| Three Months Ended September 30, | Nine Months Ended September 30, | ||||||||||||||||||||||
| 2025 | 2024 | 2025 | 2024 | ||||||||||||||||||||
| Operating Revenues: | |||||||||||||||||||||||
| Electric | $ | 2,563 | $ | 2,035 | $ | 6,223 | $ | 4,920 | |||||||||||||||
| Natural gas | 136 | 138 | 794 | 762 | |||||||||||||||||||
| Total operating revenues | 2,699 | 2,173 | 7,017 | 5,682 | |||||||||||||||||||
| Operating Expenses: | |||||||||||||||||||||||
| Fuel and purchased power | 768 | 499 | 2,064 | 1,154 | |||||||||||||||||||
| Natural gas purchased for resale | 25 | 30 | 233 | 214 | |||||||||||||||||||
| Other operations and maintenance | 502 | 520 | 1,447 | 1,455 | |||||||||||||||||||
| Depreciation and amortization | 415 | 388 | 1,168 | 1,125 | |||||||||||||||||||
| Taxes other than income taxes | 164 | 150 | 439 | 416 | |||||||||||||||||||
| Total operating expenses | 1,874 | 1,587 | 5,351 | 4,364 | |||||||||||||||||||
| Operating Income | 825 | 586 | 1,666 | 1,318 | |||||||||||||||||||
| Other Income, Net | 76 | 101 | 257 | 293 | |||||||||||||||||||
| Interest Charges | 208 | 173 | 570 | 492 | |||||||||||||||||||
| Income Before Income Taxes | 693 | 514 | 1,353 | 1,119 | |||||||||||||||||||
| Income Taxes | 52 | 57 | 145 | 140 | |||||||||||||||||||
| Net Income | 641 | 457 | 1,208 | 979 | |||||||||||||||||||
| Less: Net Income Attributable to Noncontrolling Interests | 1 | 1 | 4 | 4 | |||||||||||||||||||
| Net Income Attributable to Ameren Common Shareholders | $ | 640 | $ | 456 | $ | 1,204 | $ | 975 | |||||||||||||||
| Earnings per Common Share - Basic | $ | 2.37 | $ | 1.71 | $ | 4.46 | $ | 3.66 | |||||||||||||||
| Earnings per Common Share – Diluted | $ | 2.35 | $ | 1.70 | $ | 4.43 | $ | 3.65 | |||||||||||||||
| Weighted-average Common Shares Outstanding – Basic | 270.4 | 266.8 | 270.2 | 266.6 | |||||||||||||||||||
| Weighted-average Common Shares Outstanding – Diluted | 272.2 | 267.3 | 271.7 | 266.9 | |||||||||||||||||||
| September 30, 2025 | December 31, 2024 | ||||||||||
| ASSETS | |||||||||||
| Current Assets: | |||||||||||
| Cash and cash equivalents | $ | 9 | $ | 7 | |||||||
| Accounts receivable - trade (less allowance for doubtful accounts) | 794 | 525 | |||||||||
| Unbilled revenue | 413 | 346 | |||||||||
| Miscellaneous accounts receivable | 78 | 96 | |||||||||
| Inventories | 804 | 762 | |||||||||
| Current regulatory assets | 260 | 366 | |||||||||
| Other current assets | 252 | 162 | |||||||||
| Total current assets | 2,610 | 2,264 | |||||||||
| Property, Plant, and Equipment, Net | 38,411 | 36,304 | |||||||||
| Investments and Other Assets: | |||||||||||
| Nuclear decommissioning trust fund | 1,502 | 1,342 | |||||||||
| Goodwill | 411 | 411 | |||||||||
| Regulatory assets | 2,611 | 2,397 | |||||||||
| Pension and other postretirement benefits | 741 | 757 | |||||||||
| Other assets | 1,130 | 1,123 | |||||||||
| Total investments and other assets | 6,395 | 6,030 | |||||||||
| TOTAL ASSETS | $ | 47,416 | $ | 44,598 | |||||||
| LIABILITIES AND EQUITY | |||||||||||
| Current Liabilities: | |||||||||||
| Current maturities of long-term debt | $ | 29 | $ | 317 | |||||||
| Short-term debt | 903 | 1,143 | |||||||||
| Accounts and wages payable | 762 | 1,059 | |||||||||
| Taxes accrued | 215 | 60 | |||||||||
| Interest accrued | 183 | 196 | |||||||||
