0000001 - Document - Cover link:presentationLink link:calculationLink link:definitionLink 0000002 - Statement - CONDENSED CONSOLIDATED BALANCE SHEETS link:presentationLink link:calculationLink link:definitionLink 0000003 - Statement - CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) link:presentationLink link:calculationLink link:definitionLink 0000004 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF INCOME link:presentationLink link:calculationLink link:definitionLink 0000005 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME link:presentationLink link:calculationLink link:definitionLink 0000006 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS link:presentationLink link:calculationLink link:definitionLink 0000007 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF EQUITY link:presentationLink link:calculationLink link:definitionLink 0000008 - Statement - CONDENSED CONSOLIDATED BALANCE SHEETS - Southwest link:presentationLink link:calculationLink link:definitionLink 0000009 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF INCOME - Southwest link:presentationLink link:calculationLink link:definitionLink 0000010 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - Southwest link:presentationLink link:calculationLink link:definitionLink 0000011 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - Southwest link:presentationLink link:calculationLink link:definitionLink 0000012 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF EQUITY - Southwest link:presentationLink link:calculationLink link:definitionLink 0000013 - Disclosure - Background, Organization, and Summary of Significant Accounting Policies link:presentationLink link:calculationLink link:definitionLink 0000014 - Disclosure - Components of Net Periodic Benefit Cost link:presentationLink link:calculationLink link:definitionLink 0000015 - Disclosure - Revenue link:presentationLink link:calculationLink link:definitionLink 0000016 - Disclosure - Common Stock link:presentationLink link:calculationLink link:definitionLink 0000017 - Disclosure - Debt link:presentationLink link:calculationLink link:definitionLink 0000018 - Disclosure - Other Comprehensive Income and Accumulated Other Comprehensive Income link:presentationLink link:calculationLink link:definitionLink 0000019 - Disclosure - Segment Information link:presentationLink link:calculationLink link:definitionLink 0000020 - Disclosure - Business Acquisitions link:presentationLink link:calculationLink link:definitionLink 0000021 - Disclosure - Subsequent Events link:presentationLink link:calculationLink link:definitionLink 0000022 - Disclosure - Background, Organization, and Summary of Significant Accounting Policies (Policies) link:presentationLink link:calculationLink link:definitionLink 0000023 - Disclosure - Background, Organization, and Summary of Significant Accounting Policies (Tables) link:presentationLink link:calculationLink link:definitionLink 0000024 - Disclosure - Components of Net Periodic Benefit Cost (Tables) link:presentationLink link:calculationLink link:definitionLink 0000025 - Disclosure - Revenue (Tables) link:presentationLink link:calculationLink link:definitionLink 0000026 - Disclosure - Common Stock (Tables) link:presentationLink link:calculationLink link:definitionLink 0000027 - Disclosure - Debt (Tables) link:presentationLink link:calculationLink link:definitionLink 0000028 - Disclosure - Other Comprehensive Income and Accumulated Other Comprehensive Income (Tables) link:presentationLink link:calculationLink link:definitionLink 0000029 - Disclosure - Segment Information (Tables) link:presentationLink link:calculationLink link:definitionLink 0000030 - Disclosure - Business Acquisitions (Tables) link:presentationLink link:calculationLink link:definitionLink 0000031 - Disclosure - Background, Organization, and Summary of Significant Accounting Policies - Narratives (Details) link:presentationLink link:calculationLink link:definitionLink 0000032 - Disclosure - Background, Organization, and Summary of Significant Accounting Policies - Schedule of Other Property and Investments (Details) link:presentationLink link:calculationLink link:definitionLink 0000033 - Disclosure - Background, Organization, and