Of Equity Interest Acquired
Percentage Of Equity Interest Acquired
Percentage of voting interests acquired
Business Acquisition, Percentage of Voting Interests Acquired
VIR ownership percentage
Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage
Equity method investment amount
Equity Method Investments
Dividends received
Proceeds from Dividends Received
Exposure to loss as a result of its investment
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount
Earnings from equity method investment
Income (Loss) from Equity Method Investments
Amortization expenses
Amortization of Intangible Assets
Money market fund investments
Cash and Cash Equivalents, Fair Value Disclosure
Business combination consideration
Business Combination, Consideration Transferred
Cumulative foreign earnings
Undistributed Earnings of Foreign Subsidiaries
Gas pipe materials and operating supplies
Materials, Supplies, and Other
Prepaid and other current assets
Regulatory Assets, Current
Goodwill impairment charges
Goodwill, Impairment Loss
Intangible assets
Finite-Lived Intangible Assets, Net
Reclassification from AOCI to retained earnings resulting from TCJA
Tax Cuts and Jobs Act of 2017, Reclassification from AOCI to Retained Earnings Tax Effect
Tax Cuts and Jobs Act of 2017, reclassification from AOCI to retained earnings tax effect.
Statement of Financial Position [Abstract]
Common stock, par (in USD per share)
Common Stock, Par or Stated Value Per Share
Common stock, authorized (in shares)
Common Stock, Shares Authorized
Common stock, issued (in shares)
Common Stock, Shares, Issued
Common stock, outstanding (in shares)
Common Stock, Shares, Outstanding
Statement of Comprehensive Income [Abstract]
Statement [Table]
Statement [Table]
Statement [Line Items]
Statement [Line Items]
Net Income
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest
Net Income from continuing operations
Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest
Other comprehensive income (loss), net of tax
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest [Abstract]
Defined benefit pension plans:
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax [Abstract]
Net actuarial gain (loss)
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, after Tax
Amortization of prior service cost
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, after Tax
Amortization of net actuarial loss
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, after Tax
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.
Net defined benefit pension plans
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax
Forward-starting interest rate swaps (“FSIRS”):
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax [Abstract]
Amounts reclassified into net income
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax
Net forward-starting interest rate swaps
Foreign currency translation adjustments
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax
Comprehensive income
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest
Discontinued operations-construction services, net income
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent
Comprehensive income (loss) attributable to noncontrolling interests
Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest
Discontinued operations - utility infrastructure services, foreign currency translation adjustments
Other Comprehensive Income Foreign Currency Transaction And Translation Adjustment From Discontinued Operation Net Of Tax Portion Attributable To Parent
Other comprehensive income foreign currency transaction and translation adjustment from discontinued operation net of tax portion attributable to parent.
Discontinued operations - utility infrastructure services, comprehensive income
Comprehensive Income From Discontinued Operation Net Of Tax Including Portion Attributable To Noncontrolling Interest
Comprehensive income from discontinued operation net of tax including portion attributable to noncontrolling interest.
Discontinued operations - utility infrastructure services, comprehensive income (loss) attributable to noncontrolling interests
Other Comprehensive Income (Loss) From Discontinued Operation, Net Of Tax, Portion Attributable To Noncontrolling Interest
Other Comprehensive Income (Loss) From Discontinued Operation, Net Of Tax, Portion Attributable To Noncontrolling Interest
Comprehensive income attributable to discontinued operations – utility infrastructure services
Other Comprehensive Income Loss From Discontinued Operation Net Of Tax
Other comprehensive income loss from discontinued operation net of tax.
Comprehensive income attributable to Southwest Gas Holdings, Inc.
Comprehensive Income (Loss), Net of Tax, Attributable to Parent
Share-Based Compensation
Disclosure of Compensation Related Costs, Share-based Payments [Text Block]
Derivative Instruments, Gain (Loss) [Table]
Derivative Instruments, Gain (Loss) [Table]
Regulatory Agency [Axis]
Regulatory Agency [Axis]
Regulatory Agency [Domain]
Regulatory Agency [Domain]
Regulatory Deferral Accounting Treatment
Regulatory Deferral Accounting Treatment [Member]
Regulatory Deferral Accounting Treatment [Member]
Income Statement Location [Axis]
Income Statement Location [Axis]
Income Statement Location [Domain]
Income Statement Location [Domain]
Net cost of gas sold
Net Cost Of Gas Sold [Member]
Net Cost Of Gas Sold [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain or (loss) recognized in income on derivative
Derivative, Gain (Loss) on Derivative, Net
Retirement Benefits [Abstract]
Range [Axis]
Range [Axis]
Range [Domain]
Range [Domain]
Maximum
Maximum [Member]
Minimum
Minimum [Member]
Qualified Retirement Plan
Other Pension Plan [Member]
Maximum contribution of employer
Defined Contribution Plan, Employer Matching Contribution, Percent of Match
Deferment of annual cash compensation
Deferment Of Annual Cash Compensation
Deferment of annual cash compensation
Matching contribution of employer
Matching Contribution Of Employer
Matching contribution of employer
Period of additional option to receive payment
Additional Deferred Compensation Payment Options Period Of Payment Period
Additional Deferred Compensation Payment Options, period of payment, period
Deferred compensation, percentage of multiple interest rate
Floating Interest Rate Index
Floating Interest Rate Index
Increments of changes to the discount rate, basis points
Increments Of Changes To Discount Rate
Increments of changes to the discount rate
Future estimated funding amount
Future Estimated Funding Amount
Future estimated funding amount
Per capita cost of covered health care benefits medical rate trend assumption
Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Next Fiscal Year
Segment Reporting [Abstract]
Schedule of Segment Reporting Information, by Segment [Table]
Schedule of Segment Reporting Information, by Segment [Table]
Concentration Risk Benchmark [Axis]
Concentration Risk Benchmark [Axis]
Concentration Risk Benchmark [Domain]
Concentration Risk Benchmark [Domain]
Net Assets, Geographic Area
Net Assets, Geographic Area [Member]
Concentration Risk Type [Axis]
Concentration Risk Type [Axis]
Concentration Risk Type [Domain]
Concentration Risk Type [Domain]
Geographic Concentration Risk
Geographic Concentration Risk [Member]
United States
UNITED STATES
Segment Reporting Information [Line Items]
Segment Reporting Information [Line Items]
Long-lived assets
Concentration Risk, Percentage
Number of reportable segments
Number of Reportable Segments
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Disposal Groups, Including Discontinued Operations [Table]
Disposal Groups, Including Discontinued Operations [Table]
Segments [Axis]
Segments [Axis]
Segments [Domain]
Segments [Domain]
Utility Infrastructure Services
Construction Services [Member]
Construction Services [Member]
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]
Utility infrastructure services revenues
Disposal Group, Including Discontinued Operation, Construction Revenues
Disposal Group, Including Discontinued Operation, Construction Revenues
Operating expenses:
Disposal Group Including Discontinued Operation Operating Expense [Abstract]
Disposal Group Including Discontinued Operation Operating Expense [Abstract]
Utility infrastructure services expenses
Disposal Group, Including Discontinued Operation, Construction Expenses
Disposal Group, Including Discontinued Operation, Construction Expenses
Depreciation and amortization
Depreciation and Amortization, Discontinued Operations
Operating income
Disposal Group, Including Discontinued Operation, Operating Income (Loss)
Other income (deductions)
Disposal Group Including Discontinued Operation Other Income (Expense)
Disposal Group Including Discontinued Operation Other Income Expense
Net interest deductions
Disposal Group Including Discontinued Operation Interest Income Expense Net
Disposal Group Including Discontinued Operation Interest Income Expense Net
Income before income taxes
Discontinued Operation, Income (Loss) from Discontinued Operation, before Income Tax
Income tax expense
Discontinued Operation, Tax Effect of Discontinued Operation
Discontinued operations - utility infrastructure services, Income
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest
Net income attributable to noncontrolling interests
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Noncontrolling Interest
Discontinued operations – utility infrastructure services – net income
Condensed Income Statement [Table]
Condensed Income Statement [Table]
Condensed Income Statements, Captions [Line Items]
Condensed Income Statements, Captions [Line Items]
Utility infrastructure services revenues
Revenue from Contract with Customer, Including Assessed Tax
Net income attributable to Southwest Gas Holdings, Inc.
Net Income (Loss) Attributable to Parent
Short-Term Debt
Short-term Debt [Text Block]
Quarterly Financial Information Disclosure [Abstract]
Schedule Of Quarterly Financial Information [Table]
Schedule Of Quarterly Financial Information [Table]
Schedule Of Quarterly Financial Information [Table]
Operating Activities [Axis]
Operating Activities [Axis]
Operating Activities [Domain]
Operating Activities [Domain]
Continuing Operations
Continuing Operations [Member]
Discontinued Operations
Discontinued Operations [Member]
Schedule Of Quarterly Financial Information [Line Items]
Schedule Of Quarterly Financial Information [Line Items]
Schedule Of Quarterly Financial Information [Line Items]
Operating revenues
Regulated and Unregulated Operating Revenue
Operating income
Operating Income (Loss)
Net income (loss)
Net income attributable to Southwest Gas Holdings, Inc.
Basic earnings per common share (in USD per share)
Earnings Per Share, Basic
Diluted earnings per common share (in USD per share)
Earnings Per Share, Diluted
Average basic shares (in shares)
Weighted Average Number of Shares Outstanding, Basic
Effect of dilutive securities:
Dilutive Securities, Effect on Basic Earnings Per Share [Abstract]
Stock options (in shares)
Incremental Common Shares Attributable to Dilutive Effect of Call Options and Warrants
Management Incentive Plan shares (in shares)
Incremental Common Shares Attributable to Dilutive Effect of Equity Forward Agreements
Restricted stock units (in shares)
Incremental Common Shares Attributable to Dilutive Effect of Nonvested Shares with Forfeitable Dividends
Average diluted shares (in shares)
Weighted Average Number of Shares Outstanding, Diluted
Number of performance share units granted
Number Of Performance Share Units Granted
Number Of Performance Share Units Granted.
Schedule Of Regulatory Assets And Liabilities [Table]
Schedule Of Regulatory Assets And Liabilities [Table]
Schedule Of Regulatory Assets And Liabilities [Table]
Regulatory Asset [Axis]
Regulatory Asset [Axis]
Regulatory Asset [Domain]
Regulatory Asset [Domain]
Accrued pension and other postretirement benefit costs
Accrued Pension And Other Postretirement Benefit Costs [Member]
Accrued Pension And Other Postretirement Benefit Costs [Member]
Unrealized net loss on non-trading derivatives (Swaps)
Unrealized Loss On Non Trading Derivatives, Assets [Member]
Unrealized Loss On Non-Trading Derivatives, Assets
Deferred purchased gas costs
Deferred Purchased Gas Costs, Assets [Member]
Deferred Purchased Gas Costs, Assets
Accrued purchased gas costs
Accrued Purchased Gas Costs [Member]
Accrued Purchased Gas Costs [Member]
Unamortized premium on reacquired debt
Unamortized Premium On Reacquired Debt [Member]
Unamortized Premium On Reacquired Debt [Member]
Accrued absence time
Accrued Absence Time [Member]
Accrued absence time.
Margin & interest-tracking
Margin and Interest Tracking Accounts [Member]
Margin and interest tracking accounts.
Other regulatory assets
Regulatory Assets Other [Member]
Regulatory Assets Other [Member]
Regulatory Liability [Axis]
Regulatory Liability [Axis]
Regulatory Liability [Domain]
Regulatory Liability [Domain]
Deferred purchased gas costs
Deferred Purchased Gas Costs, Liabilities [Member]
Deferred Purchased Gas Costs, Liabilities [Member]
Accumulated removal costs
Accumulated Removal Costs [Member]
Accumulated Removal Costs [Member]
Unrealized net gain on non-trading derivatives (Swaps)
Unrealized Loss On Non Trading Derivatives, Liabilities [Member]
Unrealized Loss On Non Trading Derivatives, Liabilities [Member]
Unamortized gain on reacquired debt
Unamortized Gain On Reacquired Debt [Member]
Unamortized Gain On Reacquired Debt [Member]
Regulatory excess deferred taxes and gross -up
Regulatory Offsets To Deferred Tax Balances [Member]
Regulatory offsets to deferred tax balances.
Other regulatory liabilities
Regulatory Liabilities Other [Member]
Regulatory Liabilities Other [Member]
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]
Regulatory Assets And Liabilities [Line Items]
Regulatory Assets And Liabilities [Line Items]
Regulatory Assets And Liabilities [Line Items]
Regulatory assets, total
Regulatory Assets
Regulatory liabilities, total
Regulatory Liabilities
Net regulatory liabilities
Net Regulatory Assets
Schedule of Share-Based Plan Compensation Expense, Including Cash Award
Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table Text Block]
Schedule of Stock Options Activity
Share-based Compensation, Stock Options, Activity [Table Text Block]
Summary of Market Prices of Common Stock
Summary Of Market Value Of Company Common Stock [Table Text Block]
Summary Of Market Value Of Company Common Stock [Table Text Block]
Schedule of Nonvested Performance and Restricted Stock Unit Plans
Schedule of Nonvested Share Activity [Table Text Block]
Statement of Cash Flows [Abstract]
CASH FLOW FROM OPERATING ACTIVITIES:
Net Cash Provided by (Used in) Operating Activities [Abstract]
Net income
Income from discontinued operations
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]
Depreciation and amortization
Depreciation, Depletion and Amortization, Nonproduction
Deferred income taxes
Increase (Decrease) in Deferred Income Taxes
Changes in current assets and liabilities:
Increase (Decrease) in Operating Capital [Abstract]
Accounts receivable, net of allowances
Increase (Decrease) in Accounts Receivable
Accrued utility revenue
Increase (Decrease) in Unbilled Receivables
Deferred purchased gas costs
Increase (Decrease) in Deferred Gas Cost
Accounts payable
Increase (Decrease) in Accounts Payable
Accrued taxes
Increase (Decrease) in Accrued Taxes Payable
Other current assets and liabilities
Increase (Decrease) in Other Current Assets and Liabilities, Net
Gains on sale
Gain (Loss) on Disposition of Property Plant Equipment
Changes in undistributed stock compensation
Share-based Compensation
AFUDC
Increase (Decrease) in Allowance for Equity Funds Used During Construction
Changes in other assets and deferred charges
Increase (Decrease) in Other Operating Assets
Changes in other liabilities and deferred credits
Increase (Decrease) in Other Operating Liabilities
Net cash provided by operating activities
Net Cash Provided by (Used in) Operating Activities
Net cash provided by operating activities, continuing operations
Net Cash Provided by (Used in) Operating Activities, Continuing Operations
CASH FLOW FROM INVESTING ACTIVITIES:
Net Cash Provided by (Used in) Investing Activities [Abstract]
Construction expenditures and property additions
Payments to Acquire Property, Plant, and Equipment
Acquisition of businesses, net of cash acquired
Payments to Acquire Businesses, Net of Cash Acquired
Changes in customer advances
Increase (Decrease) in Customer Advances
Miscellaneous inflows
Proceeds From Miscellaneous Investing Activities
Proceeds from miscellaneous investing activities.
Net cash used in investing activities
Net Cash Provided by (Used in) Investing Activities
Net cash used in investing activities, continuing operations
Net Cash Provided by (Used in) Investing Activities, Continuing Operations
CASH FLOW FROM FINANCING ACTIVITIES:
Net Cash Provided by (Used in) Financing Activities [Abstract]
Issuance of common stock, net
Proceeds from Issuance of Common Stock
Contributions from parent
Proceeds from Contributions from Parent
Dividends paid
Payments of Ordinary Dividends, Common Stock
Centuri distribution to redeemable noncontrolling interest
Payments of Ordinary Dividends, Noncontrolling Interest
Issuance of long-term debt, net
Proceeds from Issuance of Long-term Debt
Retirement of long-term debt
Repayments of Long-term Debt
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
Change in short-term debt
Proceeds from (Repayments of) Short-term Debt
Principal payments on capital lease obligations
Repayments of Debt and Capital Lease Obligations
Redemption of Centuri shares from noncontrolling parties
Payments for Repurchase of Redeemable Noncontrolling Interest
Withholding remittance – share-based compensation
Payments Related to Tax Withholding for Share-based Compensation
Other
Proceeds from (Payments for) Other Financing Activities
Net cash provided by (used in) financing activities
Net Cash Provided by (Used in) Financing Activities
Net cash provided by (used in) financing activities, continuing operations
Net Cash Provided by (Used in) Financing Activities, Continuing Operations
Net cash provided by discontinued operating activities
Cash Provided by (Used in) Operating Activities, Discontinued Operations
Net cash used in discontinued investing activities
Cash Provided by (Used in) Investing Activities, Discontinued Operations
Net cash used in discontinued financing activities
Cash Provided by (Used in) Financing Activities, Discontinued Operations
Effects of currency translation on cash and cash equivalents
Effect of Exchange Rate on Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents
Effects of currency translation on cash and cash equivalents, including discontinued operations
Effect of Exchange Rate on Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Disposal Group, Including Discontinued Operations
Change in cash and cash equivalents
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect
Change in cash and cash equivalents included in discontinued operations utility infrastructure services assets
Net Cash Provided by (Used in) Discontinued Operations
Change in cash and cash equivalents of continuing operations
Net Cash Provided by (Used in) Continuing Operations
Cash and cash equivalents at beginning of period
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents
Cash and cash equivalents at end of period
Supplemental information:
Supplemental Cash Flow Information [Abstract]
Interest paid, net of amounts capitalized
Interest Paid, Excluding Capitalized Interest, Operating Activities
Income taxes paid (received)
Income Taxes Paid, Net
Schedule of Finite-Lived Intangible Assets [Table]
Schedule of Finite-Lived Intangible Assets [Table]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets [Line Items]
2019
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months
2020
Finite-Lived Intangible Assets, Amortization Expense, Year Two
2021
Finite-Lived Intangible Assets, Amortization Expense, Year Three
2022
Finite-Lived Intangible Assets, Amortization Expense, Year Four
2023
Finite-Lived Intangible Assets, Amortization Expense, Year Five
Thereafter
Finite-Lived Intangible Assets, Amortization Expense, after Year Five
Net Carrying Amount
Summary of Fair Values of Assets Acquired and Liabilities Assumed
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed [Table Text Block]
Schedule of Pro Forma Consolidated Financial Information
Business Acquisition, Pro Forma Information [Table Text Block]
Schedule of Statements of Income Operations
Condensed Income Statement [Table Text Block]
2019
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months
2020
Long-term Debt, Maturities, Repayments of Principal in Year Two
2021
Long-term Debt, Maturities, Repayments of Principal in Year Three
2022
Long-term Debt, Maturities, Repayments of Principal in Year Four
2023
Long-term Debt, Maturities, Repayments of Principal in Year Five
Schedule of Short-term Debt [Table]
Schedule of Short-term Debt [Table]
Credit Facility [Axis]
Credit Facility [Axis]
Credit Facility [Domain]
Credit Facility [Domain]
Credit Facility $100 Million Expires March 2022
Credit Facility $100 Million Expires March 2022 [Member]
Credit Facility $100 Million Expires March 2022 [Member]
Variable Rate [Axis]
Variable Rate [Axis]
Variable Rate [Domain]
Variable Rate [Domain]
Alternative Base Rate
Alternative Base Rate [Member]
Alternative Base Rate [Member]
LIBOR
London Interbank Offered Rate (LIBOR) [Member]
Short-term Debt [Line Items]
Short-term Debt [Line Items]
Credit facility maximum borrowing capacity
Line of Credit Facility, Maximum Borrowing Capacity
Applicable margin
Debt Instrument, Basis Spread on Variable Rate
Commitment fee percentage
Line of Credit Facility, Commitment Fee Percentage
Maximum current borrowing usage
Line of Credit Facility, Maximum Amount Outstanding During Period
Short term borrowings outstanding
Short-term Debt
Line of credit designated for working capital purposes
Line Of Credit Facility Working Capital Purposes
Line Of Credit Facility, Working Capital Purposes
Short-term borrowings, weighted average interest rate
Short-term Debt, Weighted Average Interest Rate, at Point in Time
Pension
2019
Defined Benefit Plan, Expected Future Benefit Payment, Next Twelve Months
2020
Defined Benefit Plan, Expected Future Benefit Payment, Year Two
2021
Defined Benefit Plan, Expected Future Benefit Payment, Year Three
2022
Defined Benefit Plan, Expected Future Benefit Payment, Year Four
2023
Defined Benefit Plan, Expected Future Benefit Payment, Year Five
2024-2028
Defined Benefit Plan, Expected Future Benefit Payment, Five Fiscal Years Thereafter
Gas Operations
Natural Gas Operations [Member]
Natural Gas Operations [Member]
Utility Infrastructure Services
Utility Infrastructure Services Segment [Member]
Utility Infrastructure Services Segment [Member]
Consolidation Items [Axis]
Consolidation Items [Axis]
Consolidation Items [Domain]
Consolidation Items [Domain]
Intersegment sales
Intersegment Eliminations [Member]
Operating Segments
Operating Segments [Member]
Other
Segment Reconciling Items [Member]
Revenues
Revenues
Interest revenue
Interest Income, Other
Interest expense
Interest Expense
Income tax expense
Income Tax Expense (Benefit)
Segment net income
Segment assets
Assets
Capital expenditures
Finite-Lived Intangible Assets by Major Class [Axis]
Finite-Lived Intangible Assets by Major Class [Axis]
Finite-Lived Intangible Assets, Major Class Name [Domain]
Finite-Lived Intangible Assets, Major Class Name [Domain]
Customer relationships
Customer Relationships [Member]
Trade names and trademarks
Trademarks and Trade Names [Member]
Customer contracts backlog
Customer Contracts [Member]
Noncompete agreements
Noncompete Agreements [Member]
Gross Carrying Amount
Finite-Lived Intangible Assets, Gross
Accumulated Amortization
Finite-Lived Intangible Assets, Accumulated Amortization
Revenue
Revenue from Contract with Customer [Text Block]
Cost of Retirement Plan
Schedule of Costs of Retirement Plans [Table Text Block]
Schedule of Assumptions Used
Schedule of Assumptions Used [Table Text Block]
Schedule of Defined Benefit Plans Disclosures
Schedule of Defined Benefit Plans Disclosures [Table Text Block]
Schedule of Accumulated Benefit Obligation
Schedule of Accumulated and Projected Benefit Obligations [Table Text Block]
Schedule of Expected Benefit Payments
Schedule of Expected Benefit Payments [Table Text Block]
Schedule of New Accounting Pronouncements
Schedule of New Accounting Pronouncements and Changes in Accounting Principles [Table Text Block]
Schedule of Net Benefit Cost
Schedule of Net Benefit Costs [Table Text Block]
Schedule of Amounts Recognized in Other Comprehensive Income
Schedule of Amounts Recognized in Other Comprehensive Income (Loss) [Table Text Block]
Schedule of Fair Value of Plan Assets
Schedule of Allocation of Plan Assets [Table Text Block]
Income Taxes
Income Tax Disclosure [Text Block]
Utility Plant and Leases
Utility Plant And Leases Disclosure [Text Block]
Utility Plant And Leases Disclosure [Text Block]
Other Comprehensive Income and Accumulated Other Comprehensive Income ("AOCI")
Stockholders' Equity Note Disclosure [Text Block]
Net actuarial loss (gain)
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, before Tax
Amortization of prior service cost
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, before Tax
Amortization of net actuarial loss
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax
Regulatory adjustment
Defined Benefit Plan Regulatory Adjustment Before Tax
Defined benefit plan, regulatory adjustment before-tax.
Recognized in other comprehensive (income) loss
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), after Reclassification Adjustment, before Tax
Net periodic benefit costs recognized in net income
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)
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
Public Utility, Property, Plant and Equipment [Table]
Public Utility, Property, Plant and Equipment [Table]
Public Utility [Axis]
Public Utility [Axis]
Utility Plant [Domain]
Utility Plant [Domain]
Gas plant
Natural Gas Processing Plant [Member]
Property, Plant and Equipment, Type [Axis]
Property, Plant and Equipment, Type [Axis]
Property, Plant and Equipment, Type [Domain]
Property, Plant and Equipment, Type [Domain]
Gas, Transmission and Distribution Plant
Gas, Transmission and Distribution Equipment [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utility, Property, Plant and Equipment [Line Items]
Annual utility depreciation and amortization expense percentage
Public Utilities, Property, Plant and Equipment, Disclosure of Composite Depreciation Rate for Plants in Service
Amortization of intangibles
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]
Summary of Income Tax Expense (Benefit)
Schedule of Components of Income Tax Expense (Benefit) [Table Text Block]
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]
Reconciliation of U.S Federal Statutory Rate to Consolidated Effective Tax Rate
Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]
Deferred Tax Assets and Liabilities
Schedule of Deferred Tax Assets and Liabilities [Table Text Block]
Reconciliation of Unrecognized Tax Benefits
Summary of Positions for which Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Table Text Block]
Summary of Income Before Taxes for Continuing and Discontinued Operations
Schedule Of Income Before Income Tax, Continuing And Discontinued Operations [Table Text Block]
Schedule Of Income Before Income Tax, Continuing And Discontinued Operations [Table Text Block]
Schedule of Stock by Class [Table]
Schedule of Stock by Class [Table]
Sale of Stock [Axis]
Sale of Stock [Axis]
Sale of Stock [Domain]
Sale of Stock [Domain]
Equity Shelf Program
Equity Shelf Program [Member]
Equity Shelf Program [Member]
Plan Name [Axis]
Plan Name [Axis]
Plan Name [Domain]
Plan Name [Domain]
Restricted Stock/Unit Plan and Management Incentive Plan
Restricted Stock/Unit Plan, And Management Incentive Plan [Member]
Restricted Stock/Unit Plan, And Management Incentive Plan [Member]
Dividend Reinvestment and Stock Purchase Plan
Dividend Reinvestment And Stock Purchase Plan [Member]
Dividend Reinvestment And Stock Purchase Plan [Member]
Class of Stock [Line Items]
Class of Stock [Line Items]
Maximum value of common stock issuance
Maximum Aggregate Market Value Of Potential Stock Issuance
The amount of maximum aggregate market value of potential stock issuance under the program.