| Customer deposits | 248 | 223 | |||||||||
| Current regulatory liabilities | 142 | 120 | |||||||||
| Other current liabilities | 323 | 295 | |||||||||
| Total current liabilities | 2,805 | 3,413 | |||||||||
| Long-term Debt, Net | 19,172 | 17,262 | |||||||||
| Deferred Credits and Other Liabilities: | |||||||||||
| Accumulated deferred income taxes and tax credits, net | 5,081 | 4,474 | |||||||||
| Regulatory liabilities | 6,089 | 5,897 | |||||||||
| Asset retirement obligations | 844 | 822 | |||||||||
| Other deferred credits and liabilities | 516 | 487 | |||||||||
| Total deferred credits and other liabilities | 12,530 | 11,680 | |||||||||
| Shareholders’ Equity: | |||||||||||
| Common stock | 3 | 3 | |||||||||
| Other paid-in capital, principally premium on common stock | 7,559 | 7,513 | |||||||||
| Retained earnings | 5,232 | 4,604 | |||||||||
| Accumulated other comprehensive loss | (14) | (6) | |||||||||
| Total shareholders’ equity | 12,780 | 12,114 | |||||||||
| Noncontrolling Interests | 129 | 129 | |||||||||
| Total equity | 12,909 | 12,243 | |||||||||
| TOTAL LIABILITIES AND EQUITY | $ | 47,416 | $ | 44,598 | |||||||
| Nine Months Ended September 30, | |||||||||||
| 2025 | 2024 | ||||||||||
| Cash Flows From Operating Activities: | |||||||||||
| Net income | $ | 1,208 | $ | 979 | |||||||
| Adjustments to reconcile net income to net cash provided by operating activities: | |||||||||||
| Depreciation and amortization | 1,199 | 1,142 | |||||||||
| Amortization of nuclear fuel | 39 | 59 | |||||||||
| Amortization of debt issuance costs and premium/discounts | 14 | 14 | |||||||||
| Deferred income taxes and tax credits, net | 255 | 145 | |||||||||
| Allowance for equity funds used during construction | (60) | (48) | |||||||||
| Stock-based compensation costs | 21 | 22 | |||||||||
| Other | 29 | 84 | |||||||||
| Changes in assets and liabilities | (308) | (451) | |||||||||
| Net cash provided by operating activities | 2,397 | 1,946 | |||||||||
| Cash Flows From Investing Activities: | |||||||||||
| Capital expenditures | (3,118) | (3,029) | |||||||||
| Nuclear fuel expenditures | (20) | (57) | |||||||||
| Purchases of securities – nuclear decommissioning trust fund | (373) | (499) | |||||||||
| Sales and maturities of securities – nuclear decommissioning trust fund | 348 | 480 | |||||||||
| Other | 51 | (1) | |||||||||
| Net cash used in investing activities | (3,112) | (3,106) | |||||||||
| Cash Flows From Financing Activities: | |||||||||||
| Dividends on common stock | (576) | (535) | |||||||||
| Dividends paid to noncontrolling interest holders | (4) | (4) | |||||||||
| Short-term debt, net | (239) | 1,002 | |||||||||
| Maturities and extinguishment of long-term debt | (324) | (849) | |||||||||
| Issuances of long-term debt | 1,960 | 1,610 | |||||||||
| Issuances of common stock | 35 | 30 | |||||||||
| Employee payroll taxes related to stock-based compensation | (13) | (8) | |||||||||
| Debt issuance costs | (17) | (19) | |||||||||
| Other | — | (15) | |||||||||
| Net cash provided by financing activities | 822 | 1,212 | |||||||||
| Net change in cash, cash equivalents, and restricted cash | 107 | 52 | |||||||||
Cash, cash equivalents, and restricted cash at beginning of year(a) | 328 | 272 | |||||||||
Cash, cash equivalents, and restricted cash at end of period(b) | $ | 435 | $ | 324 | |||||||