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Segment Information (Disaggregation of Revenues) (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
Disaggregation of Revenue [Line Items] |  |  |
External revenues | $ 7,500 | $ 7,957 | $ 6,394
Revenues from alternative revenue programs | 179 | 78 | 77
Revenue Not from Contract with Customer, Other | 0 | (94) | 68
Revenues | 7,500 | 7,957 | 6,394
Insurance recoveries related to lost sales |  | 10 | 78
Ameren Missouri |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from alternative revenue programs | (5) | 17 | (16)
Revenue Not from Contract with Customer, Other | (9) | (103) | 56
Insurance recoveries related to lost sales |  | 10 | 78
Ameren Illinois Electric Distribution |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from alternative revenue programs | 116 | 89 | 77
Revenue Not from Contract with Customer, Other | 7 | 6 | 10
Ameren Illinois Gas |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from alternative revenue programs | 49 | (19) | 5
Revenue Not from Contract with Customer, Other | 2 | 3 | 2
Ameren Transmission |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from alternative revenue programs | 19 | (9) | 11
Revenue Not from Contract with Customer, Other | 0 | 0 | 0
Electric |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 6,439 | 6,581 | 5,297
Revenues | 6,439 | 6,581 | 5,297
Electric | Residential |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 2,921 | 2,903 | 2,378
Electric | Commercial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 2,027 | 1,987 | 1,671
Electric | Industrial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 492 | 489 | 415
Electric | Other |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenue Not from Contract with Customer | 999 | 1,202 | 833
Natural gas |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 1,061 | 1,376 | 1,097
Revenues | 1,061 | 1,376 | 1,097
Natural gas | Residential |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 757 | 965 | 736
Natural gas | Commercial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 210 | 277 | 206
Natural gas | Industrial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 19 | 48 | 39
Natural gas | Other |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenue Not from Contract with Customer | 75 | 86 | 116
Ameren Illinois |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 3,482 | 3,756 | 2,895
Revenues from alternative revenue programs | 177 | 63 | 91
Revenue Not from Contract with Customer, Other | 9 | 9 | 12
Revenues | 3,482 | 3,756 | 2,895
Ameren Illinois | Residential |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 2,001 | 2,171 | 1,590
Ameren Illinois | Commercial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 911 | 989 | 717
Ameren Illinois | Industrial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 200 | 240 | 170
Ameren Illinois | Other |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenue Not from Contract with Customer | 370 | 356 | 418
Ameren Illinois | Ameren Illinois Electric Distribution |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from alternative revenue programs | 116 | 89 | 77
Revenue Not from Contract with Customer, Other | 7 | 6 | 10
Ameren Illinois | Ameren Illinois Gas |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from alternative revenue programs | 49 | (19) | 5
Revenue Not from Contract with Customer, Other | 2 | 3 | 2
Ameren Illinois | Ameren Illinois Transmission |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from alternative revenue programs | 12 | (7) | 9
Revenue Not from Contract with Customer, Other | 0 | 0 | 0
Ameren Illinois | Electric |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 2,585 | 2,576 | 1,938
Ameren Illinois | Natural gas |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 897 | 1,180 | 957
Operating Segments | Ameren Missouri |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 3,825 | 4,012 | 3,311
Revenues | 3,859 | 4,046 | 3,353
Operating Segments | Ameren Illinois Electric Distribution |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 2,217 | 2,255 | 1,635
Revenues | 2,218 | 2,256 | 1,639
Operating Segments | Ameren Illinois Gas |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 897 | 1,180 | 957
Revenues | 897 | 1,180 | 957
Operating Segments | Ameren Transmission |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 561 | 510 | 491
Revenues | 677 | 615 | 562
Operating Segments | Electric | Ameren Missouri |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues | 3,694 | 3,849 | 3,212
Operating Segments | Electric | Ameren Missouri | Residential |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 1,577 | 1,578 | 1,445
Operating Segments | Electric | Ameren Missouri | Commercial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 1,280 | 1,219 | 1,126
Operating Segments | Electric | Ameren Missouri | Industrial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 306 | 290 | 280
Operating Segments | Electric | Ameren Missouri | Other |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenue Not from Contract with Customer | 531 | 762 | 361
Operating Segments | Electric | Ameren Illinois Electric Distribution |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues | 2,218 | 2,256 | 1,639
Operating Segments | Electric | Ameren Illinois Electric Distribution | Residential |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 1,344 | 1,325 | 933
Operating Segments | Electric | Ameren Illinois Electric Distribution | Commercial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 747 | 768 | 545
Operating Segments | Electric | Ameren Illinois Electric Distribution | Industrial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 186 | 199 | 135
Operating Segments | Electric | Ameren Illinois Electric Distribution | Other |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenue Not from Contract with Customer | (59) | (36) | 26
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 | 677 | 615 | 562
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 | 677 | 615 | 562
Operating Segments | Natural gas | Ameren Missouri |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues | 165 | 197 | 141
Operating Segments | Natural gas | Ameren Missouri | Residential |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 100 | 119 | 79
Operating Segments | Natural gas | Ameren Missouri | Commercial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 46 | 56 | 34
Operating Segments | Natural gas | Ameren Missouri | Industrial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 5 | 7 | 4
Operating Segments | Natural gas | Ameren Missouri | Other |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenue Not from Contract with Customer | 14 | 15 | 24
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 | 897 | 1,180 | 957
Operating Segments | Natural gas | Ameren Illinois Gas | Residential |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 657 | 846 | 657
Operating Segments | Natural gas | Ameren Illinois Gas | Commercial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 164 | 221 | 172
Operating Segments | Natural gas | Ameren Illinois Gas | Industrial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 14 | 41 | 35
Operating Segments | Natural gas | Ameren Illinois Gas | Other |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenue Not from Contract with Customer | 62 | 72 | 93
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 | 2,218 | 2,256 | 1,639
Operating Segments | Ameren Illinois | Ameren Illinois Gas |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 897 | 1,180 | 957
Operating Segments | Ameren Illinois | Ameren Illinois Transmission |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 367 | 320 | 299
Operating Segments | Ameren Illinois | Electric | Ameren Illinois Electric Distribution |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues | 2,218 | 2,256 | 1,639
Operating Segments | Ameren Illinois | Electric | Ameren Illinois Electric Distribution | Residential |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 1,344 | 1,325 | 933
Operating Segments | Ameren Illinois | Electric | Ameren Illinois Electric Distribution | Commercial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 747 | 768 | 545
Operating Segments | Ameren Illinois | Electric | Ameren Illinois Electric Distribution | Industrial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 186 | 199 | 135
Operating Segments | Ameren Illinois | Electric | Ameren Illinois Electric Distribution | Other |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenue Not from Contract with Customer | (59) | (36) | 26
Operating Segments | Ameren Illinois | Electric | Ameren Illinois Transmission |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues | 480 | 424 | 365
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 | 480 | 424 | 365
Operating Segments | Ameren Illinois | Natural gas | Ameren Illinois Gas |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues | 897 | 1,180 | 957
Operating Segments | Ameren Illinois | Natural gas | Ameren Illinois Gas | Residential |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 657 | 846 | 657
Operating Segments | Ameren Illinois | Natural gas | Ameren Illinois Gas | Commercial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 164 | 221 | 172
Operating Segments | Ameren Illinois | Natural gas | Ameren Illinois Gas | Industrial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 14 | 41 | 35
Operating Segments | Ameren Illinois | Natural gas | Ameren Illinois Gas | Other |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenue Not from Contract with Customer | 62 | 72 | 93
Intersegment Elimination |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenue Not from Contract with Customer | (151) | (140) | (117)
Revenues | (151) | (140) | (117)
Intersegment Elimination | Ameren Missouri |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenue Not from Contract with Customer | (34) | (34) | (42)
Intersegment Elimination | Ameren Illinois Electric Distribution |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenue Not from Contract with Customer | (1) | (1) | (4)
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 | (116) | (105) | (71)
Intersegment Elimination | Electric |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues | (150) | (139) | (116)
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 | (150) | (139) | (116)
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 | (113) | (104) | (66)
Revenues | (113) | (104) | (66)
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 | (113) | (104) | (66)
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 | $ (113) | $ (104) | $ (66)

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