Risk Management, Derivative Instruments And Hedging Activities (Derivative Instruments That Contain Credit-Risk Related Contingent Features and Cash Collateral) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Mar. 31, 2012
Schedule Of Information Regarding Derivative Instruments That Contain Credit-Risk Related Contingent Features
Aggregate fair value amounts of derivative instruments in a net liability position	$ 512	$ 466
Collateral aready posted	215	163
Additional cash collateral or letters of credit in the event credit-risk-related contingent features were triggered at the end of the reporting period	202	230
Information Regarding Cash Collateral Under Master Netting Arrangements
Amounts offset against derivative positions on the net condensed Consolidated Balance Sheets, Receivables	107	73
Derivative, collateral, obligation to return cash - not offset against net derivative	108	93
Progress Energy [Member]
Schedule Of Information Regarding Derivative Instruments That Contain Credit-Risk Related Contingent Features
Aggregate fair value amounts of derivative instruments in a net liability position	230	286
Collateral aready posted	35	59
Additional cash collateral or letters of credit in the event credit-risk-related contingent features were triggered at the end of the reporting period	195	227
Information Regarding Cash Collateral Under Master Netting Arrangements
Amounts offset against derivative positions on the net condensed Consolidated Balance Sheets, Receivables	35	58
Derivative, collateral, obligation to return cash - not offset against net derivative		1
Duke Energy Progress [Member]
Schedule Of Information Regarding Derivative Instruments That Contain Credit-Risk Related Contingent Features
Aggregate fair value amounts of derivative instruments in a net liability position	79	108
Collateral aready posted	3	9
Additional cash collateral or letters of credit in the event credit-risk-related contingent features were triggered at the end of the reporting period	76	99
Information Regarding Cash Collateral Under Master Netting Arrangements
Amounts offset against derivative positions on the net condensed Consolidated Balance Sheets, Receivables	3	9
Duke Energy Florida [Member]
Schedule Of Information Regarding Derivative Instruments That Contain Credit-Risk Related Contingent Features
Aggregate fair value amounts of derivative instruments in a net liability position	151	178
Collateral aready posted	32	50
Additional cash collateral or letters of credit in the event credit-risk-related contingent features were triggered at the end of the reporting period	119	128
Information Regarding Cash Collateral Under Master Netting Arrangements
Amounts offset against derivative positions on the net condensed Consolidated Balance Sheets, Receivables	32	49
Derivative, collateral, obligation to return cash - not offset against net derivative		1
Duke Energy Ohio [Member]
Schedule Of Information Regarding Derivative Instruments That Contain Credit-Risk Related Contingent Features
Aggregate fair value amounts of derivative instruments in a net liability position	279	176
Collateral aready posted	180	104
Additional cash collateral or letters of credit in the event credit-risk-related contingent features were triggered at the end of the reporting period	7	2
Information Regarding Cash Collateral Under Master Netting Arrangements
Amounts offset against derivative positions on the net condensed Consolidated Balance Sheets, Receivables	72	15
Derivative, collateral, obligation to return cash - not offset against net derivative	$ 108	$ 92