Acquisitions and Dispositions (Midwest Generation Exit) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
(Loss) Income From Discontinued Operations, net of tax	$ 122	$ (5)	$ 124	$ 29
Duke Energy Ohio [Member]
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
(Loss) Income From Discontinued Operations, net of tax	34	(2)	36	23
Midwest Generation Business [Member]
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Operating Revenues				543
Loss on disposition		(5)		(42)
(Loss) Income before income taxes		(5)		62
Income tax (benefit) expense	122	(1)	122	29
(Loss) Income From Discontinued Operations, net of tax		(4)		33
Midwest Generation Business [Member] | Duke Energy Ohio [Member]
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Operating Revenues				412
Loss on disposition		(4)		(48)
(Loss) Income before income taxes		(4)		48
Income tax (benefit) expense	$ 34	(2)	$ 34	25
(Loss) Income From Discontinued Operations, net of tax		(2)		23
Other Disposal Groups [Member]
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
(Loss) Income From Discontinued Operations, net of tax		$ (1)		(4)
Antitrust Lawsuit [Member]
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Litigation Settlement, Expense				81
Antitrust Lawsuit [Member] | Duke Energy Ohio [Member]
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Litigation Settlement, Expense				81
Antitrust Lawsuit [Member] | Midwest Generation Business [Member] | Duke Energy Ohio [Member]
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Litigation Settlement, Expense				$ 81