Organization and Basis of Presentation (Schedule of Excise Taxes) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Organization And Basis Of Presentation [Line Items]
Excise taxes collected	$ 107	$ 107	$ 289	$ 285
Duke Energy Carolinas [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes collected	9	6	27	21
Progress Energy [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes collected	67	65	168	161
Duke Energy Progress [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes collected	5	4	14	13
Duke Energy Florida [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes collected	62	61	154	148
Duke Energy Ohio [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes collected	24	26	75	77
Duke Energy Indiana [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes collected	6	10	16	26
Piedmont Natural Gas [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes collected	$ 1	$ 1	$ 3	$ 2