Employee Benefit Plans (Components of Net Periodic Pension Costs) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Qualified Pension Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	$ 40	$ 36	$ 120	$ 109
Interest cost on projected benefit obligation	82	83	246	249
Expected return on plan assets	(136)	(128)	(408)	(386)
Amortization of actuarial loss (gain)	36	33	108	99
Amortization of prior service credit	(6)	(4)	(18)	(12)
Other	2	2	6	6
Net periodic costs	18	22	54	65
Qualified Pension Plan [Member] | Duke Energy Carolinas [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	12	12	36	36
Interest cost on projected benefit obligation	20	21	60	64
Expected return on plan assets	(35)	(35)	(106)	(106)
Amortization of actuarial loss (gain)	8	8	24	24
Amortization of prior service credit	(2)	(2)	(6)	(6)
Other		1		2
Net periodic costs	3	5	8	14
Qualified Pension Plan [Member] | Progress Energy [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	12	11	36	32
Interest cost on projected benefit obligation	25	27	75	80
Expected return on plan assets	(43)	(42)	(129)	(126)
Amortization of actuarial loss (gain)	14	14	42	41
Amortization of prior service credit	(1)	(1)	(3)	(3)
Other	1	1	3	2
Net periodic costs	8	10	24	26
Qualified Pension Plan [Member] | Duke Energy Progress [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	6	6	18	18
Interest cost on projected benefit obligation	12	12	36	37
Expected return on plan assets	(21)	(21)	(63)	(62)
Amortization of actuarial loss (gain)	6	6	18	17
Amortization of prior service credit				(1)
Other			1	1
Net periodic costs	3	3	10	10
Qualified Pension Plan [Member] | Duke Energy Florida [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	5	4	15	14
Interest cost on projected benefit obligation	13	14	39	42
Expected return on plan assets	(21)	(21)	(63)	(63)
Amortization of actuarial loss (gain)	7	7	21	21
Amortization of prior service credit		(1)		(1)
Other		1		1
Net periodic costs	4	4	12	14
Qualified Pension Plan [Member] | Duke Energy Ohio [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	1	1	3	3
Interest cost on projected benefit obligation	4	5	14	15
Expected return on plan assets	(7)	(6)	(21)	(20)
Amortization of actuarial loss (gain)	1	1	3	3
Net periodic costs	(1)	1	(1)	1
Qualified Pension Plan [Member] | Duke Energy Indiana [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	2	2	6	6
Interest cost on projected benefit obligation	7	7	21	21
Expected return on plan assets	(11)	(10)	(33)	(31)
Amortization of actuarial loss (gain)	3	3	9	9
Net periodic costs	1	2	3	5
Qualified Pension Plan [Member] | Piedmont Natural Gas [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	3	3	9	8
Interest cost on projected benefit obligation	3	2	9	7
Expected return on plan assets	(6)	(6)	(18)	(18)
Amortization of actuarial loss (gain)	3	2	9	6
Amortization of prior service credit	(1)	(1)	(3)	(2)
Other			1
Net periodic costs	2		7	1
Non-Qualified Pension Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost		1		2
Interest cost on projected benefit obligation	4	4	10	11
Amortization of actuarial loss (gain)	2	2	6	6
Amortization of prior service credit		(1)		(1)
Net periodic costs	6	6	16	18
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
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	2	3	4
Amortization of actuarial loss (gain)	1	1	3	2
Net periodic costs	2	3	6	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		2	1
Amortization of actuarial loss (gain)		1		1
Net periodic costs	1	1	2	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		2	1
Amortization of actuarial loss (gain)		1		1
Net periodic costs	1	1	2	2
Other Post-Retirement Benefit Plans [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	1		3	2
Interest cost on projected benefit obligation	9	9	27	26
Expected return on plan assets	(3)	(2)	(10)	(9)
Amortization of actuarial loss (gain)	2	2	6	5
Amortization of prior service credit	(29)	(35)	(87)	(106)
Net periodic costs	(20)	(26)	(61)	(82)
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	6	6
Expected return on plan assets	(2)	(2)	(6)	(6)
Amortization of actuarial loss (gain)			(2)	(2)
Amortization of prior service credit	(2)	(4)	(6)	(10)
Net periodic costs	(2)	(4)	(8)	(12)
Other Post-Retirement Benefit Plans [Member] | Progress Energy [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost		1		1
Interest cost on projected benefit obligation	4	4	11	11
Expected return on plan assets		(1)		(1)
Amortization of actuarial loss (gain)	5	5	15	16
Amortization of prior service credit	(21)	(26)	(63)	(77)
Net periodic costs	(12)	(17)	(37)	(50)
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	6	6
Amortization of actuarial loss (gain)	3	3	9	9
Amortization of prior service credit	(14)	(16)	(41)	(50)
Net periodic costs	(9)	(11)	(26)	(35)
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	3	6	6
Amortization of actuarial loss (gain)	2	2	6	7
Amortization of prior service credit	(8)	(8)	(23)	(26)
Net periodic costs	(4)	(3)	(11)	(13)
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)	(1)	(2)
Net periodic costs		(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	1	1	3
Expected return on plan assets				(1)
Amortization of actuarial loss (gain)				(1)
Amortization of prior service credit		(1)		(1)
Net periodic costs	$ 1		$ 1
Other Post-Retirement Benefit Plans [Member] | Piedmont Natural Gas [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost		1		1
Interest cost on projected benefit obligation				1
Expected return on plan assets				(1)
Net periodic costs		$ 1		$ 1