Rate And Regulatory Matters (Narrative-Missouri) (Details) $ in Millions	3 Months Ended					6 Months Ended
	Sep. 30, 2023 USD ($)	Jun. 30, 2023 USD ($) MWh	Sep. 30, 2022 MWh	Jun. 30, 2022 USD ($) MWh	Mar. 31, 2022 MWh	Jun. 30, 2023 USD ($) numberOfCountriesInvestigatedByTheDOC	Jun. 30, 2022 USD ($)
Rate And Regulatory Matters [Line Items]
Depreciation and amortization		$ 335		$ 316		$ 655	$ 615
Other Income, Net		82		62		160	122
Capital expenditures						1,822	1,538
Revenues		1,760		1,726		3,822	3,605
Union Electric Company
Rate And Regulatory Matters [Line Items]
Depreciation and amortization		186		178		362	342
Other Income, Net		$ 22		$ 24		41	47
Capital expenditures						$ 914	$ 806
Number of Countries Investigated by the DOC | numberOfCountriesInvestigatedByTheDOC						4
Union Electric Company | Solar generation facility
Rate And Regulatory Matters [Line Items]
Capital expenditures						$ 350
Union Electric Company | Electric | Final Rate Order
Rate And Regulatory Matters [Line Items]
Public Utilities, Approved Rate Increase (Decrease), Amount						140
Reduction to annualized base level of net energy costs						40
Depreciation and amortization						90
Other Income, Net						$ 100
Union Electric Company | Electric | MEEIA 2019 [Domain] | Subsequent Event
Rate And Regulatory Matters [Line Items]
Revenues	$ 12
Energy efficiency investments in MEEIA 2019 programs	$ 76
Union Electric Company | Build-transfer | Solar generation facility
Rate And Regulatory Matters [Line Items]
Amount of Megawatts | MWh		300		200	150
Union Electric Company | Development-transfer | Solar generation facility
Rate And Regulatory Matters [Line Items]
Amount of Megawatts | MWh		150
Union Electric Company | Self-build | Solar generation facility
Rate And Regulatory Matters [Line Items]
Amount of Megawatts | MWh		50	50
Union Electric Company | Maximum
Rate And Regulatory Matters [Line Items]
Percentage of energy sourced from renewable resources		100.00%