| Life Insurance, Corporate or Bank Owned, Amount | 130.00M | as of 2025-12-31 |
| Current Federal Tax Expense (Benefit) | 1.80M | 2025-01-01 → 2025-12-31 |
| Current State and Local Tax Expense (Benefit) | 7.20M | 2025-01-01 → 2025-12-31 |
| Current Income Tax Expense (Benefit) | 9.00M | 2025-01-01 → 2025-12-31 |
| Deferred Federal Income Tax Expense (Benefit) | 52.40M | 2025-01-01 → 2025-12-31 |
| Deferred State and Local Income Tax Expense (Benefit) | -24.50M | 2025-01-01 → 2025-12-31 |
| Asset Retirement Obligation, Liabilities Incurred | 0 | 2025-01-01 → 2025-12-31 |
| Asset Retirement Obligation, Liabilities Settled | 13.30M | 2025-01-01 → 2025-12-31 |
| Operating Lease, Liability, Current | 16.40M | as of 2025-12-31 |
| Asset Retirement Obligation, Revision of Estimate | -5.30M | 2025-01-01 → 2025-12-31 |
| Prepaid Expense and Other Assets, Current | 77.90M | as of 2025-12-31 |
| Share-based Payment Arrangement, Expense | 20.70M | 2025-01-01 → 2025-12-31 |
| Forward Contract Indexed to Issuer's Equity, Settlement Alternatives, Cash, at Fair Value | 123.60M | as of 2025-12-31 |
| Public Utilities, Allowance for Funds Used During Construction, Capitalized Cost of Equity | 22.90M | 2025-01-01 → 2025-12-31 |
| Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate, Amount | 188.50M | 2025-01-01 → 2025-12-31 |
| Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Amount | 12.10M | 2025-01-01 → 2025-12-31 |
| Energy Related Inventory, Coal | 218.60M | as of 2025-12-31 |
| Share-based Payment Arrangement, Expense, Tax Benefit | 1.90M | 2025-01-01 → 2025-12-31 |
| Energy Related Inventory | 828.90M | as of 2025-12-31 |
| Effective Income Tax Rate Reconciliation, Tax Credit, Investment, Amount | 5.30M | 2025-01-01 → 2025-12-31 |
| EffectiveIncomeTaxRateReconciliationTaxCreditEnergyRelatedAmount | 57.50M | 2025-01-01 → 2025-12-31 |
| Effective Income Tax Rate Reconciliation, Tax Credit, Other, Amount | 2.20M | 2025-01-01 → 2025-12-31 |
| Effective Income Tax Rate Reconciliation, Nondeductible Expense, Life Insurance, Amount | -10.90M | 2025-01-01 → 2025-12-31 |
| Effective Income Tax Rate Reconciliation, Nondeductible Expense, Other, Amount | -2.90M | 2025-01-01 → 2025-12-31 |
| Line of Credit Facility, Current Borrowing Capacity | 2.50B | as of 2025-12-31 |
| Line of Credit Facility, Remaining Borrowing Capacity | 1.10B | as of 2025-12-31 |
| Public Utilities, Property, Plant and Equipment, Construction Work in Progress | 2.12B | as of 2025-12-31 |
| Dividends, Common Stock, Cash | 620.80M | 2025-01-01 → 2025-12-31 |
| Public Utilities, Property, Plant and Equipment, Plant in Service | 38.22B | as of 2025-12-31 |
| Public Utilities, Property, Plant and Equipment, Accumulated Depreciation | 14.99B | as of 2025-12-31 |
| Effective Income Tax Rate Reconciliation, Other Adjustments, Amount | -4.50M | 2025-01-01 → 2025-12-31 |
| Guarantor Obligations, Maximum Exposure, Undiscounted | 786.30M | as of 2025-12-31 |
| Dividend, Share-based Payment Arrangement | 1.50M | 2025-01-01 → 2025-12-31 |
| Regulatory Assets | 2.10B | as of 2025-12-31 |
| Deferred Tax Assets, Operating Loss Carryforwards, Domestic | 4.60M | as of 2025-12-31 |
| Regulatory Liabilities | 2.97B | as of 2025-12-31 |
| Stock Issued During Period, Value, New Issues | 8.90M | 2025-01-01 → 2025-12-31 |
| Deferred Tax Assets, Tax Credit Carryforwards, General Business | 572.80M | as of 2025-12-31 |
| Unrecorded Unconditional Purchase Obligation, to be Paid, Year One | 1.41B | as of 2025-12-31 |
| Unrecorded Unconditional Purchase Obligation, to be Paid, Year Two | 1.36B | as of 2025-12-31 |
| Unrecorded Unconditional Purchase Obligation, to be Paid, Year Three | 1.13B | as of 2025-12-31 |
| Unrecorded Unconditional Purchase Obligation, to be Paid, Year Four | 497.10M | as of 2025-12-31 |
| Unrecorded Unconditional Purchase Obligation, to be Paid, Year Five | 258.50M | as of 2025-12-31 |
| Unrecorded Unconditional Purchase Obligation, to be Paid, after Year Five | 564.30M | as of 2025-12-31 |
| Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Employee Compensation | 92.90M | as of 2025-12-31 |
| Unrecorded Unconditional Purchase Obligation | 5.22B | as of 2025-12-31 |
| Operating Lease, Cost | 23.20M | 2025-01-01 → 2025-12-31 |
| Short-term Lease, Cost | 4.70M | 2025-01-01 → 2025-12-31 |
| Variable Lease, Cost | 196.60M | 2025-01-01 → 2025-12-31 |
| Lease, Cost | 244.80M | 2025-01-01 → 2025-12-31 |
| Right-of-Use Asset Obtained in Exchange for Finance Lease Liability | 56.70M | 2025-01-01 → 2025-12-31 |
