Employee Benefit Plans (Components Of Net Periodic Pension Costs) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended		9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Jun. 30, 2012		Sep. 30, 2012		Sep. 30, 2011
Special termination charges	$ 0
Defined Contribution Plan, Cost Recognized	30		18				77		68
Duke Energy Carolinas [Member]
Defined Contribution Plan, Cost Recognized	8		8				28		28
Duke Energy Ohio [Member]
Defined Contribution Plan, Cost Recognized	1		1				3		3
Duke Energy Indiana [Member]
Defined Contribution Plan, Cost Recognized	2		1				5		6
Qualified Pension Plans [Member]
Service cost	39		24		84				72
Interest cost on benefit obligation	94		58		214				174
Expected return on plan assets	(142)		(96)		(330)				(288)
Amortization of prior service cost (credit)	3		1		6				4
Amortization of net transition liability	0		0		0				0
Amortization of loss (gain)	(47)		(20)		(96)				(58)
Special termination charges	0		0						0
Other	2		4		4				13
Net periodic costs	43	[1]	11	[1]	74	[2]			33	[2]
Regulatory asset amortization	3		4				10		11
Qualified Pension Plans [Member] | Duke Energy Carolinas [Member]
Service cost	9		9				26		28
Interest cost on benefit obligation	23		21				68		64
Expected return on plan assets	(36)		(37)				(109)		(112)
Amortization of prior service cost (credit)	0		1				1		1
Amortization of net transition liability	0		0				0		0
Amortization of loss (gain)	(11)		(9)				(34)		(27)
Other	0		1				1		5
Net periodic costs	7		4				21		13
Qualified Pension Plans [Member] | Duke Energy Ohio [Member]
Service cost	2		2				5		5
Interest cost on benefit obligation	7		8				23		24
Expected return on plan assets	(11)		(11)				(33)		(33)
Amortization of loss (gain)	(2)		(2)				(7)		(6)
Other	0		1				0		2
Net periodic costs	0	[3]	2	[3]			2	[4]	4	[4]
Regulatory asset amortization	2		2				5		5
Qualified Pension Plans [Member] | Duke Energy Indiana [Member]
Service cost	2		3				7		8
Interest cost on benefit obligation	8		8				23		23
Expected return on plan assets	(12)		(12)				(35)		(34)
Amortization of prior service cost (credit)	1		0				2		1
Amortization of loss (gain)	(3)		(3)				(10)		(10)
Other	0		1				0		2
Net periodic costs	2		3				7		10
Non-Qualified Pension Plans [Member]
Service cost	0		0				1		1
Interest cost on benefit obligation	5		2				8		6
Expected return on plan assets	0		0				0		0
Amortization of prior service cost (credit)	0		0				1		1
Amortization of net transition liability	0		0				0		0
Amortization of loss (gain)	(1)		(1)				(2)		(1)
Special termination charges	0		0				0		0
Other	0		0				0		0
Net periodic costs	6		3				12		9
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	7		1				10		5
Interest cost on benefit obligation	19		8				36		26
Expected return on plan assets	(4)		(3)				(12)		(11)
Amortization of prior service cost (credit)	(2)		(2)				(6)		(6)
Amortization of net transition liability	3		2				7		7
Amortization of loss (gain)	(8)		0				(5)		2
Special termination charges	(9)		0				(9)		0
Other	0		0				0		0
Net periodic costs	40	[5]	6	[5]			49	[6]	19	[6]
Regulatory asset amortization	3		2				7		6
Other Post-Retirement Benefit plans [Member] | Duke Energy Carolinas [Member]
Service cost	1		0				2		1
Interest cost on benefit obligation	4		4				12		12
Expected return on plan assets	(3)		(2)				(8)		(7)
Amortization of prior service cost (credit)	(2)		(1)				(4)		(4)
Amortization of net transition liability	2		2				5		7
Amortization of loss (gain)	(1)		(1)				(2)		(2)
Special termination charges	(1)						(1)
Other	0		0				0		0
Net periodic costs	4		4				10		11
Other Post-Retirement Benefit plans [Member] | Duke Energy Ohio [Member]
Service cost	1		1				1		1
Interest cost on benefit obligation	1		1				2		2
Expected return on plan assets	(1)		0				(1)		0
Amortization of prior service cost (credit)			(1)						(1)
Amortization of loss (gain)	1		1				2		2
Other	0		0				0		0
Net periodic costs	0	[7]	0	[7]			0	[8]	0	[8]
Regulatory asset amortization	0		1				1		2
Other Post-Retirement Benefit plans [Member] | Duke Energy Indiana [Member]
Service cost	1		1				1		1
Interest cost on benefit obligation	1		1				5		5
Expected return on plan assets	0		0				(1)		(1)
Amortization of prior service cost (credit)	0		0				1		0
Amortization of loss (gain)	0		0				1		(1)
Other	0		0				0		0
Net periodic costs	$ 2		$ 2				$ 5		$ 6

[1] Excludes regulatory asset amortization of $3 million and $4 million for each of the three months ended September 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 $10 million and $11 million for the nine months ended September 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 $2 million for each of the three months ended September 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 $5 million for each of the nine months ended September 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 $3 million and $2 million for the three months ended September 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 $7 million and $6 million for the nine months ended September 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 an insignificant amount and $1 million for each of the three months ended September 30, 2012 and 2011, resulting from purchase accounting adjustments associated with Duke Energy’s merger with Cinergy in April 2006.

[8] Excludes regulatory asset amortization of $1 million and $2 million for the nine months ended September 30, 2012 and 2011, respectively, resulting from purchase accounting adjustments associated with Duke Energy’s merger with Cinergy in April 2006.