Segment Information (Schedule Of Segment Reporting Information By Segment) (Details) - USD ($)
$ in Millions |
3 Months Ended |
9 Months Ended |
Sep. 30, 2026 |
Sep. 30, 2025 |
Sep. 30, 2026 |
Sep. 30, 2025 |
| Segment Reporting [Line Items] |
|
|
|
|
| External revenues |
$ 2,882
|
$ 2,699
|
$ 7,150
|
$ 7,017
|
| Revenues |
2,882
|
2,699
|
7,150
|
7,017
|
| Fuel and purchased power |
(809)
|
(768)
|
(1,749)
|
(2,064)
|
| Natural gas purchased for resale |
(28)
|
(25)
|
(238)
|
(233)
|
| Other operations and maintenance expenses |
(535)
|
(502)
|
(1,547)
|
(1,447)
|
| Depreciation and amortization |
(436)
|
(415)
|
(1,254)
|
(1,168)
|
| Taxes other than income taxes |
(174)
|
(164)
|
(471)
|
(439)
|
| Other Income, Net |
112
|
76
|
320
|
257
|
| Interest charges |
(216)
|
(208)
|
(629)
|
(570)
|
| Income taxes |
(119)
|
(52)
|
(231)
|
(145)
|
| Noncontrolling interests - preferred stock dividends |
(1)
|
(1)
|
(4)
|
(4)
|
| Net income attributable to Ameren common shareholders |
676
|
640
|
1,347
|
1,204
|
| Interest income |
8
|
10
|
24
|
31
|
| Segment Reporting, Long-Lived Asset, Expenditure for Addition |
1,436
|
988
|
4,089
|
3,118
|
| Union Electric Company |
|
|
|
|
| Segment Reporting [Line Items] |
|
|
|
|
| External revenues |
1,781
|
1,705
|
3,835
|
4,002
|
| Fuel and purchased power |
(509)
|
(487)
|
(1,041)
|
(1,431)
|
| Natural gas purchased for resale |
(5)
|
(6)
|
(46)
|
(45)
|
| Other operations and maintenance expenses |
(274)
|
(260)
|
(820)
|
(748)
|
| Taxes other than income taxes |
(129)
|
(122)
|
(325)
|
(300)
|
| Other Income, Net |
58
|
45
|
171
|
135
|
| Interest charges |
(82)
|
(85)
|
(247)
|
(215)
|
| Income taxes |
(11)
|
(32)
|
(15)
|
(43)
|
| Noncontrolling interests - preferred stock dividends |
(1)
|
(1)
|
(3)
|
(3)
|
| Net income attributable to Ameren common shareholders |
582
|
518
|
815
|
710
|
| Ameren Illinois Company |
|
|
|
|
| Segment Reporting [Line Items] |
|
|
|
|
| External revenues |
1,053
|
946
|
3,180
|
2,889
|
| Revenues |
1,053
|
946
|
3,180
|
2,889
|
| Purchased Power |
(304)
|
(284)
|
(719)
|
(642)
|
| Natural gas purchased for resale |
(23)
|
(19)
|
(192)
|
(188)
|
| Other operations and maintenance expenses |
(265)
|
(241)
|
(745)
|
(702)
|
| Depreciation and amortization |
(175)
|
(162)
|
(517)
|
(484)
|
| Taxes other than income taxes |
(42)
|
(38)
|
(133)
|
(126)
|
| Other Income, Net |
25
|
30
|
80
|
101
|
| Interest charges |
(72)
|
(67)
|
(209)
|
(192)
|
| Income taxes |
(53)
|
(17)
|
(197)
|
(134)
|
| Noncontrolling interests - preferred stock dividends |
0
|
0
|
(1)
|
(1)
|
| Net Income Available to Common Shareholder |
144
|
148
|
547
|
521
|
| Net income attributable to Ameren common shareholders |
144
|
148
|
547
|
521
|
| Interest income |
5
|
7
|
16
|
24
|
| Segment Reporting, Long-Lived Asset, Expenditure for Addition |
382
|
385
|
1,088
|
1,127
|
| Operating Segments | Union Electric Company |
|
|
|
|
| Segment Reporting [Line Items] |
|
|
|
|
| External revenues |
1,770
|
1,696
|
3,801
|
3,978
|
| Revenues |
1,781
|
