Risk Management, Derivative Instruments And Hedging Activities (Location And Fair Value Amounts Of Derivatives Reflected In The Condensed Consolidated Balance Sheets) (Details) (USD $)	Sep. 30, 2011		Sep. 30, 2010
Location and fair value amounts of derivatives (Asset)	$ 149,000,000		$ 322,000,000
Location and fair value amounts of derivatives (Liability)	409,000,000		268,000,000
Designated As Hedging Instrument [Member] | Interest Rate Contracts [Member]
Location and fair value amounts of derivatives (Asset)	9,000,000.00		21,000,000
Location and fair value amounts of derivatives (Liability)	84,000,000.00		13,000,000
Designated As Hedging Instrument [Member] | Interest Rate Contracts [Member] | Current Assets, Other [Member]
Location and fair value amounts of derivatives (Asset)	5,000,000.00		5,000,000
Designated As Hedging Instrument [Member] | Interest Rate Contracts [Member] | Investments And Other Assets, Other [Member]
Location and fair value amounts of derivatives (Asset)	4,000,000.00		16,000,000
Designated As Hedging Instrument [Member] | Interest Rate Contracts [Member] | Current Liabilities, Other [Member]
Location and fair value amounts of derivatives (Liability)	13,000,000.00		13,000,000
Designated As Hedging Instrument [Member] | Interest Rate Contracts [Member] | Deferred Credits And Other Liabilities, Other [Member]
Location and fair value amounts of derivatives (Liability)	71,000,000.00
Not Designated As Hedging Instrument [Member]
Location and fair value amounts of derivatives (Asset)	140,000,000.00		301,000,000.00
Location and fair value amounts of derivatives (Liability)	325,000,000.00		255,000,000.00
Not Designated As Hedging Instrument [Member] | Interest Rate Contracts [Member] | Investments And Other Assets, Other [Member]
Location and fair value amounts of derivatives (Asset)			60,000,000.00	[1]
Not Designated As Hedging Instrument [Member] | Interest Rate Contracts [Member] | Current Liabilities, Other [Member]
Location and fair value amounts of derivatives (Liability)	94,000,000.00	[1],[2]	2,000,000.00	[1],[2]
Not Designated As Hedging Instrument [Member] | Interest Rate Contracts [Member] | Deferred Credits And Other Liabilities, Other [Member]
Location and fair value amounts of derivatives (Liability)	68,000,000.00	[3]	5,000,000.00	[3]
Not Designated As Hedging Instrument [Member] | Commodity Contracts [Member] | Current Assets, Other [Member]
Location and fair value amounts of derivatives (Asset)	73,000,000.00		108,000,000.00
Location and fair value amounts of derivatives (Liability)	30,000,000.00		54,000,000.00
Not Designated As Hedging Instrument [Member] | Commodity Contracts [Member] | Investments And Other Assets, Other [Member]
Location and fair value amounts of derivatives (Asset)	43,000,000.00		55,000,000.00
Location and fair value amounts of derivatives (Liability)	6,000,000.00		4,000,000.00
Not Designated As Hedging Instrument [Member] | Commodity Contracts [Member] | Current Liabilities, Other [Member]
Location and fair value amounts of derivatives (Asset)	15,000,000.00		75,000,000.00
Location and fair value amounts of derivatives (Liability)	50,000,000.00		118,000,000.00
Not Designated As Hedging Instrument [Member] | Commodity Contracts [Member] | Deferred Credits And Other Liabilities, Other [Member]
Location and fair value amounts of derivatives (Asset)	9,000,000.00		3,000,000.00
Location and fair value amounts of derivatives (Liability)	$ 77,000,000.00		$ 72,000,000.00

[1] As of December 31, 2010, includes $60 million related to interest rate swaps at Duke Energy Carolinas which receive regulatory accounting treatment.

[2] As of September 30, 2011, includes $92 million related to interest rate swaps at Duke Energy Carolinas which receive regulatory accounting treatment.

[3] As of September 30, 2011, includes $60 million related to interest rate swaps at Duke Energy Indiana which receive regulatory accounting treatment.