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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
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-Name Regulation S-X (SX)
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-Paragraph 13
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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Investments in Unconsolidated Affiliates (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Jan. 31, 2017
Investments In Unconsolidated Affiliates [Line Items]
Gain on sale of equity investment	$ 7	$ 17	$ 100
Distributions from equity investments	$ 104	$ 154	$ 144
National Methanol Company [Member] \| International Energy [Member]
Investments In Unconsolidated Affiliates [Line Items]
Equity method investment, ownership percentage	25.00%
Sweetwater I-V [Member] \| Commercial Power [Member]
Investments In Unconsolidated Affiliates [Line Items]
Equity method investment, ownership percentage	50.00%
DS Cornerstone [Member] \| Commercial Power [Member]
Investments In Unconsolidated Affiliates [Line Items]
Equity method investment, ownership percentage	50.00%
Duke American Transmission Co. [Member] \| Commercial Power [Member]
Investments In Unconsolidated Affiliates [Line Items]
Equity method investment, ownership percentage	50.00%
Atlantic Coast Pipeline (ACP) [Member] \| Commercial Power [Member]
Investments In Unconsolidated Affiliates [Line Items]
Equity method investment, ownership percentage	40.00%
Sabal Trail Transmission Pipeline [Member] \| Commercial Power [Member]
Investments In Unconsolidated Affiliates [Line Items]
Equity method investment, ownership percentage	7.50%
DukeNet [Member] \| Other [Member]
Investments In Unconsolidated Affiliates [Line Items]
Equity method investment, ownership percentage			50.00%
Net sales proceeds			$ 215
Gain on sale of equity investment			$ 105
Scenario, Forecast [Member] \| National Methanol Company [Member] \| International Energy [Member]
Investments In Unconsolidated Affiliates [Line Items]
Equity method investment, ownership percentage				17.50%