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Segment Information (Disaggregation of Revenues) (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022
Disaggregation of Revenue [Line Items] |  |  |
External revenues | $ 7,623 | $ 7,500 | $ 7,957
Revenues | 7,623 | 7,500 | 7,957
Revenues from alternative revenue programs | (9) | 179 | 78
Revenue Not from Contract with Customer, Other | 19 | 0 | (94)
Insurance recoveries related to lost sales |  |  | 10
Ameren Missouri |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from alternative revenue programs | 4 | (5) | 17
Revenue Not from Contract with Customer, Other | 7 | (9) | (103)
Insurance recoveries related to lost sales |  |  | 10
Ameren Illinois Electric Distribution |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from alternative revenue programs | (43) | 116 | 89
Revenue Not from Contract with Customer, Other | 10 | 7 | 6
Ameren Illinois Gas |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from alternative revenue programs | (3) | 49 | (19)
Revenue Not from Contract with Customer, Other | 2 | 2 | 3
Ameren Transmission |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from alternative revenue programs | 33 | 19 | (9)
Revenue Not from Contract with Customer, Other | 0 | 0 | 0
Electric |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 6,540 | 6,439 | 6,581
Revenues | 6,540 | 6,439 | 6,581
Electric | Residential |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 2,892 | 2,921 | 2,903
Electric | Commercial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 1,993 | 2,027 | 1,987
Electric | Industrial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 489 | 492 | 489
Electric | Other |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenue Not from Contract with Customer | 1,166 | 999 | 1,202
Natural gas |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 1,083 | 1,061 | 1,376
Revenues | 1,083 | 1,061 | 1,376
Natural gas | Residential |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 751 | 757 | 965
Natural gas | Commercial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 203 | 210 | 277
Natural gas | Industrial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 14 | 19 | 48
Natural gas | Other |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenue Not from Contract with Customer | 115 | 75 | 86
Ameren Illinois |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 3,472 | 3,482 | 3,756
Revenues | 3,472 | 3,482 | 3,756
Revenues from alternative revenue programs | (17) | 177 | 63
Revenue Not from Contract with Customer, Other | 12 | 9 | 9
Ameren Illinois | Residential |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 1,915 | 2,001 | 2,171
Ameren Illinois | Commercial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 846 | 911 | 989
Ameren Illinois | Industrial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 188 | 200 | 240
Ameren Illinois | Other |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenue Not from Contract with Customer | 523 | 370 | 356
Ameren Illinois | Ameren Illinois Electric Distribution |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from alternative revenue programs | (43) | 116 | 89
Revenue Not from Contract with Customer, Other | 10 | 7 | 6
Ameren Illinois | Ameren Illinois Gas |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from alternative revenue programs | (3) | 49 | (19)
Revenue Not from Contract with Customer, Other | 2 | 2 | 3
Ameren Illinois | Ameren Illinois Transmission |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from alternative revenue programs | 29 | 12 | (7)
Revenue Not from Contract with Customer, Other | 0 | 0 | 0
Ameren Illinois | Electric |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 2,534 | 2,585 | 2,576
Ameren Illinois | Natural gas |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 938 | 897 | 1,180
Operating Segments | Ameren Missouri |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 3,960 | 3,825 | 4,012
Revenues | 3,993 | 3,859 | 4,046
Operating Segments | Ameren Illinois Electric Distribution |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 2,088 | 2,217 | 2,255
Revenues | 2,089 | 2,218 | 2,256
Operating Segments | Ameren Illinois Gas |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 938 | 897 | 1,180
Revenues | 938 | 897 | 1,180
Operating Segments | Ameren Transmission |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 637 | 561 | 510
Revenues | 781 | 677 | 615
Operating Segments | Electric | Ameren Missouri |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues | 3,847 | 3,694 | 3,849
Operating Segments | Electric | Ameren Missouri | Residential |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 1,638 | 1,577 | 1,578
Operating Segments | Electric | Ameren Missouri | Commercial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 1,313 | 1,280 | 1,219
Operating Segments | Electric | Ameren Missouri | Industrial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 311 | 306 | 290
Operating Segments | Electric | Ameren Missouri | Other |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenue Not from Contract with Customer | 585 | 531 | 762
Operating Segments | Electric | Ameren Illinois Electric Distribution |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues | 2,089 | 2,218 | 2,256
Operating Segments | Electric | Ameren Illinois Electric Distribution | Residential |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 1,254 | 1,344 | 1,325
