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Related Party Transactions (Schedule of Capital Contributions) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Ameren Missouri
Related Party Transaction [Line Items]
Capital contribution from parent	$ 28	$ 476	$ 0
Ameren Illinois
Related Party Transaction [Line Items]
Capital contribution from parent	$ 2	$ 36	$ 91

X

- Definition

The cash inflow from parent as a source of financing that is recorded as additional paid in capital.

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