Rate And Regulatory Matters (Narrative-Illinois) (Details) - USD ($) $ in Millions	1 Months Ended			3 Months Ended	6 Months Ended		12 Months Ended
	Dec. 31, 2023	Nov. 30, 2023	Oct. 31, 2023	Sep. 30, 2024	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2027	Dec. 31, 2026	Dec. 31, 2025	Dec. 31, 2024
Rate And Regulatory Matters [Line Items]
Capital expenditures					$ 1,892	$ 1,822
Ameren Illinois Company
Rate And Regulatory Matters [Line Items]
Capital expenditures					717	$ 844
Ameren Illinois Company | Natural gas
Rate And Regulatory Matters [Line Items]
Public Utilities, Requested Equity Capital Structure, Percentage	52.00%
Public Utilities, Requested Return on Equity, Percentage	9.89%
IETL | Ameren Illinois Company | Electric Distribution | Forecast
Rate And Regulatory Matters [Line Items]
Approved return on equity percentage							8.72%	8.72%	8.72%	8.72%
Multi-year rate plan rehearing approved revenue requirement							$ 1,397	$ 1,350	$ 1,282	$ 1,196
Approved rate base							4,700	4,500	4,300	4,000
Revised multi-year rate plan requested revenue requirement							1,446	1,386	1,300	1,215
Revised multi-year rate plan requested rate base							5,000	4,800	4,500	4,300
ICC staff revised multi-year rate plan recommended revenue requirement							1,414	1,361	1,281	1,201
ICC staff revised multi-year rate plan recommended rate base							$ 4,800	$ 4,600	$ 4,400	$ 4,200
Public Utilities, Approved Equity Capital Structure, Percentage							50.00%	50.00%	50.00%	50.00%
Public Utilities, Approved Rate Increase (Decrease), Amount										$ 285
Public Utilities, Requested Rate Increase (Decrease), Amount										334
ICC staff recommended rate increase										$ 302
Pending Rate Case | Ameren Illinois Company | Electric Distribution
Rate And Regulatory Matters [Line Items]
ICC staff recommended rate increase					157
Pending Rate Case | Ameren Illinois Company | Electric Distribution | Subsequent Event
Rate And Regulatory Matters [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount				$ 158
Public Utilities, Requested Equity Capital Structure, Percentage				50.00%
Pending Rate Case | Ameren Illinois Company | Electric Energy-Efficiency
Rate And Regulatory Matters [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount					$ 26
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]
Approved return on equity percentage		9.44%
Approved rate base		$ 2,850
Public Utilities, Approved Equity Capital Structure, Percentage		50.00%
Public Utilities, Requested Rate Increase (Decrease), Amount		$ 112
Capital expenditures	$ 93	$ 93