Organization and Basis of Presentation (Schedule of Excise Taxes) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Organization And Basis Of Presentation [Line Items]
Excise taxes collected	$ 95	$ 91	$ 194	$ 182
Duke Energy Carolinas [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes collected	9	9	17	18
Progress Energy [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes collected	56	55	110	101
Duke Energy Progress [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes collected	5	4	10	9
Duke Energy Florida [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes collected	51	51	100	92
Duke Energy Ohio [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes collected	25	23	55	51
Duke Energy Indiana [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes collected	$ 5	3	11	10
Piedmont Natural Gas [Member]
Organization And Basis Of Presentation [Line Items]
Excise taxes collected		$ 1	$ 1	$ 2