Quarterly Financial Data (Unaudited) (Unusual or Infrequently Occurring Items) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Quarterly Financial Information Disclosure [Line Items]
Costs to achieve mergers	$ (30)	$ (24)	$ (22)	$ (21)	$ (33)	$ (56)	$ (61)	$ (55)	$ (97)	$ (205)
Cost Savings Initiative	(142)	0	0	0					(142)
Pretax impairment charge									(120)	(81)	$ (399)
Deferred foreign taxes									17	67	(14)
Total	(182)	(121)	(63)	(21)	(547)	421	(61)	(1,436)	(387)	(1,623)
Edwardsport Settlement [Member]
Quarterly Financial Information Disclosure [Line Items]
Settlements and penalties	(3)	(90)							(93)
Ash Basin [Member]
Quarterly Financial Information Disclosure [Line Items]
Settlements and penalties	(7)	(7)			(102)	0	0	0	(14)	(102)
Midwest Generation Business [Member]
Quarterly Financial Information Disclosure [Line Items]
State Tax Adjustment related to Midwest Generation Sale			(41)						(41)
Midwest Generation Impairment [Member]
Quarterly Financial Information Disclosure [Line Items]
Pretax impairment charge					(39)	477	0	(1,287)		(849)
International Tax Adjustment [Member]
Quarterly Financial Information Disclosure [Line Items]
Deferred foreign taxes					(373)					(373)
Ohio Valley Electric Corporation [Member]
Quarterly Financial Information Disclosure [Line Items]
Pretax impairment charge								(94)		(94)
Duke Energy Carolinas [Member]
Quarterly Financial Information Disclosure [Line Items]
Costs to achieve mergers	(16)	(11)	(11)	(9)	(17)	(25)	(38)	(29)	(47)	(109)
Cost Savings Initiative	(93)	0	0	0					(93)
Pretax impairment charge									(1)	(3)
Total	(116)	(12)	(11)	(9)	(89)	(25)	(38)	(29)	(148)	(181)
Duke Energy Carolinas [Member] | Ash Basin [Member]
Quarterly Financial Information Disclosure [Line Items]
Settlements and penalties	(7)	(1)			(72)				(8)	(72)
Progress Energy [Member]
Quarterly Financial Information Disclosure [Line Items]
Costs to achieve mergers	(10)	(8)	(8)	(8)	(13)	(21)	(12)	(19)	(34)	(65)
Cost Savings Initiative	(36)	0	0	0					(36)
Pretax impairment charge									(12)	16	(380)
Total	(46)	(14)	(8)	(8)	(43)	(21)	(12)	(19)	(76)	(95)
Progress Energy [Member] | Ash Basin [Member]
Quarterly Financial Information Disclosure [Line Items]
Settlements and penalties		(6)			(30)				(6)	(30)
Duke Energy Progress [Member]
Quarterly Financial Information Disclosure [Line Items]
Costs to achieve mergers	(6)	(6)	(5)	(5)	(10)	(15)	(3)	(14)	(22)	(42)
Cost Savings Initiative	(28)	0	0	0					(28)
Pretax impairment charge									(5)	18	(22)
Total	(34)	(12)	(5)	(5)	(40)	(15)	(3)	(14)	(56)	(72)
Duke Energy Progress [Member] | Ash Basin [Member]
Quarterly Financial Information Disclosure [Line Items]
Settlements and penalties		(6)			(30)				(6)	(30)
Duke Energy Florida [Member]
Quarterly Financial Information Disclosure [Line Items]
Costs to achieve mergers	(4)	(3)	(3)	(3)	(3)	(6)	(9)	(5)	(13)	(23)
Cost Savings Initiative	(8)	0	0	0					(8)
Pretax impairment charge									(7)	(2)	(358)
Total	(12)	(3)	(3)	(3)					(21)
Duke Energy Ohio [Member]
Quarterly Financial Information Disclosure [Line Items]
Costs to achieve mergers	(1)	(1)	(1)	(1)	(2)	(3)	(4)	(2)	(4)	(11)
Cost Savings Initiative	(2)	0	0	0					(2)
Pretax impairment charge										(94)	$ (5)
Total	(3)	(1)	(1)	(1)	(41)	474	(4)	(1,414)	(6)	(985)
Duke Energy Ohio [Member] | Midwest Generation Impairment [Member]
Quarterly Financial Information Disclosure [Line Items]
Pretax impairment charge					(39)	477	0	(1,318)		(880)
Duke Energy Ohio [Member] | Ohio Valley Electric Corporation [Member]
Quarterly Financial Information Disclosure [Line Items]
Pretax impairment charge								(94)		(94)
Duke Energy Indiana [Member]
Quarterly Financial Information Disclosure [Line Items]
Costs to achieve mergers	(2)	(2)	(1)	(2)	$ (2)	$ (3)	$ (5)	$ (2)	(7)	$ (12)
Cost Savings Initiative	(6)	0	0	0					(6)
Pretax impairment charge									(88)
Total	(11)	(92)	$ (1)	$ (2)					(106)
Duke Energy Indiana [Member] | Edwardsport Settlement [Member]
Quarterly Financial Information Disclosure [Line Items]
Settlements and penalties	$ (3)	$ (90)							$ (93)