Segment Information (Schedule Of Segment Reporting Information By Segment) (Details) - USD ($)
$ in Millions |
3 Months Ended |
6 Months Ended |
Jun. 30, 2026 |
Jun. 30, 2025 |
Jun. 30, 2026 |
Jun. 30, 2025 |
| Segment Reporting [Line Items] |
|
|
|
|
| External revenues |
$ 2,092
|
$ 2,221
|
$ 4,268
|
$ 4,318
|
| Revenues |
2,092
|
2,221
|
4,268
|
4,318
|
| Fuel and purchased power |
(507)
|
(794)
|
(940)
|
(1,296)
|
| Natural gas purchased for resale |
(39)
|
(39)
|
(210)
|
(208)
|
| Other operations and maintenance expenses |
(521)
|
(460)
|
(1,012)
|
(945)
|
| Depreciation and amortization |
(420)
|
(386)
|
(818)
|
(753)
|
| Taxes other than income taxes |
(146)
|
(131)
|
(297)
|
(275)
|
| Other Income, Net |
118
|
96
|
208
|
181
|
| Interest charges |
(209)
|
(187)
|
(413)
|
(362)
|
| Income taxes |
(52)
|
(43)
|
(112)
|
(93)
|
| Noncontrolling interests - preferred stock dividends |
(2)
|
(2)
|
(3)
|
(3)
|
| Net income attributable to Ameren common shareholders |
314
|
275
|
671
|
564
|
| Interest income |
7
|
10
|
16
|
21
|
| Segment Reporting, Long-Lived Asset, Expenditure for Addition |
1,079
|
1,066
|
2,653
|
2,130
|
| Union Electric Company |
|
|
|
|
| Segment Reporting [Line Items] |
|
|
|
|
| External revenues |
1,124
|
1,340
|
2,054
|
2,297
|
| Fuel and purchased power |
(318)
|
(614)
|
(532)
|
(944)
|
| Natural gas purchased for resale |
(7)
|
(9)
|
(41)
|
(39)
|
| Other operations and maintenance expenses |
(282)
|
(238)
|
(546)
|
(488)
|
| Taxes other than income taxes |
(101)
|
(89)
|
(196)
|
(178)
|
| Other Income, Net |
60
|
47
|
113
|
90
|
| Interest charges |
(83)
|
(70)
|
(165)
|
(130)
|
| Income taxes |
(1)
|
(7)
|
(4)
|
(11)
|
| Noncontrolling interests - preferred stock dividends |
(1)
|
(1)
|
(2)
|
(2)
|
| Net income attributable to Ameren common shareholders |
157
|
150
|
233
|
192
|
| Ameren Illinois Company |
|
|
|
|
| Segment Reporting [Line Items] |
|
|
|
|
| External revenues |
928
|
843
|
2,127
|
1,943
|
| Revenues |
928
|
843
|
2,127
|
1,943
|
| Purchased Power |
(193)
|
(183)
|
(415)
|
(358)
|
| Natural gas purchased for resale |
(32)
|
(30)
|
(169)
|
(169)
|
| Other operations and maintenance expenses |
(248)
|
(225)
|
(480)
|
(461)
|
| Depreciation and amortization |
(172)
|
(163)
|
(342)
|
(322)
|
| Taxes other than income taxes |
(39)
|
(37)
|
(91)
|
(88)
|
| Other Income, Net |
26
|
37
|
55
|
71
|
| Interest charges |
(69)
|
(63)
|
(137)
|
(125)
|
| Income taxes |
(53)
|
(41)
|
(144)
|
(117)
|
| Noncontrolling interests - preferred stock dividends |
(1)
|
(1)
|
(1)
|
(1)
|
| Net Income Available to Common Shareholder |
147
|
137
|
403
|
373
|
| Net income attributable to Ameren common shareholders |
147
|
137
|
403
|
373
|
| Interest income |
5
|
8
|
11
|
17
|
| Segment Reporting, Long-Lived Asset, Expenditure for Addition |
318
|
379
|
|
742
|
| Capital expenditures |
|
|
706
|
|
| Operating Segments | Union Electric Company |
|
|
|
|
| Segment Reporting [Line Items] |
|
|
|
|
| External revenues |
1,111
|
1,332
|
2,031
|
2,282
|
| Revenues |
1,124
|
1,340
|
2,054
|
2,297
|
| Fuel and purchased power |
(318)
|
(614)
|
(532)
|
(944)
|
| Natural gas purchased for resale |
(7)
|
(9)
|
(41)
|
(39)
|
| Other operations and maintenance expenses |
(282)
|
(238)
|
(546)
|
(488)
|
| Depreciation and amortization |
(234)
|
(209)
|
(448)
|
(403)
|
| Taxes other than income taxes |
(101)
|
(89)
|
(196)
|
(178)
|
| Other Income, Net |
60
|
47
|
113
|
90
|
| Interest charges |
(83)
|
(70)
|
(165)
|
(130)
|
| Income taxes |
(1)
|
(7)
|
(4)
|
(11)
|
| Noncontrolling interests - preferred stock dividends |
(1)
|
(1)
|
(2)
|
(2)
|
| Net Income Available to Common Shareholder |
157
|
150
|
233
|
192
|
| Interest income |
2
|
2
|
5
|
4
|
| Segment Reporting, Long-Lived Asset, Expenditure for Addition |
680
|
667
|
1,771
|
1,325
|
| Operating Segments | Ameren Illinois Electric Distribution |
|
|
|
|
| Segment Reporting [Line Items] |
|
|
|
|
| External revenues |
629
|
570
|
1,272
|
1,140
|
| Revenues |
629
|
573
|
1,272
|
1,145
|
| Fuel and purchased power |
(238)
|
(223)
|
(504)
|
(435)
|
| Natural gas purchased for resale |
0
|
0
|
0
|
0
|
| Other operations and maintenance expenses |
(165)
|
(156)
|
(325)
|
(322)
|
| Depreciation and amortization |
(98)
|
(93)
|
(194)
|
(184)
|
| Taxes other than income taxes |
(21)
|
(20)
|
(43)
|
(41)
|
| Other Income, Net |
18
|
23
|
37
|
46
|
| Interest charges |
(28)
|
(26)
|
(56)
|
(52)
|
| Income taxes |
(26)
|
(13)
|
(50)
|
(29)
|
| Noncontrolling interests - preferred stock dividends |
(1)
|
(1)
|
(1)
|
(1)
|
| Net Income Available to Common Shareholder |
70
|
64
|
136
|
127
|
| Interest income |
5
|
8
|
11
|
16
|
| Segment Reporting, Long-Lived Asset, Expenditure for Addition |
180
|
153
|
376
|
320
|
| Operating Segments | Ameren Illinois Natural Gas |
|
|
|
|
| Segment Reporting [Line Items] |
|
|
|
|
| External revenues |
176
|
158
|
612
|
569
|
| Revenues |
176
|
158
|
612
|
569
|
| Fuel and purchased power |
0
|
0
|
0
|
0
|
| Natural gas purchased for resale |
(32)
|
(30)
|
(169)
|
(169)
|
| Other operations and maintenance expenses |
(67)
|
(55)
|
(124)
|
(110)
|
| Depreciation and amortization |
(33)
|
(33)
|
(67)
|
(65)
|
| Taxes other than income taxes |
(17)
|
(16)
|
(46)
|
(45)
|
| Other Income, Net |
4
|
5
|
7
|
10
|
| Interest charges |
(17)
|
(16)
|
(33)
|
(31)
|
| Income taxes |
(5)
|
(3)
|
(49)
|
(41)
|
| Noncontrolling interests - preferred stock dividends |
0
|
0
|
0
|
0
|
| Net Income Available to Common Shareholder |
9
|
10
|
131
|
118
|
| Interest income |
0
|
0
|
0
|
0
|
| Segment Reporting, Long-Lived Asset, Expenditure for Addition |
58
|
88
|
130
|
147
|
| Operating Segments | Ameren Transmission |
|
|
|
|
| Segment Reporting [Line Items] |
|
|
|
|
| External revenues |
176
|
