Notes Receivable (Schedule Of Allowance For Loan Losses) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013 EnerBank [Member]	Dec. 31, 2012 EnerBank [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses, at beginning of period	$ 5	$ 5	$ 5	$ 5
Charge-offs	(1)	(2)	(4)	(4)
Recoveries		1	1	1
Provision for loan losses	1	1	3	3
Allowance for loan losses, at end of period	5	5	5	5
Delinquent loans					3	3
Loans modified as troubled debt restructurings					$ 1	$ 1