Gross proceeds
Proceeds From Issuance Of Common Stock, Gross
Proceeds From Issuance Of Common Stock, Gross
Less: agent commissions
Payments of Stock Issuance Costs
Net proceeds
Number of shares sold (in shares)
Stock Issued During Period, Shares, New Issues
Weighted average price per share (USD per share)
Common Stock Weighted Average Issue Price Per Share
Common stock weighted average issue price per share.
Common stock available for sale under the program
Maximum Amount Of Common Stock Available For Sale
Maximum amount of common stock available for sale.
Number of common stock sold through public offering (in shares)
Sale of Stock, Number of Shares Issued in Transaction
Sale of stock price (in USD per hare)
Sale of Stock, Price Per Share
Proceeds from sale of common stock
Sale of Stock, Consideration Received on Transaction
Underwriters discount
Payments for Underwriting Expense
Common stock issued (in shares)
Share-based Compensation Arrangement by Share-based Payment Award, Shares Issued in Period
Common stock issuances
Stock Issued During Period, Value, New Issues
Shares registered and available for issuance
Common Stock, Capital Shares Reserved for Future Issuance
Common Stock
Common Stock Disclosure [Text Block]
Common Stock Disclosure [Text Block]
Segment Information
Segment Reporting Disclosure [Text Block]
Discount rate
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate
Weighted-average rate of compensation increase
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase
Asset return assumption
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets
ASSETS
Assets [Abstract]
Utility plant:
Public Utilities, Property, Plant and Equipment, Net [Abstract]
Gas plant
Public Utilities, Property, Plant and Equipment, Plant in Service
Less: accumulated depreciation
Public Utilities, Property, Plant and Equipment, Accumulated Depreciation
Construction work in progress
Public Utilities, Property, Plant and Equipment, Construction Work in Progress
Net utility plant
Public Utilities, Property, Plant and Equipment, Net
Other property and investments
Other Property And Investments
Aggregate carrying amount, as of the balance sheet date, of other property and investments not separately presented elsewhere in the balance sheet.
Current assets:
Assets, Current [Abstract]
Cash and cash equivalents
Cash and Cash Equivalents, at Carrying Value
Accounts receivable, net of allowances
Accounts Receivable, Net, Current
Accrued utility revenue
Accrued Utility Revenue
Accrued utility revenue.
Income taxes receivable, net
Income Taxes Receivable, Current
Deferred purchased gas costs
Deferred Gas Cost
Prepaid and other current assets
Prepaid Expense and Other Assets, Current
Total current assets
Assets, Current
Noncurrent assets:
Assets, Noncurrent [Abstract]
Goodwill
Deferred income taxes
Deferred Income Tax Assets, Net
Deferred charges and other assets
Other Assets, Noncurrent
Total noncurrent assets
Assets, Noncurrent, Other than Noncurrent Investments and Property, Plant and Equipment
Total assets
CAPITALIZATION AND LIABILITIES
Liabilities and Equity [Abstract]
Capitalization:
Capitalization, Long-term Debt and Equity [Abstract]
Common stock
Common Stock, Value, Issued
Additional paid-in capital
Additional Paid in Capital, Common Stock
Accumulated other comprehensive income (loss), net
Accumulated Other Comprehensive Income (Loss), Net of Tax
Retained earnings
Retained Earnings (Accumulated Deficit)
Total Southwest Gas Holdings, Inc. equity
Noncontrolling interest
Stockholders' Equity Attributable to Noncontrolling Interest
Total equity
Redeemable noncontrolling interest
Redeemable Noncontrolling Interest, Equity, Carrying Amount
Long-term debt, less current maturities
Long-term Debt, Excluding Current Maturities
Total capitalization
Capitalization, Long-term Debt and Equity
Commitments and contingencies (Note 10)
Commitments and Contingencies
Current liabilities:
Liabilities, Current [Abstract]
Current maturities of long-term debt
Long-term Debt, Current Maturities
Short-term debt
Accounts payable
Accounts Payable, Current
Customer deposits
Customer Deposits, Current
Income taxes payable, net
Income Taxes Payable Net
Income taxes payable net.
Accrued general taxes
Accrual for Taxes Other than Income Taxes, Current
Accrued interest
Interest Payable, Current
Deferred purchased gas costs
Deferred Gas Purchases, Current
Payable to parent
Due to Affiliate, Current
Other current liabilities
Other Liabilities, Current
Total current liabilities
Liabilities, Current
Deferred income taxes and other credits:
Other Liabilities, Noncurrent [Abstract]
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.
Accumulated removal costs
Other Accrued Liabilities, Noncurrent
Other deferred credits and other long-term liabilities
Deferred Credits and Other Liabilities, Noncurrent
Total deferred income taxes and other credits
Other Liabilities, Noncurrent
Total capitalization and liabilities
Liabilities and Equity
Schedule of Operating Leased Assets [Table]
Schedule of Operating Leased Assets [Table]
Natural Gas Operations
Southwest [Member]
Southwest [Member]
Operating Leased Assets [Line Items]
Operating Leased Assets [Line Items]
2019
Operating Leases, Future Minimum Payments Due, Next Twelve Months
2020
Operating Leases, Future Minimum Payments, Due in Two Years
2021
Operating Leases, Future Minimum Payments, Due in Three Years
2022
Operating Leases, Future Minimum Payments, Due in Four Years
2023
Operating Leases, Future Minimum Payments, Due in Five Years
Thereafter
Operating Leases, Future Minimum Payments, Due Thereafter
Total minimum lease payments
Operating Leases, Future Minimum Payments Due
Restructuring and Related Activities [Abstract]
Summary of Discontinued Operations - Construction Services in Condensed Consolidated Balance Sheet and Condensed Consolidated Income Statements
Disposal Groups, Including Discontinued Operations [Table Text Block]
Nature of Operations
Nature Of Operations [Policy Text Block]
Nature Of Operations [Policy Text Block]
Basis of Presentation
Basis of Accounting, Policy [Policy Text Block]
Consolidation
Consolidation, Policy [Policy Text Block]
Fair Value Measurements
Fair Value Measurement, Policy [Policy Text Block]
Net Utility Plant
Property, Plant and Equipment, Policy [Policy Text Block]
Intangible Assets
Intangible Assets, Finite-Lived, Policy [Policy Text Block]
Cash and Cash Equivalents
Cash and Cash Equivalents, Policy [Policy Text Block]
Income Taxes
Income Tax, Policy [Policy Text Block]
Deferred Purchased Gas Costs
Deferred Purchased Costs [Policy Text Block]
Deferred Purchased Costs Policy Text Block.
Prepaids and Other Current Assets
Prepaid And Other Current Assets Policy [Policy Text Block]
Prepaid And Other Current Assets Policy [Policy Text Block]
Goodwill
Goodwill and Intangible Assets, Goodwill, Policy [Policy Text Block]
Other Current Liabilities
Other Current Liabilities [Policy Text Block]
Other Current Liabilities [Policy Text Block]
Accumulated Removal Costs
Accumulated Removal Costs [Policy Text Block]
Accumulated Removal Costs Policy Text Block.