161
|
353
|
327
|
| Revenues |
229
|
208
|
456
|
418
|
| Fuel and purchased power |
0
|
0
|
0
|
0
|
| Natural gas purchased for resale |
0
|
0
|
0
|
0
|
| Other operations and maintenance expenses |
(21)
|
(18)
|
(40)
|
(37)
|
| Depreciation and amortization |
(52)
|
(49)
|
(105)
|
(97)
|
| Taxes other than income taxes |
(3)
|
(3)
|
(5)
|
(4)
|
| Other Income, Net |
6
|
10
|
13
|
17
|
| Interest charges |
(32)
|
(29)
|
(62)
|
(58)
|
| Income taxes |
(31)
|
(33)
|
(63)
|
(64)
|
| Noncontrolling interests - preferred stock dividends |
0
|
0
|
0
|
0
|
| Net Income Available to Common Shareholder |
96
|
86
|
194
|
175
|
| Interest income |
0
|
0
|
0
|
1
|
| Segment Reporting, Long-Lived Asset, Expenditure for Addition |
166
|
158
|
370
|
331
|
| Operating Segments | Ameren Illinois Company | Ameren Illinois Electric Distribution |
|
|
|
|
| Segment Reporting [Line Items] |
|
|
|
|
| External revenues |
629
|
573
|
1,272
|
1,145
|
| Revenues |
629
|
573
|
1,272
|
1,145
|
| Purchased Power |
(238)
|
(223)
|
(504)
|
(435)
|
| Natural gas purchased for resale |
0
|
0
|
0
|
0
|
| Other operations and maintenance expenses |
(165)
|
(156)
|
(325)
|
(322)
|
| Depreciation and amortization |
(98)
|
(93)
|
(194)
|
(184)
|
| Taxes other than income taxes |
(21)
|
(20)
|
(43)
|
(41)
|
| Other Income, Net |
18
|
23
|
37
|
46
|
| Interest charges |
(28)
|
(26)
|
(56)
|
(52)
|
| Income taxes |
(26)
|
(13)
|
(50)
|
(29)
|
| Noncontrolling interests - preferred stock dividends |
(1)
|
(1)
|
(1)
|
(1)
|
| Net Income Available to Common Shareholder |
70
|
64
|
136
|
127
|
| Interest income |
5
|
8
|
11
|
16
|
| Segment Reporting, Long-Lived Asset, Expenditure for Addition |
180
|
153
|
|
320
|
| Capital expenditures |
|
|
376
|
|
| Operating Segments | Ameren Illinois Company | Ameren Illinois Natural Gas |
|
|
|
|
| Segment Reporting [Line Items] |
|
|
|
|
| External revenues |
176
|
158
|
612
|
569
|
| Revenues |
176
|
158
|
612
|
569
|
| Purchased Power |
0
|
0
|
0
|
0
|
| Natural gas purchased for resale |
(32)
|
(30)
|
(169)
|
(169)
|
| Other operations and maintenance expenses |
(67)
|
(55)
|
(124)
|
(110)
|
| Depreciation and amortization |
(33)
|
(33)
|
(67)
|
(65)
|
| Taxes other than income taxes |
(17)
|
(16)
|
(46)
|
(45)
|
| Other Income, Net |
4
|
5
|
7
|
10
|
| Interest charges |
(17)
|
(16)
|
(33)
|
(31)
|
| Income taxes |
(5)
|
(3)
|
(49)
|
(41)
|
| Noncontrolling interests - preferred stock dividends |
0
|
0
|
0
|
0
|
| Net Income Available to Common Shareholder |
9
|
10
|
131
|
118
|
| Interest income |
0
|
0
|
0
|
0
|
| Segment Reporting, Long-Lived Asset, Expenditure for Addition |
58
|
88
|
|
147
|
| Capital expenditures |
|
|
130
|
|
| Operating Segments | Ameren Illinois Company | Ameren Illinois Transmission |
|
|
|
|
| Segment Reporting [Line Items] |
|
|
|
|
| External revenues |
123
|
112
|
243
|
229
|
| Revenues |
168
|
152
|
332
|
306
|
| Purchased Power |
0
|
0
|
0
|
0
|
| Natural gas purchased for resale |
0
|
0
|
0
|
0
|
| Other operations and maintenance expenses |
(16)
|
(14)
|
(31)
|
(29)
|
| Depreciation and amortization |
(41)
|
(37)
|
(81)
|
(73)
|
| Taxes other than income taxes |
(1)
|
(1)
|
(2)
|
(2)
|
| Other Income, Net |
4
|
9
|
11
|
15
|
| Interest charges |
(24)
|
(21)
|
(48)
|
(42)
|
| Income taxes |
(22)
|
(25)
|
(45)
|
(47)
|
| Noncontrolling interests - preferred stock dividends |
0
|
0
|
0
|
0
|
| Net Income Available to Common Shareholder |
68
|
63
|
136
|
128
|
| Interest income |
0
|
0
|
0
|
1
|
| Segment Reporting, Long-Lived Asset, Expenditure for Addition |
80
|
138
|
|
275
|
| Capital expenditures |
|
|
200
|
|
| Other |
|
|
|
|
| Segment Reporting [Line Items] |
|
|
|
|
| Other operations and maintenance expenses |
(3)
|
(8)
|
(7)
|
(16)
|
| Depreciation and amortization |
(3)
|
(2)
|
(4)
|
(4)
|
| Taxes other than income taxes |
(4)
|
(3)
|
(7)
|
(7)
|
| Other Income, Net |
33
|
12
|
42
|
20
|
| Interest charges |
(52)
|
(47)
|
(101)
|
(93)
|
| Income taxes |
11
|
13
|
54
|
52
|
| Noncontrolling interests - preferred stock dividends |
0
|
0
|
0
|
0
|
| Net Income Available to Common Shareholder |
(18)
|
(35)
|
(23)
|
(48)
|
| Interest income |
3
|
1
|
4
|
2
|
| Segment Reporting, Long-Lived Asset, Expenditure for Addition |
2
|
3
|
3
|
5
|
| Intersegment Eliminations |
|
|
|
|
| Segment Reporting [Line Items] |
|
|
|
|
| Intersegment revenues |
(66)
|
(58)
|
(126)
|
(111)
|
| Revenues |
(66)
|
(58)
|
(126)
|
(111)
|
| Fuel and purchased power |
49
|
43
|
96
|
83
|
| Natural gas purchased for resale |
0
|
0
|
0
|
0
|
| Other operations and maintenance expenses |
17
|
15
|
30
|
28
|
| Depreciation and amortization |
0
|
0
|
0
|
0
|
| Taxes other than income taxes |
0
|
0
|
0
|
0
|
| Other Income, Net |
(3)
|
(1)
|
(4)
|
(2)
|
| Interest charges |
3
|
1
|
4
|
2
|
| Income taxes |
0
|
0
|
0
|
0
|
| Noncontrolling interests - preferred stock dividends |
0
|
0
|
0
|
0
|
| Interest income |
(3)
|
(1)
|
(4)
|
(2)
|
| Segment Reporting, Long-Lived Asset, Expenditure for Addition |
(7)
|
(3)
|
3
|
2
|
| Intersegment Eliminations | Union Electric Company |
|
|
|
|
| Segment Reporting [Line Items] |
|
|
|
|
| Intersegment revenues |
(13)
|
(8)
|
(23)
|
(15)
|
| Intersegment Eliminations | Ameren Illinois Electric Distribution |
|
|
|
|
| Segment Reporting [Line Items] |
|
|
|
|
| Intersegment revenues |
0
|
(3)
|
0
|
(5)
|
| 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 |
(53)
|
(47)
|
(103)
|
(91)
|
| Intersegment Eliminations | Ameren Illinois Company |
|
|
|
|
| Segment Reporting [Line Items] |
|
|
|
|
| Intersegment revenues |
(45)
|
(40)
|
(89)
|
(77)
|
| Revenues |
(45)
|
(40)
|
(89)
|
(77)
|
| Purchased Power |
(45)
|
(40)
|
(89)
|
(77)
|
| 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 |
$ (45)
|
$ (40)
|
$ (89)
|
$ (77)
|