Rate And Regulatory Matters (Narrative-Illinois) (Details) - Ameren Illinois Company $ in Millions	6 Months Ended
	Jun. 30, 2022 USD ($) numberOfProposedPerformanceMetrics
Rate And Regulatory Matters [Line Items]
Annual investment in energy-efficiency programs	$ 120
Minimum
Rate And Regulatory Matters [Line Items]
ICC required RTO cost benefit study duration	5 years
Maximum
Rate And Regulatory Matters [Line Items]
ICC required RTO cost benefit study duration	10 years
Electric Distribution
Rate And Regulatory Matters [Line Items]
Requested Return on Equity Adjustment	0.24%
Number of Proposed Performance Metrics | numberOfProposedPerformanceMetrics	8
Electric Distribution | Minimum
Rate And Regulatory Matters [Line Items]
Return on equity adjustment	0.20%
ICC Staff Recommended Return on Equity Adjustment	0.20%
Electric Distribution | Maximum
Rate And Regulatory Matters [Line Items]
Return on equity adjustment	0.60%
ICC Staff Recommended Return on Equity Adjustment	0.24%
Pending Rate Case | Electric Distribution | IEIMA
Rate And Regulatory Matters [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount	$ 84
Public Utilities, Requested Equity Capital Structure, Percentage	54.00%
ICC Staff Recommended Rate Increase (Decrease)	$ 60
ICC Staff Recommended Equity Capital Structure, Percentage	50.00%
Pending Rate Case | Electric Distribution | FEJA energy-efficiency rider
Rate And Regulatory Matters [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount	$ 17
Pending Rate Case | Natural gas
Rate And Regulatory Matters [Line Items]
Natural Gas Capital Investment Prudency Challenge	70
Challenged Recoveries Under the QIP	3
IETL
Rate And Regulatory Matters [Line Items]
Energy Transition Assistance Fund Surcharge	$ 50