Related Party Transactions (Schedule of Affiliate Receivables and Payables) (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	$ 955	$ 1,159
Accounts Receivable, Related Parties, Current	597	600
Union Electric Company \| Related Party
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	85	43
Accounts Receivable, Related Parties, Current	16	51
Union Electric Company \| Income taxes payable to parent \| Related Party
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	29	0
Union Electric Company \| Income taxes receivable from parent \| Related Party
Related Party Transaction [Line Items]
Accounts Receivable, Related Parties, Current	0	39
Ameren Illinois Company \| Related Party
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	136	93
Accounts Receivable, Related Parties, Current	11	12
Ameren Illinois Company \| Income taxes payable to parent \| Related Party
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	81	50
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.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-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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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
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