Investments In Debt And Equity Securities (Available-For-Sale Investments) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012		Dec. 31, 2011
Gross Unrealized Holding Gains	$ 562		$ 483
Gross Unrealized Holding Losses	31		42
Estimated Fair Value	2,770		2,549
Other Classification [Member]
Gross Unrealized Holding Gains	4		4
Gross Unrealized Holding Losses	10		19
Estimated Fair Value	492		415
Duke Energy Carolinas [Member] | Ndtf [Member]
Gross Unrealized Holding Gains	550	[1]	473	[1]
Gross Unrealized Holding Losses	20	[1]	22	[1]
Estimated Fair Value	2,204	[1]	2,060	[1]
Duke Energy Indiana [Member] | Grantor Trust [Member]
Gross Unrealized Holding Gains	8	[1]	6	[1]
Gross Unrealized Holding Losses	1	[1]	1	[1]
Estimated Fair Value	74	[1]	74	[1]
Equity Securities [Member] | Other Classification [Member]
Gross Unrealized Holding Gains	1		0
Gross Unrealized Holding Losses	1		1
Estimated Fair Value	20		14
Equity Securities [Member] | Duke Energy Carolinas [Member] | Ndtf [Member]
Gross Unrealized Holding Gains	522		443
Gross Unrealized Holding Losses	17		16
Estimated Fair Value	1,470		1,337
Equity Securities [Member] | Duke Energy Indiana [Member] | Grantor Trust [Member]
Gross Unrealized Holding Gains	7		5
Gross Unrealized Holding Losses	1		1
Estimated Fair Value	46		46
Corporate Debt Securities [Member] | Other Classification [Member]
Gross Unrealized Holding Gains	2		1
Gross Unrealized Holding Losses	0		1
Estimated Fair Value	295		241
Corporate Debt Securities [Member] | Duke Energy Carolinas [Member] | Ndtf [Member]
Gross Unrealized Holding Gains	10		8
Gross Unrealized Holding Losses	2		2
Estimated Fair Value	221		205
Municipal Bonds [Member] | Other Classification [Member]
Gross Unrealized Holding Gains	0		0
Gross Unrealized Holding Losses	0		0
Estimated Fair Value	1		0
Municipal Bonds [Member] | Duke Energy Carolinas [Member] | Ndtf [Member]
Gross Unrealized Holding Gains	2		2
Gross Unrealized Holding Losses	0		0
Estimated Fair Value	73		51
Municipal Bonds [Member] | Duke Energy Indiana [Member] | Grantor Trust [Member]
Gross Unrealized Holding Gains	1		1
Gross Unrealized Holding Losses	0		0
Estimated Fair Value	28		28
U.S. Government Bonds [Member] | Other Classification [Member]
Gross Unrealized Holding Gains	0		1
Gross Unrealized Holding Losses	0		0
Estimated Fair Value	28		21
U.S. Government Bonds [Member] | Duke Energy Carolinas [Member] | Ndtf [Member]
Gross Unrealized Holding Gains	12		16
Gross Unrealized Holding Losses	0		0
Estimated Fair Value	277		306
Auction Rate Securities [Member] | Other Classification [Member]
Gross Unrealized Holding Gains	0		0
Gross Unrealized Holding Losses	9		17
Estimated Fair Value	41		71
Auction Rate Securities [Member] | Duke Energy Carolinas [Member] | Other Classification [Member]
Gross Unrealized Holding Losses	1	[2]	3	[2]
Estimated Fair Value	6	[2]	12	[2]
Other Debt Securities [Member] | Other Classification [Member]
Gross Unrealized Holding Gains	1		2
Gross Unrealized Holding Losses	0		0
Estimated Fair Value	107		68
Other Debt Securities [Member] | Duke Energy Carolinas [Member] | Ndtf [Member]
Gross Unrealized Holding Gains	4		4
Gross Unrealized Holding Losses	1		4
Estimated Fair Value	$ 163		$ 161

[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 were held by Duke Energy Carolinas, respectively. Gross unrealized holding gains on these securities held by Duke Energy Carolinas were insignificant at both June 30, 2012 and December 31, 2011. Gross unrealized holding losses on these securities held by Duke Energy Carolinas were $1 million at June 30, 2012 and $3 million at December 31, 2011.