Operating Segments | Electric | Ameren Illinois Electric Distribution | Commercial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 680 | 747 | 768
Operating Segments | Electric | Ameren Illinois Electric Distribution | Industrial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 178 | 186 | 199
Operating Segments | Electric | Ameren Illinois Electric Distribution | Other |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenue Not from Contract with Customer | (23) | (59) | (36)
Operating Segments | Electric | Ameren Illinois Gas |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues | 0 | 0 | 0
Operating Segments | Electric | Ameren Illinois Gas | Residential |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 0 | 0 | 0
Operating Segments | Electric | Ameren Illinois Gas | Commercial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 0 | 0 | 0
Operating Segments | Electric | Ameren Illinois Gas | Industrial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 0 | 0 | 0
Operating Segments | Electric | Ameren Illinois Gas | Other |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenue Not from Contract with Customer | 0 | 0 | 0
Operating Segments | Electric | Ameren Transmission |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues | 781 | 677 | 615
Operating Segments | Electric | Ameren Transmission | Residential |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 0 | 0 | 0
Operating Segments | Electric | Ameren Transmission | Commercial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 0 | 0 | 0
Operating Segments | Electric | Ameren Transmission | Industrial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 0 | 0 | 0
Operating Segments | Electric | Ameren Transmission | Other |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenue Not from Contract with Customer | 781 | 677 | 615
Operating Segments | Natural gas | Ameren Missouri |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues | 146 | 165 | 197
Operating Segments | Natural gas | Ameren Missouri | Residential |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 90 | 100 | 119
Operating Segments | Natural gas | Ameren Missouri | Commercial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 37 | 46 | 56
Operating Segments | Natural gas | Ameren Missouri | Industrial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 4 | 5 | 7
Operating Segments | Natural gas | Ameren Missouri | Other |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenue Not from Contract with Customer | 15 | 14 | 15
Operating Segments | Natural gas | Ameren Illinois Electric Distribution |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues | 0 | 0 | 0
Operating Segments | Natural gas | Ameren Illinois Electric Distribution | Residential |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 0 | 0 | 0
Operating Segments | Natural gas | Ameren Illinois Electric Distribution | Commercial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 0 | 0 | 0
Operating Segments | Natural gas | Ameren Illinois Electric Distribution | Industrial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 0 | 0 | 0
Operating Segments | Natural gas | Ameren Illinois Electric Distribution | Other |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenue Not from Contract with Customer | 0 | 0 | 0
Operating Segments | Natural gas | Ameren Illinois Gas |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues | 938 | 897 | 1,180
Operating Segments | Natural gas | Ameren Illinois Gas | Residential |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 661 | 657 | 846
Operating Segments | Natural gas | Ameren Illinois Gas | Commercial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 166 | 164 | 221
Operating Segments | Natural gas | Ameren Illinois Gas | Industrial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 10 | 14 | 41
Operating Segments | Natural gas | Ameren Illinois Gas | Other |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenue Not from Contract with Customer | 101 | 62 | 72
Operating Segments | Natural gas | Ameren Transmission |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues | 0 | 0 | 0
Operating Segments | Natural gas | Ameren Transmission | Residential |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 0 | 0 | 0
Operating Segments | Natural gas | Ameren Transmission | Commercial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 0 | 0 | 0
Operating Segments | Natural gas | Ameren Transmission | Industrial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 0 | 0 | 0
Operating Segments | Natural gas | Ameren Transmission | Other |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenue Not from Contract with Customer | 0 | 0 | 0
Operating Segments | Ameren Illinois | Ameren Illinois Electric Distribution |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 2,089 | 2,218 | 2,256
Revenues | 2,089 | 2,218 | 2,256
Operating Segments | Ameren Illinois | Ameren Illinois Gas |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 938 | 897 | 1,180
Revenues | 938 | 897 | 1,180
Operating Segments | Ameren Illinois | Ameren Illinois Transmission |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 445 | 367 | 320
Revenues | 564 | 480 | 424
Operating Segments | Ameren Illinois | Electric | Ameren Illinois Electric Distribution |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues | 2,089 | 2,218 | 2,256
Operating Segments | Ameren Illinois | Electric | Ameren Illinois Electric Distribution | Residential |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 1,254 | 1,344 | 1,325
Operating Segments | Ameren Illinois | Electric | Ameren Illinois Electric Distribution | Commercial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 680 | 747 | 768
Operating Segments | Ameren Illinois | Electric | Ameren Illinois Electric Distribution | Industrial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 178 | 186 | 199
Operating Segments | Ameren Illinois | Electric | Ameren Illinois Electric Distribution | Other |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenue Not from Contract with Customer | (23) | (59) | (36)
Operating Segments | Ameren Illinois | Electric | Ameren Illinois Transmission |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues | 564 | 480 | 424
Operating Segments | Ameren Illinois | Electric | Ameren Illinois Transmission | Residential |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 0 | 0 | 0
Operating Segments | Ameren Illinois | Electric | Ameren Illinois Transmission | Commercial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 0 | 0 | 0
Operating Segments | Ameren Illinois | Electric | Ameren Illinois Transmission | Industrial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 0 | 0 | 0
Operating Segments | Ameren Illinois | Electric | Ameren Illinois Transmission | Other |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenue Not from Contract with Customer | 564 | 480 | 424
Operating Segments | Ameren Illinois | Natural gas | Ameren Illinois Gas |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues | 938 | 897 | 1,180
Operating Segments | Ameren Illinois | Natural gas | Ameren Illinois Gas | Residential |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 661 | 657 | 846
Operating Segments | Ameren Illinois | Natural gas | Ameren Illinois Gas | Commercial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 166 | 164 | 221
Operating Segments | Ameren Illinois | Natural gas | Ameren Illinois Gas | Industrial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 10 | 14 | 41
Operating Segments | Ameren Illinois | Natural gas | Ameren Illinois Gas | Other |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenue Not from Contract with Customer | 101 | 62 | 72
Intersegment Elimination |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenue Not from Contract with Customer | (178) | (151) | (140)
Revenues | (178) | (151) | (140)
Intersegment Elimination | Ameren Missouri |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenue Not from Contract with Customer | (33) | (34) | (34)
Intersegment Elimination | Ameren Illinois Electric Distribution |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenue Not from Contract with Customer | (1) | (1) | (1)
Intersegment Elimination | Ameren Illinois Gas |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenue Not from Contract with Customer | 0 | 0 | 0
Intersegment Elimination | Ameren Transmission |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenue Not from Contract with Customer | (144) | (116) | (105)
Intersegment Elimination | Electric |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues | (177) | (150) | (139)
Intersegment Elimination | Electric | Residential |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 0 | 0 | 0
Intersegment Elimination | Electric | Commercial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 0 | 0 | 0
Intersegment Elimination | Electric | Industrial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 0 | 0 | 0
Intersegment Elimination | Electric | Other |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenue Not from Contract with Customer | (177) | (150) | (139)
Intersegment Elimination | Natural gas |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues | (1) | (1) | (1)
Intersegment Elimination | Natural gas | Residential |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 0 | 0 | 0
Intersegment Elimination | Natural gas | Commercial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 0 | 0 | 0
Intersegment Elimination | Natural gas | Industrial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 0 | 0 | 0
Intersegment Elimination | Natural gas | Other |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenue Not from Contract with Customer | (1) | (1) | (1)
Intersegment Elimination | Ameren Illinois |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenue Not from Contract with Customer | (119) | (113) | (104)
Revenues | (119) | (113) | (104)
Intersegment Elimination | Ameren Illinois | Residential |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 0 | 0 | 0
Intersegment Elimination | Ameren Illinois | Commercial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 0 | 0 | 0
Intersegment Elimination | Ameren Illinois | Industrial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 0 | 0 | 0
Intersegment Elimination | Ameren Illinois | Other |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenue Not from Contract with Customer | (119) | (113) | (104)
Intersegment Elimination | Ameren Illinois | Ameren Illinois Electric Distribution |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenue Not from Contract with Customer | 0 | 0 | 0
Intersegment Elimination | Ameren Illinois | Ameren Illinois Gas |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenue Not from Contract with Customer | 0 | 0 | 0
Intersegment Elimination | Ameren Illinois | Ameren Illinois Transmission |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenue Not from Contract with Customer | $ (119) | $ (113) | $ (104)

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