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	Jun. 30, 2012		Dec. 31, 2011
Location and fair value amounts of derivatives (Asset)	$ 266		$ 283
Location and fair value amounts of derivatives (Liability)	475		473
Duke Energy Ohio [Member]
Location and fair value amounts of derivatives (Asset)	256		271
Location and fair value amounts of derivatives (Liability)	212		245
Designated As Hedging Instrument [Member]
Location and fair value amounts of derivatives (Asset)	4
Location and fair value amounts of derivatives (Liability)	113
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)	4		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)	14		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)	99		76
Not Designated As Hedging Instrument [Member]
Location and fair value amounts of derivatives (Asset)	262		277
Location and fair value amounts of derivatives (Liability)	362		386
Not Designated As Hedging Instrument [Member] | Duke Energy Ohio [Member]
Location and fair value amounts of derivatives (Asset)	252		266
Location and fair value amounts of derivatives (Liability)	212		245
Not Designated As Hedging Instrument [Member] | Interest Rate Contract [Member] | Current Liabilities, Other [Member]
Location and fair value amounts of derivatives (Liability)	2		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)	84	[1]	75
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)	76		67
Not Designated As Hedging Instrument [Member] | Commodity Contract [Member] | Current Assets, Other [Member]
Location and fair value amounts of derivatives (Asset)	192	[2]	81
Location and fair value amounts of derivatives (Liability)	124		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)	184		79
Location and fair value amounts of derivatives (Liability)	131		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)	23
Not Designated As Hedging Instrument [Member] | Commodity Contract [Member] | Investments And Other Assets, Other [Member]
Location and fair value amounts of derivatives (Asset)	17		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)	18		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)	4		136
Location and fair value amounts of derivatives (Liability)	49		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)	3		136
Location and fair value amounts of derivatives (Liability)	12		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)	49		25
Location and fair value amounts of derivatives (Liability)	103		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)	47		22
Location and fair value amounts of derivatives (Liability)	$ 59		$ 33

[1] Amount at Duke Energy includes $76 million related to interest rate swaps at Duke Energy Indiana which receive regulatory accounting treatment.

[2] Amount at Duke Energy includes $23 million related to commodity contracts at Duke Energy Indiana which receive regulatory accounting treatment.