Callaway Energy Center (Narrative) (Detail) $ in Millions	3 Months Ended
Mar. 31, 2019 USD ($)
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