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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The amount recovered from insurance. These recoveries reduce costs and losses that are reported as a separate line item under operating expenses.

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Amount, including tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value-added and excise.

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