Income Taxes (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Aug. 16, 2022
Income Taxes [Line Items]
Increase (Decrease) In Deferred Tax Liabilities	$ 123
Ameren Missouri
Income Taxes [Line Items]
Increase (Decrease) In Deferred Tax Liabilities	12
Ameren Illinois
Income Taxes [Line Items]
Increase (Decrease) In Deferred Tax Liabilities	$ 111
Federal
Income Taxes [Line Items]
Production and Investment Tax Credit Adder		10.00%
Greenhouse Emissions Reduction Target, Inflation Reduction Act		75.00%
Eligible Transfer of Tax Credits, Inflation Reduction Act		100.00%
Minimum Tax on Book Income, Inflation Reduction Act, Percent		15.00%
Minimum Adjusted Financial Statement Income Subject to Inflation Reduction Act Tax		$ 1,000