Related Party Transactions (Schedule of Affiliate Receivables and Payables) (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	$ 647	$ 1,136
Accounts Receivable, Related Parties, Current	507	494
Union Electric Company \| Related Party
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	41	53
Accounts Receivable, Related Parties, Current	47	72
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	32	56
Ameren Illinois Company \| Related Party
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	84	52
Accounts Receivable, Related Parties, Current	14	35
Ameren Illinois Company \| Income taxes payable to parent \| Related Party
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	43	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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-Publisher FASB
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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
-SubTopic 10
-Name Accounting Standards Codification
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
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-Name Accounting Standards Codification
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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(2)(c)(2)(i))
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