Callaway Energy Center (Insurance Disclosure) (Detail) € in Millions	3 Months Ended
	Mar. 31, 2017 USD ($)		Mar. 31, 2017 EUR (€)
Nuclear Waste Matters [Line Items]
Number of weeks of coverage after the first eight weeks of an outage	1 year		1 year
Threshold for which a retrospective assessment for a covered loss is necessary	$ 450,000,000
Annual payment in the event of an incident at any licensed commercial reactor	19,000,000
Amount of weekly indemnity coverage commencing eight weeks after power outage	4,500,000
Amount of additional weekly indemnity coverage commencing after initial indemnity coverage	$ 3,600,000
Inflationary adjustment prescribed by most recent Price-Anderson Act renewal, in years	5 years		5 years
Aggregate nuclear power industry insurance policy limit for losses from terrorist attacks within twelve month period	$ 3,200,000,000		€ 600
Number Of Additional Weeks After Initial Indemnity Coverage For Power Outage	1 year 4 months 10 days		1 year 4 months 10 days
Public Liability And Nuclear Worker Liability - American Nuclear Insurers
Nuclear Waste Matters [Line Items]
Maximum Coverages	$ 450,000,000
Maximum Assessments for Single Incidents	0
Public Liability And Nuclear Worker Liability - Pool Participation
Nuclear Waste Matters [Line Items]
Maximum Coverages	12,986,000,000	[1]
Maximum Assessments for Single Incidents	127,000,000	[2]
Property Damage - Nuclear Electric Insurance Ltd
Nuclear Waste Matters [Line Items]
Maximum Coverages	3,200,000,000	[3]
Maximum Assessments for Single Incidents	29,000,000	[4]
Replacement Power - Nuclear Electric Insurance Ltd
Nuclear Waste Matters [Line Items]
Maximum Coverages	490,000,000	[5]
Maximum Assessments for Single Incidents	7,000,000	[4]
Amount of weekly indemnity coverage thereafter not exceeding policy limit	490,000,000
Sub-limit of for non-nuclear events	328,000,000
Property Damage European Mutual Association for Nuclear Insurance
Nuclear Waste Matters [Line Items]
Maximum Coverages	490,000,000
Radiation Event
Nuclear Waste Matters [Line Items]
Maximum Coverages	2,700,000,000
Non-radiation event
Nuclear Waste Matters [Line Items]
Maximum Coverages	2,300,000,000
Aggregate nuclear power industry insurance policy limit for losses from terrorist attacks within twelve month period	1,800,000,000
Public Liability
Nuclear Waste Matters [Line Items]
Maximum Coverages	13,436,000,000	[6]
Maximum Assessments for Single Incidents	$ 127,000,000

[1] Provided through mandatory participation in an industrywide retrospective premium assessment program.

[2] Retrospective premium under the Price-Anderson Act. This is subject to retrospective assessment with respect to a covered loss in excess of $450 million in the event of an incident at any licensed United States commercial reactor, payable at $19 million per year.

[3] NEIL provides $2.7 billion in property damage, stabilization, decontamination, and premature decommissioning insurance for radiation events and $2.3 billion in property damage for nonradiation events. EMANI provides $490 million for both radiation and nonradiation events.

[4] All NEIL insured plants could be subject to assessments should losses exceed the accumulated funds from NEIL.

[5] Provides replacement power cost insurance in the event of a prolonged accidental outage. Weekly indemnity up to $4.5 million for 52 weeks, which commences after the first twelve weeks of an outage, plus up to $3.6 million per week for a minimum of 71 weeks thereafter for a total not exceeding the policy limit of $490 million. Nonradiation events are limited to $328 million.

[6] Limit of liability for each incident under the Price-Anderson liability provisions of the Atomic Energy Act of 1954, as amended. This limit is subject to change to account for the effects of inflation and changes in the number of licensed reactors.