Risk Management, Derivative Instruments And Hedging Activities (Notional Amounts Of Derivative Instruments Related To Interest Rate Risk) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012		Dec. 31, 2011
Cash Flow Hedges	$ 841	[1]	$ 841	[1]
Undesignated Contracts	245		247
Fair Value Hedges	275		275
Total Notional Amount	1,361		1,363
Non Recourse Long Term Debt Of Variable Interest Entities	945		949
Duke Energy Corp [Member]
Non Recourse Long Term Debt Of Variable Interest Entities	$ 466		$ 466

[1] Includes amounts related to non-recourse variable rate long-term debt of VIEs of $466 million at both March 31, 2012 and at December 31, 2011.