For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

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The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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

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Business Segments (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting Information [Line Items]
Interest expense	$ 1,622us-gaap_InterestExpense	$ 1,543us-gaap_InterestExpense	$ 1,244us-gaap_InterestExpense
Duke Energy Carolinas [Member]
Segment Reporting Information [Line Items]
Number of reportable segments	1
Interest expense	407	359	384
Progress Energy [Member]
Segment Reporting Information [Line Items]
Number of reportable segments	1
Interest expense	675	680	740
Duke Energy Progress [Member]
Segment Reporting Information [Line Items]
Number of reportable segments	1
Interest expense	234	201	207
Duke Energy Progress [Member] \| North Carolina Electric Membership Corporation [Member]
Segment Reporting Information [Line Items]
Entity-wide revenue, major customer, percentage	11.00%
Duke Energy Florida [Member]
Segment Reporting Information [Line Items]
Number of reportable segments	1
Interest expense	201	180	255
Duke Energy Ohio [Member]
Segment Reporting Information [Line Items]
Interest expense	86	74	89
Duke Energy Indiana [Member]
Segment Reporting Information [Line Items]
Number of reportable segments	1
Interest expense	171	170	138
Other Segment [Member] \| Progress Energy [Member]
Segment Reporting Information [Line Items]
Interest expense	$ 241	$ 300	$ 304
National Methanol Company [Member] \| International Energy [Member]
Segment Reporting Information [Line Items]
Equity method investment, ownership percentage	25.00%