Investments In Debt And Equity Securities (Unrealized Losses Of Available-For-Sale Debt And Equity Securities In A Continuous Loss Position) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012		Dec. 31, 2011
Fair Value	$ 604		$ 584
Unrealized Loss Position greater than 12 months	17		25
Unrealized Loss Position less than 12 months	14		17
Other Classification [Member]
Fair Value	314		284
Unrealized Loss Position greater than 12 months	10		19
Unrealized Loss Position less than 12 months	0		0
Duke Energy Carolinas [Member] | NDTF [Member]
Fair Value	272	[1]	289	[1]
Unrealized Loss Position greater than 12 months	7	[1]	6	[1]
Unrealized Loss Position less than 12 months	13	[1]	16	[1]
Duke Energy Indiana [Member] | Grantor Trust [Member]
Fair Value	18	[1]	11	[1]
Unrealized Loss Position greater than 12 months	0	[1]	0	[1]
Unrealized Loss Position less than 12 months	1	[1]	1	[1]
Equity Securities [Member] | Other Classification [Member]
Fair Value	6		4
Unrealized Loss Position greater than 12 months	1		1
Unrealized Loss Position less than 12 months	0		0
Equity Securities [Member] | Duke Energy Carolinas [Member] | NDTF [Member]
Fair Value	117		111
Unrealized Loss Position greater than 12 months	7		4
Unrealized Loss Position less than 12 months	11		12
Equity Securities [Member] | Duke Energy Indiana [Member] | Grantor Trust [Member]
Fair Value	8		8
Unrealized Loss Position greater than 12 months	0		0
Unrealized Loss Position less than 12 months	1		1
Corporate Debt Securities [Member] | Other Classification [Member]
Fair Value	243		201
Unrealized Loss Position greater than 12 months	0		1
Unrealized Loss Position less than 12 months	0		0
Corporate Debt Securities [Member] | Duke Energy Carolinas [Member] | NDTF [Member]
Fair Value	29		57
Unrealized Loss Position greater than 12 months	0		1
Unrealized Loss Position less than 12 months	1		1
Municipal Bonds [Member] | Other Classification [Member]
Fair Value	1		0
Unrealized Loss Position greater than 12 months	0		0
Unrealized Loss Position less than 12 months	0		0
Municipal Bonds [Member] | Duke Energy Carolinas [Member] | NDTF [Member]
Fair Value	21		0
Unrealized Loss Position greater than 12 months	0		0
Unrealized Loss Position less than 12 months	0		0
Municipal Bonds [Member] | Duke Energy Indiana [Member] | Grantor Trust [Member]
Fair Value	10		3
Unrealized Loss Position greater than 12 months	0		0
Unrealized Loss Position less than 12 months	0		0
US Treasury and Government [Member] | Other Classification [Member]
Fair Value	12		0
Unrealized Loss Position greater than 12 months	0		0
Unrealized Loss Position less than 12 months	0		0
US Treasury and Government [Member] | Duke Energy Carolinas [Member] | NDTF [Member]
Fair Value	27		8
Unrealized Loss Position greater than 12 months	0		0
Unrealized Loss Position less than 12 months	0		0
Auction Rate Securities [Member] | Other Classification [Member]
Fair Value	35		59
Unrealized Loss Position greater than 12 months	8		14
Unrealized Loss Position less than 12 months	0		0
Auction Rate Securities [Member] | Duke Energy Carolinas [Member] | Other Classification [Member]
Fair Value	6	[2]	12	[2]
Unrealized Loss Position greater than 12 months	1	[2]	3	[2]
Other Debt Obligations [Member] | Other Classification [Member]
Fair Value	11		8
Unrealized Loss Position greater than 12 months	0		0
Unrealized Loss Position less than 12 months	0		0
Other Debt Obligations [Member] | Duke Energy Carolinas [Member] | NDTF [Member]
Fair Value	78		113
Unrealized Loss Position greater than 12 months	0		1
Unrealized Loss Position less than 12 months	$ 1		$ 3

[1] Unrealized losses on investments within the Duke Energy Carolinas NDTF and Duke Energy Indiana grantor trust are deferred as regulatory assets pursuant to regulatory accounting treatment.

[2] At June 30, 2012 and December 31, 2011, $6 million and $12 million of these securities, respectively, were held by Duke Energy Carolinas. The gross unrealized losses on these securities held by Duke Energy Carolinas which were in an unrealized loss position greater than 12 months were $1 million at June 30, 2012 and $3 million at December 31, 2011.