Acquisitions and Dispositions (Discontinued Operations) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income From Discontinued Operations, net of tax	$ (2)	$ 180	$ (4)	$ 190
International Energy [Member] | Discontinued Operations, Disposed of by Sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Operating Revenues		245		761
Fuel used in electric generation and purchased power		60		177
Cost of natural gas		11		34
Operation, maintenance and other		85		240
Deprecation and amortization		18		62
Property and other taxes		1		6
Impairment Charges		0		194
Gains on Sales of Other Assets and Other, net		(3)		(2)
Other Income and Expenses, net		14		35
Interest Expense		19		63
Income before income taxes		62		18
Income tax expense (benefit)		4		(48)
Income From Discontinued Operations, net of tax		58		66
Other Disposal Groups [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income tax expense (benefit)		(122)		(122)
Income From Discontinued Operations, net of tax		122		124
Previously Remitted Earnings [Member] | International Energy [Member] | Discontinued Operations, Disposed of by Sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income tax expense (benefit)				(95)
Duke Energy Ohio [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income From Discontinued Operations, net of tax	$ (1)	34	$ (1)	36
Duke Energy Ohio [Member] | Midwest Generation Business [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income tax expense (benefit)		$ (34)		$ (34)