Supplemental Information (Narrative) (Details) - USD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024
Supplemental Information [Line Items]
Deferred Compensation Liability, Classified, Noncurrent	$ 79	$ 79
Ameren Illinois
Supplemental Information [Line Items]
Payables for purchased receivables	$ 47	$ 43

Aggregate carrying value as of the balance sheet date of the liabilities for all deferred compensation arrangements payable beyond one year (or the operating cycle, if longer).

No definition available.

Name:	us-gaap_DeferredCompensationLiabilityClassifiedNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant