Commitments And Contingencies (Callaway Energy Center) (Detail) (USD $)	6 Months Ended
	Jun. 30, 2012 Year
Commitments And Contingencies [Line Items]
Insurance aggregate maximum coverage	$ 12,594,000,000	[1]
coverage per incident	118,000,000
Inflationary adjustment prescribed by most recent Price-Anderson Act renewal, in years	5
Aggregate nuclear power industry insurance policy limit for losses from terrorist attacks within twelve month period	3,240,000,000
Replacement Power - Nuclear Electric Insurance Ltd [Member]
Commitments And Contingencies [Line Items]
Insurance aggregate maximum coverage	490,000,000	[2]
coverage per incident	9,000,000
Replacement Power - Energy Risk Assurance Company [Member]
Commitments And Contingencies [Line Items]
Insurance aggregate maximum coverage	64,000,000	[3]
Public Liability And Nuclear Worker Liability - American Nuclear Insurers [Member]
Commitments And Contingencies [Line Items]
Insurance aggregate maximum coverage	375,000,000
Public Liability And Nuclear Worker Liability - Pool Participation [Member]
Commitments And Contingencies [Line Items]
Insurance aggregate maximum coverage	12,219,000,000	[4]
coverage per incident	118,000,000	[5]
Property Damage - Nuclear Electric Insurance Ltd [Member]
Commitments And Contingencies [Line Items]
Insurance aggregate maximum coverage	2,750,000,000	[6]
coverage per incident	$ 23,000,000

[1] Limit of liability for each incident under the Price-Anderson liability provisions of the Atomic Energy Act of 1954, as amended. A company could be assessed up to $118 million per incident for each licensed reactor it operates with a maximum of $17.5 million per incident to be paid in a calendar year for each reactor. This limit is subject to change to account for the effects of inflation and changes in the number of licensed reactors.

[2] Provides the replacement power cost insurance in the event of a prolonged accidental outage at our nuclear energy center. Weekly indemnity up to $4.5 million for 52 weeks, which commences after the first eight 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.

[3] Provides the replacement power cost insurance in the event of a prolonged accidental outage at our nuclear energy center. The coverage commences after the first 52 weeks of insurance coverage from Nuclear Electric Insurance Ltd. and is for a weekly indemnity of $900,000 for 71 weeks in excess of the $3.6 million per week set forth above. Energy Risk Assurance Company is an affiliate and has reinsured this coverage with third-party insurance companies. See Note 8-Related Party Transactions for more information on this affiliate transaction.

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

[5] Retrospective premium under Price-Anderson. This is subject to retrospective assessment with respect to a covered loss in excess of $375 million in the event of an incident at any licensed United States commercial reactor, payable at $17.5 million per year.

[6] Provides for $500 million in property damage and decontamination, excess property insurance, and premature decommissioning coverage up to $2.25 billion for losses in excess of the $500 million primary coverage.