| Current Federal Tax Expense (Benefit) | -117.00M | 2025-01-01 → 2025-12-31 |
| Current State and Local Tax Expense (Benefit) | 0 | 2025-01-01 → 2025-12-31 |
| Deferred Federal Income Tax Expense (Benefit) | 269.00M | 2025-01-01 → 2025-12-31 |
| Deferred State and Local Income Tax Expense (Benefit) | 102.00M | 2025-01-01 → 2025-12-31 |
| Asset Retirement Obligation, Liabilities Incurred | 0 | 2025-01-01 → 2025-12-31 |
| Deferred Other Tax Expense (Benefit) | -11.00M | 2025-01-01 → 2025-12-31 |
| Asset Retirement Obligation, Liabilities Settled | 10.00M | 2025-01-01 → 2025-12-31 |
| Operating Lease, Liability, Current | 3.00M | as of 2025-12-31 |
| Asset Retirement Obligation, Revision of Estimate | 1.00M | 2025-01-01 → 2025-12-31 |
| Share-based Payment Arrangement, Expense | 28.00M | 2025-01-01 → 2025-12-31 |
| Short-term Debt, Maximum Amount Outstanding During Period | 1.60B | 2025-01-01 → 2025-12-31 |
| Public Utilities, Allowance for Funds Used During Construction, Capitalized Cost of Equity | 88.00M | 2025-01-01 → 2025-12-31 |
| Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate, Amount | 335.00M | 2025-01-01 → 2025-12-31 |
| Energy Related Inventory, Gas Stored Underground | 98.00M | as of 2025-12-31 |
| Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Amount | 74.00M | 2025-01-01 → 2025-12-31 |
| Share-based Payment Arrangement, Expense, after Tax | 21.00M | 2025-01-01 → 2025-12-31 |
| Energy Related Inventory, Coal | 101.00M | as of 2025-12-31 |
| Share-based Payment Arrangement, Expense, Tax Benefit | 7.00M | 2025-01-01 → 2025-12-31 |
| EffectiveIncomeTaxRateReconciliationTaxCreditEnergyRelatedAmount | 61.00M | 2025-01-01 → 2025-12-31 |
| Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount | 43.00M | as of 2025-12-31 |
| Effective Income Tax Rate Reconciliation, Tax Credit, Other, Amount | 3.00M | 2025-01-01 → 2025-12-31 |
| Effective Income Tax Rate Reconciliation, Nondeductible Expense, Amount | -2.00M | 2025-01-01 → 2025-12-31 |
| Noncontrolling Interest in Variable Interest Entity | 64.00M | as of 2025-12-31 |
| Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount | 0 | 2025-01-01 → 2025-12-31 |
| Effective Income Tax Rate Reconciliation, Other Adjustments, Amount | 0 | 2025-01-01 → 2025-12-31 |
| Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, after Year One Through Five | 207.00M | as of 2025-12-31 |
| Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, after Year 5 Through 10 | 139.00M | as of 2025-12-31 |
| Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, after Year 10 | 142.00M | as of 2025-12-31 |
| Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, after Year One Through Five | 208.00M | as of 2025-12-31 |
| Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, after Year 5 Through 10 | 141.00M | as of 2025-12-31 |
| Deferred Income Taxes and Other Tax Liabilities, Noncurrent | 5.18B | as of 2025-12-31 |
| Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, after Year 10 | 137.00M | as of 2025-12-31 |
| Defined Benefit Plan, Funded (Unfunded) Status of Plan | 954.00M | as of 2025-12-31 |
| Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position | 954.00M | as of 2025-12-31 |
| Goodwill, Impaired, Accumulated Impairment Loss | 0 | as of 2025-12-31 |
| Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits | 71.00M | as of 2025-12-31 |
| Public Utilities, Inventory | 575.00M | as of 2025-12-31 |
| Decommissioning Fund Investments, Fair Value | 1.51B | as of 2025-12-31 |
| Accounts Receivable, Allowance for Credit Loss, Writeoff | 49.00M | 2025-01-01 → 2025-12-31 |
| Lessee, Operating Lease, Liability, to be Paid, Year One | 6.00M | as of 2025-12-31 |
| Lessee, Operating Lease, Liability, to be Paid, Year Two | 6.00M | as of 2025-12-31 |
| Lessee, Operating Lease, Liability, to be Paid, Year Three | 6.00M | as of 2025-12-31 |
| Deferred Tax Assets, Regulatory Assets and Liabilities | 325.00M | as of 2025-12-31 |
| Lessee, Operating Lease, Liability, to be Paid, Year Four | 6.00M | as of 2025-12-31 |
| Lessee, Operating Lease, Liability, to be Paid, Year Five | 5.00M | as of 2025-12-31 |
| Lessee, Operating Lease, Liability, to be Paid, after Year Five | 129.00M | as of 2025-12-31 |
| Lessee, Operating Lease, Liability, to be Paid | 158.00M | as of 2025-12-31 |
| Utilities Operating Expense, Gas and Petroleum Purchased | 348.00M | 2025-01-01 → 2025-12-31 |
| Utilities Operating Expense, Depreciation and Amortization | 1.57B | 2025-01-01 → 2025-12-31 |
| Deferred Tax Assets, Net of Valuation Allowance | 343.00M | as of 2025-12-31 |
| Lessee, Operating Lease, Liability, Undiscounted Excess Amount | 82.00M | as of 2025-12-31 |
| Deferred Tax Liabilities, Property, Plant and Equipment | 5.31B | as of 2025-12-31 |
| Debt and Equity Securities, Gain (Loss) | 160.00M | 2025-01-01 → 2025-12-31 |
| Deferred Tax Liabilities, Other | 203.00M | as of 2025-12-31 |
| Deferred Tax Liabilities, Net | 4.92B | as of 2025-12-31 |
| Long-Term Debt, Maturity, Year One | 973.00M | as of 2025-12-31 |
| Defined Contribution Plan, Cost | 49.00M | 2025-01-01 → 2025-12-31 |
| Long-Term Debt, Maturity, Year Two | 974.00M | as of 2025-12-31 |
| Long-Term Debt, Maturity, Year Three | 966.00M | as of 2025-12-31 |
| Long-Term Debt, Maturity, Year Four | 1.21B | as of 2025-12-31 |
| Long-Term Debt, Maturity, Year Five | 917.00M | as of 2025-12-31 |
| Long-Term Debt, Maturity, after Year Five | 14.39B | as of 2025-12-31 |
| Operating Loss Carryforwards | 165.00M | as of 2025-12-31 |
| Short-term Debt, Average Outstanding Amount | 940.00M | 2025-01-01 → 2025-12-31 |
| Tax Credit Carryforward, Amount | 178.00M | as of 2025-12-31 |
| Other Receivables, Net, Current | 107.00M | as of 2025-12-31 |
| Allowance for Funds Used During Construction, Capitalized Interest | 52.00M | 2025-01-01 → 2025-12-31 |
| Debt Securities, Available-for-sale, Amortized Cost | 488.00M | as of 2025-12-31 |