| Three Months Ended December 31, | Year Ended December 31, | ||||||||||||||||||||||
| 2024 | 2023 | 2024 | 2023 | ||||||||||||||||||||
| Operating Revenues: | |||||||||||||||||||||||
| Electric | $ | 1,620 | $ | 1,343 | $ | 6,540 | $ | 6,439 | |||||||||||||||
| Natural gas | 321 | 275 | 1,083 | 1,061 | |||||||||||||||||||
| Total operating revenues | 1,941 | 1,618 | 7,623 | 7,500 | |||||||||||||||||||
| Operating Expenses: | |||||||||||||||||||||||
| Fuel and purchased power | 527 | 294 | 1,681 | 1,812 | |||||||||||||||||||
| Natural gas purchased for resale | 106 | 75 | 320 | 355 | |||||||||||||||||||
| Other operations and maintenance | 514 | 498 | 1,969 | 1,866 | |||||||||||||||||||
| Depreciation and amortization | 465 | 363 | 1,590 | 1,387 | |||||||||||||||||||
| Taxes other than income taxes | 131 | 124 | 547 | 522 | |||||||||||||||||||
| Total operating expenses | 1,743 | 1,354 | 6,107 | 5,942 | |||||||||||||||||||
| Operating Income | 198 | 264 | 1,516 | 1,558 | |||||||||||||||||||
| Other Income, Net | 124 | 87 | 417 | 348 | |||||||||||||||||||
| Interest Charges | 171 | 153 | 663 | 566 | |||||||||||||||||||
| Income Before Income Taxes | 151 | 198 | 1,270 | 1,340 | |||||||||||||||||||
| Income Taxes (Benefit) | (57) | 39 | 83 | 183 | |||||||||||||||||||
| Net Income | 208 | 159 | 1,187 | 1,157 | |||||||||||||||||||
| Less: Net Income Attributable to Noncontrolling Interests | 1 | 1 | 5 | 5 | |||||||||||||||||||
| Net Income Attributable to Ameren Common Shareholders | $ | 207 | $ | 158 | $ | 1,182 | $ | 1,152 | |||||||||||||||
| Earnings per Common Share – Basic | $ | 0.77 | $ | 0.60 | $ | 4.43 | $ | 4.39 | |||||||||||||||
| Earnings per Common Share – Diluted | $ | 0.77 | $ | 0.60 | $ | 4.42 | $ | 4.38 | |||||||||||||||
| Weighted-average Common Shares Outstanding – Basic | 267.4 | 263.5 | 266.8 | 262.8 | |||||||||||||||||||
| Weighted-average Common Shares Outstanding – Diluted | 268.9 | 264.0 | 267.4 | 263.4 | |||||||||||||||||||
| December 31, 2024 | December 31, 2023 | ||||||||||
| ASSETS | |||||||||||
| Current Assets: | |||||||||||
| Cash and cash equivalents | $ | 7 | $ | 25 | |||||||
| Accounts receivable - trade (less allowance for doubtful accounts) | 525 | 494 | |||||||||
| Unbilled revenue | 346 | 319 | |||||||||
| Miscellaneous accounts receivable | 96 | 106 | |||||||||
| Inventories | 762 | 733 | |||||||||
| Current regulatory assets | 366 | 365 | |||||||||
| Other current assets | 162 | 139 | |||||||||
| Total current assets | 2,264 | 2,181 | |||||||||
| Property, Plant, and Equipment, Net | 36,304 | 33,776 | |||||||||
| Investments and Other Assets: | |||||||||||
| Nuclear decommissioning trust fund | 1,342 | 1,150 | |||||||||
| Goodwill | 411 | 411 | |||||||||
| Regulatory assets | 2,397 | 1,810 | |||||||||
| Pension and other postretirement benefits | 757 | 581 | |||||||||
| Other assets | 1,123 | 921 | |||||||||
| Total investments and other assets | 6,030 | 4,873 | |||||||||
| TOTAL ASSETS | $ | 44,598 | $ | 40,830 | |||||||
| LIABILITIES AND EQUITY | |||||||||||
| Current Liabilities: | |||||||||||
| Current maturities of long-term debt | $ | 317 | $ | 849 | |||||||
| Short-term debt | 1,143 | 536 | |||||||||
| Accounts and wages payable | 1,059 | 1,136 | |||||||||
| Interest accrued | 196 | 147 | |||||||||
| Customer deposits | 223 | 176 | |||||||||
