Investments In Debt And Equity Securities (Available-For-Sale Investments) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011		Dec. 31, 2010
Estimated Fair Value	$ 71	[1]	$ 118	[1]
Duke Energy Indiana Grantor Trust [Member]
Gross Unrealized Holding Gains	6		6
Gross Unrealized Holding Losses	1
NDTF [Member]
Gross Unrealized Holding Gains	473		505
Gross Unrealized Holding Losses	22		32
Current [Member]
Estimated Fair Value	190
Current [Member] | Short Term Investments [Member]
Estimated Fair Value	190
Non-current [Member]
Gross Unrealized Holding Gains	483	[2]	515	[2]
Gross Unrealized Holding Losses	(42)	[2]	(65)	[2]
Estimated Fair Value	2,359		2,401
Non-current [Member] | U.S. Government Bonds [Member]
Gross Unrealized Holding Gains	17	[2]	10	[2]
Gross Unrealized Holding Losses			(1)	[2]
Estimated Fair Value	327		235
Non-current [Member] | Auction Rate Securities [Member]
Gross Unrealized Holding Gains		[2]
Gross Unrealized Holding Losses	(17)	[2]	(31)	[2]
Estimated Fair Value	71		118
Non-current [Member] | Other Debt Securities [Member]
Gross Unrealized Holding Gains	6	[2]	11	[2]
Gross Unrealized Holding Losses	(4)	[2]	(5)	[2]
Estimated Fair Value	229		274
Non-current [Member] | Equity Securities [Member]
Gross Unrealized Holding Gains	448	[2]	481	[2]
Gross Unrealized Holding Losses	(18)	[2]	(16)	[2]
Estimated Fair Value	1,397		1,435
Non-current [Member] | Corporate Debt Securities [Member]
Gross Unrealized Holding Gains	9	[2]	12	[2]
Gross Unrealized Holding Losses	(3)	[2]	(3)	[2]
Estimated Fair Value	256		270
Non-current [Member] | Municipal Bonds [Member]
Gross Unrealized Holding Gains	3	[2]	1	[2]
Gross Unrealized Holding Losses			(9)	[2]
Estimated Fair Value	$ 79		$ 69

[1] Included in Other within Investments and Other Assets on the Consolidated Balance Sheets.

[2] The table above includes unrealized gains and losses of $473 million and $22 million, respectively, at December 31, 2011 and unrealized gains and losses of $505 million and $32 million, respectively, at December 31, 2010 associated with investments held in the Duke Energy Carolinas NDTF. Additionally, the table above includes unrealized gains of $6 million and $1 million of unrealized losses at December 31, 2011, and unrealized gains of $6 million and an insignificant amount of unrealized losses, at December 31, 2010 associated with investments held in the Duke Energy Indiana grantor trust. As discussed above, unrealized losses on investments within the NDTF and Duke Energy Indiana grantor trust are deferred as a regulatory asset pursuant to regulatory accounting treatment.