Employee Benefit Plans (Components of Net Periodic Pension Costs) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Qualified Pension Plans [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	$ 36	$ 40
Interest cost on projected benefit obligation	83	82
Expected return on plan assets	(129)	(129)
Amortization of actuarial loss (gain)	33	43
Amortization of prior service cost (credit)	(4)	(4)
Other	3	2
Net periodic costs	22	34
Qualified Pension Plans [Member] | Duke Energy Carolinas [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	12	13
Interest cost on projected benefit obligation	21	21
Expected return on plan assets	(35)	(36)
Amortization of actuarial loss (gain)	8	10
Amortization of prior service cost (credit)	(2)	(2)
Other	1	1
Net periodic costs	5	7
Qualified Pension Plans [Member] | Progress Energy [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	11	11
Interest cost on projected benefit obligation	26	26
Expected return on plan assets	(42)	(43)
Amortization of actuarial loss (gain)	14	17
Amortization of prior service cost (credit)	(1)	(1)
Other	1	1
Net periodic costs	9	11
Qualified Pension Plans [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)	(20)
Amortization of actuarial loss (gain)	6	8
Net periodic costs	3	6
Qualified Pension Plans [Member] | Duke Energy Florida [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	5	5
Interest cost on projected benefit obligation	14	14
Expected return on plan assets	(21)	(22)
Amortization of actuarial loss (gain)	7	8
Net periodic costs	5	5
Qualified Pension Plans [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)	(6)
Amortization of actuarial loss (gain)	1	2
Net periodic costs		2
Qualified Pension Plans [Member] | Duke Energy Indiana [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	2	3
Interest cost on projected benefit obligation	7	7
Expected return on plan assets	(10)	(10)
Amortization of actuarial loss (gain)	3	3
Net periodic costs	2	3
Other Post-Retirement Benefit Plans [Member]
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	1	2
Interest cost on projected benefit obligation	8	9
Expected return on plan assets	(3)	(3)
Amortization of actuarial loss (gain)	1	6
Amortization of prior service cost (credit)	(35)	(35)
Net periodic costs	(28)	(21)
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)
Amortization of prior service cost (credit)	(3)	(4)
Net periodic costs	(4)	(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	7
Amortization of prior service cost (credit)	(26)	(26)
Net periodic costs	(17)	(15)
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	5
Amortization of prior service cost (credit)	(17)	(17)
Net periodic costs	(12)	(10)
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	3
Amortization of prior service cost (credit)	(9)	(9)
Net periodic costs	(5)	$ (4)
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)