Organization and Basis of Presentation (Schedule of Excise Taxes) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Organization And Basis Of Presentation [Line Items]
Excise taxes collected	$ 114	$ 107	$ 308	$ 289
Duke Energy Carolinas [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes collected	10	9	27	27
Progress Energy [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes collected	71	67	181	168
Duke Energy Progress [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes collected	5	5	15	14
Duke Energy Florida [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes collected	66	62	166	154
Duke Energy Ohio [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes collected	26	24	81	75
Duke Energy Indiana [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes collected	6	6	17	16
Piedmont Natural Gas [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes collected	$ 1	$ 1	$ 2	$ 3