Revenue Recognition
Revenue from Contract with Customer [Policy Text Block]
Operations and Maintenance Expense
Operations And Maintenance Expense [Policy Text Block]
Operations And Maintenance Expense Policy Text Block
Depreciation and Amortization
Regulatory Depreciation and Amortization, Policy [Policy Text Block]
Allowance for Funds Used During Construction ("AFUDC")
Allowance for Funds Used During Construction, Policy [Policy Text Block]
Other Income (Deductions)
Other Income Expense [Policy Text Block]
Other Income Expense [Policy Text Block]
Foreign Currency Translation
Foreign Currency Transactions and Translations Policy [Policy Text Block]
Earnings Per Share
Earnings Per Share, Policy [Policy Text Block]
Recently Accounting Standards Updates
New Accounting Pronouncements, Policy [Policy Text Block]
Subsequent Events
Subsequent Events, Policy [Policy Text Block]
Pension and Other Postretirement Benefits
Pension and Other Postretirement Benefits Disclosure [Text Block]
Rental Payments And Lease Payments Included In Operating Expenses [Table]
Rental Payments And Lease Payments Included In Operating Expenses [Table]
Rental Payments And Lease Payments Included In Operating Expenses [Table]
Rental Payments And Lease Payments Included In Operating Expenses [Line Items]
Rental Payments And Lease Payments Included In Operating Expenses [Line Items]
Rental Payments And Lease Payments Included In Operating Expenses [Line Items]
Consolidated rental payments/lease expense
Operating Leases, Rent Expense, Net
Schedule of Common Stock Activity
Schedule Of Common Stock Activity [Table Text Block]
Schedule Of Common Stock Activity [Table Text Block]
Quarterly Financial Data (Unaudited)
Quarterly Financial Information [Text Block]
Accumulated benefit obligation
Defined Benefit Plan, Accumulated Benefit Obligation
Deferred tax assets:
Deferred Tax Assets, Net [Abstract]
Deferred income taxes for future amortization of ITC and excess deferred taxes
Deferred Tax Assets, Tax Credit Carryforwards
Employee benefits
Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits
Alternative minimum tax credit
Deferred Tax Assets, Tax Credit Carryforwards, Alternative Minimum Tax
Net operating losses and credits
Deferred Tax Assets Operating Loss And Tax Credit Carryforwards Net
Deferred Tax Assets, Operating Loss and Tax Credit Carryforwards, Net
Interest rate swap
Deferred Tax Assets, Derivative Instruments
Other
Deferred Tax Assets, Other
Valuation allowance
Deferred Tax Assets, Valuation Allowance
Deferred tax assets, total
Deferred Tax Assets, Net of Valuation Allowance
Deferred tax liabilities:
Deferred Tax Liabilities, Net [Abstract]
Property-related items, including accelerated depreciation
Deferred Tax Liabilities, Property, Plant and Equipment
Regulatory balancing accounts
Deferred Tax Liabilities, Regulatory Assets and Liabilities
Unamortized ITC
Accumulated Deferred Investment Tax Credit
Debt-related costs
Deferred Tax Liabilities, Deferred Expense, Debt Issuance Costs
Intangibles
Deferred Tax Liabilities, Intangible Assets
Other
Deferred Tax Liabilities, Other
Deferred tax liabilities, total
Deferred Tax Liabilities, Net
Net deferred tax liabilities
Deferred Income Tax Liabilities, Net
Contract notional amounts
Derivative, Nonmonetary Notional Amount
Fair Values Derivatives, Balance Sheet Location, by Derivative Contract Type [Table]
Fair Values Derivatives, Balance Sheet Location, by Derivative Contract Type [Table]
Derivative Instrument [Axis]
Derivative Instrument [Axis]
Derivative Contract [Domain]
Derivative Contract [Domain]
Swaps
Swap [Member]
Other current liabilities
Other Current Liabilities [Member]
Other deferred credits
Other Deferred Credits [Member]
Other Deferred Credits [Member]
Deferred charges and other assets
Deferred Charges And Other Assets [Member]
Deferred Charges And Other Assets [Member]
Derivatives, Fair Value [Line Items]
Derivatives, Fair Value [Line Items]
Asset Derivatives
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value
Liability Derivatives
Derivative Instruments Not Designated as Hedging Instruments, Liability, at Fair Value
Net Total
Other Derivatives Not Designated as Hedging Instruments at Fair Value, Net
Customer accounts receivable
Amount of FSIRS existing AOCI losses expected to reclassified income in next twelve months
Interest Rate Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months, Net
SEC Schedule, 12-09, Valuation Allowances and Reserves Type [Axis]
SEC Schedule, 12-09, Valuation Allowances and Reserves Type [Axis]
SEC Schedule, 12-09, Valuation Allowances and Reserves [Domain]
SEC Schedule, 12-09, Valuation Allowances and Reserves [Domain]
Allowance for Uncollectibles
SEC Schedule, 12-09, Allowance, Credit Loss [Member]
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning Balance
SEC Schedule, 12-09, Valuation Allowances and Reserves, Amount
Additions charged to expense
SEC Schedule, 12-09, Valuation Allowances and Reserves, Additions, Charge to Cost and Expense
Accounts written off, less recoveries
SEC Schedule, 12-09, Valuation Allowances and Reserves, Deduction
Ending Balance
Fair Value Hierarchy and NAV [Axis]
Fair Value Hierarchy and NAV [Axis]
Fair Value Hierarchy and NAV [Domain]
Fair Value Hierarchy and NAV [Domain]
Fair Value, Inputs, Level 1 and 2
Fair Value, Inputs, Level 1, 2 and 3 [Member]
Level 1 – Quoted prices in active markets for identical financial assets
Fair Value, Inputs, Level 1 [Member]
Level 2 – Significant other observable inputs
Fair Value, Inputs, Level 2 [Member]
Insurance company general account contracts
Fair Value Measured at Net Asset Value Per Share [Member]
Defined Benefit Plan, Plan Assets, Category [Axis]
Defined Benefit Plan, Plan Assets, Category [Axis]
Defined Benefit Plan, Plan Assets, Category [Domain]
Defined Benefit Plan, Plan Assets, Category [Domain]
Mutual funds
Mutual Fund [Member]
International
International [Member]
International.
U.S. equity securities
Defined Benefit Plan, Equity Securities, US [Member]
Emerging markets
Emerging Markets [Member]
Emerging markets.
Private commingled fixed income funds
Defined Benefit Plan, Private Commingled Fixed Income Funds [Member]
Defined Benefit Plan, Private Commingled Fixed Income Funds [Member]
Pooled funds and mutual funds
Pooled Funds And Mutual Funds [Member]
Pooled funds and mutual funds.
Government fixed income and mortgage backed securities
Asset-backed Securities [Member]
Defined benefit plan, plan assets, amount
Defined Benefit Plan, Plan Assets, Amount
Commitments and Contingencies
Commitments and Contingencies Disclosure [Text Block]
Income Statement [Abstract]
Operating revenues:
Revenues [Abstract]
Gas operating revenues
Regulated Operating Revenue, Gas
Utility infrastructure services revenues
Total operating revenues
Operating expenses:
Costs and Expenses [Abstract]
Net cost of gas sold
Utilities Operating Expense, Gas and Petroleum Purchased
Operations and maintenance
Utilities Operating Expense, Maintenance and Operations
Taxes other than income taxes
Taxes, Miscellaneous
Utility infrastructure services expenses
Cost of Goods and Services Sold
Total operating expenses
Costs and Expenses
Operating income
Other income and (expenses):
Nonoperating Income (Expense) [Abstract]
Net interest deductions
Other income (deductions)
Other Nonoperating Income (Expense)
Total other income and (expenses)
Nonoperating Income (Expense)
Income tax expense
Net income from continuing operations
Net income (loss) attributable to noncontrolling interests
Net Income (Loss) Attributable to Noncontrolling Interest
Discontinued operations - utility infrastructure services, income before income taxes
Discontinued operations - utility infrastructure services, income tax expense
Discontinued operations-construction services - Noncontrolling interests
Income - discontinued operations
Net income attributable to Southwest Gas Holdings, Inc.
Basic earnings per share (in USD per share)
Diluted earnings per share (in USD per share)
Average number of common shares (in shares)
Average shares (assuming dilution) (in shares)
Derivative Assets
Derivative Asset
Derivative Liabilities
Derivative Liability
Net Assets (Liabilities)
Derivative Assets (Liabilities), at Fair Value, Net
Current:
Current Income Tax Expense (Benefit), Continuing Operations [Abstract]
Federal
Current Federal Tax Expense (Benefit)
State
Current State and Local Tax Expense (Benefit)
Foreign
Current Foreign Tax Expense (Benefit)
Total current income tax expense
Current Income Tax Expense (Benefit)
Deferred:
Deferred Income Tax Expense (Benefit), Continuing Operations [Abstract]
Federal
Deferred Federal Income Tax Expense (Benefit)
State
Deferred State and Local Income Tax Expense (Benefit)
Foreign
Deferred Foreign Income Tax Expense (Benefit)
Total deferred income tax expense
Deferred Income Tax Expense (Benefit)
Total income tax expense
Discontinued operations
Total income tax expense
Income Tax Expense (Benefit), Intraperiod Tax Allocation
Adjustments for New Accounting Pronouncements [Axis]
Adjustments for New Accounting Pronouncements [Axis]
Type of Adoption [Domain]
Type of Adoption [Domain]
Accounting Standards Update 2015-04
Accounting Standards Update 2015-04 [Member]
Restatement [Axis]
Restatement [Axis]
Restatement [Domain]
Restatement [Domain]
As Reported
Previously Reported [Member]
Reclassification
Restatement Adjustment [Member]
Schedule of Net Utility Plant
Public Utility Property, Plant, and Equipment [Table Text Block]
Schedule of Depreciation and Amortization Expense
Schedule Of Depreciation And Amortization Expense [Table Text Block]
Schedule Of Depreciation And Amortization Expense Table Text Block
Schedule of Rental Payments for Operating Leases
Schedule of Rent Expense [Table Text Block]
Schedule of Future Minimum Lease Payments for Operating Leases
Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Transaction price allocated to unsatisfied performance obligations of contracts
Revenue, Remaining Performance Obligation, Amount
Revenue, remaining performance obligation, expected timing of satisfaction, period
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period
Disaggregation of Revenue [Table]
Disaggregation of Revenue [Table]
Product and Service [Axis]
Product and Service [Axis]
Product and Service [Domain]
Product and Service [Domain]
Gas infrastructure services
Gas Infrastructure Services [Member]
Gas Infrastructure Services [Member]
Electric power infrastructure services
Electric Power Infrastructure Services [Member]
Electric Power Infrastructure Services [Member]
Other
Other Infrastructure Services [Member]
Other Infrastructure Services [Member]
Contract with Customer, Basis of Pricing [Axis]
Contract with Customer, Basis of Pricing [Axis]
Contract with Customer, Basis of Pricing [Domain]
Contract with Customer, Basis of Pricing [Domain]
Master services agreement
Master Services Agreement [Member]
Master Services Agreement [Member]
Bid contract
Bid Contract [Member]
Bid contract.
