0001001 - Document - Cover link:presentationLink link:calculationLink link:definitionLink 1001002 - Statement - CONDENSED CONSOLIDATED BALANCE SHEETS link:presentationLink link:calculationLink link:definitionLink 1002003 - Statement - CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) link:presentationLink link:calculationLink link:definitionLink 1003004 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF INCOME link:presentationLink link:calculationLink link:definitionLink 1004005 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME link:presentationLink link:calculationLink link:definitionLink 1005006 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS link:presentationLink link:calculationLink link:definitionLink 1006007 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF EQUITY link:presentationLink link:calculationLink link:definitionLink 1007008 - Statement - CONDENSED CONSOLIDATED BALANCE SHEETS - Southwest link:presentationLink link:calculationLink link:definitionLink 1008009 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF INCOME - Southwest link:presentationLink link:calculationLink link:definitionLink 1009010 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - Southwest link:presentationLink link:calculationLink link:definitionLink 1010011 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - Southwest link:presentationLink link:calculationLink link:definitionLink 1011012 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF EQUITY - Southwest link:presentationLink link:calculationLink link:definitionLink 2101101 - Disclosure - Background, Organization, and Summary of Significant Accounting Policies link:presentationLink link:calculationLink link:definitionLink 2202201 - Disclosure - Background, Organization, and Summary of Significant Accounting Policies (Policies) link:presentationLink link:calculationLink link:definitionLink 2303301 - Disclosure - Background, Organization, and Summary of Significant Accounting Policies (Tables) link:presentationLink link:calculationLink link:definitionLink 2404401 - Disclosure - Background, Organization, and Summary of Significant Accounting Policies - Narratives (Details) link:presentationLink link:calculationLink link:definitionLink 2405402 - Disclosure - Background, Organization, and Summary of Significant Accounting Policies - Schedule of Other Property and Investments (Details) link:presentationLink link:calculationLink link:definitionLink 2406403 - Disclosure - Background, Organization, and Summary of Significant Accounting Policies - Schedule of Goodwill (Details) link:presentationLink link:calculationLink link:definitionLink 2407404 - Disclosure - Background, Organization, and Summary of Significant Accounting Policies - Other Income (Deductions) (Details) link:presentationLink link:calculationLink link:definitionLink 2408405 - Disclosure - Background, Organization, and Summary of Significant Accounting Policies - Summary of Redeemable Noncontrolling Interest (Details) link:presentationLink link:calculationLink link:definitionLink 2409406 - Disclosure - Background, Organization, and Summary of Significant Accounting Policies - Schedule of Earnings Per Share (Details) link:presentationLink link:calculationLink link:definitionLink 2110102 - Disclosure - Components of Net Periodic Benefit Cost link:presentationLink link:calculationLink link:definitionLink 2311302 - Disclosure - Components of Net Periodic Benefit Cost (Tables) link:presentationLink link:calculationLink link:definitionLink 2412407 - Disclosure - Components of Net Periodic Benefit Cost (Details) link:presentationLink link:calculationLink link:definitionLink 2113103 - Disclosure - Revenue link:presentationLink link:calculationLink link:definitionLink 2314303 - Disclosure - Revenue (Tables) link:presentationLink link:calculationLink link:definitionLink 2415408 - Disclosure - Revenue - Schedule of Regulated Operations Revenues: Natural Gas Distribution Segment (Details) link:presentationLink link:calculationLink link:definitionLink 2416409 - Disclosure - Revenue - Schedule of Regulated Operations Revenues: Utility Infrastructure Services Segment (Details) link:presentationLink link:calculationLink link:definitionLink 2417410 - Disclosure - Revenue - Summary of Information about Receivables (Details) link:presentationLink link:calculationLink link:definitionLink 2418411 - Disclosure - Revenue - Narratives (Details) link:presentationLink link:calculationLink link:definitionLink 2418411 - Disclosure - Revenue - Narratives (Details) link:presentationLink link:calculationLink link:definitionLink 2419412 - Disclosure - Revenue - Schedule of Utility Infrastructure Services Contracts Receivable (Details) link:presentationLink link:calculationLink link:definitionLink 2420413 - Disclosure - Revenue - Schedule of Regulated Operations Revenues: Pipeline and Storage Segment (Details) link:presentationLink link:calculationLink link:definitionLink 2121104 - Disclosure - Common Stock link:presentationLink link:calculationLink link:definitionLink 2322304 - Disclosure - Common Stock (Tables) link:presentationLink link:calculationLink link:definitionLink 2423414 - Disclosure - Common Stock - Activity of Equity Shelf Program (Details) link:presentationLink link:calculationLink link:definitionLink 2424415 - Disclosure - Common Stock - Narratives (Details) link:presentationLink link:calculationLink link:definitionLink 2125105 - Disclosure - Debt link:presentationLink link:calculationLink link:definitionLink 2326305 - Disclosure - Debt (Tables) link:presentationLink link:calculationLink link:definitionLink 2427416 - Disclosure - Debt - Schedule of Carrying Amounts and Estimated Fair Values of Long-Term Debt (Details) link:presentationLink link:calculationLink link:definitionLink 2428417 - Disclosure - Debt - Narratives (Details) link:presentationLink link:calculationLink link:definitionLink 2129106 - Disclosure - Other Comprehensive Income and Accumulated Other Comprehensive Income link:presentationLink link:calculationLink link:definitionLink 2330306 - Disclosure - Other Comprehensive Income and Accumulated Other Comprehensive Income (Tables) link:presentationLink link:calculationLink link:definitionLink 2431418 - Disclosure - Other Comprehensive Income and Accumulated Other Comprehensive Income - Related Tax Effects Allocated to OCI (Details) link:presentationLink link:calculationLink link:definitionLink 2432419 - Disclosure - Other Comprehensive Income and Accumulated Other Comprehensive Income - AOCI Rollforward (Details) link:presentationLink link:calculationLink link:definitionLink 2433420 - Disclosure - Other Comprehensive Income and Accumulated Other Comprehensive Income - Amounts Recognized Before Tax, Defined Benefit Plans (Details) link:presentationLink link:calculationLink link:definitionLink 2134107 - Disclosure - Segment Information link:presentationLink link:calculationLink link:definitionLink 2335307 - Disclosure - Segment Information (Tables) link:presentationLink link:calculationLink link:definitionLink 2436421 - Disclosure - Segment Information - Narratives (Details) link:presentationLink link:calculationLink link:definitionLink 2437422 - Disclosure - Segment Information - Accounts Receivable Not Eliminated During Consolidation (Details) link:presentationLink link:calculationLink link:definitionLink 2438423 - Disclosure - Segment Information - Schedule of Segment Reporting Information (Details) link:presentationLink link:calculationLink link:definitionLink 2139108 - Disclosure - Business Acquisitions link:presentationLink link:calculationLink link:definitionLink 2340308 - Disclosure - Business Acquisitions (Tables) link:presentationLink link:calculationLink link:definitionLink 2441424 - Disclosure - Business Acquisitions - Narrative (Detail) link:presentationLink link:calculationLink link:definitionLink 2442425 - Disclosure - Business Acquisitions - Summary of Assets Acquired and Liabilities Assumed - Drum Acquisition (Detail) link:presentationLink link:calculationLink link:definitionLink 2443426 - Disclosure - Business Acquisitions - Summary of Assets Acquired and Liabilities Assumed - Questar Acquisition (Details) link:presentationLink link:calculationLink link:definitionLink 2144109 - Disclosure - Subsequent Events link:presentationLink link:calculationLink link:definitionLink 2445427 - Disclosure - Subsequent Events (Details) link:presentationLink link:calculationLink link:definitionLink