| Right-of-Use Asset Obtained in Exchange for Operating Lease Liability | 21.70M | 2025-01-01 → 2025-12-31 |
| Nuclear Fuel, Net of Amortization | 208.80M | as of 2025-12-31 |
| Finance Lease, Liability, to be Paid, Year One | 22.80M | as of 2025-12-31 |
| Finance Lease, Liability, to be Paid, Year Two | 22.00M | as of 2025-12-31 |
| Finance Lease, Liability, to be Paid, Year Three | 21.00M | as of 2025-12-31 |
| Finance Lease, Liability, to be Paid, Year Four | 17.10M | as of 2025-12-31 |
| Finance Lease, Liability, to be Paid, Year Five | 12.70M | as of 2025-12-31 |
| Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Accrued Liabilities | 214.80M | as of 2025-12-31 |
| Finance Lease, Liability, to be Paid, after Year Five | 78.10M | as of 2025-12-31 |
| Finance Lease, Liability, Payment, Due | 173.70M | as of 2025-12-31 |
| Accounts Receivable, Allowance for Credit Loss, Writeoff | 32.40M | 2025-01-01 → 2025-12-31 |
| Accounts Receivable, Allowance for Credit Loss, Recovery | 11.60M | 2025-01-01 → 2025-12-31 |
| Deferred Tax Assets, State Taxes | 123.50M | as of 2025-12-31 |
| Finance Lease, Liability, Undiscounted Excess Amount | 43.70M | as of 2025-12-31 |
| Lessee, Operating Lease, Liability, to be Paid, Year One | 18.90M | as of 2025-12-31 |
| Lessee, Operating Lease, Liability, to be Paid, Year Two | 15.00M | as of 2025-12-31 |
| Lessee, Operating Lease, Liability, to be Paid, Year Three | 11.80M | as of 2025-12-31 |
| Deferred Tax Assets, Regulatory Assets and Liabilities | 69.50M | as of 2025-12-31 |
| Lessee, Operating Lease, Liability, to be Paid, Year Four | 8.00M | as of 2025-12-31 |
| Lessee, Operating Lease, Liability, to be Paid, Year Five | 6.60M | as of 2025-12-31 |
| Lessee, Operating Lease, Liability, to be Paid, after Year Five | 8.60M | as of 2025-12-31 |
| Lessee, Operating Lease, Liability, to be Paid | 68.90M | as of 2025-12-31 |
| Deferred Tax Assets, Other | 94.90M | as of 2025-12-31 |
| Utilities Operating Expense, Maintenance and Operations | 995.30M | 2025-01-01 → 2025-12-31 |
| Deferred Tax Assets, Gross | 1.50B | as of 2025-12-31 |
| Deferred Tax Assets, Valuation Allowance | 7.20M | as of 2025-12-31 |
| Deferred Tax Assets, Net of Valuation Allowance | 1.49B | as of 2025-12-31 |
| Lessee, Operating Lease, Liability, Undiscounted Excess Amount | 7.90M | as of 2025-12-31 |
| Deferred Tax Liabilities, Gross | 3.51B | as of 2025-12-31 |
| Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount | -300.00K | 2025-01-01 → 2025-12-31 |
| Deferred Tax Liabilities, Property, Plant and Equipment | 2.97B | as of 2025-12-31 |
| Deferred Tax Liabilities, Regulatory Assets | 227.60M | as of 2025-12-31 |
| Deferred Tax Liabilities, Other | 81.70M | as of 2025-12-31 |
| Deferred Tax Liabilities, Net | 2.02B | as of 2025-12-31 |
| Transfers Accounted for as Secured Borrowings, Assets, Carrying Amount | 402.00M | as of 2025-12-31 |
| Transfers Accounted for as Secured Borrowings, Associated Liabilities, Carrying Amount | 402.00M | as of 2025-12-31 |
| Long-Term Debt, Maturity, Year One | 367.00M | as of 2025-12-31 |
| Defined Contribution Plan, Cost | 29.60M | 2025-01-01 → 2025-12-31 |
| Long-Term Debt, Maturity, Year Two | 2.04B | as of 2025-12-31 |
| Long-Term Debt, Maturity, Year Three | 318.80M | as of 2025-12-31 |
| Long-Term Debt, Maturity, Year Four | 819.80M | as of 2025-12-31 |
| Long-Term Debt, Maturity, Year Five | 420.80M | as of 2025-12-31 |
| Tax Credit Carryforward, Amount | 567.90M | as of 2025-12-31 |
| Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net | 109.60M | as of 2025-12-31 |
| Income Taxes Receivable, Current | 8.20M | as of 2025-12-31 |
| Amount of Restricted Net Assets for Consolidated and Unconsolidated Subsidiaries | 6.70B | as of 2025-12-31 |
| Other Receivables, Gross, Current | 110.60M | as of 2025-12-31 |
| Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss) | 66.40M | 2025-01-01 → 2025-12-31 |
| Equity Restrictions | 394.80M | as of 2025-12-31 |
| Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments | 1.30M | as of 2025-12-31 |
| Credit Derivative, Maximum Exposure, Undiscounted | 35.80M | as of 2025-12-31 |
| Derivative, Net Liability Position, Aggregate Fair Value | 35.60M | as of 2025-12-31 |
| Collateral Already Posted, Aggregate Fair Value | 5.10M | as of 2025-12-31 |
| Additional Collateral, Aggregate Fair Value | 28.80M | as of 2025-12-31 |
| APIC, Share-based Payment Arrangement, Increase for Cost Recognition | 20.70M | 2025-01-01 → 2025-12-31 |