Rate and Regulatory Matters (Narrative-Missouri) (Details)	1 Months Ended		3 Months Ended				12 Months Ended
	Nov. 30, 2023 USD ($)	Aug. 31, 2023 USD ($)	Jun. 30, 2023 MWh	Sep. 30, 2022 MWh	Jun. 30, 2022 MWh	Mar. 31, 2022 MWh	Dec. 31, 2025 USD ($)	Dec. 31, 2024 USD ($)	Dec. 31, 2023 USD ($) MWh	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Public Utilities, General Disclosures [Line Items]
Depreciation and amortization									$ 1,387,000,000	$ 1,289,000,000	$ 1,146,000,000
Other Income, Net									348,000,000	226,000,000	202,000,000
Capital expenditures									3,597,000,000	3,351,000,000	3,479,000,000
Revenues									7,500,000,000	7,957,000,000	6,394,000,000
Forecast
Public Utilities, General Disclosures [Line Items]
Capital expenditures								$ 1,800,000,000
Ameren Missouri
Public Utilities, General Disclosures [Line Items]
Depreciation and amortization									783,000,000	732,000,000	632,000,000
Other Income, Net									$ 130,000,000	99,000,000	99,000,000
Amount of Megawatts | MWh									102
Capital expenditures									$ 1,760,000,000	1,690,000,000	2,015,000,000
Ameren Missouri | Rush Island Energy Center
Public Utilities, General Disclosures [Line Items]
Costs to be securitized	$ 519,000,000
Amortization of regulatory asset	$ 15
Ameren Missouri | Solar generation facility
Public Utilities, General Disclosures [Line Items]
Capital expenditures									$ 650,000,000
Ameren Missouri | Maximum
Public Utilities, General Disclosures [Line Items]
Percentage of energy sourced from renewable resources									100.00%
Ameren Missouri | Electric | Final Rate Order
Public Utilities, General Disclosures [Line Items]
Approved rate increase (decrease), amount									$ 140,000,000
Reduction to annualized base level of net energy costs									40,000,000
Depreciation and amortization									90,000,000
Other Income, Net									100,000,000
Ameren Missouri | Build-transfer | Solar generation facility
Public Utilities, General Disclosures [Line Items]
Amount of Megawatts | MWh			300		200	150
Ameren Missouri | Development-transfer | Solar generation facility
Public Utilities, General Disclosures [Line Items]
Amount of Megawatts | MWh			150
Ameren Missouri | Self-build | Solar generation facility
Public Utilities, General Disclosures [Line Items]
Amount of Megawatts | MWh			50	50
Ameren Missouri | MEEIA 2019 | Electric
Public Utilities, General Disclosures [Line Items]
Revenues		$ 12,000,000							$ 12,000,000	$ 22,000,000	$ 9,000,000
Ameren Missouri | MEEIA 2019 | Electric | Forecast
Public Utilities, General Disclosures [Line Items]
Energy efficiency investments in MEEIA 2019 programs								$ 76,000,000
Ameren Missouri | MEEIA 2024 | Electric | Forecast
Public Utilities, General Disclosures [Line Items]
Energy efficiency investments in MEEIA 2019 programs							$ 123,000,000
Percentage of MEEIA energy efficiency goals achieved							100.00%
Incentive award if energy efficiency goals are achieved							$ 56,000,000
Incentive award if energy efficiency goals are exceeded							$ 14,000,000