Rate And Regulatory Matters (Schedule Of Regulatory Assets And Liabilities) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Regulatory assets:
Less: current regulatory assets	$ (366)	$ (365)
Noncurrent regulatory assets	2,397	1,810
Regulatory liabilities:
Noncurrent regulatory liabilities	5,897	5,512
Ameren Missouri
Regulatory assets:
Total regulatory assets	1,432	856
Less: current regulatory assets	(66)	(101)
Noncurrent regulatory assets	1,366	755
Regulatory liabilities:
Total regulatory liabilities	3,213	2,974
Less: current regulatory liabilities	(37)	(15)
Noncurrent regulatory liabilities	$ 3,176	2,959
PISA deferral percentage	85.00%
Ameren Illinois
Regulatory assets:
Total regulatory assets	$ 1,292	1,287
Less: current regulatory assets	(281)	(252)
Noncurrent regulatory assets	1,011	1,035
Regulatory liabilities:
Total regulatory liabilities	2,652	2,489
Less: current regulatory liabilities	(79)	(71)
Noncurrent regulatory liabilities	2,573	2,418
Ameren (parent)
Regulatory assets:
Total regulatory assets	2,763	2,175
Less: current regulatory assets	(366)	(365)
Noncurrent regulatory assets	2,397	1,810
Regulatory liabilities:
Total regulatory liabilities	6,017	5,599
Less: current regulatory liabilities	(120)	(87)
Noncurrent regulatory liabilities	5,897	5,512
Under-recovered FAC
Regulatory assets:
Total regulatory assets	41	72
Under-recovered FAC | Ameren Missouri
Regulatory assets:
Total regulatory assets	41	72
Under-recovered FAC | Ameren Illinois
Regulatory assets:
Total regulatory assets	0	0
MTM derivative losses
Regulatory assets:
Total regulatory assets	103	168
MTM derivative losses | Ameren Missouri
Regulatory assets:
Total regulatory assets	15	25
MTM derivative losses | Ameren Illinois
Regulatory assets:
Total regulatory assets	88	143
IEIMA revenue requirement reconciliation adjustment
Regulatory assets:
Total regulatory assets	139	239
IEIMA revenue requirement reconciliation adjustment | Ameren Missouri
Regulatory assets:
Total regulatory assets	0	0
IEIMA revenue requirement reconciliation adjustment | Ameren Illinois
Regulatory assets:
Total regulatory assets	$ 139	239
Regulatory liabilities:
Regulatory asset, amortization period	2 years
MYRP revenue requirement reconciliation adjustment
Regulatory assets:
Total regulatory assets	$ 24	0
MYRP revenue requirement reconciliation adjustment | Ameren Missouri
Regulatory assets:
Total regulatory assets	0	0
MYRP revenue requirement reconciliation adjustment | Ameren Illinois
Regulatory assets:
Total regulatory assets	24	0
Under-recovered RBA
Regulatory assets:
Total regulatory assets	22	0
Under-recovered RBA | Ameren Missouri
Regulatory assets:
Total regulatory assets	0	0
Under-recovered RBA | Ameren Illinois
Regulatory assets:
Total regulatory assets	22	0
FERC revenue requirement reconciliation adjustment
Regulatory assets:
Total regulatory assets	$ 90	54
Regulatory liabilities:
Regulatory asset, amortization period	2 years
FERC revenue requirement reconciliation adjustment | Ameren Missouri
Regulatory assets:
Total regulatory assets	$ 0	0
FERC revenue requirement reconciliation adjustment | Ameren Illinois
Regulatory assets:
Total regulatory assets	55	25
Under-recovered VBA
Regulatory assets:
Total regulatory assets	49	49
Under-recovered VBA | Ameren Missouri
Regulatory assets:
Total regulatory assets	0	0
Under-recovered VBA | Ameren Illinois
Regulatory assets:
Total regulatory assets	49	49
Income taxes
Regulatory assets:
Total regulatory assets	322	207
Regulatory liabilities:
Total regulatory liabilities	$ 1,804	1,809
Weighted-average amortization period	39 years
Income taxes | Ameren Missouri
Regulatory assets:
Total regulatory assets	$ 237	126
Regulatory liabilities:
Total regulatory liabilities	$ 1,040	999
Weighted-average amortization period	30 years
Income taxes | Ameren Illinois
Regulatory assets:
Total regulatory assets	$ 81	78
Regulatory liabilities:
Total regulatory liabilities	$ 679	724
Weighted-average amortization period	46 years
Bad debt rider
Regulatory assets:
Total regulatory assets	$ 25	43
Bad debt rider | Ameren Missouri
Regulatory assets:
Total regulatory assets	0	0
Bad debt rider | Ameren Illinois
Regulatory assets:
Total regulatory assets	25	43
Callaway refueling and maintenance outage costs
Regulatory assets:
Total regulatory assets	13	37
Callaway refueling and maintenance outage costs | Ameren Missouri
Regulatory assets:
Total regulatory assets	$ 13	37
Regulatory liabilities:
Regulatory asset, amortization period	18 months
Callaway refueling and maintenance outage costs | Ameren Illinois
Regulatory assets:
Total regulatory assets	$ 0	0
Unamortized loss on reacquired debt
Regulatory assets:
Total regulatory assets	47	50
Unamortized loss on reacquired debt | Ameren Missouri
Regulatory assets:
Total regulatory assets	42	45
Unamortized loss on reacquired debt | Ameren Illinois
Regulatory assets:
Total regulatory assets	5	5
Environmental cost riders
Regulatory assets:
Total regulatory assets	43	50
Environmental cost riders | Ameren Missouri
Regulatory assets:
Total regulatory assets	0	0
Environmental cost riders | Ameren Illinois
Regulatory assets:
Total regulatory assets	43	50
Storm costs
Regulatory assets:
Total regulatory assets	18	27
Storm costs | Ameren Missouri
Regulatory assets:
Total regulatory assets	0	0
Storm costs | Ameren Illinois
Regulatory assets:
Total regulatory assets	18	27
Customer generation rebate program
Regulatory assets:
Total regulatory assets	89	54
Customer generation rebate program | Ameren Missouri
Regulatory assets:
Total regulatory assets	0	0
Customer generation rebate program | Ameren Illinois
Regulatory assets:
Total regulatory assets	89	54
PISA
Regulatory assets:
Total regulatory assets	464	386
PISA | Ameren Missouri
Regulatory assets:
Total regulatory assets	$ 464	386
Regulatory liabilities:
Regulatory asset, amortization period	20 years
PISA | Ameren Illinois
Regulatory assets:
Total regulatory assets	$ 0	0
Rush Island Energy Center securitization
Regulatory assets:
Total regulatory assets	465	0
Rush Island Energy Center securitization | Ameren Missouri
Regulatory assets:
Total regulatory assets	465	0
Rush Island Energy Center securitization | Ameren Illinois
Regulatory assets:
Total regulatory assets	0	0
RESRAM
Regulatory assets:
Total regulatory assets	51	48
RESRAM | Ameren Missouri
Regulatory assets:
Total regulatory assets	51	48
RESRAM | Ameren Illinois
Regulatory assets:
Total regulatory assets	0	0
Certain Meramec Energy Center costs
Regulatory assets:
Total regulatory assets	26	39
Certain Meramec Energy Center costs | Ameren Missouri
Regulatory assets:
Total regulatory assets	$ 26	39
Regulatory liabilities:
Regulatory asset, amortization period	5 years
Certain Meramec Energy Center costs | Ameren Illinois
Regulatory assets:
Total regulatory assets	$ 0	0
FEJA energy-efficiency rider
Regulatory assets:
Total regulatory assets	576	500
FEJA energy-efficiency rider | Ameren Missouri
Regulatory assets:
Total regulatory assets	0	0
FEJA energy-efficiency rider | Ameren Illinois
Regulatory assets:
Total regulatory assets	576	500
Property Tax Tracker
Regulatory assets:
Total regulatory assets	$ 22	13
Regulatory liabilities:
Regulatory asset, amortization period	2 years
Property Tax Tracker | Ameren Missouri
Regulatory assets:
Total regulatory assets	$ 22	13
Property Tax Tracker | Ameren Illinois
Regulatory assets:
Total regulatory assets	0	0
Other regulatory assets
Regulatory assets:
Total regulatory assets	134	139
Other regulatory assets | Ameren Missouri
Regulatory assets:
Total regulatory assets	56	65
Other regulatory assets | Ameren Illinois
Regulatory assets:
Total regulatory assets	78	74
Over-recovered Illinois electric power costs
