0000001 - Document - Cover Page link:presentationLink link:calculationLink link:definitionLink 9952151 - Statement - Consolidated Statements of Income link:presentationLink link:calculationLink link:definitionLink 9952152 - Statement - Consolidated Statements of Comprehensive Income link:presentationLink link:calculationLink link:definitionLink 9952153 - Statement - Consolidated Statements of Comprehensive Income (Parenthetical) link:presentationLink link:calculationLink link:definitionLink 9952154 - Statement - Consolidated Balance Sheets link:presentationLink link:calculationLink link:definitionLink 9952155 - Statement - Consolidated Balance Sheets (Parenthetical) link:presentationLink link:calculationLink link:definitionLink 9952156 - Statement - Consolidated Statements of Equity link:presentationLink link:calculationLink link:definitionLink 9952157 - Statement - Consolidated Statements of Cash Flows link:presentationLink link:calculationLink link:definitionLink 9952158 - Statement - Consolidated Statements of Cash Flows (Parenthetical) link:presentationLink link:calculationLink link:definitionLink 9952159 - Disclosure - Basis of presentation link:presentationLink link:calculationLink link:definitionLink 9952160 - Disclosure - New accounting standards link:presentationLink link:calculationLink link:definitionLink 9952161 - Disclosure - Discontinued operations link:presentationLink link:calculationLink link:definitionLink 9952162 - Disclosure - Seasonality of operations link:presentationLink link:calculationLink link:definitionLink 9952163 - Disclosure - Receivables and allowance for expected credit losses link:presentationLink link:calculationLink link:definitionLink 9952164 - Disclosure - Inventories and natural gas in storage link:presentationLink link:calculationLink link:definitionLink 9952165 - Disclosure - Earnings per share link:presentationLink link:calculationLink link:definitionLink 9952166 - Disclosure - Equity link:presentationLink link:calculationLink link:definitionLink 9952167 - Disclosure - Revenue from contracts with customers link:presentationLink link:calculationLink link:definitionLink 9952168 - Disclosure - Regulatory matters link:presentationLink link:calculationLink link:definitionLink 9952169 - Disclosure - Environmental allowances and obligations link:presentationLink link:calculationLink link:definitionLink 9952170 - Disclosure - Fair value measurements link:presentationLink link:calculationLink link:definitionLink 9952171 - Disclosure - Debt link:presentationLink link:calculationLink link:definitionLink 9952172 - Disclosure - Business segment data link:presentationLink link:calculationLink link:definitionLink 9952173 - Disclosure - Employee benefit plans link:presentationLink link:calculationLink link:definitionLink 9952174 - Disclosure - Commitments and contingencies link:presentationLink link:calculationLink link:definitionLink 9955511 - Disclosure - Basis of presentation (Policies) link:presentationLink link:calculationLink link:definitionLink 9955512 - Disclosure - Discontinued operations (Tables) link:presentationLink link:calculationLink link:definitionLink 9955513 - Disclosure - Receivables and allowance for expected credit losses (Tables) link:presentationLink link:calculationLink link:definitionLink 9955514 - Disclosure - Inventories and natural gas in storage (Tables) link:presentationLink link:calculationLink link:definitionLink 9955515 - Disclosure - Earnings per share (Tables) link:presentationLink link:calculationLink link:definitionLink 9955516 - Disclosure - Equity (Tables) link:presentationLink link:calculationLink link:definitionLink 9955517 - Disclosure - Revenue from contracts with customers (Tables) link:presentationLink link:calculationLink link:definitionLink 9955518 - Disclosure - Regulatory matters (Tables) link:presentationLink link:calculationLink link:definitionLink 9955519 - Disclosure - Fair value measurements (Tables) link:presentationLink link:calculationLink link:definitionLink 9955520 - Disclosure - Debt (Tables) link:presentationLink link:calculationLink link:definitionLink 9955521 - Disclosure - Business segment data (Tables) link:presentationLink link:calculationLink link:definitionLink 9955522 - Disclosure - Employee benefit plans (Tables) link:presentationLink link:calculationLink link:definitionLink 9955523 - Disclosure - Discontinued operations - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9955524 - Disclosure - Discontinued operations - Schedule of Pretax Income (Loss) From Discontinued Operations (Details) link:presentationLink link:calculationLink link:definitionLink 9955525 - Disclosure - Receivables and allowance for expected credit losses (Details) link:presentationLink link:calculationLink link:definitionLink 9955526 - Disclosure - Inventories and natural gas in storage (Details) link:presentationLink link:calculationLink link:definitionLink 9955527 - Disclosure - Earnings per share (Details) link:presentationLink link:calculationLink link:definitionLink 9955528 - Disclosure - Equity - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9955529 - Disclosure - Equity - Schedule of ATM Offering Activity (Details) link:presentationLink link:calculationLink link:definitionLink 9955530 - Disclosure - Revenue from contracts with customers - Schedule of Disaggregation of revenue (Details) link:presentationLink link:calculationLink link:definitionLink 9955531 - Disclosure - Revenue from contracts with customers - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9955531 - Disclosure - Revenue from contracts with customers - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9955532 - Disclosure - Revenue from contracts with customers - Schedule of Remaining Performance Obligations (Details) link:presentationLink link:calculationLink link:definitionLink 9955532 - Disclosure - Revenue from contracts with customers - Schedule of Remaining Performance Obligations (Details) link:presentationLink link:calculationLink link:definitionLink 9955533 - Disclosure - Regulatory matters - Schedule of Unamortized Regulatory Assets and Liabilities (Details) link:presentationLink link:calculationLink link:definitionLink 9955534 - Disclosure - Regulatory matters - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9955535 - Disclosure - Regulatory matters - Schedule of Regulatory Proceedings (Details) link:presentationLink link:calculationLink link:definitionLink 9955536 - Disclosure - Fair value measurements - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9955537 - Disclosure - Fair value measurements - Schedule of Available-for-Sale Securities (Details) link:presentationLink link:calculationLink link:definitionLink 9955538 - Disclosure - Fair value measurements - Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis (Details) link:presentationLink link:calculationLink link:definitionLink 9955539 - Disclosure - Fair value measurements - Schedule of Fair Value of Long-Term Debt Outstanding (Details) link:presentationLink link:calculationLink link:definitionLink 9955540 - Disclosure - Debt - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9955541 - Disclosure - Debt - Schedule of Credit Facilities (Details) link:presentationLink link:calculationLink link:definitionLink 9955542 - Disclosure - Debt - Schedule of Long-Term Debt Outstanding (Details) link:presentationLink link:calculationLink link:definitionLink 9955542 - Disclosure - Debt - Schedule of Long-Term Debt Outstanding (Details) link:presentationLink link:calculationLink link:definitionLink 9955543 - Disclosure - Business Segment Data - Schedule of Segment Reporting Information (Details) link:presentationLink link:calculationLink link:definitionLink 9955544 - Disclosure - Business segment data - Schedule of Operating Revenues Reconciliation (Details) link:presentationLink link:calculationLink link:definitionLink 9955545 - Disclosure - Employee benefit plans - Schedule of Components of Net Periodic Benefit Cost (Details) link:presentationLink link:calculationLink link:definitionLink 9955546 - Disclosure - Employee benefit plans - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9955547 - Disclosure - Commitments and contingencies - Litigation (Details) link:presentationLink link:calculationLink link:definitionLink 9955548 - Disclosure - Commitments and contingencies - Guarantees (Details) link:presentationLink link:calculationLink link:definitionLink 9955549 - Disclosure - Commitments and contingencies - Leases (Details) link:presentationLink link:calculationLink link:definitionLink 9955550 - Disclosure - Commitments and contingencies - Variable Interest Entities (Details) link:presentationLink link:calculationLink link:definitionLink