Unit priced contracts
Unit Priced Contracts [Member]
Unit priced contracts.
Fixed priced contracts
Fixed-price Contract [Member]
Time and materials contracts
Time-and-materials Contract [Member]
Disaggregation of Revenue [Line Items]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers
Revenue from Contract with Customer, Excluding Assessed Tax
Significant Components Of Deferred Income Tax Expense [Table]
Significant Components Of Deferred Income Tax Expense [Table]
Significant Components Of Deferred Income Tax Expense [Table]
Income Tax Authority [Axis]
Income Tax Authority [Axis]
Income Tax Authority [Domain]
Income Tax Authority [Domain]
Property-related items
Property Related Items [Member]
Property-Related Items [Member]
Purchased gas cost adjustments
Purchased Gas Cost Adjustments [Member]
Purchased Gas Cost Adjustments [Member]
Employee benefits
Employee Benefits [Member]
Employee Benefits [Member]
Regulatory Adjustments
Regulatory Adjustments [Member]
Regulatory Adjustments [Member]
All other deferred
All Other Deferred [Member]
All Other Deferred [Member]
Significant Components Of Deferred Income Tax Expense [Line Items]
Significant Components Of Deferred Income Tax Expense [Line Items]
Significant Components Of Deferred Income Tax Expense [Line Items]
Deferred federal and state:
Total deferred federal and state
Deferred Federal And State Income Tax Expense Benefit
Deferred federal and state income tax expense benefit
Deferred ITC, net
Deferred Investment Tax Credit, Net
Deferred Investment Tax Credit, Net
Storage
Storage [Member]
Storage [Member]
Transmission
Gas Transmission [Member]
Distribution
Gas Distribution [Member]
General
General [Member]
General [Member]
Other
Other Plant in Service [Member]
Software and software-related intangibles
Computer Software, Intangible Asset [Member]
Schedule of Regulatory Liabilities [Table]
Schedule of Regulatory Liabilities [Table]
State mandated public purpose programs (including low income and conservation programs)
State Mandated Public Purpose Programs [Member]
State and mandated public purpose programs (including low income and conservation programs).
Margin and interest-tracking accounts
Environmental compliance programs
Environmental Compliance Programs [Member]
Environmental compliance programs.
Regulatory accounts for differences related to pension funding
Regulatory Accounts For Differences Related To Pension Funding [Member]
Regulatory accounts for differences related to pension funding.
Other
Other Miscellaneous Regulatory Liabilities [Member]
Other Miscellaneous Regulatory Liabilities [Member]
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]
Regulatory Liabilities [Line Items]
Regulatory Liabilities [Line Items]
Regulatory liabilities
Secured Revolving Credit Facility and Term Loan
Secured Revolving Credit Facility Term Loan [Member]
Secured Revolving Credit Facility Term Loan [Member]
Trade Names
Trade Names [Member]
Customer Contracts
Ownership percentage by noncontrolling owners
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners
Subsequent collection of acquiree's unbilled receivable
Business Combination, Subsequent Collection Of Acquiree's Unbilled Receivable
Business Combination, Subsequent Collection Of Acquiree's Unbilled Receivable
Acquiree's liabilities related to future payments to employees
Business Combination, Acquiree's Liabilities Related To Future Payments To Employees
Business Combination, Acquiree's Liabilities Related To Future Payments To Employees
Consideration held back for estimated purchase price and working capital adjustment to be paid
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Consideration Transferred
Consideration transferred related to future estimated tax payments
Business Combination, Consideration Transferred Related To Future Estimated Tax Payments
Business Combination, Consideration Transferred Related To Future Estimated Tax Payments
Payment to acquiree's employees
Business Combination, Payment To Acquiree's Employees
Business Combination, Payment To Acquiree's Employees
Net consideration of acquisition less assumed debt
Acquired intangible assets
Acquired intangible assets, weighted average useful life
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life
Acquisition costs
Acquisition Costs, Period Cost
Goodwill expected tax deductible amount
Business Acquisition, Goodwill, Expected Tax Deductible Amount
Canada
CANADA
Total Revenues
Schedule of Accounts Receivable
Schedule of Accounts, Notes, Loans and Financing Receivable [Table Text Block]
Schedule of Percent of Customers by State
Schedule Of Percent Of Customers By State [Table Text Block]
Schedule of percent of customers by state table text block.
Schedule of Allowance for Uncollectibles
SEC Schedule, 12-09, Schedule of Valuation and Qualifying Accounts Disclosure [Text Block]
Employee Investment Plan cost
Defined Contribution Plan, Cost
Accounting Standards Update 2014-09
Accounting Standards Update 2014-09 [Member]
Initial Application Period Cumulative Effect Transition [Axis]
Initial Application Period Cumulative Effect Transition [Axis]
Initial Application Period Cumulative Effect Transition [Domain]
Initial Application Period Cumulative Effect Transition [Domain]
Difference between Revenue Guidance in Effect before and after Topic 606
Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
Number of operating segment
Number of Operating Segments
Number of types of services provided to customers
Number Of Types Of Services Provided To Customers
Number Of Types Of Services Provided To Customers
Number of customers
Number Of Customers
Number Of Customers
Number of types of agreements with customers
Number Of Types Of Agreements With Customers
Number Of Types Of Agreements With Customers
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
Revenue earned on contracts in progress in excess of billings
Contract with Customer, Asset, Net
Increases due to amounts billed to customers in excess of revenue earned during the period
Increases Due to Amounts Billed to Customers in Excess of Revenue Earned During Period
Increases due to amounts billed to customers in excess of revenue earned during the period.
Change in contract liability, revenue recognized
Contract with Customer, Liability, Revenue Recognized
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
Accounts Receivable for Services
Accounts Receivable For Services [Table Text Block]
Accounts Receivable For Services Table Text Block.
Schedule of Revenues by Geographic Area
Revenue from External Customers by Geographic Areas [Table Text Block]
Schedule of Segment Reporting Information
Schedule of Segment Reporting Information, by Segment [Table Text Block]
Regulatory assets/(liabilities) offsetting the derivatives at fair value
Derivative Fair Value Of Regulatory Assets Liabilities Offset Amount
The net amount as of the balance sheet date of the fair value of derivative assets and (liabilities) that in accordance with regulatory treatment is recoverable in utility rates.
Schedule of Quarterly Financial Information
Quarterly Financial Information [Table Text Block]
Statement of Stockholders' Equity [Abstract]
Common Stock
Common Stock [Member]
Dividends declared (in USD pre share)
Common Stock, Dividends, Per Share, Declared
Reorganization Impacts - Discontinued Operations Solely Related to Southwest Gas Corporation
Restructuring and Related Activities Disclosure [Text Block]
Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Abstract]
Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Table]
Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Table]
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]
Income from discontinued operations before income taxes
Total income before income taxes
Income (Loss), Including Portion Attributable to Noncontrolling Interest, before Tax
Schedule of Regulatory Assets [Table]
Schedule of Regulatory Assets [Table]
Infrastructure replacement programs and similar
Infrastructure Replacement Programs and Similar [Member]
Infrastructure replacement programs and similar.
