Notes Receivable (Schedule Of Allowance For Loan Losses) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013 EnerBank [Member]	Dec. 31, 2012 EnerBank [Member]
Allowance for loan losses, at beginning of period	$ 5	$ 5	$ 5	$ 5
Charge-offs	(2)	(1)	(3)	(2)
Recoveries	1		1
Provision for loan losses	1	1	2	2
Allowance for loan losses, at end of period	5	5	5	5
Delinquent loans					2	3
Loans modified as troubled debt restructurings					$ 1	$ 1