Income Taxes (Effective Tax Rates) (Details) - USD ($) $ in Millions	2 Months Ended	3 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Oct. 31, 2016	Dec. 31, 2015	Oct. 31, 2015
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 of 35%			$ 1,493	$ 1,307		$ 1,369
State income tax, net of federal income tax effect			69	64		109
AFUDC equity income			(81)	(70)		(58)
Renewable energy production tax credits			(132)	(97)		(72)
Tax Act			(112)
Audit Adjustment				5		(22)
Tax true-up			(52)	(14)		2
Other items, net			11	(39)		(72)
Income tax expense (benefit) from continuing operations			$ 1,196	$ 1,156		$ 1,256
Effective tax rate			28.00%	31.00%		32.10%
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 of 35%			$ 653	$ 630		$ 598
State income tax, net of federal income tax effect			36	46		46
AFUDC equity income			(37)	(36)		(34)
Tax Act		$ 15	15
Audit Adjustment				3
Tax true-up			(24)	(14)		2
Other items, net			9	5		15
Income tax expense (benefit) from continuing operations			$ 652	$ 634		$ 627
Effective tax rate			34.90%	35.20%		36.70%
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 of 35%			$ 536	$ 548		$ 555
State income tax, net of federal income tax effect			25	20		18
AFUDC equity income			(32)	(26)		(19)
Renewable energy production tax credits						(1)
Tax Act		(246)	(246)
Audit Adjustment						(23)
Tax true-up			(19)	(11)		(3)
Other items, net				(4)		(5)
Income tax expense (benefit) from continuing operations			$ 264	$ 527		$ 522
Effective tax rate			17.20%	33.70%		32.90%
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 of 35%			$ 353	$ 315		$ 302
State income tax, net of federal income tax effect			8	10		15
AFUDC equity income			(17)	(17)		(17)
Tax Act		(40)	(40)
Audit Adjustment						1
Tax true-up			(13)	(3)		(4)
Other items, net			1	(4)		(3)
Income tax expense (benefit) from continuing operations			$ 292	$ 301		$ 294
Effective tax rate			29.00%	33.40%		34.20%
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 of 35%			$ 265	$ 306		$ 330
State income tax, net of federal income tax effect			26	30		33
AFUDC equity income			(16)	(9)		(3)
Tax Act		(226)	(226)
Audit Adjustment						(24)
Tax true-up			(7)	(9)		2
Other items, net			4	4		4
Income tax expense (benefit) from continuing operations			$ 46	$ 322		$ 342
Effective tax rate			6.10%	36.90%		36.30%
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 of 35%			$ 88	$ 95		$ 81
State income tax, net of federal income tax effect			(1)	(2)		2
AFUDC equity income			(4)	(2)		(1)
Tax Act		(23)	(23)
Tax true-up			(5)	(16)		(5)
Other items, net			4	3		4
Income tax expense (benefit) from continuing operations			$ 59	$ 78		$ 81
Effective tax rate			23.40%	28.90%		35.20%
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 of 35%			$ 229	$ 212		$ 168
State income tax, net of federal income tax effect			23	11		2
AFUDC equity income			(8)	(6)		(4)
Tax Act		$ 55	55
Tax true-up			(6)	2		(9)
Other items, net			8	6		6
Income tax expense (benefit) from continuing operations			$ 301	$ 225		$ 163
Effective tax rate			46.00%	37.10%		34.00%
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 of 35%	$ 30		$ 70		$ 111		$ 79
State income tax, net of federal income tax effect	1		3		11		9
Tax Act			(12)
Other items, net	1		1		2		2
Income tax expense (benefit) from continuing operations	$ 32		$ 62		$ 124		$ 90
Effective tax rate	37.20%		30.80%		39.10%		39.70%