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v3.25.4

Segment Information (Disaggregation of Revenues) (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2025 | Dec. 31, 2024 | Dec. 31, 2023
Disaggregation of Revenue [Line Items] |  |  |
External revenues | $ 8,799 | $ 7,623 | $ 7,500
Revenues | 8,799 | 7,623 | 7,500
Revenues from alternative revenue programs | (200) | (9) | 179
Revenue Not from Contract with Customer, Other | 18 | 19 | 0
Ameren Missouri |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from alternative revenue programs | (5) | 4 | (5)
Ameren Illinois Electric Distribution |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from alternative revenue programs | (135) | (43) | 116
Ameren Illinois Gas |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from alternative revenue programs | (34) | (3) | 49
Ameren Transmission |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from alternative revenue programs | (26) | 33 | 19
Electric |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 7,668 | 6,540 | 6,439
Revenues | 7,668 | 6,540 | 6,439
Electric | Residential |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 3,322 | 2,892 | 2,921
Electric | Commercial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 2,235 | 1,993 | 2,027
Electric | Industrial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 541 | 489 | 492
Electric | Other |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenue Not from Contract with Customer | 1,570 | 1,166 | 999
Natural gas |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 1,131 | 1,083 | 1,061
Revenues | 1,131 | 1,083 | 1,061
Natural gas | Residential |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 781 | 751 | 757
Natural gas | Commercial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 229 | 203 | 210
Natural gas | Industrial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 17 | 14 | 19
Natural gas | Other |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenue Not from Contract with Customer | 104 | 115 | 75
Ameren Illinois |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 3,844 | 3,472 | 3,482
Revenues | 3,844 | 3,472 | 3,482
Revenues from alternative revenue programs | (188) | (17) | 177
Revenue Not from Contract with Customer, Other | 16 | 12 | 9
Ameren Illinois | Residential |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 2,163 | 1,915 | 2,001
Ameren Illinois | Commercial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 970 | 846 | 911
Ameren Illinois | Industrial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 211 | 188 | 200
Ameren Illinois | Other |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenue Not from Contract with Customer | 500 | 523 | 370
Ameren Illinois | Ameren Illinois Electric Distribution |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from alternative revenue programs | (135) | (43) | 116
Revenue Not from Contract with Customer, Other | 13 | 10 | 7
Ameren Illinois | Ameren Illinois Gas |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from alternative revenue programs | (34) | (3) | 49
Revenue Not from Contract with Customer, Other | 3 | 2 | 2
Ameren Illinois | Ameren Illinois Transmission |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues from alternative revenue programs | (19) | 29 | 12
Revenue Not from Contract with Customer, Other | 0 | 0 | 0
Ameren Illinois | Electric |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 2,876 | 2,534 | 2,585
Ameren Illinois | Natural gas |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 968 | 938 | 897
Operating Segments | Ameren Missouri |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 4,763 | 3,960 | 3,825
Revenues | 4,795 | 3,993 | 3,859
Revenue Not from Contract with Customer, Other | 6 | 7 | (9)
Operating Segments | Ameren Illinois Electric Distribution |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 2,393 | 2,088 | 2,217
Revenues | 2,399 | 2,089 | 2,218
Revenue Not from Contract with Customer, Other | 13 | 10 | 7
Operating Segments | Ameren Illinois Gas |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 968 | 938 | 897
Revenues | 968 | 938 | 897
Revenue Not from Contract with Customer, Other | 3 | 2 | 2
Operating Segments | Ameren Transmission |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 675 | 637 | 561
Revenues | 862 | 781 | 677
Revenue Not from Contract with Customer, Other | 0 | 0 | 0
Operating Segments | Electric | Ameren Missouri |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues | 4,631 | 3,847 | 3,694
Operating Segments | Electric | Ameren Missouri | Residential |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 1,839 | 1,638 | 1,577
Operating Segments | Electric | Ameren Missouri | Commercial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 1,450 | 1,313 | 1,280
Operating Segments | Electric | Ameren Missouri | Industrial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 342 | 311 | 306
Operating Segments | Electric | Ameren Missouri | Other |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenue Not from Contract with Customer | 1,000 | 585 | 531
Operating Segments | Electric | Ameren Illinois Electric Distribution |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues | 2,399 | 2,089 | 2,218
Operating Segments | Electric | Ameren Illinois Electric Distribution | Residential |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 1,483 | 1,254 | 1,344
Operating Segments | Electric | Ameren Illinois Electric Distribution | Commercial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 785 | 680 | 747
Operating Segments | Electric | Ameren Illinois Electric Distribution | Industrial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 199 | 178 | 186
Operating Segments | Electric | Ameren Illinois Electric Distribution | Other |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenue Not from Contract with Customer | (68) | (23) | (59)
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 | 862 | 781 | 677
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 | 862 | 781 | 677
Operating Segments | Natural gas | Ameren Missouri |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues | 164 | 146 | 165
Operating Segments | Natural gas | Ameren Missouri | Residential |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 101 | 90 | 100
Operating Segments | Natural gas | Ameren Missouri | Commercial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 44 | 37 | 46
Operating Segments | Natural gas | Ameren Missouri | Industrial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 5 | 4 | 5
Operating Segments | Natural gas | Ameren Missouri | Other |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenue Not from Contract with Customer | 14 | 15 | 14
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 | 968 | 938 | 897
Operating Segments | Natural gas | Ameren Illinois Gas | Residential |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 680 | 661 | 657
Operating Segments | Natural gas | Ameren Illinois Gas | Commercial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 185 | 166 | 164
Operating Segments | Natural gas | Ameren Illinois Gas | Industrial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 12 | 10 | 14
Operating Segments | Natural gas | Ameren Illinois Gas | Other |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenue Not from Contract with Customer | 91 | 101 | 62
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 | 2,399 | 2,089 | 2,218
Revenues | 2,399 | 2,089 | 2,218
Operating Segments | Ameren Illinois | Ameren Illinois Gas |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 968 | 938 | 897
Revenues | 968 | 938 | 897
Operating Segments | Ameren Illinois | Ameren Illinois Transmission |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 477 | 445 | 367
Revenues | 637 | 564 | 480
Operating Segments | Ameren Illinois | Electric | Ameren Illinois Electric Distribution |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues | 2,399 | 2,089 | 2,218
Operating Segments | Ameren Illinois | Electric | Ameren Illinois Electric Distribution | Residential |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 1,483 | 1,254 | 1,344
Operating Segments | Ameren Illinois | Electric | Ameren Illinois Electric Distribution | Commercial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 785 | 680 | 747
Operating Segments | Ameren Illinois | Electric | Ameren Illinois Electric Distribution | Industrial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 199 | 178 | 186
Operating Segments | Ameren Illinois | Electric | Ameren Illinois Electric Distribution | Other |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenue Not from Contract with Customer | (68) | (23) | (59)
Operating Segments | Ameren Illinois | Electric | Ameren Illinois Transmission |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues | 637 | 564 | 480
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 | 637 | 564 | 480
Operating Segments | Ameren Illinois | Natural gas | Ameren Illinois Gas |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues | 968 | 938 | 897
Operating Segments | Ameren Illinois | Natural gas | Ameren Illinois Gas | Residential |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 680 | 661 | 657
Operating Segments | Ameren Illinois | Natural gas | Ameren Illinois Gas | Commercial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 185 | 166 | 164
Operating Segments | Ameren Illinois | Natural gas | Ameren Illinois Gas | Industrial |  |  |
Disaggregation of Revenue [Line Items] |  |  |
External revenues | 12 | 10 | 14
Operating Segments | Ameren Illinois | Natural gas | Ameren Illinois Gas | Other |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenue Not from Contract with Customer | 91 | 101 | 62
Intersegment Elimination |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenue Not from Contract with Customer | (225) | (178) | (151)
Revenues | (225) | (178) | (151)
Revenue Not from Contract with Customer, Other | (4) | 0 | 0
Intersegment Elimination | Ameren Missouri |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenue Not from Contract with Customer | (32) | (33) | (34)
Intersegment Elimination | Ameren Illinois Electric Distribution |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenue Not from Contract with Customer | (6) | (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 | (187) | (144) | (116)
Intersegment Elimination | Electric |  |  |
Disaggregation of Revenue [Line Items] |  |  |
Revenues | (224) | (177) | (150)
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 | (224) | (177) | (150)
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 | (160) | (119) | (113)
Revenues | (160) | (119) | (113)
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 | (160) | (119) | (113)
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 | $ (160) | $ (119) | $ (113)

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