Derivatives and Hedging (Derivative Instruments with Credit-Risk Related Contingent Features and Cash Collateral) (Details) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
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	$ 171	$ 334
Fair value of collateral already posted		30
Additional cash collateral or letters of credit in the event credit-risk-related contingent features were triggered	171	304
Information Regarding Cash Collateral Under Master Netting Arrangements
Amount of right to receive cash collateral, offset against derivative liability		30
Duke Energy Carolinas [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	99	45
Additional cash collateral or letters of credit in the event credit-risk-related contingent features were triggered	99	45
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	72	290
Fair value of collateral already posted		30
Additional cash collateral or letters of credit in the event credit-risk-related contingent features were triggered	72	260
Information Regarding Cash Collateral Under Master Netting Arrangements
Amount of right to receive cash collateral, offset against derivative liability		30
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	12	93
Additional cash collateral or letters of credit in the event credit-risk-related contingent features were triggered	12	93
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	60	194
Fair value of collateral already posted		30
Additional cash collateral or letters of credit in the event credit-risk-related contingent features were triggered	$ 60	164
Information Regarding Cash Collateral Under Master Netting Arrangements
Amount of right to receive cash collateral, offset against derivative liability		$ 30