Retirement Benefits (Narrative) (Details) $ in Millions	Dec. 31, 2020 USD ($)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined benefit plan estimated future employer contributions over next five years	$ 60

The employer's best estimate, as soon as it can be reasonably determined, of the contributions expected to be paid to the plan during the next five fiscal years beginning after the date of the latest statement of financial position. Estimated contributions may be presented in the aggregate combining (1) contributions required by funding regulations or laws, (2) discretionary contributions, and (3) noncash contributions.

No definition available.

Name:	aee_DefinedBenefitPlanEstimatedFutureEmployerContributionsOverNextFiveYears
Namespace Prefix:	aee_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant