Related Party Transactions (Schedule of Affiliate Receivables and Payables) (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	$ 717	$ 1,136
Accounts Receivable, Related Parties, Current	651	494
Union Electric Company \| Related Party
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	63	53
Accounts Receivable, Related Parties, Current	22	72
Union Electric Company \| Income taxes payable to parent \| Related Party
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	20	0
Union Electric Company \| Income taxes receivable from parent \| Related Party
Related Party Transaction [Line Items]
Accounts Receivable, Related Parties, Current	0	56
Ameren Illinois Company \| Related Party
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	147	52
Accounts Receivable, Related Parties, Current	17	35
Ameren Illinois Company \| Income taxes payable to parent \| Related Party
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	105	2
Ameren Illinois Company \| Income taxes receivable from parent \| Related Party
Related Party Transaction [Line Items]
Accounts Receivable, Related Parties, Current	$ 0	$ 22

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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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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