Income Taxes (Effective Tax Rates) (Details) - USD ($) $ in Millions	2 Months Ended	3 Months Ended				12 Months Ended
	Dec. 31, 2016	Dec. 31, 2018	Sep. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Oct. 31, 2016
Reconciliation of Income Tax Expense at the U.S. Federal Statutory Tax Rate to the Actual Tax Expense from Continuing Operations [Abstract]
Income tax expense, computed at the statutory rate						$ 645	$ 1,493	$ 1,307
State income tax, net of federal income tax effect						30	69	64
Amortization of excess deferred income tax						(61)
AFUDC equity income						(42)	(81)	(70)
AFUDC equity depreciation						31
Renewable energy production tax credits						(129)	(132)	(97)
Other tax credits						(28)
Tax Act						20	(112)
Audit Adjustment								5
Tax true up							(52)	(14)
Other items, net						(18)	11	(39)
Income tax expense (benefit) from continuing operations						$ 448	$ 1,196	$ 1,156
Effective tax rate						14.60%	28.00%	31.00%
Duke Energy Carolinas [Member]
Reconciliation of Income Tax Expense at the U.S. Federal Statutory Tax Rate to the Actual Tax Expense from Continuing Operations [Abstract]
Income tax expense, computed at the statutory rate						$ 288	$ 653	$ 630
State income tax, net of federal income tax effect						14	36	46
AFUDC equity income						(15)	(37)	(36)
AFUDC equity depreciation						18
Other tax credits						(7)
Tax Act			$ 1		$ 15	1	15
Audit Adjustment								3
Tax true up							(24)	(14)
Other items, net						4	9	5
Income tax expense (benefit) from continuing operations						$ 303	$ 652	$ 634
Effective tax rate						22.10%	34.90%	35.20%
Progress Energy [Member]
Reconciliation of Income Tax Expense at the U.S. Federal Statutory Tax Rate to the Actual Tax Expense from Continuing Operations [Abstract]
Income tax expense, computed at the statutory rate						$ 263	$ 536	$ 548
State income tax, net of federal income tax effect						13	25	20
Amortization of excess deferred income tax						(55)
AFUDC equity income						(22)	(32)	(26)
AFUDC equity depreciation						9
Other tax credits						(13)
Tax Act		$ 19	5	$ 1	(246)	25	(246)
Tax true up							(19)	(11)
Other items, net						(2)		(4)
Income tax expense (benefit) from continuing operations						$ 218	$ 264	$ 527
Effective tax rate						17.40%	17.20%	33.70%
Duke Energy Progress [Member]
Reconciliation of Income Tax Expense at the U.S. Federal Statutory Tax Rate to the Actual Tax Expense from Continuing Operations [Abstract]
Income tax expense, computed at the statutory rate						$ 174	$ 353	$ 315
State income tax, net of federal income tax effect						(17)	8	10
Amortization of excess deferred income tax						(1)
AFUDC equity income						(12)	(17)	(17)
AFUDC equity depreciation						5
Other tax credits						(5)
Tax Act		15	4		(40)	19	(40)
Tax true up							(13)	(3)
Other items, net						(3)	1	(4)
Income tax expense (benefit) from continuing operations						$ 160	$ 292	$ 301
Effective tax rate						19.30%	29.00%	33.40%
Duke Energy Florida [Member]
Reconciliation of Income Tax Expense at the U.S. Federal Statutory Tax Rate to the Actual Tax Expense from Continuing Operations [Abstract]
Income tax expense, computed at the statutory rate						$ 137	$ 265	$ 306
State income tax, net of federal income tax effect						28	26	30
Amortization of excess deferred income tax						(54)
AFUDC equity income						(10)	(16)	(9)
AFUDC equity depreciation						4
Other tax credits						(8)
Tax Act		(2)	$ 2		(226)		(226)
Tax true up							(7)	(9)
Other items, net						4	4	4
Income tax expense (benefit) from continuing operations						$ 101	$ 46	$ 322
Effective tax rate						15.40%	6.10%	36.90%
Duke Energy Ohio [Member]
Reconciliation of Income Tax Expense at the U.S. Federal Statutory Tax Rate to the Actual Tax Expense from Continuing Operations [Abstract]
Income tax expense, computed at the statutory rate						$ 46	$ 88	$ 95
State income tax, net of federal income tax effect						2	(1)	(2)
Amortization of excess deferred income tax						(3)
AFUDC equity income						(2)	(4)	(2)
AFUDC equity depreciation						1
Other tax credits						(1)
Tax Act		$ 2			(23)	2	(23)
Tax true up							(5)	(16)
Other items, net						(2)	4	3
Income tax expense (benefit) from continuing operations						$ 43	$ 59	$ 78
Effective tax rate						19.60%	23.40%	28.90%
Duke Energy Indiana [Member]
Reconciliation of Income Tax Expense at the U.S. Federal Statutory Tax Rate to the Actual Tax Expense from Continuing Operations [Abstract]
Income tax expense, computed at the statutory rate						$ 109	$ 229	$ 212
State income tax, net of federal income tax effect						20	23	11
Amortization of excess deferred income tax						(2)
AFUDC equity income						(2)	(8)	(6)
AFUDC equity depreciation						4
Other tax credits						(1)
Tax Act					$ 55		55
Tax true up							(6)	2
Other items, net							8	6
Income tax expense (benefit) from continuing operations						$ 128	$ 301	$ 225
Effective tax rate						24.60%	46.00%	37.10%
Piedmont Natural Gas [Member]
Reconciliation of Income Tax Expense at the U.S. Federal Statutory Tax Rate to the Actual Tax Expense from Continuing Operations [Abstract]
Income tax expense, computed at the statutory rate	$ 30					$ 35	$ 70		$ 111
State income tax, net of federal income tax effect	1					4	3		11
Other tax credits						(3)
Tax Act							(12)
Other items, net	1					1	1		2
Income tax expense (benefit) from continuing operations	$ 32					$ 37	$ 62		$ 124
Effective tax rate	37.20%					22.30%	30.80%		39.10%