1,705
|
3,835
|
4,002
|
| Fuel and purchased power |
(509)
|
(487)
|
(1,041)
|
(1,431)
|
| Natural gas purchased for resale |
(5)
|
(6)
|
(46)
|
(45)
|
| Other operations and maintenance expenses |
(274)
|
(260)
|
(820)
|
(748)
|
| Depreciation and amortization |
(246)
|
(239)
|
(694)
|
(642)
|
| Taxes other than income taxes |
(129)
|
(122)
|
(325)
|
(300)
|
| Other Income, Net |
58
|
45
|
171
|
135
|
| Interest charges |
(82)
|
(85)
|
(247)
|
(215)
|
| Income taxes |
(11)
|
(32)
|
(15)
|
(43)
|
| Noncontrolling interests - preferred stock dividends |
(1)
|
(1)
|
(3)
|
(3)
|
| Net Income Available to Common Shareholder |
582
|
518
|
815
|
710
|
| Interest income |
3
|
3
|
8
|
7
|
| Segment Reporting, Long-Lived Asset, Expenditure for Addition |
979
|
548
|
2,750
|
1,873
|
| Operating Segments | Ameren Illinois Electric Distribution |
|
|
|
|
| Segment Reporting [Line Items] |
|
|
|
|
| External revenues |
774
|
698
|
2,046
|
1,838
|
| Revenues |
777
|
699
|
2,049
|
1,844
|
| Fuel and purchased power |
(360)
|
(330)
|
(864)
|
(765)
|
| Natural gas purchased for resale |
0
|
0
|
0
|
0
|
| Other operations and maintenance expenses |
(182)
|
(171)
|
(507)
|
(493)
|
| Depreciation and amortization |
(100)
|
(92)
|
(294)
|
(276)
|
| Taxes other than income taxes |
(23)
|
(22)
|
(66)
|
(63)
|
| Other Income, Net |
17
|
20
|
54
|
66
|
| Interest charges |
(30)
|
(28)
|
(86)
|
(80)
|
| Income taxes |
(27)
|
(19)
|
(77)
|
(48)
|
| Noncontrolling interests - preferred stock dividends |
0
|
0
|
(1)
|
(1)
|
| Net Income Available to Common Shareholder |
72
|
57
|
208
|
184
|
| Interest income |
5
|
6
|
16
|
22
|
| Segment Reporting, Long-Lived Asset, Expenditure for Addition |
223
|
163
|
599
|
483
|
| Operating Segments | Ameren Illinois Natural Gas |
|
|
|
|
| Segment Reporting [Line Items] |
|
|
|
|
| External revenues |
136
|
117
|
748
|
686
|
| Revenues |
136
|
117
|
748
|
686
|
| Fuel and purchased power |
0
|
0
|
0
|
0
|
| Natural gas purchased for resale |
(23)
|
(19)
|
(192)
|
(188)
|
| Other operations and maintenance expenses |
(58)
|
(55)
|
(182)
|
(165)
|
| Depreciation and amortization |
(34)
|
(33)
|
(101)
|
(98)
|
| Taxes other than income taxes |
(17)
|
(15)
|
(63)
|
(60)
|
| Other Income, Net |
3
|
4
|
10
|
14
|
| Interest charges |
(18)
|
(16)
|
(51)
|
(47)
|
| Income taxes |
4
|
4
|
(45)
|
(37)
|
| Noncontrolling interests - preferred stock dividends |
0
|
0
|
0
|
0
|
| Net Income Available to Common Shareholder |
(7)
|
(13)
|
124
|
105
|
| Interest income |
0
|
0
|
0
|
0
|
| Segment Reporting, Long-Lived Asset, Expenditure for Addition |
81
|
78
|
211
|
225
|
| Operating Segments | Ameren Transmission |
|
|
|
|
| Segment Reporting [Line Items] |
|
|
|
|
| External revenues |
202
|
188
|
555
|
515
|
| Revenues |
266
|
240
|
722
|
658
|
| Fuel and purchased power |
0
|
0
|
0
|
0
|
| Natural gas purchased for resale |
0
|
0
|
0
|
0
|
| Other operations and maintenance expenses |
(34)
|
(19)
|
(74)
|
(56)
|
| Depreciation and amortization |
(55)
|
(49)
|
(160)
|
(146)
|
