v3.25.2
Income Taxes (Schedule of Effective Income Tax Rate Reconciliation) (Details)
3 Months Ended 6 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Jun. 30, 2025
Jun. 30, 2024
Income Taxes [Line Items]        
Federal statutory corporate income tax rate 21.00% 21.00% 21.00% 21.00%
Increases (decreases) from:        
Amortization of excess deferred taxes (7.00%) (8.00%) (7.00%) (8.00%)
Amortization of deferred investment tax credit (1.00%) 0.00% (1.00%) 0.00%
Renewable and other tax credits (4.00%) (4.00%) (4.00%) (4.00%)
State tax 5.00% 5.00% 5.00% 5.00%
Depreciation differences (1.00%) (1.00%)    
Effective income tax rate 13.00% 13.00% 14.00% 14.00%
Union Electric Company        
Income Taxes [Line Items]        
Federal statutory corporate income tax rate 21.00% 21.00% 21.00% 21.00%
Increases (decreases) from:        
Amortization of excess deferred taxes (10.00%) (14.00%) (10.00%) (14.00%)
Amortization of deferred investment tax credit (1.00%) 0.00% (1.00%) 0.00%
Renewable and other tax credits (7.00%) (8.00%) (7.00%) (8.00%)
State tax 3.00% 3.00% 3.00% 3.00%
Depreciation differences (1.00%) (1.00%)    
Effective income tax rate 5.00% 1.00% 6.00% 2.00%
Ameren Illinois Company        
Income Taxes [Line Items]        
Federal statutory corporate income tax rate 21.00% 21.00% 21.00% 21.00%
Increases (decreases) from:        
Amortization of excess deferred taxes (4.00%) (4.00%) (4.00%) (4.00%)
Amortization of deferred investment tax credit 0.00% 0.00% 0.00% 0.00%
Renewable and other tax credits 0.00% 0.00% 0.00% 0.00%
State tax 7.00% 7.00% 7.00% 7.00%
Depreciation differences (1.00%) 0.00%    
Effective income tax rate 23.00% 24.00% 24.00% 24.00%