Risk Management, Derivative Instruments And Hedging Activities (Notional Amounts Of Derivative Instruments Related To Interest Rate Risk) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012		Dec. 31, 2011
Cash Flow Hedges	$ 869	[1]	$ 841	[1]
Undesignated Contracts	342		247
Fair Value Hedges	275		275
Total Notional Amount	1,486		1,363
Non Recourse Long Term Debt Of Variable Interest Entities	911		949
Cash Flow Hedging [Member]
Non Recourse Long Term Debt Of Variable Interest Entities	442		466
Duke Energy Carolinas [Member]
Cash Flow Hedges	0		0
Undesignated Contracts	0		0
Fair Value Hedges	25		25
Total Notional Amount	25		25
Non Recourse Long Term Debt Of Variable Interest Entities	300		300
Duke Energy Ohio [Member]
Cash Flow Hedges	0		0
Undesignated Contracts	27		27
Fair Value Hedges	250		250
Total Notional Amount	277		277
Duke Energy Indiana [Member]
Cash Flow Hedges	0		0
Undesignated Contracts	200		200
Fair Value Hedges	0		0
Total Notional Amount	$ 200		$ 200

[1] Includes amounts related to non-recourse variable rate long-term debt of VIEs of $442 million at September 30, 2012 and $466 million at December 31, 2011.