| Revenue | $3B | $3.3B | $2.8B | $3B | $3.4B | $4.2B | $3.4B | $3.5B |
| Cash Provided by (Used in) Operating Activity, Including Discontinued Operation | $1.8B | $1.2B | $1.3B | $1.2B | $1.2B | $1.4B | $1.5B | $1.4B |
| Revenues Adjustments For Certain Risk Management Activities Costs | $1.4B | $1.4B | $874M | $923M | $1.2B | $2.2B | $1.3B | $1.3B |
| Cash Provided by (Used in) Financing Activity, Including Discontinued Operation | -$477M | -$281M | -$1.3B | $0 | -$850M | -$223M | $377M | -$1.3B |
| Cash Provided by (Used in) Investing Activity, Including Discontinued Operation | -$1.3B | -$2.4B | -$620M | -$737M | -$1.1B | -$1.2B | -$1B | -$1B |
| Payments to Acquire Property, Plant, and Equipment | $671M | $544M | $579M | $682M | $768M | $1B | $972M | $954M |
| Repayments of Long-Term Debt | $613M | $1B | $1.3B | $12M | $660M | $853M | $122M | $758M |
| Revenue Not from Contract with Customer, Other | $8.8B | $868M | $363M | $541M | $576M | $1.1B | $671M | $704M |
| Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest | $1.1B | $672M | $429M | $728M | $593M | $729M | $584M | $679M |
| Comprehensive Income (Loss), Net of Tax, Attributable to Parent | $1.1B | $642M | $404M | $693M | $562M | $691M | $547M | $643M |
| Dividends, Common Stock, Cash | $544M | $579M | $579M | $579M | $579M | $610M | $611M | $611M |
| Payments of Ordinary Dividends, Common Stock | $544M | $579M | $579M | $579M | $579M | $610M | $611M | $611M |
| Provision (benefit) for deferred income taxes | $365M | $152M | $106M | $209M | $39M | $107M | $79M | $256M |
| Proportional Modified EBITDA Equity Method Investments | $246M | $228M | $238M | $227M | $216M | $236M | $231M | $250M |
| Distributions of earnings from equity method investees | $189M | $188M | $206M | $186M | $209M | $158M | $254M | $188M |
| Federal | $317M | $127M | $90M | $178M | $77M | $89M | $63M | $185M |
| Accounts payable | — | -$309M | $90M | -$98M | $456M | -$29M | -$236M | -$94M |
| Increase (Decrease) in Accounts and Notes Receivable | — | -$314M | $44M | -$97M | $536M | -$82M | -$219M | -$83M |
| State | $50M | $25M | $16M | $31M | — | $18M | $16M | $71M |
| Minority Interest Decrease From Distributions To Noncontrolling Interest Holders | $39M | $64M | $66M | $48M | $64M | $69M | $62M | $66M |
| Increase (Decrease) in Derivative Assets and Liabilities | -$28M | $68M | $73M | — | $212M | -$4M | -$15M | -$58M |
| Stockholders' Equity, Period Increase (Decrease) | $548M | $39M | -$184M | $119M | -$25M | $25M | -$60M | $55M |
| All other operating activities | -$76M | -$61M | -$90M | -$49M | -$45M | -$29M | -$48M | -$51M |
| Unrealized Gain (Loss) on Derivatives and Commodity Contracts | $227M | -$92M | -$131M | $0 | -$157M | -$32M | $36M | $51M |
| Payments To Retire Proceeds From Sale Of Property Plant And Equipment | $18M | -$5M | $32M | $46M | $32M | $0 | $40M | $40M |
| Less: comprehensive income attributable to noncontrolling interest | $30M | $30M | $25M | $35M | $31M | $38M | $37M | $36M |
| Net Income Loss Attributable To Noncontrolling Interest | $30M | $30M | $25M | $35M | $31M | $38M | $37M | $36M |
| Contract With Customer Liability Cumulative Catch Up Adjustment To Revenue Change In Measure Of Progress | -$26M | -$42M | -$75M | -$33M | -$33M | -$34M | -$86M | -$32M |
| Stockholders' Equity, Other | $6M | $4M | $3M | $4M | $7M | $5M | $2M | -$26M |
| Shares Issued, Value, Share-Based Payment Arrangement, after Forfeiture | $16M | -$12M | $25M | $22M | $32M | -$25M | $17M | $24M |
| Asset Retirement Obligation Accretion Expense For Nonregulated Operations | $16M | $18M | $21M | $17M | $25M | $24M | $24M | $23M |
| Other income, net (Note 6) | $30M | $31M | $33M | $31M | $13M | $14M | $16M | $21M |
| Stock-based compensation | $18M | $24M | $24M | $21M | $30M | $30M | $19M | $21M |
| Investment and other (expense) income, net | $63M | $24M | $18M | $290M | $11M | $8M | $4M | $19M |
| Other income, net | — | $17M | $27M | $25M | — | $10M | -$13M | -$14M |
| Increase (decrease) to net contractual service agreements due to billings | $50M | $41M | $40M | $44M | $45M | $30M | $28M | $13M |
| Payments to Acquire Equity Method Investments | $61M | $52M | $30M | $19M | $13M | $163M | $16M | $13M |
| Federal | — | $35M | $19M | $11M | $60M | $79M | $84M | -$8M |
| Increase (Decrease) in Other Current Assets | -$65M | -$9M | -$3M | $28M | -$25M | $40M | — | $7M |
| Contract with Customer, Asset, Reclassified to Receivable | $87M | $27M | $23M | $23M | $71M | $23M | $30M | $5M |
| Increase (Decrease) in Inventories | — | -$34M | $37M | $3M | $3M | -$28M | $89M | $5M |
