Employee Benefit Plans (Components Of Net Periodic Pension Costs) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2012		Jun. 30, 2011		Jun. 30, 2012		Jun. 30, 2011
Defined Contribution Plan, Cost Recognized	$ 19				$ 47		$ 50
Duke Energy Carolinas [Member]
Defined Contribution Plan, Cost Recognized	9		8		20		20
Duke Energy Ohio [Member]
Defined Contribution Plan, Cost Recognized	1		1		2		2
Duke Energy Indiana [Member]
Defined Contribution Plan, Cost Recognized	1		2		3		5
Qualified Pension Plans [Member]
Service cost	22		24		45		48
Interest cost on benefit obligation	59		58		120		116
Expected return on plan assets	(94)		(96)		(188)		(192)
Amortization of prior service cost (credit)	2		1		3		3
Amortization of net transition liability	0		0		0		0
Amortization of loss (gain)	25		19		49		38
Other	1		5		2		9
Net periodic costs	15	[1]	11	[1]	31	[2]	22	[2]
Regulatory asset amortization	4		3		7		7
Qualified Pension Plans [Member] | Duke Energy Carolinas [Member]
Service cost	8		10		17		19
Interest cost on benefit obligation	22		22		45		43
Expected return on plan assets	(37)		(38)		(73)		(75)
Amortization of prior service cost (credit)	1		0		1		0
Amortization of net transition liability	0		0		0		0
Amortization of loss (gain)	12		9		23		18
Other	1		2		1		4
Net periodic costs	7		5		14		9
Qualified Pension Plans [Member] | Duke Energy Ohio [Member]
Service cost	1		1		3		3
Interest cost on benefit obligation	8		8		16		16
Expected return on plan assets	(11)		(11)		(22)		(22)
Amortization of prior service cost (credit)					5		4
Amortization of loss (gain)	3		2
Other	0		1		0		1
Net periodic costs	1	[3]	1	[3]	2	[4]	2	[4]
Regulatory asset amortization	1		1		3		3
Qualified Pension Plans [Member] | Duke Energy Indiana [Member]
Service cost	3		2		5		5
Interest cost on benefit obligation	7		8		15		15
Expected return on plan assets	(11)		(11)		(23)		(22)
Amortization of prior service cost (credit)	0		1		1		1
Amortization of loss (gain)	4		3		7		7
Other	0		1		0		1
Net periodic costs	3		4		5		7
Non-Qualified Pension Plans [Member]
Service cost	0		1		1		1
Interest cost on benefit obligation	1		2		3		4
Expected return on plan assets	0		0		0		0
Amortization of prior service cost (credit)	1		0		1		1
Amortization of net transition liability	0		0		0		0
Amortization of loss (gain)	1		0		1		0
Other	0		0		0		0
Net periodic costs	3		3		6		6
Non-Qualified Pension Plans [Member] | Duke Energy Carolinas [Member]
Service cost					0		0
Interest cost on benefit obligation					1		1
Expected return on plan assets					0		0
Amortization of prior service cost (credit)					0		0
Amortization of net transition liability					0		0
Amortization of loss (gain)					0		0
Other					0		0
Net periodic costs					1		1
Other Post-Retirement Benefit plans [Member]
Service cost	1		3		3		4
Interest cost on benefit obligation	9		9		17		18
Expected return on plan assets	(4)		(4)		(8)		(8)
Amortization of prior service cost (credit)	(2)		(2)		(4)		(4)
Amortization of net transition liability	2		2		4		5
Amortization of loss (gain)	(1)		(1)		(3)		(2)
Other	0		0		0		0
Net periodic costs	5	[5]	7	[5]	9	[6]	13	[6]
Regulatory asset amortization	2		2		4		4
Other Post-Retirement Benefit plans [Member] | Duke Energy Carolinas [Member]
Service cost	0		1		1		1
Interest cost on benefit obligation	4		4		8		8
Expected return on plan assets	(2)		(3)		(5)		(5)
Amortization of prior service cost (credit)	(1)		(2)		(2)		(3)
Amortization of net transition liability	2		3		3		5
Amortization of loss (gain)	0		0		1		1
Other	0		0		0		0
Net periodic costs	3		3		6		7
Other Post-Retirement Benefit plans [Member] | Duke Energy Ohio [Member]
Service cost					0		0
Interest cost on benefit obligation					1		1
Expected return on plan assets					0		0
Amortization of prior service cost (credit)					(1)		(1)
Other					0		0
Net periodic costs					0	[7]	0	[7]
Regulatory asset amortization					1		1
Other Post-Retirement Benefit plans [Member] | Duke Energy Indiana [Member]
Service cost	0		0		0		0
Interest cost on benefit obligation	2		2		4		4
Expected return on plan assets	(1)		(1)		(1)		(1)
Amortization of prior service cost (credit)	1		0		1		0
Amortization of loss (gain)	(1)		1		(1)		1
Other	0		0		0		0
Net periodic costs	$ 1		$ 2		$ 3		$ 4

[1] Excludes regulatory asset amortization of $4 million and $3 million for each of the three months ended June 30, 2012 and 2011, respectively, resulting from purchase accounting adjustments associated with Duke Energy’s merger with Cinergy in April 2006.

[2] Excludes regulatory asset amortization of $7 million for each of the six months ended June 30, 2012 and 2011, resulting from purchase accounting adjustments associated with Duke Energy’s merger with Cinergy in April 2006.

[3] Excludes regulatory asset amortization of $1 million for each of the three months ended June 30, 2012 and 2011, resulting from purchase accounting adjustments associated with Duke Energy’s merger with Cinergy in April 2006.

[4] Excludes regulatory asset amortization of $3 million for each of the six months ended June 30, 2012 and 2011, resulting from purchase accounting adjustments associated with Duke Energy’s merger with Cinergy in April 2006.

[5] Excludes regulatory asset amortization of $2 million for each of the three months ended June 30, 2012 and 2011, resulting from purchase accounting adjustments associated with Duke Energy’s merger with Cinergy in April 2006.

[6] Excludes regulatory asset amortization of $4 million for each of the six months ended June 30, 2012 and 2011, resulting from purchase accounting adjustments associated with Duke Energy’s merger with Cinergy in April 2006.

[7] Excludes regulatory asset amortization of $1 million for each of the six months ended June 30, 2012 and 2011, resulting from purchase accounting adjustments associated with Duke Energy’s merger with Cinergy in April 2006.