Related Party Transactions (Schedule of Affiliate Receivables and Payables) (Details) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	$ 702	$ 1,059
Accounts Receivable, Related Parties, Current	667	525
Union Electric Company \| Related Party
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	42	50
Accounts Receivable, Related Parties, Current	44	40
Union Electric Company \| Income taxes payable to parent \| Related Party
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	0	0
Union Electric Company \| Income taxes receivable from parent \| Related Party
Related Party Transaction [Line Items]
Accounts Receivable, Related Parties, Current	29	28
Ameren Illinois Company \| Related Party
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	71	74
Accounts Receivable, Related Parties, Current	22	15
Ameren Illinois Company \| Income taxes payable to parent \| Related Party
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	32	32
Ameren Illinois Company \| Income taxes receivable from parent \| Related Party
Related Party Transaction [Line Items]
Accounts Receivable, Related Parties, Current	$ 0	$ 0

Sum of the carrying values as of the balance sheet date of obligations incurred through that date and due within one year (or the operating cycle, if longer), including liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received, taxes, interest, rent and utilities, accrued salaries and bonuses, payroll taxes and fringe benefits.

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- Definition

Amount, after allowance for credit loss, of right to consideration from customer for product sold and service rendered in normal course of business, classified as current.

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-Topic 310
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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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-Topic 310
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