Callaway Energy Center (Insurance Disclosure) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Apr. 01, 2020
Nuclear Waste Matters [Line Items]
Number Of Years The Limit Of Liability And The Maximum Potential Annual Payments Are Adjusted	5 years
Number Of Weeks Of Coverage After The First Twelve Weeks Of An Outage	1
Number Of Additional Weeks After Initial Indemnity Coverage For Power Outage	1.365
Public Liability And Nuclear Worker Liability - American Nuclear Insurers
Nuclear Waste Matters [Line Items]
Maximum Coverages		$ 450.0
Maximum Assessments for Single Incidents		0.0
Public Liability And Nuclear Worker Liability - Pool Participation
Nuclear Waste Matters [Line Items]
Maximum Coverages		13,348.0
Maximum Assessments for Single Incidents		138.0
Threshold For Which A Retrospective Assessment For A Covered Loss Is Necessary	$ 450.0
Annual Payment In The Event Of An Incident At Any Licensed Commercial Reactor	21.0
Public Liability And Nuclear Worker Liability
Nuclear Waste Matters [Line Items]
Maximum Coverages		13,798.0
Maximum Assessments for Single Incidents		138.0
Property Damage - Nuclear Electric Insurance Ltd
Nuclear Waste Matters [Line Items]
Maximum Coverages		3,200.0
Maximum Assessments for Single Incidents		25.0
Replacement Power - Nuclear Electric Insurance Ltd
Nuclear Waste Matters [Line Items]
Maximum Coverages		490.0
Maximum Assessments for Single Incidents		7.0
Amount Of Weekly Indemnity Coverage Commencing Twelve Weeks After Power Outage	4.5
Amount Of Additional Weekly Indemnity Coverage Commencing After Initial Indemnity Coverage	3.6
Amount Of Weekly Indemnity Coverage Thereafter Not Exceeding Policy Limit	490.0
Sub-Limit Of Amount Of Weekly Indemnity Coverage Thereafter Not Exceeding Policy Limit For Non-Nuclear Events	328.0
Radiation Event
Nuclear Waste Matters [Line Items]
Maximum Coverages		2,700.0
Aggregate Nuclear Power Industry Insurance Policy Limit For Losses From Terrorist Attacks Within Twelve Month Period	3,200.0
Non-Radiation Event
Nuclear Waste Matters [Line Items]
Maximum Coverages		2,300.0
Aggregate Nuclear Power Industry Insurance Policy Limit For Losses From Terrorist Attacks Within Twelve Month Period	$ 1,800.0
Property Damage European Mutual Association for Nuclear Insurance
Nuclear Waste Matters [Line Items]
Maximum Coverages		$ 490.0