Callaway Energy Center (Insurance Disclosure) (Detail) $ in Millions	9 Months Ended
	Sep. 30, 2019 USD ($)
Nuclear Waste Matters [Line Items]
Inflationary Adjustment Prescribed By Most Recent Price-Anderson Act Renewal, In Years	five 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	13,486.0
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
Nuclear Waste Matters [Line Items]
Maximum Coverages	13,936.0
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	28.0
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