Property And Plant, Net (Schedule Of Property And Plant, Net) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2021 USD ($) equipment	Dec. 31, 2020 USD ($)
Property, Plant and Equipment [Line Items]
Property and plant, at original cost	$ 41,602	$ 39,719
Accumulated depreciation and amortization	14,214	13,773
Property and plant, before construction work in progress	27,388	25,946
Property, Plant and Equipment, Net	$ 29,261	26,807
Number of combustion turbine electric generation equipment with related financing obligations | equipment	2
Number of financing obligations | equipment	2
Gross asset value, financing obligations	$ 243	240
Total accumulated depreciation, financing obligations	105	99
Coal Fired Electric Generation Equipment
Property, Plant and Equipment [Line Items]
Property and plant, at original cost	3,955	4,875
Plant To Be Abandoned, Net	604
Natural Gas and Oil Fired Electric Generation Equipment
Property, Plant and Equipment [Line Items]
Property and plant, at original cost	1,105	1,097
Nuclear Powered Electric Generation Equipment
Property, Plant and Equipment [Line Items]
Property and plant, at original cost	5,615	5,608
Renewable Electric Generation Equipment
Property, Plant and Equipment [Line Items]
Property and plant, at original cost	1,889	1,301
Electric distribution
Property, Plant and Equipment [Line Items]
Property and plant, at original cost	14,303	13,433
Electric transmission
Property, Plant and Equipment [Line Items]
Property and plant, at original cost	7,533	6,831
Natural gas
Property, Plant and Equipment [Line Items]
Property and plant, at original cost	4,193	3,869
Other
Property, Plant and Equipment [Line Items]
Property and plant, at original cost	3,009	2,705
Construction work in progress	1,136	786
Nuclear fuel in process
Property, Plant and Equipment [Line Items]
Construction work in progress	133	75
Oil Fired Electric Generation Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and plant, at original cost	29	36
Union Electric Company
Property, Plant and Equipment [Line Items]
Property and plant, at original cost	23,669	23,098
Accumulated depreciation and amortization	9,784	9,689
Property and plant, before construction work in progress	13,885	13,409
Property, Plant and Equipment, Net	15,296	13,879
Union Electric Company | Coal Fired Electric Generation Equipment
Property, Plant and Equipment [Line Items]
Property and plant, at original cost	3,955	4,875
Plant To Be Abandoned, Net	604
Union Electric Company | Natural Gas and Oil Fired Electric Generation Equipment
Property, Plant and Equipment [Line Items]
Property and plant, at original cost	1,105	1,097
Union Electric Company | Nuclear Powered Electric Generation Equipment
Property, Plant and Equipment [Line Items]
Property and plant, at original cost	5,615	5,608
Union Electric Company | Renewable Electric Generation Equipment
Property, Plant and Equipment [Line Items]
Property and plant, at original cost	1,889	1,301
Union Electric Company | Electric distribution
Property, Plant and Equipment [Line Items]
Property and plant, at original cost	7,286	6,784
Union Electric Company | Electric transmission
Property, Plant and Equipment [Line Items]
Property and plant, at original cost	1,628	1,482
Union Electric Company | Natural gas
Property, Plant and Equipment [Line Items]
Property and plant, at original cost	607	561
Union Electric Company | Other
Property, Plant and Equipment [Line Items]
Property and plant, at original cost	1,584	1,390
Construction work in progress	674	395
Union Electric Company | Nuclear fuel in process
Property, Plant and Equipment [Line Items]
Construction work in progress	133	75
Ameren Illinois Company
Property, Plant and Equipment [Line Items]
Property and plant, at original cost	15,891	14,602
Accumulated depreciation and amortization	4,100	3,780
Property and plant, before construction work in progress	11,791	10,822
Property, Plant and Equipment, Net	12,223	11,201
Ameren Illinois Company | Coal Fired Electric Generation Equipment
Property, Plant and Equipment [Line Items]
Property and plant, at original cost	0	0
Plant To Be Abandoned, Net	0
Ameren Illinois Company | Natural Gas and Oil Fired Electric Generation Equipment
Property, Plant and Equipment [Line Items]
Property and plant, at original cost	0	0
Ameren Illinois Company | Nuclear Powered Electric Generation Equipment
Property, Plant and Equipment [Line Items]
Property and plant, at original cost	0	0
Ameren Illinois Company | Renewable Electric Generation Equipment
Property, Plant and Equipment [Line Items]
Property and plant, at original cost	0	0
Ameren Illinois Company | Electric distribution
Property, Plant and Equipment [Line Items]
Property and plant, at original cost	7,017	6,649
Ameren Illinois Company | Electric transmission
Property, Plant and Equipment [Line Items]
Property and plant, at original cost	4,105	3,575
Ameren Illinois Company | Natural gas
Property, Plant and Equipment [Line Items]
Property and plant, at original cost	3,586	3,308
Ameren Illinois Company | Other
Property, Plant and Equipment [Line Items]
Property and plant, at original cost	1,183	1,070
Construction work in progress	432	379
Ameren Illinois Company | Nuclear fuel in process
Property, Plant and Equipment [Line Items]
Construction work in progress	0	0
Other
Property, Plant and Equipment [Line Items]
Property and plant, at original cost	2,042	2,019
Accumulated depreciation and amortization	330	304
Property and plant, before construction work in progress	1,712	1,715
Property, Plant and Equipment, Net	1,742	1,727
Other | Coal Fired Electric Generation Equipment
Property, Plant and Equipment [Line Items]
Property and plant, at original cost	0	0
Plant To Be Abandoned, Net	0
Other | Natural Gas and Oil Fired Electric Generation Equipment
Property, Plant and Equipment [Line Items]
Property and plant, at original cost	0	0
Other | Nuclear Powered Electric Generation Equipment
Property, Plant and Equipment [Line Items]
Property and plant, at original cost	0	0
Other | Renewable Electric Generation Equipment
Property, Plant and Equipment [Line Items]
Property and plant, at original cost	0	0
Other | Electric distribution
Property, Plant and Equipment [Line Items]
Property and plant, at original cost	0	0
Other | Electric transmission
Property, Plant and Equipment [Line Items]
Property and plant, at original cost	1,800	1,774
Other | Natural gas
Property, Plant and Equipment [Line Items]
Property and plant, at original cost	0	0
Other | Other
Property, Plant and Equipment [Line Items]
Property and plant, at original cost	242	245
Construction work in progress	30	12
Other | Nuclear fuel in process
Property, Plant and Equipment [Line Items]
Construction work in progress	$ 0	$ 0
Minimum | Electric distribution
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	20 years
Minimum | Electric transmission
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	50 years
Minimum | Natural gas
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	20 years
Minimum | Other
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	2 years
Minimum | Electric generation
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	5 years
Maximum | Electric distribution
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	80 years
Maximum | Electric transmission
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	75 years
Maximum | Natural gas
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	80 years
Maximum | Other
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	55 years
Maximum | Electric generation
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	72 years
Maximum | Union Electric Company | Electric generation
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	150 years