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Segment Information (Disaggregation of Revenue) (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2024 | Sep. 30, 2023 | Sep. 30, 2024 | Sep. 30, 2023
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | $ 2,173 | $ 2,060 | $ 5,682 | $ 5,882
Revenues | 2,173 | 2,060 | 5,682 | 5,882
Revenues from alternative revenue programs | (155) | (109) | (69) | 63
Other revenues not from contracts with customers | 4 | 1 | 11 | (1)
Union Electric Company |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from alternative revenue programs | 0 | (9) | (7) | (11)
Other revenues not from contracts with customers | 2 | (1) | 4 | (9)
Ameren Illinois Electric Distribution |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from alternative revenue programs | (144) | (94) | (83) | 30
Other revenues not from contracts with customers | 2 | 2 | 5 | 6
Ameren Illinois Natural Gas |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from alternative revenue programs | (9) | (1) | 10 | 36
Other revenues not from contracts with customers | 0 | 0 | 2 | 2
Ameren Transmission |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from alternative revenue programs | (2) | (5) | 11 | 8
Other revenues not from contracts with customers | 0 | 0 | 0 | 0
Electric |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 2,035 | 1,921 | 4,920 | 5,096
Revenues | 2,035 | 1,921 | 4,920 | 5,096
Electric | Residential |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 929 | 920 | 2,273 | 2,323
Electric | Commercial |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 649 | 657 | 1,560 | 1,608
Electric | Industrial |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 146 | 147 | 376 | 379
Electric | Other |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 311 | 197 | 711 | 786
Natural gas |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 138 | 139 | 762 | 786
Revenues | 138 | 139 | 762 | 786
Natural gas | Residential |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 86 | 84 | 528 | 543
Natural gas | Commercial |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 24 | 24 | 137 | 155
Natural gas | Industrial |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 2 | 2 | 10 | 14
Natural gas | Other |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 26 | 29 | 87 | 74
Ameren Illinois Company |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 793 | 783 | 2,559 | 2,663
Revenues | 793 | 783 | 2,559 | 2,663
Revenues from alternative revenue programs | (154) | (101) | (64) | 70
Other revenues not from contracts with customers | 2 | 2 | 7 | 8
Ameren Illinois Company | Residential |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 416 | 405 | 1,413 | 1,518
Ameren Illinois Company | Commercial |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 203 | 208 | 623 | 703
Ameren Illinois Company | Industrial |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 40 | 41 | 137 | 146
Ameren Illinois Company | Other |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 134 | 129 | 386 | 296
Ameren Illinois Company | Ameren Illinois Electric Distribution |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from alternative revenue programs | (144) | (94) | (83) | 30
Other revenues not from contracts with customers | 2 | 2 | 5 | 6
Ameren Illinois Company | Ameren Illinois Natural Gas |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from alternative revenue programs | (9) | (1) | 10 | 36
Other revenues not from contracts with customers | 0 | 0 | 2 | 2
Ameren Illinois Company | Ameren Illinois Transmission |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues from alternative revenue programs | (1) | (6) | 9 | 4
Other revenues not from contracts with customers | 0 | 0 | 0 | 0
Ameren Illinois Company | Electric |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 672 | 661 | 1,899 | 1,998
Ameren Illinois Company | Natural gas |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 121 | 122 | 660 | 665
Operating Segments | Union Electric Company |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 1,333 | 1,228 | 2,980 | 3,074
Revenues | 1,342 | 1,237 | 3,005 | 3,101
Operating Segments | Ameren Illinois Electric Distribution |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 551 | 557 | 1,566 | 1,721
Revenues | 552 | 558 | 1,567 | 1,722
Operating Segments | Ameren Illinois Natural Gas |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 121 | 121 | 660 | 664
Revenues | 121 | 122 | 660 | 665
Operating Segments | Ameren Transmission |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 168 | 154 | 476 | 423
Revenues | 210 | 188 | 586 | 512
Operating Segments | Electric | Union Electric Company |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 1,324 | 1,219 | 2,902 | 2,978
Operating Segments | Electric | Union Electric Company | Residential |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 590 | 590 | 1,326 | 1,274
Operating Segments | Electric | Union Electric Company | Commercial |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 465 | 468 | 1,048 | 1,026
Operating Segments | Electric | Union Electric Company | Industrial |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 108 | 107 | 246 | 243
Operating Segments | Electric | Union Electric Company | Other |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 161 | 54 | 282 | 435
Operating Segments | Electric | Ameren Illinois Electric Distribution |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 552 | 558 | 1,567 | 1,722
