0000001 - Document - Cover link:presentationLink link:calculationLink link:definitionLink 9952151 - Statement - CONDENSED CONSOLIDATED BALANCE SHEETS link:presentationLink link:calculationLink link:definitionLink 9952152 - Statement - CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) link:presentationLink link:calculationLink link:definitionLink 9952153 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF INCOME link:presentationLink link:calculationLink link:definitionLink 9952153 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF INCOME link:presentationLink link:calculationLink link:definitionLink 9952154 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME link:presentationLink link:calculationLink link:definitionLink 9952155 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) link:presentationLink link:calculationLink link:definitionLink 9952156 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS link:presentationLink link:calculationLink link:definitionLink 9952157 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF EQUITY link:presentationLink link:calculationLink link:definitionLink 9952158 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF EQUITY (Parenthetical) link:presentationLink link:calculationLink link:definitionLink 9952159 - Statement - CONDENSED CONSOLIDATED BALANCE SHEETS - Southwest link:presentationLink link:calculationLink link:definitionLink 9952160 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF INCOME - Southwest link:presentationLink link:calculationLink link:definitionLink 9952161 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - Southwest link:presentationLink link:calculationLink link:definitionLink 9952162 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) - Southwest link:presentationLink link:calculationLink link:definitionLink 9952163 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - Southwest link:presentationLink link:calculationLink link:definitionLink 9952164 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF EQUITY - Southwest link:presentationLink link:calculationLink link:definitionLink 9952165 - Disclosure - Background and Organization link:presentationLink link:calculationLink link:definitionLink 9952166 - Disclosure - Summary of Significant Accounting Policies link:presentationLink link:calculationLink link:definitionLink 9952167 - Disclosure - Components of Net Periodic Benefit Cost link:presentationLink link:calculationLink link:definitionLink 9952168 - Disclosure - Revenue link:presentationLink link:calculationLink link:definitionLink 9952169 - Disclosure - Debt link:presentationLink link:calculationLink link:definitionLink 9952170 - Disclosure - Segment Information link:presentationLink link:calculationLink link:definitionLink 9952171 - Disclosure - Centuri Separation link:presentationLink link:calculationLink link:definitionLink 9955511 - Disclosure - Summary of Significant Accounting Policies (Policies) link:presentationLink link:calculationLink link:definitionLink 9955512 - Disclosure - Summary of Significant Accounting Policies (Tables) link:presentationLink link:calculationLink link:definitionLink 9955513 - Disclosure - Components of Net Periodic Benefit Cost (Tables) link:presentationLink link:calculationLink link:definitionLink 9955514 - Disclosure - Revenue (Tables) link:presentationLink link:calculationLink link:definitionLink 9955515 - Disclosure - Debt (Tables) link:presentationLink link:calculationLink link:definitionLink 9955516 - Disclosure - Segment Information (Tables) link:presentationLink link:calculationLink link:definitionLink 9955517 - Disclosure - Centuri Separation (Tables) link:presentationLink link:calculationLink link:definitionLink 9955518 - Disclosure - Background and Organization (Details) link:presentationLink link:calculationLink link:definitionLink 9955519 - Disclosure - Summary of Significant Accounting Policies - Schedule of Other Property and Investments (Details) link:presentationLink link:calculationLink link:definitionLink 9955520 - Disclosure - Summary of Significant Accounting Policies - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9955521 - Disclosure - Summary of Significant Accounting Policies - Schedule of Goodwill (Details) link:presentationLink link:calculationLink link:definitionLink 9955522 - Disclosure - Summary of Significant Accounting Policies - Other Income (Deductions) (Details) link:presentationLink link:calculationLink link:definitionLink 9955523 - Disclosure - Summary of Significant Accounting Policies - Schedule of Redeemable Noncontrolling Interest (Details) link:presentationLink link:calculationLink link:definitionLink 9955524 - Disclosure - Summary of Significant Accounting Policies - Schedule of Earnings Per Share (Details) link:presentationLink link:calculationLink link:definitionLink 9955525 - Disclosure - Components of Net Periodic Benefit Cost (Details) link:presentationLink link:calculationLink link:definitionLink 9955526 - Disclosure - Revenue - Schedule of Regulated Operations Revenues: Natural Gas Distribution Segment (Details) link:presentationLink link:calculationLink link:definitionLink 9955527 - Disclosure - Revenue - Schedule of Regulated Operations Revenues: Utility Infrastructure Services Segment (Details) link:presentationLink link:calculationLink link:definitionLink 9955528 - Disclosure - Revenue - Schedule of Information about Receivables (Details) link:presentationLink link:calculationLink link:definitionLink 9955529 - Disclosure - Revenue - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9955529 - Disclosure - Revenue - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9955530 - Disclosure - Revenue - Schedule of Utility Infrastructure Services Contracts Receivable (Details) link:presentationLink link:calculationLink link:definitionLink 9955531 - Disclosure - Debt - Schedule of Carrying Amounts and Estimated Fair Values of Long-Term Debt (Details) link:presentationLink link:calculationLink link:definitionLink 9955532 - Disclosure - Debt - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9955533 - Disclosure - Segment Information - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9955534 - Disclosure - Segment Information - Schedule of Accounts Receivable Not Eliminated During Consolidation (Details) link:presentationLink link:calculationLink link:definitionLink 9955535 - Disclosure - Segment Information - Schedule of Revenues by Geographic Area (Details) link:presentationLink link:calculationLink link:definitionLink 9955536 - Disclosure - Segment Information - Schedule of Segment Reporting Information (Details) link:presentationLink link:calculationLink link:definitionLink 9955537 - Disclosure - Centuri Separation- Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9955538 - Disclosure - Centuri Separation - Schedule of Ownership Interests (Details) link:presentationLink link:calculationLink link:definitionLink