Risk Management, Derivative Instruments And Hedging Activities (Location And Fair Value Amounts Of Derivatives Reflected In The Condensed Consolidated Balance Sheets) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012		Dec. 31, 2011
Location and fair value amounts of derivatives (Asset)	$ 244		$ 283
Location and fair value amounts of derivatives (Liability)	931		473
Duke Energy Ohio [Member]
Location and fair value amounts of derivatives (Asset)	177		271
Location and fair value amounts of derivatives (Liability)	183		245
Designated As Hedging Instrument [Member]
Location and fair value amounts of derivatives (Asset)	5
Location and fair value amounts of derivatives (Liability)	119
Designated As Hedging Instrument [Member] | Duke Energy Ohio [Member]
Location and fair value amounts of derivatives (Asset)	4
Designated As Hedging Instrument [Member] | Interest Rate Contract [Member]
Location and fair value amounts of derivatives (Asset)			6
Location and fair value amounts of derivatives (Liability)			87
Designated As Hedging Instrument [Member] | Interest Rate Contract [Member] | Duke Energy Ohio [Member]
Location and fair value amounts of derivatives (Asset)			5
Designated As Hedging Instrument [Member] | Interest Rate Contract [Member] | Current Assets, Other [Member]
Location and fair value amounts of derivatives (Asset)	5		4
Designated As Hedging Instrument [Member] | Interest Rate Contract [Member] | Current Assets, Other [Member] | Duke Energy Ohio [Member]
Location and fair value amounts of derivatives (Asset)	4		3
Designated As Hedging Instrument [Member] | Interest Rate Contract [Member] | Investments And Other Assets, Other [Member]
Location and fair value amounts of derivatives (Asset)			2
Designated As Hedging Instrument [Member] | Interest Rate Contract [Member] | Investments And Other Assets, Other [Member] | Duke Energy Ohio [Member]
Location and fair value amounts of derivatives (Asset)			2
Designated As Hedging Instrument [Member] | Interest Rate Contract [Member] | Current Liabilities, Other [Member]
Location and fair value amounts of derivatives (Liability)	11		11
Designated As Hedging Instrument [Member] | Interest Rate Contract [Member] | Deferred Credits And Other Liabilities, Other [Member]
Location and fair value amounts of derivatives (Liability)	107		76
Designated As Hedging Instrument [Member] | Commodity Contract [Member] | Current Liabilities, Other [Member]
Location and fair value amounts of derivatives (Liability)	1
Not Designated As Hedging Instrument [Member]
Location and fair value amounts of derivatives (Asset)	239		277
Location and fair value amounts of derivatives (Liability)	812		386
Not Designated As Hedging Instrument [Member] | Duke Energy Ohio [Member]
Location and fair value amounts of derivatives (Asset)	173		266
Location and fair value amounts of derivatives (Liability)	183		245
Not Designated As Hedging Instrument [Member] | Interest Rate Contract [Member] | Current Liabilities, Other [Member]
Location and fair value amounts of derivatives (Liability)	96	[1]	2
Not Designated As Hedging Instrument [Member] | Interest Rate Contract [Member] | Current Liabilities, Other [Member] | Duke Energy Ohio [Member]
Location and fair value amounts of derivatives (Liability)	1		1
Not Designated As Hedging Instrument [Member] | Interest Rate Contract [Member] | Deferred Credits And Other Liabilities, Other [Member]
Location and fair value amounts of derivatives (Liability)	8		75	[2]
Not Designated As Hedging Instrument [Member] | Interest Rate Contract [Member] | Deferred Credits And Other Liabilities, Other [Member] | Duke Energy Ohio [Member]
Location and fair value amounts of derivatives (Liability)	8		8
Not Designated As Hedging Instrument [Member] | Interest Rate Contract [Member] | Deferred Credits And Other Liabilities, Other [Member] | Duke Energy Indiana [Member]
Location and fair value amounts of derivatives (Liability)	71		67
Not Designated As Hedging Instrument [Member] | Commodity Contract [Member] | Current Assets, Other [Member]
Location and fair value amounts of derivatives (Asset)	55	[3]	81
Location and fair value amounts of derivatives (Liability)	5		31
Not Designated As Hedging Instrument [Member] | Commodity Contract [Member] | Current Assets, Other [Member] | Duke Energy Ohio [Member]
Location and fair value amounts of derivatives (Asset)	33		79
Location and fair value amounts of derivatives (Liability)	12		39
Not Designated As Hedging Instrument [Member] | Commodity Contract [Member] | Current Assets, Other [Member] | Duke Energy Indiana [Member]
Location and fair value amounts of derivatives (Asset)	17
Not Designated As Hedging Instrument [Member] | Commodity Contract [Member] | Investments And Other Assets, Other [Member]
Location and fair value amounts of derivatives (Asset)	35		35
Location and fair value amounts of derivatives (Liability)			17
Not Designated As Hedging Instrument [Member] | Commodity Contract [Member] | Investments And Other Assets, Other [Member] | Duke Energy Ohio [Member]
Location and fair value amounts of derivatives (Asset)	16		29
Location and fair value amounts of derivatives (Liability)	1		18
Not Designated As Hedging Instrument [Member] | Commodity Contract [Member] | Current Liabilities, Other [Member]
Location and fair value amounts of derivatives (Asset)	94		136
Location and fair value amounts of derivatives (Liability)	377		168
Not Designated As Hedging Instrument [Member] | Commodity Contract [Member] | Current Liabilities, Other [Member] | Duke Energy Ohio [Member]
Location and fair value amounts of derivatives (Asset)	85		136
Location and fair value amounts of derivatives (Liability)	110		146
Not Designated As Hedging Instrument [Member] | Commodity Contract [Member] | Deferred Credits And Other Liabilities, Other [Member]
Location and fair value amounts of derivatives (Asset)	55		25
Location and fair value amounts of derivatives (Liability)	325		93
Not Designated As Hedging Instrument [Member] | Commodity Contract [Member] | Deferred Credits And Other Liabilities, Other [Member] | Duke Energy Ohio [Member]
Location and fair value amounts of derivatives (Asset)	39		22
Location and fair value amounts of derivatives (Liability)	$ 51		$ 33

[1] Amount at Duke Energy includes $71 million related to interest rate swaps at Duke Energy Indiana which receive regulatory accounting treatment.

[2] Amounts at Duke Energy include $67 million related to interest rate swaps at Duke Energy Indiana which receive regulatory accounting treatment.

[3] Amount at Duke Energy includes $17 million related to commodity contracts at Duke Energy Indiana which receive regulatory accounting treatment.