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Income Taxes (Schedule Of Effective Income Tax Rate Reconciliation) (Details)
12 Months Ended
Dec. 31, 2022
Dec. 31, 2021
Dec. 31, 2020
Income Taxes [Line Items]      
Federal statutory corporate income tax rate 21.00% 21.00% 21.00%
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Amortization of Excess Deferred Taxes, Percent (8.00%) (8.00%) (9.00%)
Amortization of deferred investment tax credit 0.00% 0.00% (1.00%)
Effective Income Tax Rate Reconciliation, Tax Credit, Percent (4.00%) (3.00%)  
State tax 5.00% 5.00% 5.00%
Stock-based compensation   (1.00%) (1.00%)
Effective income tax rate 14.00% 14.00% 15.00%
Union Electric Company      
Income Taxes [Line Items]      
Federal statutory corporate income tax rate 21.00% 21.00% 21.00%
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Amortization of Excess Deferred Taxes, Percent (15.00%) (15.00%) (16.00%)
Amortization of deferred investment tax credit (1.00%) (1.00%) (1.00%)
Effective Income Tax Rate Reconciliation, Tax Credit, Percent (10.00%) (7.00%)  
State tax 3.00% 3.00% 3.00%
Stock-based compensation   0.00% 0.00%
Effective income tax rate (2.00%) 1.00% 7.00%
Ameren Illinois Company      
Income Taxes [Line Items]      
Federal statutory corporate income tax rate 21.00% 21.00% 21.00%
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Amortization of Excess Deferred Taxes, Percent (2.00%) (3.00%) (3.00%)
Amortization of deferred investment tax credit 0.00% 0.00% (1.00%)
Effective Income Tax Rate Reconciliation, Tax Credit, Percent 0.00% 0.00%  
State tax 7.00% 7.00% 7.00%
Stock-based compensation   0.00% 0.00%
Effective income tax rate 26.00% 25.00% 24.00%