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 9952154 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME link:presentationLink link:calculationLink link:definitionLink 9952155 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS link:presentationLink link:calculationLink link:definitionLink 9952156 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF EQUITY link:presentationLink link:calculationLink link:definitionLink 9952157 - Statement - CONDENSED CONSOLIDATED BALANCE SHEETS - Southwest link:presentationLink link:calculationLink link:definitionLink 9952158 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF INCOME - Southwest link:presentationLink link:calculationLink link:definitionLink 9952159 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - Southwest link:presentationLink link:calculationLink link:definitionLink 9952160 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - Southwest link:presentationLink link:calculationLink link:definitionLink 9952161 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF EQUITY - Southwest link:presentationLink link:calculationLink link:definitionLink 9952162 - Disclosure - Background, Organization, and Summary of Significant Accounting Policies link:presentationLink link:calculationLink link:definitionLink 9952163 - Disclosure - Components of Net Periodic Benefit Cost link:presentationLink link:calculationLink link:definitionLink 9952164 - Disclosure - Revenue link:presentationLink link:calculationLink link:definitionLink 9952165 - Disclosure - Common Stock link:presentationLink link:calculationLink link:definitionLink 9952166 - Disclosure - Debt link:presentationLink link:calculationLink link:definitionLink 9952167 - Disclosure - Other Comprehensive Income and Accumulated Other Comprehensive Income link:presentationLink link:calculationLink link:definitionLink 9952168 - Disclosure - Segment Information link:presentationLink link:calculationLink link:definitionLink 9952169 - Disclosure - Centuri Separation link:presentationLink link:calculationLink link:definitionLink 9954471 - Disclosure - Background, Organization, and Summary of Significant Accounting Policies (Policies) link:presentationLink link:calculationLink link:definitionLink 9954472 - Disclosure - Background, Organization, and Summary of Significant Accounting Policies (Tables) link:presentationLink link:calculationLink link:definitionLink 9954473 - Disclosure - Components of Net Periodic Benefit Cost (Tables) link:presentationLink link:calculationLink link:definitionLink 9954474 - Disclosure - Revenue (Tables) link:presentationLink link:calculationLink link:definitionLink 9954475 - Disclosure - Debt (Tables) link:presentationLink link:calculationLink link:definitionLink 9954476 - Disclosure - Other Comprehensive Income and Accumulated Other Comprehensive Income (Tables) link:presentationLink link:calculationLink link:definitionLink 9954477 - Disclosure - Segment Information (Tables) link:presentationLink link:calculationLink link:definitionLink 9954478 - Disclosure - Centuri Separation (Tables) link:presentationLink link:calculationLink link:definitionLink 9954479 - Disclosure - Background, Organization, and Summary of Significant Accounting Policies - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9954480 - Disclosure - Background, Organization, and Summary of Significant Accounting Policies - Schedule of Other Property and Investments (Details) link:presentationLink link:calculationLink link:definitionLink 9954481 - Disclosure - Background, Organization, and Summary of Significant Accounting Policies - Schedule of Goodwill (Details) link:presentationLink link:calculationLink link:definitionLink 9954482 - Disclosure - Background, Organization, and Summary of Significant Accounting Policies - Other Income (Deductions) (Details) link:presentationLink link:calculationLink link:definitionLink 9954483 - Disclosure - Background, Organization, and Summary of Significant Accounting Policies - Schedule of Redeemable Noncontrolling Interest (Details) link:presentationLink link:calculationLink link:definitionLink 9954484 - Disclosure - Background, Organization, and Summary of Significant Accounting Policies - Schedule of Earnings Per Share (Details) link:presentationLink link:calculationLink link:definitionLink 9954485 - Disclosure - Components of Net Periodic Benefit Cost (Details) link:presentationLink link:calculationLink link:definitionLink 9954486 - Disclosure - Revenue - Schedule of Regulated Operations Revenues: Natural Gas Distribution Segment (Details) link:presentationLink link:calculationLink link:definitionLink 9954487 - Disclosure - Revenue - Schedule of Regulated Operations Revenues: Utility Infrastructure Services Segment (Details) link:presentationLink link:calculationLink link:definitionLink 9954488 - Disclosure - Revenue - Summary of Information about Receivables (Details) link:presentationLink link:calculationLink link:definitionLink 9954489 - Disclosure - Revenue - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9954489 - Disclosure - Revenue - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9954490 - Disclosure - Revenue - Schedule of Utility Infrastructure Services Contracts Receivable (Details) link:presentationLink link:calculationLink link:definitionLink 9954491 - Disclosure - Common Stock (Details) link:presentationLink link:calculationLink link:definitionLink 9954492 - Disclosure - Debt - Schedule of Carrying Amounts and Estimated Fair Values of Long-Term Debt (Details) link:presentationLink link:calculationLink link:definitionLink 9954492 - Disclosure - Debt - Schedule of Carrying Amounts and Estimated Fair Values of Long-Term Debt (Details) link:presentationLink link:calculationLink link:definitionLink 9954493 - Disclosure - Debt - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9954494 - Disclosure - Other Comprehensive Income and Accumulated Other Comprehensive Income - Related Tax Effects Allocated to OCI (Details) link:presentationLink link:calculationLink link:definitionLink 9954495 - Disclosure - Other Comprehensive Income and Accumulated Other Comprehensive Income - AOCI Rollforward (Details) link:presentationLink link:calculationLink link:definitionLink 9954496 - Disclosure - Other Comprehensive Income and Accumulated Other Comprehensive Income - Amounts Recognized Before Tax, Defined Benefit Plans (Details) link:presentationLink link:calculationLink link:definitionLink 9954497 - Disclosure - Segment Information - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9954498 - Disclosure - Segment Information - Accounts Receivable Not Eliminated During Consolidation (Details) link:presentationLink link:calculationLink link:definitionLink 9954499 - Disclosure - Segment Information - Schedule of Segment Reporting Information (Details) link:presentationLink link:calculationLink link:definitionLink 9954500 - Disclosure - Centuri Separation- Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9954501 - Disclosure - Centuri Separation - Schedule of Ownership Interests (Details) link:presentationLink link:calculationLink link:definitionLink