Risk Management, Derivative Instruments And Hedging Activities (Information Regarding Cash Collateral Under Master Netting Arrangements) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Amounts offset against derivative positions on the net condensed Consolidated Balance Sheets, Receivables	$ 0	$ 10
Amounts not offset against net derivative positions on the Condensed Consolidated Balance Sheets, Receivables	73	30
Amounts offset against derivative positions on the net condensed Consolidated Balance Sheets, Payables	1
Duke Energy Ohio [Member]
Amounts offset against derivative positions on the net condensed Consolidated Balance Sheets, Receivables	0	9
Amounts not offset against net derivative positions on the Condensed Consolidated Balance Sheets, Receivables	$ 49	$ 28