| Other comprehensive income (loss) | — | $10M | $3M | -$13M | $76M | $0 | $1M | -$4M |
| Proceeds from Issuance of Common Stock | — | $5M | $0 | $3M | $2M | $5M | — | $4M |
| Contributions From Noncontrolling Interests | — | $26M | $10M | — | — | $5M | $14M | $3M |
| Pension and other postretirement benefit, tax | -$1M | $0 | $1M | $0 | -$1M | — | $1M | $3M |
| Payments of Debt Issuance Costs | $2M | $16M | $2M | $13M | $1M | $12M | $14M | $3M |
| Proceeds from Noncontrolling Interests | — | $26M | $10M | — | — | $5M | $14M | $3M |
| Financing — other | -$2M | -$17M | -$1M | -$16M | -$2M | -$54M | -$3M | -$3M |
| Current State And Local Tax Expense Benefit | $10M | $6M | $4M | $7M | — | $7M | $11M | -$2M |
| Other Comprehensive Income Loss Reclassification Adjustment From AOCI Pension And Other Postretirement Benefit Plans For Net Gain Loss Tax | $1M | $0 | $0 | $0 | $1M | — | $0 | $2M |
| Other Significant Noncash Transaction, Value of Consideration Received | $2M | $2M | $2M | $2M | $2M | $2M | $2M | $1M |
| Dividends declared (in dollars per share) | $0.4 | $0.5 | $0.5 | $0.5 | $0.5 | $0.5 | $0.5 | $0.5 |
| Derivative, Additional Notional Amount | — | $237.5M | $237.5M | $237.5M | $237.5M | — | — | — |
| Asset Retirement Obligation Liabilities Incurred | $10.5M | $118.5M | $118.5M | $118.5M | $118.5M | — | — | — |
| Asset Retirement Obligation, Liabilities Settled | $10.8M | $17M | $17M | $17M | $17M | — | — | — |
| Changes in estimated cash flows | $18.5M | $7.8M | $7.8M | $7.8M | $7.8M | — | — | — |
| Gain resulting from acquisition of joint venture | $7.5M | $31.8M | $31.8M | $31.8M | $31.8M | — | — | — |
| Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Period Increase (Decrease), Including Exchange Rate Effect and Discontinued Operation | $76M | -$1.5B | -$612M | — | -$702M | $40M | $803M | — |
| Contract with Customer, Asset, Increase (Decrease) for Contract Acquired in Business Combination | $0 | — | — | $36M | — | — | — | $0 |
| Other | $118M | — | — | $53M | — | — | — | $0 |
| Deferred Tax Assets, Tax Credit Carryforwards, Foreign, Expired | — | $8.8M | $8.8M | $8.8M | $8.8M | — | — | — |
| Defined Contribution Plan Cost Recognized | $15M | $17.3M | $17.3M | $17.3M | $17.3M | — | — | — |
| Defined Contribution Plan Employer Matching Contribution Percent Of Match | — | — | — | — | 6.0% | — | — | — |
| Depreciation | $425M | $450M | $450M | $450M | $450M | — | — | — |
| Derivative Notional Amount Terminated | — | $437.5M | $437.5M | $437.5M | $437.5M | — | — | — |
| Equity Method Investment Realized Gain Loss On Disposal | $0 | $37.3M | $37.3M | $37.3M | $37.3M | — | — | — |
| Transfers into Level 3 | $0 | $250K | $250K | $250K | $250K | — | — | — |
| Transfers out of Level 3 | -$500K | $0 | $0 | $0 | $0 | — | — | — |
| Purchases, issuances, and settlements | $5M | -$250K | -$250K | -$250K | -$250K | — | — | — |
| Realized and unrealized gains (losses): Included in income (loss) | $22.8M | -$1.3M | -$1.3M | -$1.3M | -$1.3M | — | — | — |
| Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate, Amount | $231.3M | $156.8M | $156.8M | $156.8M | $156.8M | — | — | — |
| Effective Income Tax Rate Reconciliation, Noncontrolling Interest Income (Loss), Amount | $6.5M | $6.3M | $6.3M | $6.3M | $6.3M | — | — | — |
| Federal settlements | $0 | $0 | $0 | $0 | $0 | — | — | — |
| Income taxes paid | $7.8M | $17M | $17M | $17M | $17M | — | — | — |
| Increase (decrease) in other current liabilities | -$4.8M | -$218M | $142M | -$32M | $143M | -$70M | $220M | — |
| Interest capitalized | $13.5M | $17M | $17M | $17M | $17M | — | — | — |
| Investment Income Nonoperating Other | -$250K | $0 | $0 | $0 | $0 | — | — | — |
| Net gains (losses) deferred | — | $11M | $4M | -$13M | $4M | $1M | $2M | $0 |
| Payment for (Proceeds from) Other Investing Activity | -$56M | -$6M | -$14M | — | — | -$6M | -$4M | — |
| Payments to Acquire Businesses, Net of Cash Acquired | $544M | $1.9B | $0 | $151M | $249M | $1M | — | — |
| Payments to Acquire Productive Assets | $1.1B | $1.4B | $1.4B | $1.4B | $1.4B | — | — | — |
| Debt issued (Note 13) | $1M | $2.1B | $1M | $1.5B | $0 | $1.5B | $1.5B | — |
| Proceeds from legal settlements | $156.8M | — | — | — | — | — | — | — |
| Net change in commercial paper | $724M | -$723M | — | -$628M | — | -$132M | -$322M | — |
| Sales of and distributions from equity method investments | $0 | $40.3M | $40.3M | $40.3M | $40.3M | — | — | — |
| Related Party Transaction, Rate | — | — | — | — | 4.0% | 4.0% | — | — |
| Treasury stock, value, acquired | — | $0 | $0 | $0 | $0 | $0 | $0 | $0 |
