Summary of Significant Accounting Policies (Excise Taxes) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Oct. 31, 2016
Organization And Basis Of Presentation [Line Items]
Excise taxes	$ 405	$ 376	$ 362
Duke Energy Carolinas [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes	35	36	31
Progress Energy [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes	241	220	213
Duke Energy Progress [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes	19	19	18
Duke Energy Florida [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes	222	201	195
Duke Energy Ohio [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes	105	98	100
Duke Energy Indiana [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes	22	20	$ 17
Piedmont Natural Gas [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes	$ 2	$ 2		$ 2