Notes Receivable (Tables) (EnerBank USA [Member])
9 Months Ended
Sep. 30, 2011
EnerBank USA [Member]
 
Schedule of Allowance for Loan Losses
                 
In Millions  
    Three months     Nine months  
    ended     ended  
September 30   2011     2011  
 
Allowance for loan losses, at beginning of period
   $ 5     $ 5  
Charge-offs
     (1 )     (4 )
Recoveries
     —       1  
Provision for loan losses
     1       3  
 
Allowance for loan losses, at end of period
   $ 5     $ 5  
 
Schedule of Delinquency Status of EnerBank's Consumer Loans
                                         
In Millions  
Past Due   Past Due     Past Due     Total             Total  
30-59 Days   60-89 Days     Over 90 Days     Delinquent     Current     Outstanding  
 
$            1
   $ 1     $ —     $ 2     $ 437     $ 439