Summary of Significant Accounting Policies - Schedule of Goodwill (Details) link:presentationLink link:calculationLink link:definitionLink 0000034 - Disclosure - Background, Organization, and Summary of Significant Accounting Policies - Other Income (Deductions) (Details) link:presentationLink link:calculationLink link:definitionLink 0000035 - Disclosure - Background, Organization, and Summary of Significant Accounting Policies - Summary of Redeemable Noncontrolling Interest (Details) link:presentationLink link:calculationLink link:definitionLink 0000036 - Disclosure - Background, Organization, and Summary of Significant Accounting Policies - Schedule of Earnings Per Share (Details) link:presentationLink link:calculationLink link:definitionLink 0000037 - Disclosure - Components of Net Periodic Benefit Cost (Details) link:presentationLink link:calculationLink link:definitionLink 0000038 - Disclosure - Revenue - Schedule of Regulated Operations Revenues: Natural Gas Distribution Segment (Details) link:presentationLink link:calculationLink link:definitionLink 0000039 - Disclosure - Revenue - Schedule of Regulated Operations Revenues: Utility Infrastructure Services Segment (Details) link:presentationLink link:calculationLink link:definitionLink 0000040 - Disclosure - Revenue - Summary of Information about Receivables (Details) link:presentationLink link:calculationLink link:definitionLink 0000041 - Disclosure - Revenue - Narratives (Details) link:presentationLink link:calculationLink link:definitionLink 0000041 - Disclosure - Revenue - Narratives (Details) link:presentationLink link:calculationLink link:definitionLink 0000042 - Disclosure - Revenue - Schedule of Utility Infrastructure Services Contracts Receivable (Details) link:presentationLink link:calculationLink link:definitionLink 0000043 - Disclosure - Revenue - Schedule of Regulated Operations Revenues: Pipeline and Storage Segment (Details) link:presentationLink link:calculationLink link:definitionLink 0000044 - Disclosure - Common Stock - Narratives (Details) link:presentationLink link:calculationLink link:definitionLink 0000045 - Disclosure - Common Stock - Activity of Equity Shelf Program (Details) link:presentationLink link:calculationLink link:definitionLink 0000046 - Disclosure - Debt - Schedule of Carrying Amounts and Estimated Fair Values of Long-Term Debt (Details) link:presentationLink link:calculationLink link:definitionLink 0000047 - Disclosure - Debt - Narratives (Details) link:presentationLink link:calculationLink link:definitionLink 0000048 - Disclosure - Other Comprehensive Income and Accumulated Other Comprehensive Income - Related Tax Effects Allocated to OCI (Details) link:presentationLink link:calculationLink link:definitionLink 0000049 - Disclosure - Other Comprehensive Income and Accumulated Other Comprehensive Income - AOCI Rollforward (Details) link:presentationLink link:calculationLink link:definitionLink 0000050 - Disclosure - Other Comprehensive Income and Accumulated Other Comprehensive Income - Amounts Recognized Before Tax, Defined Benefit Plans (Details) link:presentationLink link:calculationLink link:definitionLink 0000051 - Disclosure - Segment Information - Narratives (Details) link:presentationLink link:calculationLink link:definitionLink 0000052 - Disclosure - Segment Information - Accounts Receivable Not Eliminated During Consolidation (Details) link:presentationLink link:calculationLink link:definitionLink 0000053 - Disclosure - Segment Information - Schedule of Segment Reporting Information (Details) link:presentationLink link:calculationLink link:definitionLink 0000054 - Disclosure - Business Acquisitions - Narrative (Detail) link:presentationLink link:calculationLink link:definitionLink 0000055 - Disclosure - Business Acquisitions - Summary of Assets Acquired and Liabilities Assumed - Drum Acquisition (Detail) link:presentationLink link:calculationLink link:definitionLink 0000056 - Disclosure - Business Acquisitions - Summary of Assets Acquired and Liabilities Assumed - Questar Acquisition (Details) link:presentationLink link:calculationLink link:definitionLink 0000057 - Disclosure - Subsequent Events (Details) link:presentationLink link:calculationLink link:definitionLink