Notes Receivable (Disclosure of Delinquency Status of EnerBank's Consumer Loans) (Details) (USD $) In Millions	Sep. 30, 2011		Dec. 31, 2010
Total Outstanding	$ 439	[1]	$ 386	[1]
EnerBank USA [Member]
Past Due 30-59 Days	1
Past Due 60-89 Days	1
Past Due Over 90 Days
Total Delinquent	2
Current	437
Total Outstanding	$ 439		$ 386

[1] 1 Includes current portion of notes receivable of $16 million at September 30, 2011 and $11 million at December 31, 2010.