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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Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Business Segments (Narrative) (Details) $ in Millions	12 Months Ended
Business Segments (Narrative) (Details) $ in Millions	Dec. 31, 2015 USD ($) segment	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Segment Reporting Information [Line Items]
Interest expense	$ 1,613	$ 1,622	$ 1,543
Duke Energy Carolinas [Member]
Segment Reporting Information [Line Items]
Number of reportable segments \| segment	1
Interest expense	$ 412	407	359
Progress Energy [Member]
Segment Reporting Information [Line Items]
Number of reportable segments \| segment	1
Interest expense	$ 670	675	680
Duke Energy Progress [Member]
Segment Reporting Information [Line Items]
Number of reportable segments \| segment	1
Interest expense	$ 235	234	201
Duke Energy Progress [Member] \| North Carolina Electric Membership Corporation [Member]
Segment Reporting Information [Line Items]
Entity-wide revenue, major customer, percentage	10.00%
Duke Energy Florida [Member]
Segment Reporting Information [Line Items]
Number of reportable segments \| segment	1
Interest expense	$ 198	201	180
Duke Energy Ohio [Member]
Segment Reporting Information [Line Items]
Interest expense	$ 79	86	74
Duke Energy Indiana [Member]
Segment Reporting Information [Line Items]
Number of reportable segments \| segment	1
Interest expense	$ 176	171	170
Other Segment [Member] \| Progress Energy [Member]
Segment Reporting Information [Line Items]
Interest expense	$ 240	$ 241	$ 300
National Methanol Company [Member] \| International Energy [Member]
Segment Reporting Information [Line Items]
Equity method investment, ownership percentage	25.00%