Rate And Regulatory Matters (Narrative-Missouri) (Details) $ in Millions	1 Months Ended			2 Months Ended	3 Months Ended					9 Months Ended		63 Months Ended
	Jul. 31, 2026 MWh	Jun. 30, 2026 MWh	May 31, 2026 MWh	Jun. 30, 2026 MWh	Mar. 31, 2028 USD ($)	Sep. 30, 2025 MWh	Jun. 30, 2025 MWh	Sep. 30, 2024 MWh	Dec. 31, 2023 MWh	Sep. 30, 2026 USD ($) MWh	Sep. 30, 2025 USD ($)	Dec. 31, 2031 USD ($)
Rate And Regulatory Matters [Line Items]
Capital expenditures										$ 4,089	$ 3,118
Forecast
Rate And Regulatory Matters [Line Items]
Capital expenditures					$ 1,200
Union Electric Company
Rate And Regulatory Matters [Line Items]
Capital expenditures										2,750	$ 1,873
Union Electric Company \| Generation Facilities \| Forecast
Rate And Regulatory Matters [Line Items]
Capital expenditures												$ 5,000
Union Electric Company \| Split Rail Solar Project
Rate And Regulatory Matters [Line Items]
Capital expenditures										600
Union Electric Company \| Self-build \| Solar generation facility
Rate And Regulatory Matters [Line Items]
Amount of Megawatts \| MWh						250			50
Union Electric Company \| Self-build \| Natural Gas Generation Facility
Rate And Regulatory Matters [Line Items]
Amount of Megawatts \| MWh	2,100						800	800
Union Electric Company \| Self-build \| Energy Storage Facility
Rate And Regulatory Matters [Line Items]
Amount of Megawatts \| MWh		200	250	95			400
Union Electric Company \| Build-transfer \| Solar generation facility
Rate And Regulatory Matters [Line Items]
Amount of Megawatts \| MWh		225	175						300
Union Electric Company \| Electric \| Pending Rate Case
Rate And Regulatory Matters [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount										$ 343
Public Utilities, Requested Return on Equity, Percentage										10.25%
Public Utilities, Requested Equity Capital Structure, Percentage										52.00%
Requested rate base										$ 16,700
Amount of Megawatts \| MWh										400
Months to complete a rate proceeding										11 months