Business Segments (Narrative) (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($) segment	Jun. 30, 2016 USD ($)	Oct. 02, 2016
Segment Reporting Information [Line Items]
Net income	$ 686	$ 509	$ 1,402	$ 1,203
Interest Expense	486	478	$ 977	967
Duke Energy Carolinas [Member]
Segment Reporting Information [Line Items]
Number of Reportable Segments | segment			1
Net income	273	261	$ 543	532
Interest Expense	103	107	$ 206	214
Progress Energy [Member]
Segment Reporting Information [Line Items]
Number of Reportable Segments | segment			1
Net income	274	272	$ 473	481
Interest Expense	196	160	$ 402	320
Duke Energy Progress [Member]
Segment Reporting Information [Line Items]
Number of Reportable Segments | segment			1
Net income	154	131	$ 301	268
Interest Expense	70	64	$ 152	127
Duke Energy Florida [Member]
Segment Reporting Information [Line Items]
Number of Reportable Segments | segment			1
Net income	158	171	$ 248	281
Interest Expense	70	40	$ 140	81
Duke Energy Ohio [Member]
Segment Reporting Information [Line Items]
Number of Reportable Segments | segment			2
Net income	30	23	$ 72	82
Interest Expense	23	21	$ 45	41
Duke Energy Indiana [Member]
Segment Reporting Information [Line Items]
Number of Reportable Segments | segment			1
Net income	106	85	$ 197	180
Interest Expense	44	47	$ 88	91
Piedmont Natural Gas [Member]
Segment Reporting Information [Line Items]
Number of Reportable Segments | segment			1
Net income	(8)	3	$ 87	106
Interest Expense	19	16	39	33
Other [Member] | Progress Energy [Member]
Segment Reporting Information [Line Items]
Interest Expense	$ 56	55	$ 111	111
National Methanol Company [Member] | Other [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Equity Method Investment, Ownership Percentage	25.00%		25.00%
SouthStar [Member] | Piedmont Natural Gas [Member]
Segment Reporting Information [Line Items]
Equity Method Investment, Ownership Percentage					15.00%
Net income		$ 3		$ 10