Goodwill (Schedule of Amortization Expense) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Finite-Lived Intangible Assets [Line Items]
Amortization of Intangible Assets	$ 14	$ 10	$ 24
Duke Energy Ohio [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization of Intangible Assets	12	8	20
Duke Energy Indiana [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization of Intangible Assets	$ 1	$ 1	$ 1