Employee Benefit Plans (Components of Net Periodic Pension Costs) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Qualified Pension Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	$ 40	$ 36
Interest cost on projected benefit obligation	82	83
Expected return on plan assets	(136)	(129)
Amortization of actuarial loss (gain)	36	33
Amortization of prior service credit	(6)	(4)
Other	2	3
Net periodic costs	18	22
Qualified Pension Plan [Member] | Duke Energy Carolinas [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	12	12
Interest cost on projected benefit obligation	20	21
Expected return on plan assets	(35)	(35)
Amortization of actuarial loss (gain)	8	8
Amortization of prior service credit	(2)	(2)
Other		1
Net periodic costs	3	5
Qualified Pension Plan [Member] | Progress Energy [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	12	11
Interest cost on projected benefit obligation	25	26
Expected return on plan assets	(43)	(42)
Amortization of actuarial loss (gain)	14	14
Amortization of prior service credit	(1)	(1)
Other	1	1
Net periodic costs	8	9
Qualified Pension Plan [Member] | Duke Energy Progress [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	6	6
Interest cost on projected benefit obligation	12	12
Expected return on plan assets	(21)	(21)
Amortization of actuarial loss (gain)	6	6
Net periodic costs	3	3
Qualified Pension Plan [Member] | Duke Energy Florida [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	5	5
Interest cost on projected benefit obligation	13	14
Expected return on plan assets	(21)	(21)
Amortization of actuarial loss (gain)	7	7
Net periodic costs	4	5
Qualified Pension Plan [Member] | Duke Energy Ohio [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	1	1
Interest cost on projected benefit obligation	5	5
Expected return on plan assets	(7)	(7)
Amortization of actuarial loss (gain)	1	1
Qualified Pension Plan [Member] | Duke Energy Indiana [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	2	2
Interest cost on projected benefit obligation	7	7
Expected return on plan assets	(11)	(10)
Amortization of actuarial loss (gain)	3	3
Net periodic costs	1	2
Qualified Pension Plan [Member] | Piedmont Natural Gas [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	3	3
Interest cost on projected benefit obligation	3	2
Expected return on plan assets	(6)	(6)
Amortization of actuarial loss (gain)	3	2
Amortization of prior service credit	(1)
Net periodic costs	2	1
Other Post-Retirement Benefit Plans [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	1	1
Interest cost on projected benefit obligation	9	8
Expected return on plan assets	(3)	(3)
Amortization of actuarial loss (gain)	2	1
Amortization of prior service credit	(29)	(35)
Net periodic costs	(20)	(28)
Other Post-Retirement Benefit Plans [Member] | Duke Energy Carolinas [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Interest cost on projected benefit obligation	2	2
Expected return on plan assets	(2)	(2)
Amortization of actuarial loss (gain)	(1)	(1)
Amortization of prior service credit	(2)	(3)
Net periodic costs	(3)	(4)
Other Post-Retirement Benefit Plans [Member] | Progress Energy [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Interest cost on projected benefit obligation	4	4
Amortization of actuarial loss (gain)	5	5
Amortization of prior service credit	(21)	(26)
Net periodic costs	(12)	(17)
Other Post-Retirement Benefit Plans [Member] | Duke Energy Progress [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Interest cost on projected benefit obligation	2	2
Amortization of actuarial loss (gain)	3	3
Amortization of prior service credit	(14)	(17)
Net periodic costs	(9)	(12)
Other Post-Retirement Benefit Plans [Member] | Duke Energy Florida [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Interest cost on projected benefit obligation	2	2
Amortization of actuarial loss (gain)	2	2
Amortization of prior service credit	(8)	(9)
Net periodic costs	$ (4)	(5)
Other Post-Retirement Benefit Plans [Member] | Duke Energy Indiana [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Interest cost on projected benefit obligation		1
Amortization of actuarial loss (gain)		$ (1)