Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Unbilled Revenues)(Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Organization And Basis Of Presentation [Line Items]
Unbilled receivables	$ 827	$ 937
Duke Energy Carolinas [Member]
Organization And Basis Of Presentation [Line Items]
Unbilled receivables	295	323
Progress Energy [Member]
Organization And Basis Of Presentation [Line Items]
Unbilled receivables	217	189
Duke Energy Progress [Member]
Organization And Basis Of Presentation [Line Items]
Unbilled receivables	135	120
Duke Energy Florida [Member]
Organization And Basis Of Presentation [Line Items]
Unbilled receivables	82	69
Duke Energy Ohio [Member]
Organization And Basis Of Presentation [Line Items]
Unbilled receivables		55
Duke Energy Indiana [Member]
Organization And Basis Of Presentation [Line Items]
Unbilled receivables	27	5
Cinergy Receivables [Member] | Duke Energy Ohio [Member]
Organization And Basis Of Presentation [Line Items]
Unbilled receivables	79	89
Cinergy Receivables [Member] | Duke Energy Indiana [Member]
Organization And Basis Of Presentation [Line Items]
Unbilled receivables	$ 112	$ 144