Callaway Energy Center (Narrative) (Detail) - Nuclear Plant $ in Millions	3 Months Ended
Mar. 31, 2018 USD ($) mill
Nuclear Waste Matters [Line Items]
Number of mills charged for NWF fee \| mill	1
Annual decommissioning costs included in costs of service \| $	$ 7

The number of mills per nuclear-generated kilowatt hour sold (one mill = 1/10 of one cent) charged by the Department of Energy for future disposal of spent nuclear fuel, referred to as the NWF fee. This fee is collected from electric customers who use power generated by the Callaway nuclear plant.

No definition available.

Name:	aee_NwfFeeNumberOfMills
Namespace Prefix:	aee_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration