Investments In Debt And Equity Securities (Available-For-Sale Investments) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012		Dec. 31, 2011
Gross Unrealized Holding Gains	$ 1,216		$ 483
Gross Unrealized Holding Losses	41		42
Estimated Fair Value	4,890		2,549
Other Classification [Member]
Gross Unrealized Holding Gains	10		4
Gross Unrealized Holding Losses	11		19
Estimated Fair Value	658		415
Duke Energy Carolinas [Member] | Ndtf [Member]
Gross Unrealized Holding Gains	623	[1]	473	[1]
Gross Unrealized Holding Losses	7	[1]	22	[1]
Estimated Fair Value	2,311	[1]	2,060	[1]
Duke Energy Indiana [Member] | Grantor Trust [Member]
Gross Unrealized Holding Gains	10	[1]	6	[1]
Gross Unrealized Holding Losses			1	[1]
Estimated Fair Value	77	[1]	74	[1]
Progress Energy [Member] | Ndtf [Member]
Gross Unrealized Holding Gains	573	[1]
Gross Unrealized Holding Losses	23	[1]
Estimated Fair Value	1,844	[1]
Equity Securities [Member] | Duke Energy Carolinas [Member] | Ndtf [Member]
Gross Unrealized Holding Gains	587		443
Gross Unrealized Holding Losses	5		16
Estimated Fair Value	1,553		1,337
Equity Securities [Member] | Duke Energy Indiana [Member] | Grantor Trust [Member]
Gross Unrealized Holding Gains	9		5
Gross Unrealized Holding Losses			1
Estimated Fair Value	49		46
Equity Securities [Member] | Progress Energy [Member] | Ndtf [Member]
Gross Unrealized Holding Gains	534
Gross Unrealized Holding Losses	21
Estimated Fair Value	1,226
Corporate Debt Securities [Member] | Other Classification [Member]
Gross Unrealized Holding Gains	3		1
Gross Unrealized Holding Losses	0		1
Estimated Fair Value	384		241
Corporate Debt Securities [Member] | Duke Energy Carolinas [Member] | Ndtf [Member]
Gross Unrealized Holding Gains	13		8
Gross Unrealized Holding Losses	1		2
Estimated Fair Value	234		205
Corporate Debt Securities [Member] | Progress Energy [Member] | Ndtf [Member]
Gross Unrealized Holding Gains	9
Gross Unrealized Holding Losses	0
Estimated Fair Value	85
Municipal Bonds [Member] | Other Classification [Member]
Gross Unrealized Holding Gains	3		0
Gross Unrealized Holding Losses	0		0
Estimated Fair Value	40		0
Municipal Bonds [Member] | Duke Energy Carolinas [Member] | Ndtf [Member]
Gross Unrealized Holding Gains	3		2
Gross Unrealized Holding Losses	0		0
Estimated Fair Value	62		51
Municipal Bonds [Member] | Duke Energy Indiana [Member] | Grantor Trust [Member]
Gross Unrealized Holding Gains	1		1
Gross Unrealized Holding Losses			0
Estimated Fair Value	28		28
Municipal Bonds [Member] | Progress Energy [Member] | Ndtf [Member]
Gross Unrealized Holding Gains	10
Gross Unrealized Holding Losses	1
Estimated Fair Value	134
U.S. Government Bonds [Member] | Other Classification [Member]
Gross Unrealized Holding Gains	0		1
Gross Unrealized Holding Losses	0		0
Estimated Fair Value	46		21
U.S. Government Bonds [Member] | Duke Energy Carolinas [Member] | Ndtf [Member]
Gross Unrealized Holding Gains	13		16
Gross Unrealized Holding Losses	0		0
Estimated Fair Value	306		306
U.S. Government Bonds [Member] | Progress Energy [Member] | Ndtf [Member]
Gross Unrealized Holding Gains	17
Gross Unrealized Holding Losses	0
Estimated Fair Value	295
Auction Rate Securities [Member] | Other Classification [Member]
Gross Unrealized Holding Gains	0		0
Gross Unrealized Holding Losses	8		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	2		2
Gross Unrealized Holding Losses	1		0
Estimated Fair Value	128		68
Other Debt Securities [Member] | Duke Energy Carolinas [Member] | Ndtf [Member]
Gross Unrealized Holding Gains	7		4
Gross Unrealized Holding Losses	1		4
Estimated Fair Value	156		161
Other Debt Securities [Member] | Progress Energy [Member] | Ndtf [Member]
Gross Unrealized Holding Gains	3
Gross Unrealized Holding Losses	1
Estimated Fair Value	$ 104

[1] Unrealized gains and losses on investments within the Duke Energy Carolinas NDTF, Progress Energy NDTF, and the Duke Energy Indiana and Progress Energy grantor trusts are deferred as regulatory assets and regulatory liabilities, respectively, pursuant to regulatory accounting treatment.

[2] At September 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 September 30, 2012 and December 31, 2011. Gross unrealized holding losses on these securities held by Duke Energy Carolinas were $1 million at September 30, 2012 and $3 million at December 31, 2011.