Employee Benefit Plans (Components of Net Periodic Pension Costs) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Qualified Pension Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	$ 47	$ 40	$ 137	$ 120
Interest cost on projected benefit obligation	74	82	224	246
Expected return on plan assets	(140)	(136)	(420)	(408)
Amortization of actuarial loss (gain)	33	36	99	108
Amortization of prior service (credit) cost	(8)	(6)	(24)	(18)
Other		2		6
Net periodic costs	6	18	16	54
Qualified Pension Plan [Member] | Duke Energy Carolinas [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	15	12	45	36
Interest cost on projected benefit obligation	18	20	54	60
Expected return on plan assets	(37)	(35)	(111)	(106)
Amortization of actuarial loss (gain)	7	8	21	24
Amortization of prior service (credit) cost	(2)	(2)	(6)	(6)
Net periodic costs	1	3	3	8
Qualified Pension Plan [Member] | Progress Energy [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	13	12	39	36
Interest cost on projected benefit obligation	24	25	70	75
Expected return on plan assets	(45)	(43)	(133)	(129)
Amortization of actuarial loss (gain)	11	14	33	42
Amortization of prior service (credit) cost	(1)	(1)	(3)	(3)
Other		1		3
Net periodic costs	2	8	6	24
Qualified Pension Plan [Member] | Duke Energy Progress [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	7	6	22	18
Interest cost on projected benefit obligation	10	12	31	36
Expected return on plan assets	(21)	(21)	(63)	(63)
Amortization of actuarial loss (gain)	6	6	16	18
Amortization of prior service (credit) cost			(1)
Other				1
Net periodic costs	2	3	5	10
Qualified Pension Plan [Member] | Duke Energy Florida [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	5	5	16	15
Interest cost on projected benefit obligation	13	13	38	39
Expected return on plan assets	(23)	(21)	(69)	(63)
Amortization of actuarial loss (gain)	6	7	18	21
Amortization of prior service (credit) cost			(1)
Net periodic costs	1	4	2	12
Qualified Pension Plan [Member] | Duke Energy Ohio [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	2	1	4	3
Interest cost on projected benefit obligation	4	4	13	14
Expected return on plan assets	(7)	(7)	(21)	(21)
Amortization of actuarial loss (gain)	1	1	3	3
Net periodic costs		(1)	(1)	(1)
Qualified Pension Plan [Member] | Duke Energy Indiana [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	2	2	7	6
Interest cost on projected benefit obligation	6	7	18	21
Expected return on plan assets	(10)	(11)	(31)	(33)
Amortization of actuarial loss (gain)	2	3	6	9
Net periodic costs		1		3
Qualified Pension Plan [Member] | Piedmont Natural Gas [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	2	3	6	9
Interest cost on projected benefit obligation	3	3	9	9
Expected return on plan assets	(6)	(6)	(18)	(18)
Amortization of actuarial loss (gain)	3	3	9	9
Amortization of prior service (credit) cost	(3)	(1)	(9)	(3)
Other				1
Net periodic costs	(1)	2	(3)	7
Non-Qualified Pension Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost			1
Interest cost on projected benefit obligation	3	4	9	10
Amortization of actuarial loss (gain)	2	2	6	6
Amortization of prior service (credit) cost			(1)
Net periodic costs	5	6	15	16
Non-Qualified Pension Plan [Member] | Duke Energy Carolinas [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost			1
Interest cost on projected benefit obligation				1
Net periodic costs			1	1
Non-Qualified Pension Plan [Member] | Progress Energy [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Interest cost on projected benefit obligation	1	1	3	3
Amortization of actuarial loss (gain)		1		3
Amortization of prior service (credit) cost			1
Net periodic costs	1	2	4	6
Non-Qualified Pension Plan [Member] | Duke Energy Progress [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Interest cost on projected benefit obligation		1	1	2
Net periodic costs		1	1	2
Non-Qualified Pension Plan [Member] | Duke Energy Florida [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Interest cost on projected benefit obligation		1	1	2
Net periodic costs		1	1	2
Other Post-Retirement Benefit Plans [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	2	1	5	3
Interest cost on projected benefit obligation	7	9	21	27
Expected return on plan assets	(4)	(3)	(10)	(10)
Amortization of actuarial loss (gain)	2	2	5	6
Amortization of prior service (credit) cost	(5)	(29)	(15)	(87)
Net periodic costs	2	(20)	6	(61)
Other Post-Retirement Benefit Plans [Member] | Duke Energy Carolinas [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost			1
Interest cost on projected benefit obligation	2	2	5	6
Expected return on plan assets	(2)	(2)	(6)	(6)
Amortization of actuarial loss (gain)	1		2	(2)
Amortization of prior service (credit) cost	(1)	(2)	(3)	(6)
Net periodic costs		(2)	(1)	(8)
Other Post-Retirement Benefit Plans [Member] | Progress Energy [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Interest cost on projected benefit obligation	3	4	9	11
Amortization of actuarial loss (gain)		5	1	15
Amortization of prior service (credit) cost	(2)	(21)	(6)	(63)
Net periodic costs	1	(12)	4	(37)
Other Post-Retirement Benefit Plans [Member] | Duke Energy Progress [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Interest cost on projected benefit obligation	2	2	5	6
Amortization of actuarial loss (gain)		3		9
Amortization of prior service (credit) cost		(14)		(41)
Net periodic costs	2	(9)	5	(26)
Other Post-Retirement Benefit Plans [Member] | Duke Energy Florida [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Interest cost on projected benefit obligation	1	2	4	6
Amortization of actuarial loss (gain)		2		6
Amortization of prior service (credit) cost	(1)	(8)	(4)	(23)
Net periodic costs		(4)		(11)
Other Post-Retirement Benefit Plans [Member] | Duke Energy Ohio [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Interest cost on projected benefit obligation			1
Amortization of actuarial loss (gain)				(1)
Net periodic costs			1	(1)
Other Post-Retirement Benefit Plans [Member] | Duke Energy Indiana [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Interest cost on projected benefit obligation	1	1	3	1
Amortization of actuarial loss (gain)	1		3
Net periodic costs	$ 2	$ 1	6	$ 1
Other Post-Retirement Benefit Plans [Member] | Piedmont Natural Gas [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Amortization of prior service (credit) cost			(1)
Net periodic costs			$ (1)