Acquisitions and Dispositions (Assets Held For Sale) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Income (Loss) From Discontinued Operations, net of tax	$ 91	$ (843)
Disposal Group, Including Discontinued Operation, Classified Balance Sheet Disclosures [Abstract]
Current assets	354		364
Current liabilities	146		262
Duke Energy Ohio [Member]
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Income (Loss) From Discontinued Operations, net of tax	90	(875)
Disposal Group, Including Discontinued Operation, Classified Balance Sheet Disclosures [Abstract]
Current assets	295		316
Current liabilities	129		246
Midwest Generation Business [Member]
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Operating Revenues	543	368
Estimated loss on disposition	(43)	(1,287)
Income (loss) before income taxes	147	(1,303)
Income tax expense (benefit)	51	(466)
Income (Loss) From Discontinued Operations, net of tax	96	(837)
Disposal Group, Including Discontinued Operation, Classified Balance Sheet Disclosures [Abstract]
Current assets	354
Investments and other assets	50
Property, plant and equipment	2,553
Total Assets held for sale	2,957
Current liabilities	146
Deferred credits and other liabilities	26
Total Liabilities associated with assets held for sale	172
Midwest Generation Business [Member] \| Duke Energy Ohio [Member]
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Operating Revenues	412	195
Estimated loss on disposition	(44)	(1,323)
Income (loss) before income taxes	140	(1,354)
Income tax expense (benefit)	50	(479)
Disposal Group, Including Discontinued Operation, Classified Balance Sheet Disclosures [Abstract]
Current assets	295
Investments and other assets	45
Property, plant and equipment	2,520
Total Assets held for sale	2,860
Current liabilities	129
Deferred credits and other liabilities	25
Total Liabilities associated with assets held for sale	154
Other Disposal Groups [Member]
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Income (Loss) From Discontinued Operations, net of tax	$ (5)	$ (6)

Amount classified as assets attributable to disposal group held for sale or disposed of.

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Overall income (loss) from a disposal group that is classified as a component of the entity, before income tax, reported as a separate component of income before extraordinary items. Includes the following (before income tax): income (loss) from operations during the phase-out period, gain (loss) on disposal, provision (or any reversals of earlier provisions) for loss on disposal, and adjustments of a prior period gain (loss) on disposal.

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Amount, before tax, of loss recognized for the write-down to fair value, less cost to sell, of a disposal group. Includes before tax gain for a subsequent increase in fair value (less cost to sell) up to the cumulative loss previously recognized through write-downs.

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Tax effect allocated to a disposal group that is classified as a component of the entity reported as a separate component of income before extraordinary items. Includes the tax effects of the following: income (loss) from operations during the phase-out period, gain (loss) on disposal, provision (or any reversals of earlier provisions) for loss on disposal, and adjustments of a prior period gain (loss) on disposal.

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Amount classified as other assets attributable to disposal group held for sale or disposed of, expected to be disposed of after one year or the normal operating cycle, if longer.

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Amount classified as other liabilities attributable to disposal group held for sale or disposed of, expected to be disposed of beyond one year or the normal operating cycle, if longer.

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Amount classified as property, plant and equipment attributable to disposal group held for sale or disposed of.

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Amount of sales or other form of revenues attributable to the disposal group, including a component of the entity (discontinued operation), during the reporting period.

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Amount of income (loss) from a disposal group, net of income tax before extraordinary items allocable to noncontrolling interests. Includes, net of tax, income (loss) from operations during the phase-out period, gain (loss) on disposal, provision (or any reversals of earlier provisions) for loss on disposal, and adjustments of a prior period gain (loss) on disposal.

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Amount classified as liabilities attributable to disposal group held for sale or disposed of.

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Amount classified as liabilities attributable to disposal group held for sale or disposed of, expected to be disposed of within one year or the normal operating cycle, if longer.

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