Acquisitions and Dispositions (Midwest Generation Exit) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income tax expense (benefit)									$ (30)	$ 89	$ 149
Income (Loss) From Discontinued Operations, net of tax	$ (598)	$ 180	$ (112)	$ 122	$ 49	$ 45	$ (29)	$ 112	(408)	177	(649)
Duke Energy Ohio [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income tax expense (benefit)									(36)	22	(300)
Income (Loss) From Discontinued Operations, net of tax		$ 34		$ 2		$ (2)	$ (65)	$ 90	36	23	(563)
Midwest Generation Business [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Operating Revenues										543	1,748
Loss on disposition										(45)	(929)
Income (loss) before income taxes										59	(818)
Income tax expense (benefit)									(36)	26	(294)
Income (Loss) From Discontinued Operations, net of tax									36	33	(524)
Midwest Generation Business [Member] | Duke Energy Ohio [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Operating Revenues										412	1,299
Loss on disposition										(52)	(959)
Income (loss) before income taxes										44	(863)
Income tax expense (benefit)									(36)	21	(300)
Income (Loss) From Discontinued Operations, net of tax									$ 36	23	$ (563)
Antitrust Lawsuit [Member] | Duke Energy Ohio [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Litigation Settlement, Expense										81
Antitrust Lawsuit [Member] | Midwest Generation Business [Member] | Duke Energy Ohio [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Litigation Settlement, Expense										$ 81