| Taxes other than income taxes |
(2)
|
(3)
|
(7)
|
(7)
|
| Other Income, Net |
6
|
(3)
|
19
|
14
|
| Interest charges |
(32)
|
(31)
|
(94)
|
(89)
|
| Income taxes |
(39)
|
16
|
(102)
|
(48)
|
| Noncontrolling interests - preferred stock dividends |
0
|
0
|
0
|
0
|
| Net Income Available to Common Shareholder |
110
|
151
|
304
|
326
|
| Interest income |
0
|
1
|
0
|
2
|
| Segment Reporting, Long-Lived Asset, Expenditure for Addition |
153
|
174
|
523
|
505
|
| Operating Segments | Ameren Illinois Company | Ameren Illinois Electric Distribution |
|
|
|
|
| Segment Reporting [Line Items] |
|
|
|
|
| External revenues |
777
|
699
|
2,049
|
1,844
|
| Revenues |
777
|
699
|
2,049
|
1,844
|
| Purchased Power |
(360)
|
(330)
|
(864)
|
(765)
|
| Natural gas purchased for resale |
0
|
0
|
0
|
0
|
| Other operations and maintenance expenses |
(182)
|
(171)
|
(507)
|
(493)
|
| Depreciation and amortization |
(100)
|
(92)
|
(294)
|
(276)
|
| Taxes other than income taxes |
(23)
|
(22)
|
(66)
|
(63)
|
| Other Income, Net |
17
|
20
|
54
|
66
|
| Interest charges |
(30)
|
(28)
|
(86)
|
(80)
|
| Income taxes |
(27)
|
(19)
|
(77)
|
(48)
|
| Noncontrolling interests - preferred stock dividends |
|
|
(1)
|
(1)
|
| Net Income Available to Common Shareholder |
72
|
57
|
208
|
184
|
| Interest income |
5
|
6
|
16
|
22
|
| Segment Reporting, Long-Lived Asset, Expenditure for Addition |
223
|
163
|
599
|
483
|
| Operating Segments | Ameren Illinois Company | Ameren Illinois Natural Gas |
|
|
|
|
| Segment Reporting [Line Items] |
|
|
|
|
| External revenues |
136
|
117
|
748
|
686
|
| Revenues |
136
|
117
|
748
|
686
|
| Purchased Power |
0
|
0
|
0
|
0
|
| Natural gas purchased for resale |
(23)
|
(19)
|
(192)
|
(188)
|
| Other operations and maintenance expenses |
(58)
|
(55)
|
(182)
|
(165)
|
| Depreciation and amortization |
(34)
|
(33)
|
(101)
|
(98)
|
| Taxes other than income taxes |
(17)
|
(15)
|
(63)
|
(60)
|
| Other Income, Net |
3
|
4
|
10
|
14
|
| Interest charges |
(18)
|
(16)
|
(51)
|
(47)
|
| Income taxes |
4
|
4
|
(45)
|
(37)
|
| Noncontrolling interests - preferred stock dividends |
|
|
0
|
0
|
| Net Income Available to Common Shareholder |
(7)
|
(13)
|
124
|
105
|
| Interest income |
0
|
0
|
0
|
0
|
| Segment Reporting, Long-Lived Asset, Expenditure for Addition |
81
|
78
|
211
|
225
|
| Operating Segments | Ameren Illinois Company | Ameren Illinois Transmission |
|
|
|
|
| Segment Reporting [Line Items] |
|
|
|
|
| External revenues |
140
|
130
|
383
|
359
|
| Revenues |
196
|
176
|
528
|
482
|
| Purchased Power |
0
|
0
|
0
|
0
|
| Natural gas purchased for resale |
0
|
0
|
0
|
0
|
| Other operations and maintenance expenses |
(25)
|
(15)
|
(56)
|
(44)
|
| Depreciation and amortization |
(41)
|
(37)
|
(122)
|
(110)
|
| Taxes other than income taxes |
(2)
|
(1)
|
(4)
|
(3)
|
| Other Income, Net |
5
|
6
|
16
|
21
|
| Interest charges |
(24)
|
(23)
|
(72)
|
(65)
|
| Income taxes |
(30)
|
(2)
|
(75)
|
(49)
|
| Noncontrolling interests - preferred stock dividends |
|
|
0
|
0
|
| Net Income Available to Common Shareholder |
