Business Segments (Net Loss) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Segment Reporting Information [Line Items]
Segment income	$ 600	$ 722	$ 1,373	$ 1,468
Interest expense	403	403	806	807
Duke Energy Carolinas [Member]
Segment Reporting Information [Line Items]
Interest expense	106	102	208	203
Duke Energy Carolinas [Member] | Other [Member]
Segment Reporting Information [Line Items]
Segment income	(10)	(27)	(18)	(48)
Progress Energy [Member]
Segment Reporting Information [Line Items]
Interest expense	166	167	334	336
Progress Energy [Member] | Other [Member]
Segment Reporting Information [Line Items]
Segment income	(42)	(45)	(84)	(97)
Interest expense	59	60	119	123
Duke Energy Progress [Member]
Segment Reporting Information [Line Items]
Interest expense	56	58	116	115
Duke Energy Progress [Member] | Other [Member]
Segment Reporting Information [Line Items]
Segment income	(4)	(3)	(8)	(13)
Duke Energy Florida [Member]
Segment Reporting Information [Line Items]
Interest expense	50	50	99	99
Duke Energy Florida [Member] | Other [Member]
Segment Reporting Information [Line Items]
Segment income	(3)	(7)	(6)	(11)
Duke Energy Indiana [Member]
Segment Reporting Information [Line Items]
Interest expense	43	44	88	87
Duke Energy Indiana [Member] | Other [Member]
Segment Reporting Information [Line Items]
Segment income	$ (2)	$ (4)	$ (4)	$ (7)