Business Segments (Schedule of Segment Reporting Information, by Segment) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Segment Reporting Information [Line Items]
Segment income	$ 688	$ 624	$ 1,404	$ 1,198
Duke Energy Carolinas [Member] | Other [Member]
Segment Reporting Information [Line Items]
Segment income	(6)	(17)	(12)	(34)
Progress Energy [Member] | Other [Member]
Segment Reporting Information [Line Items]
Segment income	(45)	(45)	(88)	(94)
Duke Energy Progress [Member] | Other [Member]
Segment Reporting Information [Line Items]
Segment income	(4)	(8)	(7)	(16)
Duke Energy Florida [Member] | Other [Member]
Segment Reporting Information [Line Items]
Segment income	(3)	(5)	(5)	(9)
Duke Energy Indiana [Member] | Other [Member]
Segment Reporting Information [Line Items]
Segment income	(1)	(5)	(3)	(7)
Piedmont Natural Gas [Member] | Other [Member]
Segment Reporting Information [Line Items]
Segment income	$ (9)	$ 1	$ (13)	$ 7