Risk Management, Derivative Instruments And Hedging Activities (Schedule Of Information Regarding Derivative Instruments That Contain Credit-Risk Related Contingent Features) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Aggregate Fair Value Amounts of Derivative Instruments in a Net Liability Position	$ 193	$ 96
Collateral Already Posted	67	36
Additional Cash Collateral or Letters of Credit in the Event Credit-risk-related Contingent Features were Triggered at the End of the Reporting Period	6	5
Duke Energy Ohio [Member]
Aggregate Fair Value Amounts of Derivative Instruments in a Net Liability Position	189	94
Collateral Already Posted	44	35
Additional Cash Collateral or Letters of Credit in the Event Credit-risk-related Contingent Features were Triggered at the End of the Reporting Period	$ 4	$ 5