Employee Benefit Plans (Components of Net Periodic Pension Costs) (Details) - USD ($) $ in Millions	2 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Oct. 31, 2016	Dec. 31, 2015	Oct. 31, 2015
Pension Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Amortization of Regulatory Asset		$ 7	$ 8		$ 9
Pension Plan [Member] | Qualified Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost		159	147		159
Interest cost		328	335		324
Expected return on plan assets		(545)	(519)		(516)
Amortization of actuarial loss (gain)		146	134		166
Amortization of prior service cost (credit)		(24)	(17)		(15)
Settlement charge		12	3
Other		8	8		8
Net periodic costs		84	91		126
Pension Plan [Member] | Nonqualified Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost		2	2		3
Interest cost		13	14		13
Amortization of actuarial loss (gain)		8	8		6
Amortization of prior service cost (credit)		(2)	(1)		(1)
Net periodic costs		21	23		21
Pension Plan [Member] | Duke Energy Carolinas [Member] | Qualified Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost		48	48		50
Interest cost		79	86		83
Expected return on plan assets		(142)	(142)		(139)
Amortization of actuarial loss (gain)		31	33		39
Amortization of prior service cost (credit)		(8)	(8)		(7)
Other		2	2		2
Net periodic costs		10	19		28
Pension Plan [Member] | Duke Energy Carolinas [Member] | Nonqualified Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost		1
Interest cost		1	1		1
Amortization of actuarial loss (gain)			1
Net periodic costs		2	2		1
Pension Plan [Member] | Progress Energy [Member] | Qualified Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost		45	42		44
Interest cost		100	106		104
Expected return on plan assets		(167)	(168)		(171)
Amortization of actuarial loss (gain)		52	51		65
Amortization of prior service cost (credit)		(3)	(3)		(3)
Other		2	3		3
Net periodic costs		29	31		42
Pension Plan [Member] | Progress Energy [Member] | Nonqualified Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost					1
Interest cost		5	5		4
Amortization of actuarial loss (gain)		2	1		2
Amortization of prior service cost (credit)					(1)
Net periodic costs		7	6		6
Pension Plan [Member] | Duke Energy Progress [Member] | Qualified Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost		26	24		23
Interest cost		47	49		48
Expected return on plan assets		(82)	(82)		(79)
Amortization of actuarial loss (gain)		23	23		33
Amortization of prior service cost (credit)		(2)	(2)		(2)
Other		1	1		1
Net periodic costs		13	13		24
Pension Plan [Member] | Duke Energy Progress [Member] | Nonqualified Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Interest cost		1	1		1
Amortization of actuarial loss (gain)		1	1		1
Net periodic costs		2	2		2
Pension Plan [Member] | Duke Energy Florida [Member] | Qualified Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost		19	19		20
Interest cost		53	55		54
Expected return on plan assets		(85)	(84)		(87)
Amortization of actuarial loss (gain)		29	29		31
Amortization of prior service cost (credit)		(1)	(1)		(1)
Other		1	1		1
Net periodic costs		16	19		18
Pension Plan [Member] | Duke Energy Florida [Member] | Nonqualified Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Interest cost		2	2		2
Amortization of actuarial loss (gain)		1	1		2
Net periodic costs		3	3		4
Pension Plan [Member] | Duke Energy Ohio [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Amortization of Regulatory Asset		3	4		4
Pension Plan [Member] | Duke Energy Ohio [Member] | Qualified Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost		4	4		4
Interest cost		18	19		18
Expected return on plan assets		(27)	(27)		(26)
Amortization of actuarial loss (gain)		5	4		7
Amortization of prior service cost (credit)		(1)
Other			1
Net periodic costs		(1)	1		3
Pension Plan [Member] | Duke Energy Indiana [Member] | Qualified Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost		9	9		10
Interest cost		26	28		27
Expected return on plan assets		(42)	(42)		(42)
Amortization of actuarial loss (gain)		12	11		13
Amortization of prior service cost (credit)		(2)	(1)		1
Other		1	1		1
Net periodic costs		4	6		10
Pension Plan [Member] | Duke Energy Indiana [Member] | Nonqualified Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Amortization of actuarial loss (gain)					1
Net periodic costs					1
Pension Plan [Member] | Piedmont Natural Gas [Member] | Qualified Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	$ 2	10		$ 11		$ 11
Interest cost	2	14		9		12
Expected return on plan assets	(4)	(24)		(24)		(24)
Amortization of actuarial loss (gain)	2	11		8		9
Amortization of prior service cost (credit)	(1)	(2)		(2)		(2)
Settlement charge	3	12
Other		1
Net periodic costs	$ 4	22		2		6
Pension Plan [Member] | Piedmont Natural Gas [Member] | Nonqualified Plan [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Amortization of prior service cost (credit)						1
Settlement charge				1
Net periodic costs				1		1
Other Post-Retirement Benefit Plans [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost		4	3		6
Interest cost		34	35		36
Expected return on plan assets		(14)	(12)		(13)
Amortization of actuarial loss (gain)		10	6		16
Amortization of prior service cost (credit)		(115)	(141)		(140)
Curtailment credit		(30)
Net periodic costs		(111)	(109)		(95)
Amortization of Regulatory Asset		7	8		10
Other Post-Retirement Benefit Plans [Member] | Duke Energy Carolinas [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost		1	1		1
Interest cost		8	8		9
Expected return on plan assets		(8)	(8)		(8)
Amortization of actuarial loss (gain)		(2)	(3)		(2)
Amortization of prior service cost (credit)		(10)	(14)		(14)
Curtailment credit		(4)
Net periodic costs		(15)	(16)		(14)
Other Post-Retirement Benefit Plans [Member] | Progress Energy [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost			1		1
Interest cost		13	15		15
Amortization of actuarial loss (gain)		21	22		28
Amortization of prior service cost (credit)		(84)	(103)		(102)
Curtailment credit		(16)
Net periodic costs		(66)	(65)		(58)
Other Post-Retirement Benefit Plans [Member] | Duke Energy Progress [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost					1
Interest cost		7	8		8
Amortization of actuarial loss (gain)		12	13		18
Amortization of prior service cost (credit)		(54)	(68)		(68)
Net periodic costs		(35)	(47)		(41)
Other Post-Retirement Benefit Plans [Member] | Duke Energy Florida [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost			1		1
Interest cost		6	7		7
Amortization of actuarial loss (gain)		9	9		10
Amortization of prior service cost (credit)		(30)	(35)		(35)
Curtailment credit		(16)
Net periodic costs		(31)	(18)		(17)
Other Post-Retirement Benefit Plans [Member] | Duke Energy Ohio [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Interest cost		1	1		2
Expected return on plan assets					(1)
Amortization of actuarial loss (gain)		(2)	(2)		(2)
Curtailment credit		(2)
Net periodic costs		(3)	(1)		(1)
Amortization of Regulatory Asset		2	2		3
Other Post-Retirement Benefit Plans [Member] | Duke Energy Indiana [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost					1
Interest cost		3	4		4
Expected return on plan assets		(1)	(1)		(1)
Amortization of actuarial loss (gain)		(1)	(1)		(2)
Amortization of prior service cost (credit)		(1)	(1)
Curtailment credit		(2)
Net periodic costs		(2)	$ 1		$ 2
Other Post-Retirement Benefit Plans [Member] | Piedmont Natural Gas [Member]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost		1		1		1
Interest cost		1		1		2
Expected return on plan assets		(2)		(2)		(2)
Amortization of actuarial loss (gain)		1		1
Net periodic costs		$ 1		$ 1		$ 1