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Segment Information (Disaggregation of Revenue) (Details) - USD ($) $ in Millions | 3 Months Ended
--- | ---
Mar. 31, 2024 | Mar. 31, 2023
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | $ 1,816 | $ 2,062
Revenues | 1,816 | 2,062
Revenues from alternative revenue programs | 61 | 98
Other revenues not from contracts with customers | 4 | (3)
Union Electric Company |  |
Disaggregation of Revenue [Line Items] |  |
Revenues from alternative revenue programs | (6) | (2)
Other revenues not from contracts with customers | 1 | (6)
Ameren Illinois Electric Distribution |  |
Disaggregation of Revenue [Line Items] |  |
Revenues from alternative revenue programs | 39 | 64
Other revenues not from contracts with customers | 2 | 2
Ameren Illinois Natural Gas |  |
Disaggregation of Revenue [Line Items] |  |
Revenues from alternative revenue programs | 19 | 28
Other revenues not from contracts with customers | 1 | 1
Ameren Transmission |  |
Disaggregation of Revenue [Line Items] |  |
Revenues from alternative revenue programs | 9 | 8
Other revenues not from contracts with customers | 0 | 0
Electric |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 1,364 | 1,590
Revenues | 1,364 | 1,590
Electric | Residential |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 638 | 706
Electric | Commercial |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 424 | 447
Electric | Industrial |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 106 | 109
Electric | Other |  |
Disaggregation of Revenue [Line Items] |  |
Revenues | 196 | 328
Natural gas |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 452 | 472
Revenues | 452 | 472
Natural gas | Residential |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 327 | 348
Natural gas | Commercial |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 84 | 100
Natural gas | Industrial |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 6 | 9
Natural gas | Other |  |
Disaggregation of Revenue [Line Items] |  |
Revenues | 35 | 15
Ameren Illinois Company |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 1,000 | 1,101
Revenues | 1,000 | 1,101
Revenues from alternative revenue programs | 66 | 99
Other revenues not from contracts with customers | 3 | 3
Ameren Illinois Company | Residential |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 584 | 678
Ameren Illinois Company | Commercial |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 233 | 277
Ameren Illinois Company | Industrial |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 49 | 55
Ameren Illinois Company | Other |  |
Disaggregation of Revenue [Line Items] |  |
Revenues | 134 | 91
Ameren Illinois Company | Ameren Illinois Electric Distribution |  |
Disaggregation of Revenue [Line Items] |  |
Revenues from alternative revenue programs | 39 | 64
Other revenues not from contracts with customers | 2 | 2
Ameren Illinois Company | Ameren Illinois Natural Gas |  |
Disaggregation of Revenue [Line Items] |  |
Revenues from alternative revenue programs | 19 | 28
Other revenues not from contracts with customers | 1 | 1
Ameren Illinois Company | Ameren Illinois Transmission |  |
Disaggregation of Revenue [Line Items] |  |
Revenues from alternative revenue programs | 8 | 7
Other revenues not from contracts with customers | 0 | 0
Ameren Illinois Company | Electric |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 609 | 710
Ameren Illinois Company | Natural gas |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 391 | 391
Operating Segments | Union Electric Company |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 768 | 913
Revenues | 775 | 923
Operating Segments | Ameren Illinois Electric Distribution |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 506 | 624
Revenues | 506 | 624
Operating Segments | Ameren Illinois Natural Gas |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 391 | 391
Revenues | 391 | 391
Operating Segments | Ameren Transmission |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 151 | 134
Revenues | 185 | 163
Operating Segments | Electric | Union Electric Company |  |
Disaggregation of Revenue [Line Items] |  |
Revenues | 714 | 841
Operating Segments | Electric | Union Electric Company | Residential |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 341 | 324
Operating Segments | Electric | Union Electric Company | Commercial |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 259 | 247
Operating Segments | Electric | Union Electric Company | Industrial |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 61 | 61
Operating Segments | Electric | Union Electric Company | Other |  |
Disaggregation of Revenue [Line Items] |  |
Revenues | 53 | 209
Operating Segments | Electric | Ameren Illinois Electric Distribution |  |
Disaggregation of Revenue [Line Items] |  |
Revenues | 506 | 624
Operating Segments | Electric | Ameren Illinois Electric Distribution | Residential |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 297 | 382
Operating Segments | Electric | Ameren Illinois Electric Distribution | Commercial |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 165 | 200
Operating Segments | Electric | Ameren Illinois Electric Distribution | Industrial |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 45 | 48
Operating Segments | Electric | Ameren Illinois Electric Distribution | Other |  |
Disaggregation of Revenue [Line Items] |  |
Revenues | (1) | (6)
Operating Segments | Electric | Ameren Illinois Natural Gas |  |
Disaggregation of Revenue [Line Items] |  |
Revenues | 0 | 0
Operating Segments | Electric | Ameren Illinois Natural Gas | Residential |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 0 | 0
Operating Segments | Electric | Ameren Illinois Natural Gas | Commercial |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 0 | 0
Operating Segments | Electric | Ameren Illinois Natural Gas | Industrial |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 0 | 0
Operating Segments | Electric | Ameren Illinois Natural Gas | Other |  |
Disaggregation of Revenue [Line Items] |  |
Revenues | 0 | 0
Operating Segments | Electric | Ameren Transmission |  |
Disaggregation of Revenue [Line Items] |  |
Revenues | 185 | 163
Operating Segments | Electric | Ameren Transmission | Residential |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 0 | 0
Operating Segments | Electric | Ameren Transmission | Commercial |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 0 | 0
Operating Segments | Electric | Ameren Transmission | Industrial |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 0 | 0
Operating Segments | Electric | Ameren Transmission | Other |  |
Disaggregation of Revenue [Line Items] |  |
Revenues | 185 | 163
Operating Segments | Natural gas | Union Electric Company |  |
Disaggregation of Revenue [Line Items] |  |
Revenues | 61 | 82
Operating Segments | Natural gas | Union Electric Company | Residential |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 40 | 52
Operating Segments | Natural gas | Union Electric Company | Commercial |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 16 | 23
Operating Segments | Natural gas | Union Electric Company | Industrial |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 2 | 2
Operating Segments | Natural gas | Union Electric Company | Other |  |
Disaggregation of Revenue [Line Items] |  |
Revenues | 3 | 5
Operating Segments | Natural gas | Ameren Illinois Electric Distribution |  |
Disaggregation of Revenue [Line Items] |  |
Revenues | 0 | 0
Operating Segments | Natural gas | Ameren Illinois Electric Distribution | Residential |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 0 | 0
Operating Segments | Natural gas | Ameren Illinois Electric Distribution | Commercial |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 0 | 0
Operating Segments | Natural gas | Ameren Illinois Electric Distribution | Industrial |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 0 | 0
Operating Segments | Natural gas | Ameren Illinois Electric Distribution | Other |  |
Disaggregation of Revenue [Line Items] |  |
Revenues | 0 | 0
Operating Segments | Natural gas | Ameren Illinois Natural Gas |  |
Disaggregation of Revenue [Line Items] |  |
Revenues | 391 | 391
Operating Segments | Natural gas | Ameren Illinois Natural Gas | Residential |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 287 | 296
Operating Segments | Natural gas | Ameren Illinois Natural Gas | Commercial |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 68 | 77
Operating Segments | Natural gas | Ameren Illinois Natural Gas | Industrial |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 4 | 7
Operating Segments | Natural gas | Ameren Illinois Natural Gas | Other |  |
Disaggregation of Revenue [Line Items] |  |
Revenues | 32 | 11
Operating Segments | Natural gas | Ameren Transmission |  |
Disaggregation of Revenue [Line Items] |  |
Revenues | 0 | 0
Operating Segments | Natural gas | Ameren Transmission | Residential |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 0 | 0
Operating Segments | Natural gas | Ameren Transmission | Commercial |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 0 | 0
Operating Segments | Natural gas | Ameren Transmission | Industrial |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 0 | 0
Operating Segments | Natural gas | Ameren Transmission | Other |  |
Disaggregation of Revenue [Line Items] |  |
Revenues | 0 | 0
Operating Segments | Ameren Illinois Company | Ameren Illinois Electric Distribution |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 506 | 624
Operating Segments | Ameren Illinois Company | Ameren Illinois Natural Gas |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 391 | 391
Operating Segments | Ameren Illinois Company | Ameren Illinois Transmission |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 103 | 86
Operating Segments | Ameren Illinois Company | Electric | Ameren Illinois Electric Distribution |  |
Disaggregation of Revenue [Line Items] |  |
Revenues | 506 | 624
Operating Segments | Ameren Illinois Company | Electric | Ameren Illinois Electric Distribution | Residential |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 297 | 382
Operating Segments | Ameren Illinois Company | Electric | Ameren Illinois Electric Distribution | Commercial |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 165 | 200
Operating Segments | Ameren Illinois Company | Electric | Ameren Illinois Electric Distribution | Industrial |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 45 | 48
Operating Segments | Ameren Illinois Company | Electric | Ameren Illinois Electric Distribution | Other |  |
Disaggregation of Revenue [Line Items] |  |
Revenues | (1) | (6)
Operating Segments | Ameren Illinois Company | Electric | Ameren Illinois Transmission |  |
Disaggregation of Revenue [Line Items] |  |
Revenues | 131 | 114
Operating Segments | Ameren Illinois Company | Electric | Ameren Illinois Transmission | Residential |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 0 | 0
Operating Segments | Ameren Illinois Company | Electric | Ameren Illinois Transmission | Commercial |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 0 | 0
Operating Segments | Ameren Illinois Company | Electric | Ameren Illinois Transmission | Industrial |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 0 | 0
Operating Segments | Ameren Illinois Company | Electric | Ameren Illinois Transmission | Other |  |
Disaggregation of Revenue [Line Items] |  |
Revenues | 131 | 114
Operating Segments | Ameren Illinois Company | Natural gas | Ameren Illinois Natural Gas |  |
Disaggregation of Revenue [Line Items] |  |
Revenues | 391 | 391
Operating Segments | Ameren Illinois Company | Natural gas | Ameren Illinois Natural Gas | Residential |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 287 | 296
Operating Segments | Ameren Illinois Company | Natural gas | Ameren Illinois Natural Gas | Commercial |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 68 | 77
Operating Segments | Ameren Illinois Company | Natural gas | Ameren Illinois Natural Gas | Industrial |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 4 | 7
Operating Segments | Ameren Illinois Company | Natural gas | Ameren Illinois Natural Gas | Other |  |
Disaggregation of Revenue [Line Items] |  |
Revenues | 32 | 11
Intersegment Eliminations |  |
Disaggregation of Revenue [Line Items] |  |
Revenues | (41) | (39)
Revenues | (41) | (39)
Intersegment Eliminations | Union Electric Company |  |
Disaggregation of Revenue [Line Items] |  |
Revenues | (7) | (10)
Intersegment Eliminations | Ameren Illinois Electric Distribution |  |
Disaggregation of Revenue [Line Items] |  |
Revenues | 0 | 0
Intersegment Eliminations | Ameren Illinois Natural Gas |  |
Disaggregation of Revenue [Line Items] |  |
Revenues | 0 | 0
Intersegment Eliminations | Ameren Transmission |  |
Disaggregation of Revenue [Line Items] |  |
Revenues | (34) | (29)
Intersegment Eliminations | Electric |  |
Disaggregation of Revenue [Line Items] |  |
Revenues | (41) | (38)
Intersegment Eliminations | Electric | Residential |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 0 | 0
Intersegment Eliminations | Electric | Commercial |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 0 | 0
Intersegment Eliminations | Electric | Industrial |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 0 | 0
Intersegment Eliminations | Electric | Other |  |
Disaggregation of Revenue [Line Items] |  |
Revenues | (41) | (38)
Intersegment Eliminations | Natural gas |  |
Disaggregation of Revenue [Line Items] |  |
Revenues | 0 | (1)
Intersegment Eliminations | Natural gas | Residential |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 0 | 0
Intersegment Eliminations | Natural gas | Commercial |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 0 | 0
Intersegment Eliminations | Natural gas | Industrial |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 0 | 0
Intersegment Eliminations | Natural gas | Other |  |
Disaggregation of Revenue [Line Items] |  |
Revenues | 0 | (1)
Intersegment Eliminations | Ameren Illinois Company |  |
Disaggregation of Revenue [Line Items] |  |
Revenues | (28) | (28)
Revenues | (28) | (28)
Intersegment Eliminations | Ameren Illinois Company | Residential |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 0 | 0
Intersegment Eliminations | Ameren Illinois Company | Commercial |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 0 | 0
Intersegment Eliminations | Ameren Illinois Company | Industrial |  |
Disaggregation of Revenue [Line Items] |  |
Operating Revenues | 0 | 0
Intersegment Eliminations | Ameren Illinois Company | Other |  |
Disaggregation of Revenue [Line Items] |  |
Revenues | (28) | (28)
Intersegment Eliminations | Ameren Illinois Company | Ameren Illinois Electric Distribution |  |
Disaggregation of Revenue [Line Items] |  |
Revenues | 0 | 0
Intersegment Eliminations | Ameren Illinois Company | Ameren Illinois Natural Gas |  |
Disaggregation of Revenue [Line Items] |  |
Revenues | 0 | 0
Intersegment Eliminations | Ameren Illinois Company | Ameren Illinois Transmission |  |
Disaggregation of Revenue [Line Items] |  |
Revenues | $ (28) | $ (28)

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