Summary of Significant Accounting Policies (Excise Taxes) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Organization And Basis Of Presentation [Line Items]
Excise taxes	$ 415	$ 421	$ 405
Duke Energy Carolinas
Organization And Basis Of Presentation [Line Items]
Excise taxes	43	39	35
Progress Energy
Organization And Basis Of Presentation [Line Items]
Excise taxes	249	256	241
Duke Energy Progress
Organization And Basis Of Presentation [Line Items]
Excise taxes	26	21	19
Duke Energy Florida
Organization And Basis Of Presentation [Line Items]
Excise taxes	223	235	222
Duke Energy Ohio
Organization And Basis Of Presentation [Line Items]
Excise taxes	96	101	105
Duke Energy Indiana
Organization And Basis Of Presentation [Line Items]
Excise taxes	25	23	22
Piedmont
Organization And Basis Of Presentation [Line Items]
Excise taxes	$ 2	$ 2	$ 2