Rate And Regulatory Matters (Schedule Of Regulatory Assets And Liabilities) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Feb. 28, 2021
Regulatory assets:
Total regulatory assets	$ 2,175	$ 1,780
Less: current regulatory assets	(365)	(354)
Noncurrent regulatory assets	1,810	1,426
Regulatory liabilities:
Total regulatory liabilities	5,599	5,445
Less: current regulatory liabilities	(87)	(136)
Noncurrent regulatory liabilities	5,512	5,309
Ameren Missouri
Regulatory assets:
Total regulatory assets	856	848
Less: current regulatory assets	(101)	(254)
Noncurrent regulatory assets	755	594
Regulatory liabilities:
Total regulatory liabilities	2,974	2,941
Less: current regulatory liabilities	(15)	(70)
Noncurrent regulatory liabilities	$ 2,959	2,871
PISA deferral percentage	85.00%
Ameren Illinois
Regulatory assets:
Total regulatory assets	$ 1,287	908
Less: current regulatory assets	(252)	(87)
Noncurrent regulatory assets	1,035	821
Regulatory liabilities:
Total regulatory liabilities	2,489	2,377
Less: current regulatory liabilities	(71)	(64)
Noncurrent regulatory liabilities	2,418	2,313
Under-recovered FAC
Regulatory assets:
Total regulatory assets	72	140
Under-recovered FAC | Ameren Missouri
Regulatory assets:
Total regulatory assets	72	140
Under-recovered FAC | Ameren Illinois
Regulatory assets:
Total regulatory assets	0	0
Under-recovered Illinois electric power costs
Regulatory assets:
Total regulatory assets	10	33
Under-recovered Illinois electric power costs | Ameren Missouri
Regulatory assets:
Total regulatory assets	0	0
Under-recovered Illinois electric power costs | Ameren Illinois
Regulatory assets:
Total regulatory assets	10	33
Under-recovered PGA
Regulatory assets:
Total regulatory assets	6	23
Under-recovered PGA | Ameren Missouri
Regulatory assets:
Total regulatory assets	6	23	$ 53
Under-recovered PGA | Ameren Illinois
Regulatory assets:
Total regulatory assets	0	0
MTM derivative losses
Regulatory assets:
Total regulatory assets	168	136
MTM derivative losses | Ameren Missouri
Regulatory assets:
Total regulatory assets	25	68
MTM derivative losses | Ameren Illinois
Regulatory assets:
Total regulatory assets	143	68
IEIMA revenue requirement reconciliation adjustment
Regulatory assets:
Total regulatory assets	239	134
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	$ 239	134
Regulatory liabilities:
Regulatory asset, amortization period	2 years
FERC revenue requirement reconciliation adjustment
Regulatory assets:
Total regulatory assets	$ 54	33
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	25	11
Under-recovered VBA
Regulatory assets:
Total regulatory assets	49	0
Under-recovered VBA | Ameren Missouri
Regulatory assets:
Total regulatory assets	0	0
Under-recovered VBA | Ameren Illinois
Regulatory assets:
Total regulatory assets	49	0
Income taxes
Regulatory assets:
Total regulatory assets	207	185
Regulatory liabilities:
Total regulatory liabilities	$ 1,809	1,931
Weighted-average amortization period	36 years
Income taxes | Ameren Missouri
Regulatory assets:
Total regulatory assets	$ 126	111
Regulatory liabilities:
Total regulatory liabilities	$ 999	1,095
Weighted-average amortization period	28 years
Income taxes | Ameren Illinois
Regulatory assets:
Total regulatory assets	$ 78	72
Regulatory liabilities:
Total regulatory liabilities	$ 724	749
Weighted-average amortization period	43 years
Bad debt rider
Regulatory assets:
Total regulatory assets	$ 43	5
Regulatory liabilities:
Total regulatory liabilities	7	21
Bad debt rider | Ameren Missouri
Regulatory assets:
Total regulatory assets	0	0
Regulatory liabilities:
Total regulatory liabilities	0	0
Bad debt rider | Ameren Illinois
Regulatory assets:
Total regulatory assets	43	5
Regulatory liabilities:
Total regulatory liabilities	7	21
Callaway refueling and maintenance outage costs
Regulatory assets:
Total regulatory assets	37	33
Callaway refueling and maintenance outage costs | Ameren Missouri
Regulatory assets:
Total regulatory assets	$ 37	33
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	50	54
Unamortized loss on reacquired debt | Ameren Missouri
Regulatory assets:
Total regulatory assets	45	47
Unamortized loss on reacquired debt | Ameren Illinois
Regulatory assets:
Total regulatory assets	5	7
Environmental cost riders
Regulatory assets:
Total regulatory assets	50	64
Environmental cost riders | Ameren Missouri
Regulatory assets:
Total regulatory assets	0	0
Environmental cost riders | Ameren Illinois
Regulatory assets:
Total regulatory assets	50	64
Storm costs
Regulatory assets:
Total regulatory assets	27	14
Storm costs | Ameren Missouri
Regulatory assets:
Total regulatory assets	0	0
Storm costs | Ameren Illinois
Regulatory assets:
Total regulatory assets	27	14
Allowance for funds used during construction for pollution control equipment
Regulatory assets:
Total regulatory assets	10	11
Allowance for funds used during construction for pollution control equipment | Ameren Missouri
