Income Taxes (Components of Income Tax Expense) (Details) - USD ($) $ in Millions	2 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Oct. 31, 2016	Dec. 31, 2015	Oct. 31, 2015
Current Income Tax Expense (Benefit), Continuing Operations [Abstract]
Current federal taxes		$ (247)
Current state taxes		4	$ (15)		$ (12)
Current foreign taxes		3	2		4
Total current income taxes		(240)	(13)		(8)
Deferred Income Tax Expense (Benefit), Continuing Operations [Abstract]
Deferred federal taxes		1,344	1,064		1,097
Deferred state taxes		102	117		181
Total deferred income taxes		1,446	1,181		1,278
Investment tax credit amortization		(10)	(12)		(14)
Income tax expense (benefit) from continuing operations		1,196	1,156		1,256
Tax expense (benefit) from discontinued operations		(6)	(30)		89
Total income tax expense included in Consolidated Statements of Operations		1,190	1,126		1,345
Net operating loss carry forward		428	648		264
Duke Energy Income from Continuing Operations Before Income Taxes [Abstract]
Domestic		4,207	3,689		3,831
Foreign		59	45		79
Total income from continuing operations before income taxes		4,266	3,734		3,910
Equity in losses of unconsolidated affiliates		(119)	15		(69)
Tax Act [Member]
Duke Energy Income from Continuing Operations Before Income Taxes [Abstract]
Equity in losses of unconsolidated affiliates		16
Duke Energy Carolinas [Member]
Current Income Tax Expense (Benefit), Continuing Operations [Abstract]
Current federal taxes		221	139		216
Current state taxes		20	25		14
Total current income taxes		241	164		230
Deferred Income Tax Expense (Benefit), Continuing Operations [Abstract]
Deferred federal taxes		381	430		345
Deferred state taxes		35	45		57
Total deferred income taxes		416	475		402
Investment tax credit amortization		(5)	(5)		(5)
Income tax expense (benefit) from continuing operations		652	634		627
Total income tax expense included in Consolidated Statements of Operations		652	634		627
Net operating loss carry forward		(10)	4		15
Duke Energy Income from Continuing Operations Before Income Taxes [Abstract]
Total income from continuing operations before income taxes		1,866	1,800		1,708
Progress Energy [Member]
Current Income Tax Expense (Benefit), Continuing Operations [Abstract]
Current federal taxes		(436)	15		(193)
Current state taxes		(5)	(19)		1
Total current income taxes		(441)	(4)		(192)
Deferred Income Tax Expense (Benefit), Continuing Operations [Abstract]
Deferred federal taxes		664	486		694
Deferred state taxes		44	50		27
Total deferred income taxes		708	536		721
Investment tax credit amortization		(3)	(5)		(7)
Income tax expense (benefit) from continuing operations		264	527		522
Tax expense (benefit) from discontinued operations			1		(1)
Total income tax expense included in Consolidated Statements of Operations		264	528		521
Net operating loss carry forward		74	190		119
Duke Energy Income from Continuing Operations Before Income Taxes [Abstract]
Total income from continuing operations before income taxes		1,532	1,566		1,587
Duke Energy Progress [Member]
Current Income Tax Expense (Benefit), Continuing Operations [Abstract]
Current federal taxes		(95)	(59)		(56)
Current state taxes		2	(25)		(4)
Total current income taxes		(93)	(84)		(60)
Deferred Income Tax Expense (Benefit), Continuing Operations [Abstract]
Deferred federal taxes		378	350		334
Deferred state taxes		10	40		27
Total deferred income taxes		388	390		361
Investment tax credit amortization		(3)	(5)		(7)
Income tax expense (benefit) from continuing operations		292	301		294
Total income tax expense included in Consolidated Statements of Operations		292	301		294
Net operating loss carry forward		(1)	60		21
Duke Energy Income from Continuing Operations Before Income Taxes [Abstract]
Total income from continuing operations before income taxes		1,007	900		860
Duke Energy Florida [Member]
Current Income Tax Expense (Benefit), Continuing Operations [Abstract]
Current federal taxes		(188)	76		1
Current state taxes		(11)	22		(7)
Total current income taxes		(199)	98		(6)
Deferred Income Tax Expense (Benefit), Continuing Operations [Abstract]
Deferred federal taxes		194	199		290
Deferred state taxes		51	25		58
Total deferred income taxes		245	224		348
Income tax expense (benefit) from continuing operations		46	322		342
Total income tax expense included in Consolidated Statements of Operations		46	322		342
Net operating loss carry forward		36	49		84
Duke Energy Income from Continuing Operations Before Income Taxes [Abstract]
Total income from continuing operations before income taxes		758	873		941
Duke Energy Ohio [Member]
Current Income Tax Expense (Benefit), Continuing Operations [Abstract]
Current federal taxes		(37)	(7)		(18)
Current state taxes		2	(13)		(1)
Total current income taxes		(35)	(20)		(19)
Deferred Income Tax Expense (Benefit), Continuing Operations [Abstract]
Deferred federal taxes		99	88		96
Deferred state taxes		(4)	11		5
Total deferred income taxes		95	99		101
Investment tax credit amortization		(1)	(1)		(1)
Income tax expense (benefit) from continuing operations		59	78		81
Tax expense (benefit) from discontinued operations			(36)		22
Total income tax expense included in Consolidated Statements of Operations		59	42		103
Net operating loss carry forward		17	26		3
Duke Energy Income from Continuing Operations Before Income Taxes [Abstract]
Total income from continuing operations before income taxes		252	270		230
Duke Energy Indiana [Member]
Current Income Tax Expense (Benefit), Continuing Operations [Abstract]
Current federal taxes		128	7		(86)
Current state taxes		21	6		(12)
Total current income taxes		149	13		(98)
Deferred Income Tax Expense (Benefit), Continuing Operations [Abstract]
Deferred federal taxes		138	202		245
Deferred state taxes		14	11		17
Total deferred income taxes		152	213		262
Investment tax credit amortization			(1)		(1)
Income tax expense (benefit) from continuing operations		301	225		163
Total income tax expense included in Consolidated Statements of Operations		301	225		163
Net operating loss carry forward		42	58		45
Duke Energy Income from Continuing Operations Before Income Taxes [Abstract]
Total income from continuing operations before income taxes		655	606		$ 479
Piedmont Natural Gas [Member]
Current Income Tax Expense (Benefit), Continuing Operations [Abstract]
Current federal taxes	$ 4	(90)		$ 27		$ (1)
Current state taxes	(2)	(3)		12		1
Total current income taxes	2	(93)		39
Deferred Income Tax Expense (Benefit), Continuing Operations [Abstract]
Deferred federal taxes	24	147		79		78
Deferred state taxes	6	8		6		12
Total deferred income taxes	30	155		85		90
Income tax expense (benefit) from continuing operations	32	62		124		90
Total income tax expense included in Consolidated Statements of Operations		62
Net operating loss carry forward	(17)	79		(91)		(46)
Duke Energy Income from Continuing Operations Before Income Taxes [Abstract]
Total income from continuing operations before income taxes	86	201		317		227
Equity in losses of unconsolidated affiliates	$ (2)	$ 6		$ (29)		$ (34)
Previously Remitted Earnings [Member]
Deferred Income Tax Expense (Benefit), Continuing Operations [Abstract]
Tax expense (benefit) from discontinued operations			$ (95)