Regulatory liabilities:
Total regulatory liabilities	34	36
Over-recovered Illinois electric power costs | Ameren Missouri
Regulatory liabilities:
Total regulatory liabilities	0	0
Over-recovered Illinois electric power costs | Ameren Illinois
Regulatory liabilities:
Total regulatory liabilities	$ 34	36
Amortization period	1 year
Over-recovered PGA
Regulatory liabilities:
Total regulatory liabilities	$ 35	40
Over-recovered PGA | Ameren Missouri
Regulatory liabilities:
Total regulatory liabilities	2	7
Over-recovered PGA | Ameren Illinois
Regulatory liabilities:
Total regulatory liabilities	33	33
MTM derivative gains
Regulatory liabilities:
Total regulatory liabilities	16	22
MTM derivative gains | Ameren Missouri
Regulatory liabilities:
Total regulatory liabilities	10	19
MTM derivative gains | Ameren Illinois
Regulatory liabilities:
Total regulatory liabilities	6	3
Cost of removal
Regulatory liabilities:
Total regulatory liabilities	2,294	2,186
Cost of removal | Ameren Missouri
Regulatory liabilities:
Total regulatory liabilities	1,118	1,098
Cost of removal | Ameren Illinois
Regulatory liabilities:
Total regulatory liabilities	1,115	1,038
AROs
Regulatory liabilities:
Total regulatory liabilities	691	524
AROs | Ameren Missouri
Regulatory liabilities:
Total regulatory liabilities	691	524
AROs | Ameren Illinois
Regulatory liabilities:
Total regulatory liabilities	0	0
Pension and postretirement benefit costs
Regulatory liabilities:
Total regulatory liabilities	358	346
Pension and postretirement benefit costs | Ameren Missouri
Regulatory liabilities:
Total regulatory liabilities	202	202
Pension and postretirement benefit costs | Ameren Illinois
Regulatory liabilities:
Total regulatory liabilities	156	144
Pension and postretirement benefit costs tracker
Regulatory liabilities:
Total regulatory liabilities	70	111
Pension and postretirement benefit costs tracker | Ameren Missouri
Regulatory liabilities:
Total regulatory liabilities	$ 70	111
Regulatory liability, amortization period	2 years
Pension and postretirement benefit costs tracker | Ameren Illinois
Regulatory liabilities:
Total regulatory liabilities	$ 0	0
Renewable energy credits and zero emission credits
Regulatory liabilities:
Total regulatory liabilities	586	489
Renewable energy credits and zero emission credits | Ameren Missouri
Regulatory liabilities:
Total regulatory liabilities	0	0
Renewable energy credits and zero emission credits | Ameren Illinois
Regulatory liabilities:
Total regulatory liabilities	586	489
Certain Rush Island Energy Center Costs
Regulatory liabilities:
Total regulatory liabilities	66	0
Certain Rush Island Energy Center Costs | Ameren Missouri
Regulatory liabilities:
Total regulatory liabilities	66	0
Certain Rush Island Energy Center Costs | Ameren Illinois
Regulatory liabilities:
Total regulatory liabilities	0	0
Other regulatory liabilities
Regulatory liabilities:
Total regulatory liabilities	63	36
Other regulatory liabilities | Ameren Missouri
Regulatory liabilities:
Total regulatory liabilities	14	14
Other regulatory liabilities | Ameren Illinois
Regulatory liabilities:
Total regulatory liabilities	$ 43	22
FAC adjustments | Ameren Missouri
Regulatory liabilities:
Accumulation period	4 months
Regulatory asset, amortization period	8 months
Asset Retirement Obligation - Nuclear decommissioning trust fund balance | Ameren Missouri
Regulatory liabilities:
Total regulatory liabilities	$ 1,342	1,150
Asset Retirement Obligation - removal costs | Ameren Missouri
Regulatory liabilities:
Total regulatory liabilities	$ 651	$ 626
Minimum | FEJA energy-efficiency rider | Ameren Illinois
Regulatory liabilities:
Regulatory asset, amortization period	2 years
Maximum | FEJA energy-efficiency rider | Ameren Illinois
Regulatory liabilities:
Regulatory asset, amortization period	12 years