Regulatory assets:
Total regulatory assets	10	11
Allowance for funds used during construction for pollution control equipment | Ameren Illinois
Regulatory assets:
Total regulatory assets	0	0
Customer generation rebate program
Regulatory assets:
Total regulatory assets	54	50
Customer generation rebate program | Ameren Missouri
Regulatory assets:
Total regulatory assets	0	0
Customer generation rebate program | Ameren Illinois
Regulatory assets:
Total regulatory assets	54	50
PISA
Regulatory assets:
Total regulatory assets	386	320
PISA | Ameren Missouri
Regulatory assets:
Total regulatory assets	$ 386	320
Regulatory liabilities:
Regulatory asset, amortization period	20 years
PISA | Ameren Illinois
Regulatory assets:
Total regulatory assets	$ 0	0
RESRAM
Regulatory assets:
Total regulatory assets	48	6
RESRAM | Ameren Missouri
Regulatory assets:
Total regulatory assets	48	6
RESRAM | Ameren Illinois
Regulatory assets:
Total regulatory assets	0	0
Certain Meramec Energy Center costs
Regulatory assets:
Total regulatory assets	39	51
Certain Meramec Energy Center costs | Ameren Missouri
Regulatory assets:
Total regulatory assets	$ 39	51
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	500	416
FEJA energy-efficiency rider | Ameren Missouri
Regulatory assets:
Total regulatory assets	0	0
FEJA energy-efficiency rider | Ameren Illinois
Regulatory assets:
Total regulatory assets	500	416
Property Tax Tracker
Regulatory assets:
Total regulatory assets	$ 13	3
Regulatory liabilities:
Regulatory asset, amortization period	2 years
Property Tax Tracker | Ameren Missouri
Regulatory assets:
Total regulatory assets	$ 13	3
Property Tax Tracker | Ameren Illinois
Regulatory assets:
Total regulatory assets	0	0
Other regulatory assets
Regulatory assets:
Total regulatory assets	113	69
Other regulatory assets | Ameren Missouri
Regulatory assets:
Total regulatory assets	49	35
Other regulatory assets | Ameren Illinois
Regulatory assets:
Total regulatory assets	64	34
Over-recovered Illinois electric power costs
Regulatory liabilities:
Total regulatory liabilities	36	0
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	$ 36	0
Amortization period	1 year
Over-recovered PGA
Regulatory liabilities:
Total regulatory liabilities	$ 40	10
Over-recovered PGA | Ameren Missouri
Regulatory liabilities:
Total regulatory liabilities	7	0
Over-recovered PGA | Ameren Illinois
Regulatory liabilities:
Total regulatory liabilities	33	10
MTM derivative gains
Regulatory liabilities:
Total regulatory liabilities	22	91
MTM derivative gains | Ameren Missouri
Regulatory liabilities:
Total regulatory liabilities	19	51
MTM derivative gains | Ameren Illinois
Regulatory liabilities:
Total regulatory liabilities	3	40
Cost of removal
Regulatory liabilities:
Total regulatory liabilities	2,186	2,091
Cost of removal | Ameren Missouri
Regulatory liabilities:
Total regulatory liabilities	1,098	1,064
Cost of removal | Ameren Illinois
Regulatory liabilities:
Total regulatory liabilities	1,038	989
AROs
Regulatory liabilities:
Total regulatory liabilities	524	365
AROs | Ameren Missouri
Regulatory liabilities:
Total regulatory liabilities	524	365
AROs | Ameren Illinois
Regulatory liabilities:
Total regulatory liabilities	0	0
Pension and postretirement benefit costs
Regulatory liabilities:
Total regulatory liabilities	346	404
Pension and postretirement benefit costs | Ameren Missouri
Regulatory liabilities:
Total regulatory liabilities	202	242
Pension and postretirement benefit costs | Ameren Illinois
Regulatory liabilities:
Total regulatory liabilities	144	162
Pension and postretirement benefit costs tracker
Regulatory liabilities:
Total regulatory liabilities	111	60
Pension and postretirement benefit costs tracker | Ameren Missouri
Regulatory liabilities:
Total regulatory liabilities	$ 111	60
Regulatory liability, amortization period	3 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	489	373
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	489	373
Other regulatory liabilities
Regulatory liabilities:
Total regulatory liabilities	29	99
Other regulatory liabilities | Ameren Missouri
Regulatory liabilities:
Total regulatory liabilities	14	64
Other regulatory liabilities | Ameren Illinois
Regulatory liabilities:
Total regulatory liabilities	$ 15	33
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	$ 1,150	958
Asset Retirement Obligation - removal costs | Ameren Missouri
Regulatory liabilities:
Total regulatory liabilities	$ 626	$ 593
Minimum | Under-recovered PGA | Ameren Missouri
Regulatory liabilities:
Regulatory asset, amortization period	12 months
Minimum | FEJA energy-efficiency rider | Ameren Illinois
Regulatory liabilities:
Regulatory asset, amortization period	3 years
Maximum | Under-recovered PGA | Ameren Missouri
Regulatory liabilities:
Regulatory asset, amortization period	36 months
Maximum | FEJA energy-efficiency rider | Ameren Illinois
Regulatory liabilities:
Regulatory asset, amortization period	12 years