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Commitments And Contingent Liabilities (Minimum Fuel Purchase Requirements) (Detail) (Power [Member], USD $)
In Millions, unless otherwise specified
3 Months Ended
Mar. 31, 2013
Long-term Purchase Commitment [Line Items]  
Coverage percentage of nuclear fuel commitments of uranium, enrichment, and fabrication requirements 100.00%
Commitments Through 2017 [Member] | Nuclear Fuel Uranium [Member]
 
Long-term Purchase Commitment [Line Items]  
Total minimum purchase requirements $ 483
Commitments Through 2017 [Member] | Nuclear Fuel Enrichment [Member]
 
Long-term Purchase Commitment [Line Items]  
Total minimum purchase requirements 444
Commitments Through 2017 [Member] | Nuclear Fuel Fabrication [Member]
 
Long-term Purchase Commitment [Line Items]  
Total minimum purchase requirements 145
Commitments Through 2017 [Member] | Natural Gas [Member]
 
Long-term Purchase Commitment [Line Items]  
Total minimum purchase requirements 1,035
Commitments Through 2017 [Member] | Coal [Member]
 
Long-term Purchase Commitment [Line Items]  
Total minimum purchase requirements $ 508