79
|
104
|
215
|
232
|
| Interest income |
0
|
1
|
0
|
2
|
| Segment Reporting, Long-Lived Asset, Expenditure for Addition |
78
|
144
|
278
|
419
|
| Other |
|
|
|
|
| Segment Reporting [Line Items] |
|
|
|
|
| Other operations and maintenance expenses |
(5)
|
(10)
|
(12)
|
(26)
|
| Depreciation and amortization |
(1)
|
(2)
|
(5)
|
(6)
|
| Taxes other than income taxes |
(3)
|
(2)
|
(10)
|
(9)
|
| Other Income, Net |
30
|
11
|
72
|
31
|
| Interest charges |
(56)
|
(49)
|
(157)
|
(142)
|
| Income taxes |
(46)
|
(21)
|
8
|
31
|
| Noncontrolling interests - preferred stock dividends |
0
|
0
|
0
|
0
|
| Net Income Available to Common Shareholder |
(81)
|
(73)
|
(104)
|
(121)
|
| Interest income |
2
|
1
|
6
|
3
|
| Segment Reporting, Long-Lived Asset, Expenditure for Addition |
0
|
1
|
3
|
6
|
| Intersegment Eliminations |
|
|
|
|
| Segment Reporting [Line Items] |
|
|
|
|
| Intersegment revenues |
(78)
|
(62)
|
(204)
|
(173)
|
| Revenues |
(78)
|
(62)
|
(204)
|
(173)
|
| Fuel and purchased power |
60
|
49
|
156
|
132
|
| Natural gas purchased for resale |
0
|
0
|
0
|
0
|
| Other operations and maintenance expenses |
18
|
13
|
48
|
41
|
| Depreciation and amortization |
0
|
0
|
0
|
0
|
| Taxes other than income taxes |
0
|
0
|
0
|
0
|
| Other Income, Net |
(2)
|
(1)
|
(6)
|
(3)
|
| Interest charges |
2
|
1
|
6
|
3
|
| Income taxes |
0
|
0
|
0
|
0
|
| Noncontrolling interests - preferred stock dividends |
0
|
0
|
0
|
0
|
| Interest income |
(2)
|
(1)
|
(6)
|
(3)
|
| Segment Reporting, Long-Lived Asset, Expenditure for Addition |
0
|
24
|
3
|
26
|
| Intersegment Eliminations | Union Electric Company |
|
|
|
|
| Segment Reporting [Line Items] |
|
|
|
|
| Intersegment revenues |
(11)
|
(9)
|
(34)
|
(24)
|
| Intersegment Eliminations | Ameren Illinois Electric Distribution |
|
|
|
|
| Segment Reporting [Line Items] |
|
|
|
|
| Intersegment revenues |
(3)
|
(1)
|
(3)
|
(6)
|
| Intersegment Eliminations | Ameren Illinois Natural Gas |
|
|
|
|
| Segment Reporting [Line Items] |
|
|
|
|
| Intersegment revenues |
0
|
0
|
0
|
0
|
| Intersegment Eliminations | Ameren Transmission |
|
|
|
|
| Segment Reporting [Line Items] |
|
|
|
|
| Intersegment revenues |
(64)
|
(52)
|
(167)
|
(143)
|
| Intersegment Eliminations | Ameren Illinois Company |
|
|
|
|
| Segment Reporting [Line Items] |
|
|
|
|
| Intersegment revenues |
(56)
|
(46)
|
(145)
|
(123)
|
| Revenues |
(56)
|
(46)
|
(145)
|
(123)
|
| Purchased Power |
(56)
|
(46)
|
(145)
|
(123)
|
| Intersegment Eliminations | Ameren Illinois Company | Ameren Illinois Electric Distribution |
|
|
|
|
| Segment Reporting [Line Items] |
|
|
|
|
| Intersegment revenues |
0
|
0
|
0
|
0
|
| Intersegment Eliminations | Ameren Illinois Company | Ameren Illinois Natural Gas |
|
|
|
|
| Segment Reporting [Line Items] |
|
|
|
|
| Intersegment revenues |
0
|
0
|
0
|
0
|
| Intersegment Eliminations | Ameren Illinois Company | Ameren Illinois Transmission |
|
|
|
|
| Segment Reporting [Line Items] |
|
|
|
|
| Intersegment revenues |
$ (56)
|
$ (46)
|
$ (145)
|
$ (123)
|