| Three Months Ended December 31, | Year Ended December 31, | ||||||||||||||||||||||
| 2023 | 2022 | 2023 | 2022 | ||||||||||||||||||||
| Operating Revenues: | |||||||||||||||||||||||
| Electric | $ | 1,343 | $ | 1,610 | $ | 6,439 | $ | 6,581 | |||||||||||||||
| Natural gas | 275 | 436 | 1,061 | 1,376 | |||||||||||||||||||
| Total operating revenues | 1,618 | 2,046 | 7,500 | 7,957 | |||||||||||||||||||
| Operating Expenses: | |||||||||||||||||||||||
| Fuel | 91 | 97 | 514 | 473 | |||||||||||||||||||
| Purchased power | 203 | 489 | 1,298 | 1,547 | |||||||||||||||||||
| Natural gas purchased for resale | 75 | 226 | 355 | 657 | |||||||||||||||||||
| Other operations and maintenance | 498 | 510 | 1,866 | 1,937 | |||||||||||||||||||
| Depreciation and amortization | 363 | 324 | 1,387 | 1,289 | |||||||||||||||||||
| Taxes other than income taxes | 124 | 124 | 522 | 539 | |||||||||||||||||||
| Total operating expenses | 1,354 | 1,770 | 5,942 | 6,442 | |||||||||||||||||||
| Operating Income | 264 | 276 | 1,558 | 1,515 | |||||||||||||||||||
| Other Income, Net | 87 | 46 | 348 | 226 | |||||||||||||||||||
| Interest Charges | 153 | 130 | 566 | 486 | |||||||||||||||||||
| Income Before Income Taxes | 198 | 192 | 1,340 | 1,255 | |||||||||||||||||||
| Income Taxes | 39 | 28 | 183 | 176 | |||||||||||||||||||
| Net Income | 159 | 164 | 1,157 | 1,079 | |||||||||||||||||||
| Less: Net Income Attributable to Noncontrolling Interests | 1 | 1 | 5 | 5 | |||||||||||||||||||
| Net Income Attributable to Ameren Common Shareholders | $ | 158 | $ | 163 | $ | 1,152 | $ | 1,074 | |||||||||||||||
| Earnings per Common Share – Basic | $ | 0.60 | $ | 0.63 | $ | 4.39 | $ | 4.16 | |||||||||||||||
| Earnings per Common Share – Diluted | $ | 0.60 | $ | 0.63 | $ | 4.38 | $ | 4.14 | |||||||||||||||
| Weighted-average Common Shares Outstanding – Basic | 263.5 | 259.1 | 262.8 | 258.4 | |||||||||||||||||||
| Weighted-average Common Shares Outstanding – Diluted | 264.0 | 260.2 | 263.4 | 259.5 | |||||||||||||||||||
| December 31, 2023 | December 31, 2022 | ||||||||||
| ASSETS | |||||||||||
| Current Assets: | |||||||||||
| Cash and cash equivalents | $ | 25 | $ | 10 | |||||||
| Accounts receivable - trade (less allowance for doubtful accounts) | 494 | 600 | |||||||||
| Unbilled revenue | 319 | 446 | |||||||||
| Miscellaneous accounts receivable | 106 | 54 | |||||||||
| Inventories | 733 | 667 | |||||||||
| Current regulatory assets | 365 | 354 | |||||||||
| Investments in industrial development revenue bonds | — | 240 | |||||||||
| Current collateral assets | 14 | 142 | |||||||||
| Other current assets | 125 | 155 | |||||||||
| Total current assets | 2,181 | 2,668 | |||||||||
| Property, Plant, and Equipment, Net | 33,776 | 31,262 | |||||||||
| Investments and Other Assets: | |||||||||||
| Nuclear decommissioning trust fund | 1,150 | 958 | |||||||||
| Goodwill | 411 | 411 | |||||||||
| Regulatory assets | 1,810 | 1,426 | |||||||||
| Pension and other postretirement benefits | 581 | 411 | |||||||||
| Other assets | 921 | 768 | |||||||||
| Total investments and other assets | 4,873 | 3,974 | |||||||||
| TOTAL ASSETS | $ | 40,830 | $ | 37,904 | |||||||
| LIABILITIES AND EQUITY | |||||||||||
| Current Liabilities: | |||||||||||
| Current maturities of long-term debt | $ | 849 | $ | 340 | |||||||
| Short-term debt | 536 | 1,070 | |||||||||
| Accounts and wages payable | 1,136 | 1,159 | |||||||||
| Customer deposits | 176 | 115 | |||||||||
| Other current liabilities | 648 | 682 | |||||||||
| Total current liabilities | 3,345 | 3,366 | |||||||||
| Long-term Debt, Net | 15,121 | 13,685 | |||||||||
| Deferred Credits and Other Liabilities: | |||||||||||
| Accumulated deferred income taxes and investment tax credits, net | 4,176 | 3,804 | |||||||||
| Regulatory liabilities | 5,512 | 5,309 | |||||||||
| Asset retirement obligations | 772 | 763 | |||||||||
| Other deferred credits and liabilities | 426 | 340 | |||||||||
| Total deferred credits and other liabilities | 10,886 | 10,216 | |||||||||
| Shareholders’ Equity: | |||||||||||
| Common stock | 3 | 3 | |||||||||
| Other paid-in capital, principally premium on common stock | 7,216 | 6,860 | |||||||||
| Retained earnings | 4,136 | 3,646 | |||||||||
| Accumulated other comprehensive loss | (6) | (1) | |||||||||
| Total shareholders’ equity | 11,349 | 10,508 | |||||||||
| Noncontrolling Interests | 129 | 129 | |||||||||
| Total equity | 11,478 | 10,637 | |||||||||
| TOTAL LIABILITIES AND EQUITY | $ | 40,830 | $ | 37,904 | |||||||
| Year Ended December 31, | |||||||||||
| 2023 | 2022 | ||||||||||
| Cash Flows From Operating Activities: | |||||||||||
| Net income | $ | 1,157 | $ | 1,079 | |||||||
| Adjustments to reconcile net income to net cash provided by operating activities: | |||||||||||
| Depreciation and amortization | 1,432 | 1,373 | |||||||||
| Amortization of nuclear fuel | 68 | 65 | |||||||||
| Amortization of debt issuance costs and premium/discounts | 16 | 21 | |||||||||
| Deferred income taxes and investment tax credits, net | 229 | 170 | |||||||||
| Allowance for equity funds used during construction | (54) | (43) | |||||||||
| Stock-based compensation costs | 26 | 24 | |||||||||
| Other | 16 | 68 | |||||||||
| Changes in assets and liabilities | (326) | (494) | |||||||||
| Net cash provided by operating activities | 2,564 | 2,263 | |||||||||
| Cash Flows From Investing Activities: | |||||||||||
| Capital expenditures | (3,597) | (3,351) | |||||||||
| Nuclear fuel expenditures | (174) | (29) | |||||||||
| Purchases of securities – nuclear decommissioning trust fund | (266) | (229) | |||||||||
| Sales and maturities of securities – nuclear decommissioning trust fund | 240 | 216 | |||||||||
| Other | (1) | 23 | |||||||||
| Net cash used in investing activities | (3,798) | (3,370) | |||||||||
| Cash Flows From Financing Activities: | |||||||||||
| Dividends on common stock | (662) | (610) | |||||||||
| Dividends paid to noncontrolling interest holders | (5) | (5) | |||||||||
| Short-term debt, net | (533) | 522 | |||||||||
| Maturities of long-term debt | (100) | (505) | |||||||||
| Issuances of long-term debt | 2,295 | 1,467 | |||||||||
| Issuances of common stock | 346 | 333 | |||||||||
| Employee payroll taxes related to stock-based compensation | (20) | (16) | |||||||||
| Debt issuance costs | (21) | (18) | |||||||||
| Other | (10) | — | |||||||||
| Net cash provided by financing activities | 1,290 | 1,168 | |||||||||
| Net change in cash, cash equivalents, and restricted cash | 56 | 61 | |||||||||
| Cash, cash equivalents, and restricted cash at beginning of year | 216 | 155 | |||||||||
| Cash, cash equivalents, and restricted cash at end of year | $ | 272 | $ | 216 | |||||||