Summary of Significant Accounting Policies (Excise Taxes) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Organization And Basis Of Presentation [Line Items]
Excise taxes	$ 421	$ 405	$ 376
Duke Energy Carolinas
Organization And Basis Of Presentation [Line Items]
Excise taxes	39	35	36
Progress Energy
Organization And Basis Of Presentation [Line Items]
Excise taxes	256	241	220
Duke Energy Progress
Organization And Basis Of Presentation [Line Items]
Excise taxes	21	19	19
Duke Energy Florida
Organization And Basis Of Presentation [Line Items]
Excise taxes	235	222	201
Duke Energy Ohio
Organization And Basis Of Presentation [Line Items]
Excise taxes	101	105	98
Duke Energy Indiana
Organization And Basis Of Presentation [Line Items]
Excise taxes	23	22	20
Piedmont
Organization And Basis Of Presentation [Line Items]
Excise taxes	$ 2	$ 2	$ 2