Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill.

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Amount of the cost of borrowed funds accounted for as interest expense.

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Business Segments (Narrative) (Details) $ in Millions	3 Months Ended		9 Months Ended
Business Segments (Narrative) (Details) $ in Millions	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($) segment	Sep. 30, 2016 USD ($)	Oct. 31, 2017	Oct. 02, 2016
Segment Reporting Information [Line Items]
Impairment charges	$ 207	$ 10	$ 216	$ 14
Net income	954	1,176	2,356	2,379
Interest Expense	498	464	$ 1,475	1,431
Duke Energy Carolinas [Member]
Segment Reporting Information [Line Items]
Number of Reportable Segments \| segment			1
Net income	466	494	$ 1,009	1,026
Interest Expense	108	102	314	316
Progress Energy [Member]
Segment Reporting Information [Line Items]
Impairment charges	135	1	$ 137	4
Number of Reportable Segments \| segment			1
Net income	341	446	$ 814	927
Interest Expense	193	177	$ 595	497
Duke Energy Progress [Member]
Segment Reporting Information [Line Items]
Impairment charges		1		1
Number of Reportable Segments \| segment			1
Net income	246	271	$ 547	539
Interest Expense	65	61	217	188
Duke Energy Florida [Member]
Segment Reporting Information [Line Items]
Impairment charges	135	1	$ 137	4
Number of Reportable Segments \| segment			1
Net income	120	206	$ 368	487
Interest Expense	71	62	211	143
Duke Energy Ohio [Member]
Segment Reporting Information [Line Items]
Impairment charges			$ 1
Number of Reportable Segments \| segment			2
Net income	55	89	$ 127	171
Interest Expense	22	22	$ 67	63
Duke Energy Indiana [Member]
Segment Reporting Information [Line Items]
Impairment charges		8		8
Number of Reportable Segments \| segment			1
Net income	121	129	$ 318	309
Interest Expense	44	45	132	136
Piedmont Natural Gas [Member]
Segment Reporting Information [Line Items]
Impairment charges			$ 7
Number of Reportable Segments \| segment			1
Net income	(11)	(12)	$ 76	94
Interest Expense	20	17	59	50
Commercial Renewables [Member]
Segment Reporting Information [Line Items]
Impairment charges	69		69
Equity Method Investment, Other than Temporary Impairment		71		71
Other [Member] \| Progress Energy [Member]
Segment Reporting Information [Line Items]
Interest Expense	$ 56	55	$ 167	166
National Methanol Company [Member] \| Other [Member]
Segment Reporting Information [Line Items]
Equity Method Investment, Ownership Percentage	25.00%		25.00%
National Methanol Company [Member] \| Other [Member] \| Subsequent Event [Member]
Segment Reporting Information [Line Items]
Equity Method Investment, Ownership Percentage					17.50%
SouthStar [Member] \| Piedmont Natural Gas [Member]
Segment Reporting Information [Line Items]
Equity Method Investment, Ownership Percentage						15.00%
Net income		$ 2		$ 12