Employee Benefit Plans (Components of Net Periodic Pension Costs) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Qualified Pension Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	$ 40	$ 37	$ 80	$ 73
Interest cost on projected benefit obligation	82	83	164	166
Expected return on plan assets	(136)	(129)	(272)	(258)
Amortization of actuarial loss (gain)	36	33	72	66
Amortization of prior service credit	(6)	(4)	(12)	(8)
Other	2	1	4	4
Net periodic costs	18	21	36	43
Qualified Pension Plan [Member] | Duke Energy Carolinas [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	12	12	24	24
Interest cost on projected benefit obligation	20	22	40	43
Expected return on plan assets	(36)	(36)	(71)	(71)
Amortization of actuarial loss (gain)	8	8	16	16
Amortization of prior service credit	(2)	(2)	(4)	(4)
Other				1
Net periodic costs	2	4	5	9
Qualified Pension Plan [Member] | Progress Energy [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	12	10	24	21
Interest cost on projected benefit obligation	25	27	50	53
Expected return on plan assets	(43)	(42)	(86)	(84)
Amortization of actuarial loss (gain)	14	13	28	27
Amortization of prior service credit	(1)	(1)	(2)	(2)
Other	1		2	1
Net periodic costs	8	7	16	16
Qualified Pension Plan [Member] | Duke Energy Progress [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	6	6	12	12
Interest cost on projected benefit obligation	12	13	24	25
Expected return on plan assets	(21)	(20)	(42)	(41)
Amortization of actuarial loss (gain)	6	5	12	11
Amortization of prior service credit		(1)		(1)
Other	1	1	1	1
Net periodic costs	4	4	7	7
Qualified Pension Plan [Member] | Duke Energy Florida [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	5	5	10	10
Interest cost on projected benefit obligation	13	14	26	28
Expected return on plan assets	(21)	(21)	(42)	(42)
Amortization of actuarial loss (gain)	7	7	14	14
Net periodic costs	4	5	8	10
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	5	5	10	10
Expected return on plan assets	(7)	(7)	(14)	(14)
Amortization of actuarial loss (gain)	1	1	2	2
Qualified Pension Plan [Member] | Duke Energy Indiana [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	2	2	4	4
Interest cost on projected benefit obligation	7	7	14	14
Expected return on plan assets	(11)	(11)	(22)	(21)
Amortization of actuarial loss (gain)	3	3	6	6
Net periodic costs	1	1	2	3
Qualified Pension Plan [Member] | Piedmont Natural Gas [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	3	2	6	5
Interest cost on projected benefit obligation	3	3	6	5
Expected return on plan assets	(6)	(6)	(12)	(12)
Amortization of actuarial loss (gain)	3	2	6	4
Amortization of prior service credit	(1)	(1)	(2)	(1)
Other	1		1
Net periodic costs	3		5	1
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	7
Amortization of actuarial loss (gain)	2	2	4	4
Net periodic costs	5	6	10	12
Non-Qualified Pension Plan [Member] | Duke Energy Carolinas [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Interest cost on projected benefit obligation	1	1	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	1
Net periodic costs	2	1	4	3
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	1	1	2	2
Interest cost on projected benefit obligation	9	9	18	17
Expected return on plan assets	(4)	(4)	(7)	(7)
Amortization of actuarial loss (gain)	2	2	4	3
Amortization of prior service credit	(29)	(36)	(58)	(71)
Net periodic costs	(21)	(28)	(41)	(56)
Other Post-Retirement Benefit Plans [Member] | Duke Energy Carolinas [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Interest cost on projected benefit obligation	2	2	4	4
Expected return on plan assets	(2)	(2)	(4)	(4)
Amortization of actuarial loss (gain)	(1)	(1)	(2)	(2)
Amortization of prior service credit	(2)	(3)	(4)	(6)
Net periodic costs	(3)	(4)	(6)	(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	3	7	7
Amortization of actuarial loss (gain)	5	6	10	11
Amortization of prior service credit	(21)	(25)	(42)	(51)
Net periodic costs	(13)	(16)	(25)	(33)
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	4	4
Amortization of actuarial loss (gain)	3	3	6	6
Amortization of prior service credit	(13)	(17)	(27)	(34)
Net periodic costs	(8)	(12)	(17)	(24)
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	1	4	3
Amortization of actuarial loss (gain)	2	3	4	5
Amortization of prior service credit	(7)	(9)	(15)	(18)
Net periodic costs	(3)	(5)	(7)	(10)
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)	(1)	(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		2
Expected return on plan assets		$ (1)		(1)
Amortization of actuarial loss (gain)				(1)
Other Post-Retirement Benefit Plans [Member] | Piedmont Natural Gas [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Interest cost on projected benefit obligation				1
Expected return on plan assets				$ (1)