Risk Management, Derivative Instruments And Hedging Activities (Undesignated Contracts - Location And Amount Of Pre-Tax Gains And (Losses) Recognized In Income Or As Regulatory Assets Or Liabilities) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended			9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011		Sep. 30, 2012	Sep. 30, 2011
Total Pre-tax Gains (Losses) Recognized as Regulatory Assets or Liabilities	$ 80	$ (202)		$ 92	$ (202)
Pre-tax gains losses on derivative instruments in AOCI - Non Interest rate contracts	(190)			(154)	(26)
Duke Energy Ohio [Member]
Total Pre-tax Gains (Losses) Recognized as Regulatory Assets or Liabilities	0	(2)		(1)	(3)
Pre-tax gains losses on derivative instruments in AOCI - Non Interest rate contracts	(42)	(6)		32	(30)
Revenue, regulated electric | Commodity Contracts [Member]
Pre-tax gains losses on derivative instruments in AOCI - Non Interest rate contracts	(22)			(22)
Revenue, Non-Regulated Electric, Natural Gas And Other [Member] | Commodity Contracts [Member]
Pre-tax gains losses on derivative instruments in AOCI - Non Interest rate contracts	(28)			8	(25)
Revenue, Non-Regulated Electric, Natural Gas And Other [Member] | Commodity Contracts [Member] | Duke Energy Ohio [Member]
Pre-tax gains losses on derivative instruments in AOCI - Non Interest rate contracts	(42)	(6)		33	(28)
Fuel Used In Electric Generation And Purchased Power - Regulated | Commodity Contracts [Member]
Pre-tax gains losses on derivative instruments in AOCI - Non Interest rate contracts	(135)			(135)
Fuel Used In Electric Generation And Purchased Power-Non-Regulated [Member] | Commodity Contracts [Member]
Pre-tax gains losses on derivative instruments in AOCI - Non Interest rate contracts					(1)
Fuel Used In Electric Generation And Purchased Power-Non-Regulated [Member] | Commodity Contracts [Member] | Duke Energy Ohio [Member]
Pre-tax gains losses on derivative instruments in AOCI - Non Interest rate contracts					(1)
Other Income and Expenses | Commodity Contracts [Member]
Pre-tax gains losses on derivative instruments in AOCI - Non Interest rate contracts	(1)			(1)
Interest Expense [Member] | Interest Rate Contracts [Member]
Total Pre-tax Gains (Losses) Recognized in Earnings - Interest Expense	(4)			(4)
Interest Expense [Member] | Interest Rate Contracts [Member] | Duke Energy Ohio [Member]
Total Pre-tax Gains (Losses) Recognized in Earnings - Interest Expense				(1)	(1)
Regulatory Asset [Member] | Interest Rate Contracts [Member]
Total Pre-tax Gains (Losses) Recognized as Regulatory Assets or Liabilities	7	(146)	[1]	(3)	(155)	[2]
Regulatory Asset [Member] | Interest Rate Contracts [Member] | Duke Energy Carolinas [Member]
Total Pre-tax Gains (Losses) Recognized as Regulatory Assets or Liabilities		82			91
Regulatory Asset [Member] | Interest Rate Contracts [Member] | Duke Energy Ohio [Member]
Total Pre-tax Gains (Losses) Recognized as Regulatory Assets or Liabilities		(4)			(4)
Regulatory Asset [Member] | Interest Rate Contracts [Member] | Duke Energy Indiana [Member]
Total Pre-tax Gains (Losses) Recognized as Regulatory Assets or Liabilities		60			60
Regulatory Asset [Member] | Commodity Contracts [Member]
Total Pre-tax Gains (Losses) Recognized as Regulatory Assets or Liabilities	61	2		61	1
Regulatory Asset [Member] | Commodity Contracts [Member] | Duke Energy Ohio [Member]
Total Pre-tax Gains (Losses) Recognized as Regulatory Assets or Liabilities		2		(2)	1
Regulatory Liability [Member] | Interest Rate Contracts [Member]
Total Pre-tax Gains (Losses) Recognized as Regulatory Assets or Liabilities		(60)			(60)
Regulatory Liability [Member] | Commodity Contracts [Member]
Total Pre-tax Gains (Losses) Recognized as Regulatory Assets or Liabilities	12	2		34	12
Regulatory Liability [Member] | Commodity Contracts [Member] | Duke Energy Ohio [Member]
Total Pre-tax Gains (Losses) Recognized as Regulatory Assets or Liabilities				1
Regulatory Liability [Member] | Commodity Contracts [Member] | Duke Energy Indiana [Member]
Total Pre-tax Gains (Losses) Recognized as Regulatory Assets or Liabilities	$ 12			$ 34

[1] Includes $82 million and $60 million related to interest rate swaps at Duke Energy Carolinas and Duke Energy Indiana, respectively for the three months ended September 30, 2011.

[2] Includes $91 million and $60 million related to interest rate swaps at Duke Energy Carolinas and Duke Energy Indiana, respectively for the nine months ended September 30, 2011.