Derivatives and Hedging (Derivative Instruments That Contain Credit-Risk Related Contingent Features and Cash Collateral) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Schedule Of Information Regarding Derivative Instruments That Contain Credit-Risk Related Contingent Features
Aggregate fair value of derivatives in a net liability position	$ 59	$ 34
Additional cash collateral or letters of credit in the event credit-risk-related contingent features were triggered	59	34
Duke Energy Carolinas [Member]
Schedule Of Information Regarding Derivative Instruments That Contain Credit-Risk Related Contingent Features
Aggregate fair value of derivatives in a net liability position	35	16
Additional cash collateral or letters of credit in the event credit-risk-related contingent features were triggered	35	16
Progress Energy [Member]
Schedule Of Information Regarding Derivative Instruments That Contain Credit-Risk Related Contingent Features
Aggregate fair value of derivatives in a net liability position	25	18
Additional cash collateral or letters of credit in the event credit-risk-related contingent features were triggered	25	18
Duke Energy Progress [Member]
Schedule Of Information Regarding Derivative Instruments That Contain Credit-Risk Related Contingent Features
Aggregate fair value of derivatives in a net liability position	15	6
Additional cash collateral or letters of credit in the event credit-risk-related contingent features were triggered	15	6
Duke Energy Florida [Member]
Schedule Of Information Regarding Derivative Instruments That Contain Credit-Risk Related Contingent Features
Aggregate fair value of derivatives in a net liability position	10	12
Additional cash collateral or letters of credit in the event credit-risk-related contingent features were triggered	$ 10	$ 12