Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Amounts Attributable to Controlling Interests) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Organization And Basis Of Presentation [Line Items]
Income (Loss) from Continuing Operations, Including Portion Attributable to Noncontrolling Interest	$ 99	$ 891	$ 725	$ 750	$ 689	$ 946	$ 292	$ 663	$ 2,465	$ 2,590	$ 1,611
Income (Loss) from Continuing Operations Attributable to Noncontrolling Interest									14	16	18
Income from continuing operations attributable to Duke Energy common stockholders, as adjusted for participating securities - basic and diluted									2,451	2,574	1,593
Income (Loss) From Discontinued Operations, net of tax	1	378	(112)	(843)	3	62	50	(29)	(576)	86	171
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Noncontrolling Interest									(8)	(5)	(4)
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent									(568)	91	175
Net income	100	1,269	613	(93)	692	1,008	342	634	1,889	2,676	1,782
Net Income (Loss) Attributable to Noncontrolling Interest									6	11	14
Net Income (Loss) Attributable to Parent	97	1,274	609	(97)	688	1,004	339	634	1,883	2,665	1,768
Progress Energy [Member]
Organization And Basis Of Presentation [Line Items]
Income (Loss) from Continuing Operations, Including Portion Attributable to Noncontrolling Interest	139	330	207	204	190	328	(13)	154	880	659	355
Income (Loss) from Continuing Operations Attributable to Noncontrolling Interest									5	3	7
Income from continuing operations attributable to Duke Energy common stockholders, as adjusted for participating securities - basic and diluted									875	656	348
Income (Loss) From Discontinued Operations, net of tax									(6)	16	52
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent									(6)	16	52
Net income	139	330	202	203	196	342	(17)	154	874	675	407
Net Income (Loss) Attributable to Noncontrolling Interest									5	3	7
Net Income (Loss) Attributable to Parent	$ 136	$ 329	$ 202	$ 202	$ 195	$ 341	$ (17)	$ 153	$ 869	$ 672	$ 400