| Other current liabilities | 475 | 501 | |||||||||
| Total current liabilities | 3,413 | 3,345 | |||||||||
| Long-term Debt, Net | 17,262 | 15,121 | |||||||||
| Deferred Credits and Other Liabilities: | |||||||||||
| Accumulated deferred income taxes and production and investment tax credits, net | 4,474 | 4,176 | |||||||||
| Regulatory liabilities | 5,897 | 5,512 | |||||||||
| Asset retirement obligations | 822 | 772 | |||||||||
| Other deferred credits and liabilities | 487 | 426 | |||||||||
| Total deferred credits and other liabilities | 11,680 | 10,886 | |||||||||
| Shareholders’ Equity: | |||||||||||
| Common stock | 3 | 3 | |||||||||
| Other paid-in capital, principally premium on common stock | 7,513 | 7,216 | |||||||||
| Retained earnings | 4,604 | 4,136 | |||||||||
| Accumulated other comprehensive loss | (6) | (6) | |||||||||
| Total shareholders’ equity | 12,114 | 11,349 | |||||||||
| Noncontrolling Interests | 129 | 129 | |||||||||
| Total equity | 12,243 | 11,478 | |||||||||
| TOTAL LIABILITIES AND EQUITY | $ | 44,598 | $ | 40,830 | |||||||
| Year Ended December 31, | |||||||||||
| 2024 | 2023 | ||||||||||
| Cash Flows From Operating Activities: | |||||||||||
| Net income | $ | 1,187 | $ | 1,157 | |||||||
| Adjustments to reconcile net income to net cash provided by operating activities: | |||||||||||
| Depreciation and amortization | 1,524 | 1,432 | |||||||||
| Amortization of nuclear fuel | 81 | 68 | |||||||||
| Amortization of debt issuance costs and premium/discounts | 19 | 16 | |||||||||
| Deferred income taxes and production and investment tax credits, net | 127 | 229 | |||||||||
| Allowance for equity funds used during construction | (76) | (54) | |||||||||
| Stock-based compensation costs | 28 | 26 | |||||||||
| Other | 87 | 16 | |||||||||
| Changes in assets and liabilities | (214) | (326) | |||||||||
| Net cash provided by operating activities | 2,763 | 2,564 | |||||||||
| Cash Flows From Investing Activities: | |||||||||||
| Capital expenditures | (4,319) | (3,597) | |||||||||
| Nuclear fuel expenditures | (91) | (174) | |||||||||
| Purchases of securities – nuclear decommissioning trust fund | (584) | (266) | |||||||||
| Sales and maturities of securities – nuclear decommissioning trust fund | 564 | 240 | |||||||||
| Other | (26) | (1) | |||||||||
| Net cash used in investing activities | (4,456) | (3,798) | |||||||||
| Cash Flows From Financing Activities: | |||||||||||
| Dividends on common stock | (714) | (662) | |||||||||
| Dividends paid to noncontrolling interest holders | (5) | (5) | |||||||||
| Short-term debt, net | 607 | (533) | |||||||||
| Maturities and extinguishment of long-term debt | (893) | (100) | |||||||||
| Issuances of long-term debt | 2,535 | 2,295 | |||||||||
| Issuances of common stock | 273 | 346 | |||||||||
| Employee payroll taxes related to stock-based compensation | (8) | (20) | |||||||||
| Debt issuance costs | (31) | (21) | |||||||||
| Other | (15) | (10) | |||||||||
| Net cash provided by financing activities | 1,749 | 1,290 | |||||||||
| Net change in cash, cash equivalents, and restricted cash | 56 | 56 | |||||||||
Cash, cash equivalents, and restricted cash at beginning of year(a) | 272 | 216 | |||||||||
Cash, cash equivalents, and restricted cash at end of year(b) | $ | 328 | $ | 272 | |||||||