Business Segments (Net Loss) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Segment Reporting Information [Line Items]
Segment income	$ 937	$ 888	$ 2,310	$ 2,356
Interest expense	402	405	1,208	1,212
Duke Energy Carolinas [Member]
Segment Reporting Information [Line Items]
Interest expense	105	104	313	307
Duke Energy Carolinas [Member] | Other [Member]
Segment Reporting Information [Line Items]
Segment income	(10)	(19)	(28)	(67)
Progress Energy [Member]
Segment Reporting Information [Line Items]
Segment income		329		739
Interest expense	170	166	504	502
Progress Energy [Member] | Other [Member]
Segment Reporting Information [Line Items]
Segment income	(3)	(48)	(87)	(145)
Interest expense	61	58	180	181
Duke Energy Progress [Member]
Segment Reporting Information [Line Items]
Interest expense	59	57	175	172
Duke Energy Progress [Member] | Other [Member]
Segment Reporting Information [Line Items]
Segment income	(4)	(10)	(12)	(23)
Duke Energy Florida [Member]
Segment Reporting Information [Line Items]
Interest expense	50	51	149	150
Duke Energy Florida [Member] | Other [Member]
Segment Reporting Information [Line Items]
Segment income	(3)	(5)	(9)	(16)
Duke Energy Indiana [Member]
Segment Reporting Information [Line Items]
Interest expense	44	40	132	127
Duke Energy Indiana [Member] | Other [Member]
Segment Reporting Information [Line Items]
Segment income	$ (2)	$ (3)	$ (6)	$ (10)