Risk Management, Derivative Instruments And Hedging Activities (Notional Amounts Of Derivative Instruments Related To Interest Rate Risk) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011		Dec. 31, 2010
Cash Flow Hedges	$ 841	[1]	$ 492	[1]
Undesignated Contracts	247		561
Fair Value Hedges	275		275
Total Notional Amount	1,363		1,328
Non Recourse Long Term Debt Of Variable Interest Entities	949		976
Duke Energy Corp [Member]
Non Recourse Long Term Debt Of Variable Interest Entities	$ 466		$ 492

[1] Includes amounts related to non-recourse variable rate long-term debt of VIEs of $466 million at December 31, 2011 and $492 million at December 31, 2010.