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Summary Of Significant Accounting Policies (Tables)
 12 Months Ended
Dec. 31, 2012
Summary Of Significant Accounting Policies [Abstract]  
Schedule Of Estimated Useful Lives And Balances Of Utility's Property, Plant And Equipment
 
 
Estimated Useful
 
Balance at December 31,
(in millions, except estimated useful lives)
Lives (years)
 
2012
 
2011
Electricity generating facilities (1)
10 to 100
 
$
8,253      
      
$
6,488      
Electricity distribution facilities
10 to 55
 
      
23,767      
      
      
22,395      
Electricity transmission
10 to 70
 
      
7,681      
      
      
6,968      
Natural gas distribution facilities
20 to 53
 
      
8,257      
      
      
7,832      
Natural gas transportation and storage
5 to 48
 
      
4,314      
      
      
4,099      
Construction work in progress
 
 
      
1,894      
      
      
1,770      
Total property, plant, and equipment
 
 
      
54,166      
      
      
49,552      
Accumulated depreciation
 
 
      
(16,643)      
      
      
(15,898)      
Net property, plant, and equipment
 
 
$
37,523      
      
$
33,654      
 
 
 
 
 
 
 
 
 (1) Balance includes nuclear fuel inventories.  Stored nuclear fuel inventory is stated at weighted average cost.  Nuclear fuel in the reactor is expensed as it is used based on the amount of energy output.  (See Note 15 below.)
Schedule Of Changes In Asset Retirement Obligations
 
 
(in millions)
 
 
ARO liability at December 31, 2010
$
1,586      
Revision in estimated cash flows
      
10      
Accretion
      
100      
Liabilities settled
      
(87)      
ARO liability at December 31, 2011
      
1,609      
Revision in estimated cash flows
      
1,301      
Accretion
      
101      
Liabilities settled
      
(92)      
ARO liability at December 31, 2012
$
2,919