Operating Segments | Electric | Ameren Illinois Electric Distribution | Residential |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 339 | 330 | 947 | 1,049
Operating Segments | Electric | Ameren Illinois Electric Distribution | Commercial |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 184 | 189 | 512 | 582
Operating Segments | Electric | Ameren Illinois Electric Distribution | Industrial |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 38 | 40 | 130 | 136
Operating Segments | Electric | Ameren Illinois Electric Distribution | Other |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | (9) | (1) | (22) | (45)
Operating Segments | Electric | Ameren Illinois Natural Gas |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 0 | 0 | 0 | 0
Operating Segments | Electric | Ameren Illinois Natural Gas | Residential |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 0 | 0 | 0 | 0
Operating Segments | Electric | Ameren Illinois Natural Gas | Commercial |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 0 | 0 | 0 | 0
Operating Segments | Electric | Ameren Illinois Natural Gas | Industrial |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 0 | 0 | 0 | 0
Operating Segments | Electric | Ameren Illinois Natural Gas | Other |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 0 | 0 | 0 | 0
Operating Segments | Electric | Ameren Transmission |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 210 | 188 | 586 | 512
Operating Segments | Electric | Ameren Transmission | Residential |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 0 | 0 | 0 | 0
Operating Segments | Electric | Ameren Transmission | Commercial |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 0 | 0 | 0 | 0
Operating Segments | Electric | Ameren Transmission | Industrial |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 0 | 0 | 0 | 0
Operating Segments | Electric | Ameren Transmission | Other |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 210 | 188 | 586 | 512
Operating Segments | Natural gas | Union Electric Company |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 18 | 18 | 103 | 123
Operating Segments | Natural gas | Union Electric Company | Residential |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 9 | 9 | 62 | 74
Operating Segments | Natural gas | Union Electric Company | Commercial |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 5 | 5 | 26 | 34
Operating Segments | Natural gas | Union Electric Company | Industrial |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 0 | 1 | 3 | 4
Operating Segments | Natural gas | Union Electric Company | Other |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 4 | 3 | 12 | 11
Operating Segments | Natural gas | Ameren Illinois Electric Distribution |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 0 | 0 | 0 | 0
Operating Segments | Natural gas | Ameren Illinois Electric Distribution | Residential |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 0 | 0 | 0 | 0
Operating Segments | Natural gas | Ameren Illinois Electric Distribution | Commercial |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 0 | 0 | 0 | 0
Operating Segments | Natural gas | Ameren Illinois Electric Distribution | Industrial |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 0 | 0 | 0 | 0
Operating Segments | Natural gas | Ameren Illinois Electric Distribution | Other |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 0 | 0 | 0 | 0
Operating Segments | Natural gas | Ameren Illinois Natural Gas |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 121 | 122 | 660 | 665
Operating Segments | Natural gas | Ameren Illinois Natural Gas | Residential |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 77 | 75 | 466 | 469
Operating Segments | Natural gas | Ameren Illinois Natural Gas | Commercial |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 19 | 19 | 111 | 121
Operating Segments | Natural gas | Ameren Illinois Natural Gas | Industrial |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 2 | 1 | 7 | 10
Operating Segments | Natural gas | Ameren Illinois Natural Gas | Other |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 23 | 27 | 76 | 65
Operating Segments | Natural gas | Ameren Transmission |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 0 | 0 | 0 | 0
Operating Segments | Natural gas | Ameren Transmission | Residential |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 0 | 0 | 0 | 0
Operating Segments | Natural gas | Ameren Transmission | Commercial |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 0 | 0 | 0 | 0
Operating Segments | Natural gas | Ameren Transmission | Industrial |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 0 | 0 | 0 | 0
Operating Segments | Natural gas | Ameren Transmission | Other |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 0 | 0 | 0 | 0
Operating Segments | Ameren Illinois Company | Ameren Illinois Electric Distribution |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 552 | 558 | 1,567 | 1,722
Operating Segments | Ameren Illinois Company | Ameren Illinois Natural Gas |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 121 | 122 | 660 | 665
Operating Segments | Ameren Illinois Company | Ameren Illinois Transmission |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 120 | 103 | 332 | 276
Operating Segments | Ameren Illinois Company | Electric | Ameren Illinois Electric Distribution |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 552 | 558 | 1,567 | 1,722