Other
Other Miscellaneous Regulatory Asset [Member]
Other Miscellaneous Regulatory Asset [Member]
Self-insurance cost
Self-Insurance Cost [Member]
Self-Insurance Cost [Member]
Regulatory Assets [Line Items]
Regulatory Assets [Line Items]
Regulatory assets
Contracts receivable, net
Amounts billed in excess of revenue earned on contracts
Contract with Customer, Liability
Derivatives
Derivative Instruments and Hedging Activities Disclosure [Text Block]
Additional Paid-in Capital
Additional Paid-in Capital [Member]
Accumulated Other Comprehensive Income (Loss)
Retained Earnings
Retained Earnings [Member]
Non- controlling Interest
Noncontrolling Interest [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance (in shares)
Common stock issuances (in shares)
Net income (loss)
Net Income (Loss), Including Portion Attributable to Nonredeemable Noncontrolling Interest
Redemption value adjustments
Noncontrolling Interest, Change in Redemption Value
Foreign currency exchange translation adjustment
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, before Tax, Portion Attributable to Parent
Net actuarial gain (loss) arising during the period, less amortization of unamortized benefit plan cost, net of tax
FSIRS amounts reclassified to net income, net of tax
Reclassification of excess deferred taxes
Change in ownership of noncontrolling interest
Noncontrolling Interest, Increase from Subsidiary Equity Issuance
Stock-based compensation
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition
Dividends declared
Dividends, Common Stock
Contributions from Southwest Gas Holdings, Inc.
Adjustments To Additional Paid In Capital Contributions From Parent
Adjustments to additional paid in capital contributions from parent.
Ending balance (in shares)
Increase (Decrease) in Temporary Equity [Roll Forward]
Increase (Decrease) in Temporary Equity [Roll Forward]
Beginning balance
Temporary Equity, Carrying Amount, Including Portion Attributable to Noncontrolling Interests
Redeemable noncontrolling interest acquired
Temporary Equity, Stock Issued During Period, Value, New Issues
Net income (loss)
Temporary Equity, Net Income
Redemption value adjustments
Temporary Equity, Accretion to Redemption Value, Adjustment
Foreign currency exchange translation adjustment
Temporary Equity, Foreign Currency Translation Adjustments
Redemption of Centuri shares from noncontrolling parties
Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests
Centuri distribution to redeemable noncontrolling interest
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders
Ending balance
U.S.
Income (Loss) from Continuing Operations before Income Taxes, Domestic
Foreign
Income (Loss) from Continuing Operations before Income Taxes, Foreign
Total income before income taxes
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest
Southwest Gas Credit Facility
Southwest Gas Credit Facility [Member]
Southwest Gas Credit Facility [Member]
Commercial Paper Program
Commercial Paper Program [Member]
Commercial Paper Program [Member]
Centuri term loan facility
Centuri Term Loan Facility [Member]
Centuri term loan facility.
Line of Credit
Line of Credit [Member]
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.
Canadian Dealer Offered Rate
Canadian Dealer Offered Rate [Member]
Canadian Dealer Offered Rate [Member]
Alternative Base Rate
Base Rate [Member]
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
Long-term debt
Long-term Debt
Borrowings outstanding under facility
Long-term Line of Credit
Minimum current borrowing usage
Line Of Credit Facility Minimum Amount Outstanding During Period
Line Of Credit Facility Minimum Amount Outstanding During Period
Notes payable
Notes Payable
Debt instrument interest rate
Debt Instrument, Interest Rate, Stated Percentage
Debt instrument discount rate
Debt Instrument Discount Rate
Debt Instrument Discount Rate
Debt secured by assets
Debt Instrument, Collateral Amount
Issuance of additional debt
Debt Instrument Covenant Compliance Credit Risk Exposure Amount
Debt instrument covenant compliance credit risk exposure amount.
Equity cushion relating to minimum net worth requirement
Equity Cushion Relating To Minimum Net Worth Requirement
Equity cushion relating to minimum net worth requirement.
Equity cushion relating to minimum fixed charge ratio coverage requirement
Equity Cushion Relating To Minimum Fixed Charge Ratio Coverage Requirement
Equity cushion relating to minimum fixed charge ratio coverage requirement.
Percentage of maximum dividend payout restriction
Percentage Of Maximum Dividend Payout Restriction
Percentage of maximum dividend payout restriction.
Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table]
Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table]
Management Incentive Plan
Management Incentive Plan [Member]
Management incentive plan.
Restricted Stock/Unit Plan
Restricted Stock/Unit Plan [Member]
Restricted Stock/Unit Plan [Member]
Award Type [Axis]
Award Type [Axis]
Equity Award [Domain]
Equity Award [Domain]
Performance Shares
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of nonvested/unissued shares
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Nonvested/unissued at beginning of year (in shares)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number
Granted (in shares)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period
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
Forfeited or expired (in shares)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period
Vested and issued (in shares)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period
Nonvested/unissued at year end (in shares)
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]
Beginning balance (in USD per share)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value
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
Forfeited or expired (in USD per share)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value
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
Ending balance (in USD per share)
Schedule of Goodwill [Table]
Schedule of Goodwill [Table]
Goodwill [Line Items]
Goodwill [Line Items]
Goodwill [Roll Forward]
Goodwill [Roll Forward]
Goodwill, Beginning balance
Goodwill from Neuco acquisition
Goodwill, Acquired During Period
Foreign currency translation adjustment
Goodwill, Foreign Currency Translation Gain (Loss)
Goodwill, Ending balance
Summary of Redeemable Noncontrolling Interest
Redeemable Noncontrolling Interest [Table Text Block]
Regulatory Assets and Liabilities
Schedule of Regulatory Assets and Liabilities [Text Block]
Business Acquisitions
Business Combination Disclosure [Text Block]
Related Tax Effects Allocated to Each Component of Other Comprehensive Income (Loss)
Schedule Of Related Tax Effects Allocated To Components Of Other Comprehensive Income (Loss) [Table Text Block]
Related tax effects of defined benefit pension plans and designated hedging activities reclassifications and amounts arising during the period included in other comprehensive income (loss).
Schedule of Estimated Amounts Amortized from Accumulated Other Comprehensive Income or Regulatory Assets into Net Periodic Benefit Cost
Schedule Of Estimated Amounts Amortized From Accumulated Other Comprehensive Income Or Regulatory Assets Into Net Periodic Benefit Cost [Table Text Block]
Schedule Of Estimated Amounts Amortized From Accumulated Other Comprehensive Income Or Regulatory Assets Into Net Periodic Benefit Cost Table Text Block.
Rollforward of Accumulated Other Comprehensive Income
Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]
Amount Recognized Before Income Tax in Accumulated Other Comprehensive Income
Paid to counterparties
Payments For Derivative Instrument Operating Activities
The cash outflow for derivative instruments during the period, which are classified as operating activities, excluding those designated as hedging instruments.
Received from counterparties
Proceeds from Derivative Instrument, Investing Activities
Noncontrolling Interest [Table]
Noncontrolling Interest [Table]
Noncontrolling Interest [Line Items]
Noncontrolling Interest [Line Items]
Purchase price of the previous owners' equity interest in Centuri
Payments to Acquire Interest in Subsidiaries and Affiliates
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
Redeemable noncontrolling interest, fair value
Redeemable Noncontrolling Interest, Equity, Fair Value
Summary of Revenue Disaggregated by Service Type and Contract Type
Disaggregation of Revenue [Table Text Block]
Summary of Information about Receivables, Revenue Earned on Contracts in Progress in Excess of Billings, Which are Included Within Accounts Receivable, Net of Allowances, and Amounts Billed in Excess of Revenue Earned on Contracts
Schedule of information about receivables, revenue earned on contracts in progress in excess of billings, and amounts billed in excess of revenue earned on contracts [Table Text Block]
Schedule of information about receivables, revenue earned on contracts in progress in excess of billings, and amounts billed in excess of revenue earned on contracts.
Schedule of Construction Services Contracts Receivable
Schedule of Construction Services Contracts Receivable [Table Text Block]
Schedule of Construction Services Contracts Receivable [Table Text Block]
Measurement Basis [Axis]
Measurement Basis [Axis]
Fair Value Measurement [Domain]
Fair Value Measurement [Domain]
Portion at Fair Value Measurement [Member]
Portion at Fair Value Measurement [Member]
Carrying Amount
Reported Value Measurement [Member]
Market Value
Estimate of Fair Value Measurement [Member]
Debt Instrument [Axis]
Debt Instrument [Axis]
Debt Instrument, Name [Domain]
Debt Instrument, Name [Domain]
Debentures
Debentures [Member]
Debentures [Member]
IDRBs
Industrial Development Revenue Bonds [Member]
Industrial Development Revenue Bonds [Member]
Notes, 4.45%, due 2020
Debentures Notes Four Point Four Five Percentage Due Two Thousand And Twenty [Member]
Debentures Notes Four Point Four Five Percentage Due Two Thousand And Twenty [Member]
Notes, 6.1%, due 2041
Debentures Notes Six Point One Percentage Due Two Thousand And Forty One [Member]
Debentures Notes Six Point One Percentage Due Two Thousand And Forty One [Member]
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]
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]
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.
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]
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]
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]
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]
Revolving credit facility and commercial paper
Revolving Credit Facility And Commercial Paper [Member]
Revolving Credit Facility And Commercial Paper [Member]
Centuri other debt obligations
Centuri Other Debt Obligations [Member]
Centuri Other Debt Obligations [Member]
Centuri secured revolving credit facility
Centuri Secured Revolving Credit Facility [Member]
Centuri secured revolving credit facility.
