Investments In Debt And Equity Securities (Available-For-Sale Investments) (Details) (USD $) In Millions	Sep. 30, 2011		Dec. 31, 2010
Current [Member]
Estimated Fair Value	$ 146
Current [Member] | Short-term Investments [Member]
Estimated Fair Value	146	[1]
Auction Rate Securities [Member] | Non-current [Member]
Gross Unrealized Holding Gains		[2],[3]		[2],[3]
Gross Unrealized Holding Losses	(19)	[2],[3]	(31)	[2],[3]
Estimated Fair Value	72	[2]	118	[2]
Non-current [Member]
Gross Unrealized Holding Gains	370	[3]	515	[3]
Gross Unrealized Holding Losses	(85)	[3]	(65)	[3]
Estimated Fair Value	2,237		2,401
Non-current [Member] | Equity Securities [Member]
Gross Unrealized Holding Gains	334	[3]	481	[3]
Gross Unrealized Holding Losses	(60)	[3]	(16)	[3]
Estimated Fair Value	1,261		1,435
Non-current [Member] | Corporate Debt Securities [Member]
Gross Unrealized Holding Gains	8	[3]	12	[3]
Gross Unrealized Holding Losses	(4)	[3]	(3)	[3]
Estimated Fair Value	226		270
Non-current [Member] | Municipal Bonds [Member]
Gross Unrealized Holding Gains	2	[3]	1	[3]
Gross Unrealized Holding Losses			(9)	[3]
Estimated Fair Value	62		69
Non-current [Member] | U.S. Government Bonds [Member]
Gross Unrealized Holding Gains	21	[3]	10	[3]
Gross Unrealized Holding Losses			(1)	[3]
Estimated Fair Value	373		235
Non-current [Member] | Other Debt Securities [Member]
Gross Unrealized Holding Gains	5	[3]	11	[3]
Gross Unrealized Holding Losses	(2)	[3]	(5)	[3]
Estimated Fair Value	243		274
NDTF [Member]
Gross Unrealized Holding Gains	364		505
Gross Unrealized Holding Losses	63		32
Auction Rate Securities [Member]
Other	72
Other short-term investments	25
Duke Energy Indiana Grantor Trust [Member]
Gross Unrealized Holding Gains	2		6
Gross Unrealized Holding Losses	$ 1

[1] At September 30, 2011, auction rate securities estimated fair value of $25 million are classified as Short-Term Investments on the Condensed Consolidated Balance Sheets.

[2] At September 30, 2011, auction rate securities estimated fair value of $72 million are included in Other within Investments and Other Assets on the Condensed Consolidated Balance Sheets.

[3] The table above includes unrealized gains and losses of $364 million and $63 million, respectively, at September 30, 2011 and unrealized gains and losses of $505 million and $32 million, respectively, at December 31, 2010 associated with investments held in the NDTF. Additionally, the table above includes unrealized gains and losses of $2 million and $1 million respectively, at September 30, 2011 and unrealized gains of $6 million and an insignificant amount of unrealized losses, respectively, 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.