Employee Benefit Plans (Components of Net Periodic Pension Costs) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Qualified Pension Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	$ 45	$ 40	$ 90	$ 80
Interest cost on projected benefit obligation	75	82	150	164
Expected return on plan assets	(140)	(136)	(280)	(272)
Amortization of actuarial loss (gain)	33	36	66	72
Amortization of prior service (credit) cost	(8)	(6)	(16)	(12)
Other		2		4
Net periodic costs	5	18	10	36
Qualified Pension Plan [Member] | Duke Energy Carolinas [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	15	12	30	24
Interest cost on projected benefit obligation	18	20	36	40
Expected return on plan assets	(37)	(36)	(74)	(71)
Amortization of actuarial loss (gain)	7	8	14	16
Amortization of prior service (credit) cost	(2)	(2)	(4)	(4)
Net periodic costs	1	2	2	5
Qualified Pension Plan [Member] | Progress Energy [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	13	12	26	24
Interest cost on projected benefit obligation	22	25	46	50
Expected return on plan assets	(43)	(43)	(88)	(86)
Amortization of actuarial loss (gain)	11	14	22	28
Amortization of prior service (credit) cost	(1)	(1)	(2)	(2)
Other		1		2
Net periodic costs	2	8	4	16
Qualified Pension Plan [Member] | Duke Energy Progress [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	8	6	15	12
Interest cost on projected benefit obligation	10	12	21	24
Expected return on plan assets	(21)	(21)	(42)	(42)
Amortization of actuarial loss (gain)	5	6	10	12
Amortization of prior service (credit) cost	(1)		(1)
Other		1		1
Net periodic costs	1	4	3	7
Qualified Pension Plan [Member] | Duke Energy Florida [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	6	5	11	10
Interest cost on projected benefit obligation	12	13	25	26
Expected return on plan assets	(23)	(21)	(46)	(42)
Amortization of actuarial loss (gain)	6	7	12	14
Amortization of prior service (credit) cost	(1)		(1)
Net periodic costs		4	1	8
Qualified Pension Plan [Member] | Duke Energy Ohio [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	1	1	2	2
Interest cost on projected benefit obligation	4	5	9	10
Expected return on plan assets	(7)	(7)	(14)	(14)
Amortization of actuarial loss (gain)	1	1	2	2
Net periodic costs	(1)		(1)
Qualified Pension Plan [Member] | Duke Energy Indiana [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	3	2	5	4
Interest cost on projected benefit obligation	6	7	12	14
Expected return on plan assets	(11)	(11)	(21)	(22)
Amortization of actuarial loss (gain)	2	3	4	6
Net periodic costs		1		2
Qualified Pension Plan [Member] | Piedmont Natural Gas [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	2	3	4	6
Interest cost on projected benefit obligation	3	3	6	6
Expected return on plan assets	(6)	(6)	(12)	(12)
Amortization of actuarial loss (gain)	3	3	6	6
Amortization of prior service (credit) cost	(3)	(1)	(6)	(2)
Other		1		1
Net periodic costs	(1)	3	(2)	5
Non-Qualified Pension Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	1		1
Interest cost on projected benefit obligation	3	3	6	6
Amortization of actuarial loss (gain)	2	2	4	4
Amortization of prior service (credit) cost	(1)		(1)
Net periodic costs	5	5	10	10
Non-Qualified Pension Plan [Member] | Duke Energy Carolinas [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	1		1
Interest cost on projected benefit obligation		1		1
Net periodic costs	1	1	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	2	2
Amortization of actuarial loss (gain)		1		2
Amortization of prior service (credit) cost			1
Net periodic costs	1	2	3	4
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	1
Net periodic costs	1		1	1
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	1
Net periodic costs	1		1	1
Other Post-Retirement Benefit Plans [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	2	1	3	2
Interest cost on projected benefit obligation	7	9	14	18
Expected return on plan assets	(4)	(4)	(6)	(7)
Amortization of actuarial loss (gain)	2	2	3	4
Amortization of prior service (credit) cost	(5)	(29)	(10)	(58)
Net periodic costs	2	(21)	4	(41)
Other Post-Retirement Benefit Plans [Member] | Duke Energy Carolinas [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	1		1
Interest cost on projected benefit obligation	1	2	3	4
Expected return on plan assets	(2)	(2)	(4)	(4)
Amortization of actuarial loss (gain)	1	(1)	1	(2)
Amortization of prior service (credit) cost	(1)	(2)	(2)	(4)
Net periodic costs		(3)	(1)	(6)
Other Post-Retirement Benefit Plans [Member] | Progress Energy [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Interest cost on projected benefit obligation	2	3	6	7
Amortization of actuarial loss (gain)	1	5	1	10
Amortization of prior service (credit) cost	(2)	(21)	(4)	(42)
Net periodic costs	1	(13)	3	(25)
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	3	4
Amortization of actuarial loss (gain)		3		6
Amortization of prior service (credit) cost		(13)		(27)
Net periodic costs	2	(8)	3	(17)
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	2	2	3	4
Amortization of actuarial loss (gain)		2		4
Amortization of prior service (credit) cost	(2)	(7)	(3)	(15)
Net periodic costs		(3)		(7)
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		1
Amortization of actuarial loss (gain)		(1)		(1)
Net periodic costs	1	$ (1)	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		2
Amortization of actuarial loss (gain)	1		2
Net periodic costs	2		4
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)		(1)
Net periodic costs	$ (1)		$ (1)