Notes payable, fair value disclosure
Notes Payable, Fair Value Disclosure
Line of credit facility, fair value
Lines of Credit, Fair Value Disclosure
Unsecured debt, fair value
Long-term Debt, Fair Value
Unamortized discount and debt issuance costs
Debt Instrument Unamortized Discount And Debt Issuance Costs
Debt instrument unamortized discount and debt issuance costs.
Unsecured debt
Unsecured Debt
Line of credit facility
Less: current maturities
Long-term debt, less current maturities
Unamortized debt issuance costs
Unamortized Debt Issuance Expense
Long-term Debt, Current and Noncurrent Abstract
Long-term Debt, Current and Noncurrent [Abstract]
Long-term debt
Long-term debt, less current maturities
Centuri term loan/secured revolving credit facility
Secured Debt
Centuri other debt obligations
Other Long-term Debt
Change in benefit obligations
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation for service rendered to date at beginning of year (PBO/PBO/APBO)
Defined Benefit Plan, Benefit Obligation
Service cost
Defined Benefit Plan, Service Cost
Interest cost
Defined Benefit Plan, Interest Cost
Actuarial loss (gain)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)
Benefits paid
Defined Benefit Plan, Benefit Obligation, Benefits Paid
Benefit obligation at end of year (PBO/PBO/APBO)
Change in plan assets
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Market value of plan assets at beginning of year
Actual return on plan assets
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)
Employer contributions
Defined Benefit Plan, Plan Assets, Contributions by Employer
Benefits paid
Defined Benefit Plan, Plan Assets, Benefits Paid
Market value of plan assets at end of year
Funded status at year end
Defined Benefit Plan, Funded (Unfunded) Status of Plan
Weighted-average assumptions (benefit obligation)
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract]
Discount rate
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate
Weighted-average rate of compensation increase
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Rate of Compensation Increase
Receivables and Related Allowances
Loans, Notes, Trade and Other Receivables Disclosure [Text Block]
Corporate and administrative
Corporate, Non-Segment [Member]
Other income (deductions)
Other Nonoperating Income (Expense) [Abstract]
Increase (decrease) in COLI policies
Life Insurance, Corporate or Bank Owned, Change in Value
Interest income
Equity AFUDC
Public Utilities, Allowance for Funds Used During Construction, Capitalized Cost of Equity
Non-service post-retirement benefit cost
Defined Benefit Plan, Actuarial Gain (Loss), Immediate Recognition as Component in Net Periodic Benefit (Cost) Credit
Foreign transaction gain (loss)
Foreign Currency Transaction Gain (Loss), Realized
Equity in earnings of unconsolidated investment – Western
Miscellaneous income and (expense)
Miscellaneous Income Expense
Miscellaneous income (expense).
Total other income (deductions)
Total operating revenues
Business Acquisition, Pro Forma Revenue
Net income attributable to Southwest Gas Holdings, Inc.
Business Acquisition, Pro Forma Net Income (Loss)
Basic earnings per share (in USD per Share)
Business Acquisition, Pro Forma Earnings Per Share, Basic
Diluted earnings per share (in USD per Share)
Business Acquisition, Pro Forma Earnings Per Share, Diluted
Depreciation and amortization expense
Debt portion
Public Utilities, Allowance for Funds Used During Construction, Capitalized, Debt Portion
Public Utilities, Allowance for Funds Used During Construction, Capitalized, Debt Portion
Equity portion
AFUDC capitalized as part of utility plant
Public Utilities, Allowance for Funds Used During Construction, Additions
AFUDC rate
Public Utilities, Allowance for Funds Used During Construction, Rate
Market value of Company stock
Share Price
Expected return on plan assets
Defined Benefit Plan, Expected Return (Loss) on Plan Assets
Amortization of prior service cost
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)
Amortization of net actuarial loss
Defined Benefit Plan, Amortization of Gain (Loss)
Net periodic benefit cost
Weighted-average assumptions (net benefit cost)
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Expected return on plan assets
Accounts receivable for Centuri services
Due from Related Parties, Current
Investment [Table]
Investment [Table]
Investment [Line Items]
Investment [Line Items]
Net cash surrender value of COLI policies
Cash Surrender Value of Life Insurance
Other property
Property, Plant and Equipment, Other, Net
Total
Centuri property, equipment, and intangibles
Property Plant Equipment And Intangible Assets Gross
Property plant equipment and intangible assets gross.
Centuri accumulated provision for depreciation and amortization
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment
Movement In Redeemable Noncontrolling Interest [Roll Forward]
Movement In Redeemable Noncontrolling Interest [Roll Forward]
Movement In Redeemable Noncontrolling Interest [Roll Forward]
Balance, December 31, 2016
Net Income (loss) attributable to redeemable noncontrolling interest
Net Income (Loss) Attributable to Redeemable Noncontrolling Interest
Foreign currency exchange translation adjustment
Adjustment to redemption value
Consolidation Less Than Wholly Owned Subsidiary Parent Ownership Interest Changes Issuance Of Equity By Subsidiary To Noncontrolling Interest And Temporary Equity Redemption Value Adjustment
Consolidation less than wholly owned subsidiary parent ownership interest changes issuance of equity by subsidiary to noncontrolling interest and temporary equity redemption value adjustment.
Balance, December 31, 2017
Net actuarial gain/(loss)
Foreign Currency Items
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Net actuarial (loss) gain
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), Gain (Loss), before Tax
Prior service cost
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, Prior Service Cost (Credit), before Tax
Less: amount recognized in regulatory assets
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), Amount Recognized Regulatory Assets, Before Tax
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), Amount Recognized Regulatory Assets, Before Tax
Recognized in AOCI
Defined Benefit Plan, Accumulated Other Comprehensive (Income) Loss, before Tax
Vesting [Axis]
Vesting [Axis]
Vesting [Domain]
Vesting [Domain]
Vesting Tranche One
Share-based Compensation Award, Tranche One [Member]
Vesting Tranche Two
Share-based Compensation Award, Tranche Two [Member]
Vesting Tranche Three
Share-based Compensation Award, Tranche Three [Member]
Subsequent Event Type [Axis]
Subsequent Event Type [Axis]
Subsequent Event Type [Domain]
Subsequent Event Type [Domain]
Subsequent Event
Subsequent Event [Member]
Number of stock-based compensation plans
Share-based Compensation Arrangement By Share-based Payment Award, Number Of Plans
Share-based Compensation Arrangement By Share-based Payment Award, Number Of Plans
Award vesting period
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period
Number of shares, granted (in shares)
Award vesting percentage
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage
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
Compensation expense
Weighted average grant date fair value (in USD per share)
Compensation cost related to nonvested management incentive plan shares, performance shares, and restricted stock/units not yet recognized
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized
Compensation cost not yet recognized, period for recognition
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition
Customer [Axis]
Customer [Axis]
Customer [Domain]
Customer [Domain]
Residential
Residential [Member]
Residential.
Small commercial
Small Commercial [Member]
Small commercial.
Large commercial
Large Commercial [Member]
Large commercial.
Industrial/other
Industrial/other [Member]
Industrial/other.
Transportation
Transportation [Member]
Transportation.
Tax Reform Savings Revenue Adjustments
Tax Reform Savings Revenue Adjustments [Member]
Tax reform savings revenue adjustments.
Alternative revenue program revenues (deferrals)
Alternative Revenue Program Revenues (Deferrals)
Alternative revenue program revenues (deferrals).
Other revenues
Other Revenue
Other Revenue
Total Gas operating revenues
Income Tax Disclosure [Table]
Income Tax Disclosure [Table]
Income Tax Disclosure [Table]
Federal
Domestic Tax Authority [Member]
Tax Credit Carryforward [Axis]
Tax Credit Carryforward [Axis]
Tax Credit Carryforward, Name [Domain]
Tax Credit Carryforward, Name [Domain]
Capital Loss Carryforward
Capital Loss Carryforward [Member]
Income Tax Disclosure [Line Items]
Income Tax Disclosure [Line Items]
Income Tax Disclosure [Line Items]
Regulatory liability related to TCJA
Tax Cuts And Jobs Act Of 2017, Regulatory Liability
Tax Cuts And Jobs Act Of 2017, Regulatory Liability
Operating loss carryforward
Operating Loss Carryforwards
Tax credit carryforward
Tax Credit Carryforward, Amount
Unrecognized tax benefits that, if recognized, would affect the effective tax rate
Unrecognized Tax Benefits that Would Impact Effective Tax Rate
Significant increases or decreases in unrecognized tax benefit within the next 12 months
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit
Tax-related interest income
Income Tax Examination, Interest Expense