Callaway Energy Center (Narrative) (Details) - Union Electric Company - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Nuclear Waste Matters [Line Items]
Litigation Settlement, Amount	$ 21	$ 11	$ 3
Nuclear Plant
Nuclear Waste Matters [Line Items]
Annual decommissioning costs included in costs of service	$ 7

Amount of anticipated decommissioning costs included in annual costs of service used to establish electric rates.

No definition available.

Name:	aee_AnnualDecommissioningCostsIncludedInCostsOfService
Namespace Prefix:	aee_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration