Rate And Regulatory Matters (Narrative-Illinois) (Details) - USD ($) $ in Millions	1 Months Ended			3 Months Ended			12 Months Ended
	Dec. 31, 2023	Nov. 30, 2023	Oct. 31, 2023	Jun. 30, 2024	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2027	Dec. 31, 2026	Dec. 31, 2025	Dec. 31, 2024
Rate And Regulatory Matters [Line Items]
Capital expenditures					$ 890	$ 931
Ameren Illinois Company
Rate And Regulatory Matters [Line Items]
Capital expenditures					$ 373	$ 407
Ameren Illinois Company | Natural gas
Rate And Regulatory Matters [Line Items]
Public Utilities, Requested Return on Equity, Percentage	9.89%
Public Utilities, Requested Equity Capital Structure, Percentage	52.00%
IETL | Ameren Illinois Company | Electric Distribution | Forecast
Rate And Regulatory Matters [Line Items]
Multi-year rate plan rehearing requested revenue requirement										$ 1,213
Multi-year rate plan rehearing requested rate base										$ 4,200
Public Utilities, Approved Equity Capital Structure, Percentage							50.00%	50.00%	50.00%	50.00%
Approved return on equity percentage							8.72%	8.72%	8.72%	8.72%
ICC staff multi-year rate plan rehearing recommended revenue requirement										$ 1,195
ICC staff multi-year rate plan rehearing recommended rate base										4,000
Multi-year rate plan approved revenue requirement							$ 1,255	$ 1,242	$ 1,210	1,162
Approved rate base							3,900	3,900	3,900	3,900
Multi-year rate plan requested revenue requirement							1,433	1,371	1,286	1,207
Multi-year rate plan requested rate base							$ 4,900	$ 4,700	$ 4,400	$ 4,200
Public Utilities, Requested Return on Equity, Percentage							9.24%	9.24%	9.24%	9.24%
Public Utilities, Approved Rate Increase (Decrease), Amount										$ 142
Public Utilities, Requested Rate Increase (Decrease), Amount										$ 321
Pending Rate Case | Ameren Illinois Company | Electric Distribution | Subsequent Event
Rate And Regulatory Matters [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount				$ 160
Public Utilities, Requested Equity Capital Structure, Percentage				50.00%
Pending Rate Case | Ameren Illinois Company | Natural gas
Rate And Regulatory Matters [Line Items]
Capital expenditures			$ 53
Over-Recovery Challenged by the Attorney General			$ 3
Final Rate Order | Ameren Illinois Company | Natural gas
Rate And Regulatory Matters [Line Items]
Public Utilities, Approved Equity Capital Structure, Percentage		50.00%
Approved return on equity percentage		9.44%
Approved rate base		$ 2,850
Public Utilities, Requested Rate Increase (Decrease), Amount		112
Capital expenditures	$ 93	$ 93