Operating Segments | Ameren Illinois Company | Electric | Ameren Illinois Electric Distribution | Residential |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 339 | 330 | 947 | 1,049
Operating Segments | Ameren Illinois Company | Electric | Ameren Illinois Electric Distribution | Commercial |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 184 | 189 | 512 | 582
Operating Segments | Ameren Illinois Company | Electric | Ameren Illinois Electric Distribution | Industrial |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 38 | 40 | 130 | 136
Operating Segments | Ameren Illinois Company | Electric | Ameren Illinois Electric Distribution | Other |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | (9) | (1) | (22) | (45)
Operating Segments | Ameren Illinois Company | Electric | Ameren Illinois Transmission |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 155 | 136 | 422 | 363
Operating Segments | Ameren Illinois Company | Electric | Ameren Illinois Transmission | Residential |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 0 | 0 | 0 | 0
Operating Segments | Ameren Illinois Company | Electric | Ameren Illinois Transmission | Commercial |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 0 | 0 | 0 | 0
Operating Segments | Ameren Illinois Company | Electric | Ameren Illinois Transmission | Industrial |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 0 | 0 | 0 | 0
Operating Segments | Ameren Illinois Company | Electric | Ameren Illinois Transmission | Other |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 155 | 136 | 422 | 363
Operating Segments | Ameren Illinois Company | Natural gas | Ameren Illinois Natural Gas |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 121 | 122 | 660 | 665
Operating Segments | Ameren Illinois Company | Natural gas | Ameren Illinois Natural Gas | Residential |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 77 | 75 | 466 | 469
Operating Segments | Ameren Illinois Company | Natural gas | Ameren Illinois Natural Gas | Commercial |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 19 | 19 | 111 | 121
Operating Segments | Ameren Illinois Company | Natural gas | Ameren Illinois Natural Gas | Industrial |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 2 | 1 | 7 | 10
Operating Segments | Ameren Illinois Company | Natural gas | Ameren Illinois Natural Gas | Other |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 23 | 27 | 76 | 65
Intersegment Eliminations |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | (52) | (45) | (136) | (118)
Revenues | (52) | (45) | (136) | (118)
Intersegment Eliminations | Union Electric Company |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | (9) | (9) | (25) | (27)
Intersegment Eliminations | Ameren Illinois Electric Distribution |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | (1) | (1) | (1) | (1)
Intersegment Eliminations | Ameren Illinois Natural Gas |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 0 | (1) | 0 | (1)
Intersegment Eliminations | Ameren Transmission |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | (42) | (34) | (110) | (89)
Intersegment Eliminations | Electric |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | (51) | (44) | (135) | (116)
Intersegment Eliminations | Electric | Residential |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 0 | 0 | 0 | 0
Intersegment Eliminations | Electric | Commercial |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 0 | 0 | 0 | 0
Intersegment Eliminations | Electric | Industrial |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 0 | 0 | 0 | 0
Intersegment Eliminations | Electric | Other |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | (51) | (44) | (135) | (116)
Intersegment Eliminations | Natural gas |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | (1) | (1) | (1) | (2)
Intersegment Eliminations | Natural gas | Residential |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 0 | 0 | 0 | 0
Intersegment Eliminations | Natural gas | Commercial |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 0 | 0 | 0 | 0
Intersegment Eliminations | Natural gas | Industrial |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 0 | 0 | 0 | 0
Intersegment Eliminations | Natural gas | Other |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | (1) | (1) | (1) | (2)
Intersegment Eliminations | Ameren Illinois Company |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | (35) | (33) | (90) | (87)
Revenues | (35) | (33) | (90) | (87)
Intersegment Eliminations | Ameren Illinois Company | Residential |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 0 | 0 | 0 | 0
Intersegment Eliminations | Ameren Illinois Company | Commercial |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 0 | 0 | 0 | 0
Intersegment Eliminations | Ameren Illinois Company | Industrial |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Operating Revenues | 0 | 0 | 0 | 0
Intersegment Eliminations | Ameren Illinois Company | Other |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | (35) | (33) | (90) | (87)
Intersegment Eliminations | Ameren Illinois Company | Ameren Illinois Electric Distribution |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 0 | 0 | 0 | 0
Intersegment Eliminations | Ameren Illinois Company | Ameren Illinois Natural Gas |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | 0 | 0 | 0 | 0
Intersegment Eliminations | Ameren Illinois Company | Ameren Illinois Transmission |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Revenues | $ (35) | $ (33) | $ (90) | $ (87)

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